行政院環境保護署

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1 行 政 院 環 境 保 護 署 計 畫 編 號 EPA-94-J 以 二 氧 化 氯 做 為 飲 用 水 水 質 處 理 藥 劑 之 評 估 專 案 工 作 計 畫 期 末 報 告 ( 定 稿 本 ) 委 辦 機 構 : 行 政 院 環 境 保 護 署 執 行 機 構 : 國 立 中 興 大 學 環 境 工 程 學 系 執 行 期 間 : ~ 中 華 民 國 94 年 12 月

2 行 政 院 環 境 保 護 署 計 畫 編 號 EPA-94-J 以 二 氧 化 氯 做 為 飲 用 水 水 質 處 理 藥 劑 之 評 估 專 案 工 作 計 畫 期 末 報 告 ( 定 稿 本 ) 委 辦 機 構 : 行 政 院 環 境 保 護 署 執 行 機 構 : 國 立 中 興 大 學 環 境 工 程 學 系 計 畫 主 持 人 : 謝 永 旭 教 授 執 行 期 間 : ~ 計 畫 經 費 :24 萬 6 仟 元 整 中 華 民 國 94 年 12 月

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4 統 一 編 號 : * 本 報 告 僅 係 受 託 單 位 或 個 人 之 意 見, 僅 供 環 保 署 施 政 之 參 考 * 本 報 告 之 著 作 財 產 權 屬 環 保 署 所 有, 非 經 環 保 署 同 意, 任 何 人 均 不 得 重 製 仿 製 或 為 其 他 之 侵 害

5 行 政 院 環 境 保 護 署 以 二 氧 化 氯 做 為 飲 用 水 水 質 處 理 藥 劑 之 評 估 期 末 報 告 ( 定 稿 本 ) EPA-94-J

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7 以 二 氧 化 氯 做 為 飲 用 水 水 質 處 理 藥 劑 之 評 估 計 畫 期 末 報 告 基 本 資 料 表 甲 委 辦 單 位 行 政 院 環 境 保 護 署 乙 執 行 單 位 國 立 中 興 大 學 環 境 工 程 學 系 丙 年 度 94 年 度 計 畫 編 號 EPA-94-J 丁 研 究 性 質 基 礎 研 究 戊 研 究 領 域 環 境 保 護 己 計 畫 屬 性 科 技 類 非 科 技 類 庚 全 程 期 間 辛 本 期 期 間 壬 本 期 經 費 94 年 05 月 01 日 至 94 年 11 月 30 日 94 年 05 月 01 日 至 94 年 11 月 30 日 246 千 元 摘 要 關 鍵 詞 : 二 氧 化 氯, 飲 用 水, 消 毒 劑 資 本 支 出 0 千 元 經 常 支 出 土 地 建 築 0 千 元 人 事 費 114 千 元 儀 器 設 備 0 千 元 業 務 費 86.4 千 元 其 他 0 千 元 差 旅 費 21 千 元 Keyword: chlorine dioxide, drinking water, disinfectant agent 參 與 計 畫 人 力 資 料 : 參 與 計 畫 人 員 姓 名 工 作 要 項 或 撰 稿 章 節 現 職 與 簡 要 學 經 歷 謝 永 旭 規 劃 及 執 行 本 中 興 大 學 環 境 計 劃, 出 席 相 工 程 學 系 教 授 關 會 議 提 供 專 業 諮 詢 劉 謹 銓 協 助 文 獻 與 規 中 興 大 學 環 境 範 收 集 協 助 工 程 學 系 博 士 報 告 撰 寫 班 研 究 生 周 聖 環 協 助 資 料 收 集 中 興 大 學 環 境 工 程 學 系 碩 士 班 研 究 生 參 與 時 間 ( 人 月 ) 行 政 管 理 費 24.6 千 元 聯 絡 電 話 及 帳 號 1 人 7 月 #535 [email protected] u.tw 1 人 7 月 #615 [email protected] 1 人 20 日 #615

8 一 中 文 計 畫 名 稱 : 以 二 氧 化 氯 做 為 飲 用 水 水 質 處 理 藥 劑 之 評 估 二 英 文 計 畫 名 稱 : The Assessment on Using Chlorine Dioxide as Treatment Chemical for Drinking Water Quality 三 計 畫 編 號 : EPA-94-J 四 執 行 單 位 : 國 立 中 興 大 學 環 境 工 程 學 系 五 計 畫 主 持 人 : 謝 永 旭 六 執 行 開 始 時 間 : 94/05/01 七 執 行 結 束 時 間 : 94/11/30 八 報 告 完 成 日 期 : 94/11/21 九 報 告 總 頁 數 : 十 使 用 語 文 : 中 文, 英 文 十 一 報 告 電 子 檔 名 稱 : EPA94J pdf 十 二 報 告 電 子 檔 格 式 : Adobe Acrobat PDF 十 三 中 文 摘 要 關 鍵 詞 : 二 氧 化 氯, 飲 用 水, 消 毒 劑 十 四 英 文 摘 要 關 鍵 詞 : chlorine dioxide, drinking water, disinfectant 十 五 中 文 摘 要 : 本 計 畫 以 二 氧 化 氯 為 對 象, 探 討 其 做 為 飲 用 水 水 質 處 理 藥 劑 公 告 對 象 時 所 須 考 量 及 評 估 之 藥 劑 主 成 份 與 不 純 物 等 相 關 特 性, 以 提 供 環 保 署 對 飲 用 水 水 質 處 理 藥 劑 進 行 公 告 作 業 程 序 時 之 重 要 參 考 依 據 依 據 所 收 集 的 資 料, 目 前 僅 有 美 國 環 保 署 世 界 衛 生 組 織 及 德 國 有 對 二 氧 化 氯 的 相 關 規 範 製 造 二 氧 化 氯 會 伴 隨 產 生 無 機 副 產 物 亞 氯 酸 根 及 氯 酸 根, 其 中 亞 氯 酸 根 的 毒 害 性 較 大 為 了 減 少 無 機 副 產 物 的 產 生 與 其 他 不 純 物 的 汙 染, 本 計 畫 建 議 公 告 氣 態 二 氧 化 氯 並 參 考 國 外 規 範, 建 議 最 大 添 加 劑 量 為 1.4 mg/l, 另 添 加 後 最 高 殘 餘 濃 度 0.8 mg/l 及 添 加 後 亞 氯 酸 根 濃 度 限 值 1.0 mg/l 則 可 增 訂 在 飲 用 水 水 質 標 準 中

9 十 六 英 文 摘 要 (Abstract): The purpose of this research is to study the related characteristics on proper major component and impurities of chlorine dioxide, which is considered to be an allowable treatment chemical for drinking water quality, in order to offer some important consideration and concerns to EPA for the legal announcement process. According to those collected information, USEPA, WHO and Germany are the few organization or countries who have established the related regulation on the use of chlorine dioxide at the present time. The generation of chlorine dioxide may produce some inorganic by-products at meantime, such as chlorite and chlorate. It has been noted that the toxicity of chlorite is more obvious. In order to minimize the production of inorganic by-products and the pollution from other impurities, it is suggested by this research that only gaseous chlorine dioxide can be used and added into the drinking water, and 1.4 mg/l and 0.8 mg/l are set as the maximum applied dosage and maximum allowable residual concentration, respectively, according to those referred regulations. Moreover, 1.0 mg/l as the upper limit or the residual chlorite concentration is also suggested.

10 目 錄 頁 次 第 一 章 專 案 緣 起 與 目 的 計 畫 緣 起 計 畫 目 標 第 二 章 執 行 方 法 第 三 章 本 年 度 主 要 工 作 內 容 及 重 要 發 現 與 成 果 二 氧 化 氯 的 基 本 性 質 二 氧 化 氯 的 結 構 與 物 化 特 性 二 氧 化 氯 的 製 造 方 法 實 驗 室 常 用 二 氧 化 氯 製 備 方 法 及 分 析 方 法 二 氧 化 氯 在 水 中 的 反 應 二 氧 化 氯 與 水 中 含 氯 物 種 之 交 互 反 應 二 氧 化 氯 與 水 中 有 機 物 之 反 應 二 氧 化 氯 在 淨 水 工 程 的 應 用 二 氧 化 氯 與 其 他 消 毒 劑 的 比 較 相 關 法 令 國 內 相 關 法 令 國 外 相 關 規 範 公 告 建 議 市 售 樣 品 分 析 分 析 方 法 分 析 結 果 第 四 章 主 要 意 見 及 未 來 或 後 續 執 行 建 議 I

11 目 錄 ( 續 ) 頁 次 4.1 結 論 建 議 參 考 文 獻 附 錄 一 附 錄 二 附 錄 三 附 錄 四 附 錄 五 附 錄 六 附 錄 七 附 錄 八 附 錄 九 附 錄 十 附 錄 十 一 二 氧 化 氯 公 告 草 案 期 中 報 告 審 查 委 員 意 見 答 覆 諮 商 會 委 員 意 見 答 覆 期 末 報 告 審 查 委 員 意 見 答 覆 飲 用 水 管 理 條 例 飲 用 水 水 質 標 準 USEPA National Primary Drinking Water Standards WHO Chemical summary tables Japan Supply of Drinking Water with Clean and Safe WATER AND WASTEWATER DISINFECTION-National Report from Germany Korea Drinking water test item and water quality standard 附 錄 十 二 USEPA Alternative Disinfectants and Oxidants Guidance Manual 附 錄 十 三 WHO Concise International Chemical Assessment Document 37 CHLORINE DIOXIDE (GAS) 附 錄 十 四 Standard Methods for Examination of Water and Wastewater 4500-ClO 2 Chlorine Dioxide II

12 表 目 錄 頁 次 表 3-1 物 質 安 全 資 料 表 中 二 氧 化 氯 的 基 本 性 質 表 3-2 二 氧 化 氯 產 製 型 態 一 覽 表 (EPA Guidance Manual, 1999) 表 3-3 含 氯 物 種 的 交 互 反 應 Gordon(2001) 表 3-4 二 氧 化 氯 與 水 中 有 機 物 的 反 應 (Katz, 1992) 表 3-5 各 類 消 毒 劑 可 能 衍 生 之 消 毒 副 產 物 (Craun et al., 1994) 表 3-6 各 種 消 毒 劑 之 優 缺 點 ( 張, 1996) 表 3-7 金 屬 離 子 分 析 方 法 表 3-8 台 灣 紙 業 股 份 有 限 公 司 二 氧 化 氯 產 品 分 析 結 果 表 3-9 阿 瑪 奇 生 化 科 技 股 份 有 限 公 司 二 氧 化 氯 產 品 分 析 結 果 表 3-10 注 溢 生 化 科 技 股 份 有 限 公 司 二 氧 化 氯 產 品 分 析 結 果 III

13 圖 目 錄 頁 次 圖 3-1 二 氧 化 氯 生 成 裝 置 圖 3-2 以 DPD 法 測 定 自 由 餘 氯 步 驟 IV

14 主 計 畫 名 稱 : 以 二 氧 化 氯 做 為 飲 用 水 水 質 處 理 藥 劑 之 評 估 計 畫 編 號 :EPA-94-J 執 行 單 位 : 國 立 中 興 大 學 環 境 工 程 學 系 計 畫 主 持 人 : 謝 永 旭 計 畫 期 程 : 九 十 四 年 五 月 一 日 起 九 十 四 年 十 一 月 三 十 日 止 計 畫 經 費 : 貳 拾 肆 萬 陸 仟 元 整 摘 要 : 本 計 畫 以 二 氧 化 氯 為 對 象, 探 討 其 做 為 飲 用 水 水 質 處 理 藥 劑 公 告 對 象 時 所 須 考 量 及 評 估 之 藥 劑 主 成 份 與 不 純 物 等 相 關 特 性, 以 提 供 環 保 署 對 飲 用 水 水 質 處 理 藥 劑 進 行 公 告 作 業 程 序 時 之 重 要 參 考 依 據 依 據 所 收 集 的 資 料, 目 前 僅 有 美 國 環 保 署 世 界 衛 生 組 織 及 德 國 有 對 二 氧 化 氯 的 相 關 規 範 製 造 二 氧 化 氯 會 伴 隨 產 生 無 機 副 產 物 亞 氯 酸 根 及 氯 酸 根, 其 中 亞 氯 酸 根 的 毒 害 性 較 大 為 了 減 少 無 機 副 產 物 的 產 生 與 其 他 不 純 物 的 汙 染, 本 計 畫 建 議 公 告 氣 態 二 氧 化 氯 並 參 考 國 外 規 範, 建 議 最 大 添 加 劑 量 為 1.4 mg/l 添 加 後 最 高 殘 餘 濃 度 0.8 mg/l 及 添 加 後 亞 氯 酸 根 濃 度 限 值 1.0 mg/l The purpose of this research is to study the related characteristics on proper major component and impurities of chlorine dioxide, which is considered to be an allowable treatment chemical for drinking water quality, in order to offer

15 some important consideration and concerns to EPA for the legal announcement process. According to those collected information, USEPA, WHO and Germany are the few organization or countries who have established the related regulation on the use of chlorine dioxide at the present time. The generation of chlorine dioxide may produce some inorganic by-products at meantime, such as chlorite and chlorate. It has been noted that the toxicity of chlorite is more obvious. In order to minimize the production of inorganic by-products and the pollution from other impurities, it is suggested by this research that only gaseous chlorine dioxide can be used and added into the drinking water, and 1.4 mg/l and 0.8 mg/l are set as the maximum applied dosage and maximum allowable residual concentration, respectively, according to those referred regulations. Moreover, 1.0 mg/l as the upper limit or the residual chlorite concentration is also suggested. 前 言 二 氧 化 氯 屬 於 新 一 代 的 消 毒 藥 劑, 除 了 比 傳 統 加 氯 消 毒 所 產 生 的 有 害 消 毒 副 產 物 為 少 之 外, 更 具 有 不 會 與 氨 氮 反 應 形 成 氯 胺 ph 操 作 範 圍 較 廣 消 毒 能 力 較 強 等 優 點 本 計 劃 收 集 國 內 外 文 獻, 提 供 環 保 署 對 飲 用 水 水 質 處 理 藥 劑 進 行 公 告 作 業 程 序 時 之 重 要 參 考 依 據 研 究 方 法 收 集 二 氧 化 氯 國 內 外 相 關 文 獻, 以 了 解 二 氧 化 氯 的 各 種 特 性 ; 參 考 歐 美 先 進 國 間 與 亞 洲 鄰 近 國 家 與 二 氧 化 氯 相 關 的 飲 用 水 水 質 規 範, 作 為 公 告

16 二 氧 化 氯 為 飲 用 水 添 加 藥 劑 之 參 考 ; 收 集 市 面 上 二 氧 化 氯 產 品 進 行 分 析 以 作 為 參 考 ; 配 合 環 保 署 列 席 相 關 會 議, 提 供 二 氧 化 氯 公 告 程 序 之 諮 詢 意 見 結 果 計 畫 針 對 二 氧 化 氯 國 內 外 相 關 文 獻 進 行 收 集 與 探 討, 分 別 就 二 氧 化 氯 的 基 本 特 性 在 淨 水 工 程 上 的 應 用 與 二 氧 化 氯 與 其 他 消 毒 劑 的 比 較 上 進 行 說 明 參 考 美 國 WHO 德 國 日 本 韓 國 的 飲 用 水 水 質 規 範 及 研 究, 並 依 據 期 中 報 告 會 議 與 諮 商 會 上 委 員 的 各 項 意 見, 建 議 公 告 二 氧 化 氯 限 制 於 氣 態, 並 建 議 最 大 添 加 劑 量 為 1.4 mg/l 添 加 後 最 高 殘 餘 濃 度 限 值 0.8 mg/l 及 添 加 後 亞 氯 酸 根 濃 度 限 值 1.0 mg/l 收 集 三 種 市 面 樣 品 進 行 分 析, 其 中 兩 種 屬 於 直 接 以 水 吸 收 二 氧 化 氯 之 藥 劑, 另 一 種 則 為 使 用 前 須 先 兩 種 藥 劑 混 合 混 合 藥 劑 含 較 高 濃 度 之 二 氧 化 氯, 但 也 伴 隨 著 不 純 物 的 問 題 結 論 二 氧 化 氯 是 相 當 具 有 潛 力 的 消 毒 劑, 但 應 用 上 需 注 意 其 特 性 建 議 公 告 二 氧 化 氯 限 制 於 氣 態, 並 建 議 最 大 添 加 劑 量 為 1.4 mg/l 添 加 後 最 高 殘 餘 濃 度 限 值 0.8 mg/l 及 添 加 後 亞 氯 酸 根 濃 度 限 值 1.0 mg/l 建 議 事 項 建 議 後 續 可 針 對 二 氧 化 氯 的 使 用 再 進 行 研 究, 且 建 議 將 二 氧 化 氯 及 其

17 無 機 副 產 物 納 入 飲 用 水 水 質 標 準 中 以 及 公 告 分 析 方 法

18 第 一 章 專 案 緣 起 與 目 的 第 一 章 專 案 緣 起 與 目 的 二 氧 化 氯 屬 於 新 一 代 的 消 毒 藥 劑, 除 了 比 傳 統 加 氯 消 毒 所 產 生 的 有 害 消 毒 副 產 物 為 少 之 外, 更 具 有 不 會 與 氨 氮 反 應 形 成 氯 胺 ph 操 作 範 圍 較 廣 消 毒 能 力 較 強 等 優 點 本 計 劃 收 集 國 內 外 文 獻, 提 供 環 保 署 對 飲 用 水 水 質 處 理 藥 劑 進 行 公 告 作 業 程 序 時 之 重 要 參 考 依 據 1.1 計 畫 緣 起 為 符 合 飲 用 水 水 質 標 準, 以 確 保 飲 用 水 的 安 全 品 質, 在 飲 用 水 的 處 理 程 序 中 經 常 須 要 適 度 的 添 加 一 些 水 質 處 理 藥 劑 依 據 飲 用 水 管 理 條 例 第 十 三 條 之 規 定 : 飲 用 水 水 質 處 理 所 使 用 之 藥 劑, 以 經 中 央 主 管 機 關 指 定 公 告 者 為 限 環 保 署 於 民 國 八 十 七 年 三 月 公 告 飲 用 水 水 質 處 理 藥 劑 一 般 規 定 事 項, 並 將 臭 氧 硫 酸 鋁 等 十 九 種 處 理 藥 劑 納 入 公 告 之 對 象 ; 同 年 五 月 再 將 使 用 於 處 理 供 人 飲 用 之 水 時 的 微 生 物 製 劑 予 以 納 入 公 告 對 象 在 目 前 已 經 公 告 之 飲 用 水 水 質 處 理 藥 劑 中, 被 用 做 消 毒 與 氧 化 目 的 者 包 括 了 臭 氧 液 氯 次 氯 酸 鈉 次 氯 酸 鈣 氯 化 石 灰 高 錳 酸 鉀 等 六 種 飲 用 水 的 消 毒 最 初 於 1897 年 英 國 的 Maidston 水 廠 採 用, 當 時 僅 在 傷 寒 流 行 才 使 用 漂 白 粉 消 毒 傳 統 的 飲 用 水 加 氯 消 毒 始 於 1902 年 的 比 利 時, 之 後 便 開 始 普 及, 而 傳 統 淨 水 程 序 中 以 氯 或 其 衍 生 物 ( 次 氯 酸 鈉 與 次 氯 酸 鈣 ) 做 為 消 毒 劑 已 有 一 百 年 的 歷 史 ; 由 於 氯 所 特 有 的 強 氧 化 力 與 操 作 使 用 上 的 便 利 性, 加 以 單 位 成 本 低 廉, 所 以 至 今 一 直 仍 被 廣 泛 使 用 在 水 處 理 程 序 上 1970 年 初 期, 美 國 環 保 署 在 紐 奧 良 市 淨 水 廠 消 毒 後 的 自 來 水 中 發 現 到 含 有 三 鹵 甲 烷, 之 後 陸 續 有 研 究 報 告 指 出 加 氯 消 毒 程 序 中 氯 與 水 中 有 機 物 質 反 應 會 產 生 危 害 人 體 健 康 的 消 毒 副 產 物 在 歐 美 國 家 以 二 氧 化 氯 做 為 飲 用 水 處 理 時 的 替 代 消 毒 劑 已 行 之 有 年, 除 了 比 傳 統 加 氯 消 毒 所 產 生 的 有 害 消 毒 副 產 物 為 少 之 外, 更 具 有 不 會 與 氨 氮 反 應 形 成 氯 胺 ph 操 作 範 圍 較 廣 消 毒 能 力 較 強 等 優 點 ; 此 外, 國 內 已 有 多 家 藥 品 供 應 商 1-1

19 以 二 氧 化 氯 做 為 飲 用 水 水 質 理 藥 劑 之 評 估 擬 向 環 保 署 申 請 將 二 氧 化 氯 做 為 飲 用 水 水 質 處 理 藥 劑, 因 此 環 保 署 有 必 要 在 公 告 二 氧 化 氯 做 為 飲 用 水 水 質 處 理 藥 劑 前 進 行 相 關 之 評 估 研 究 1.2 計 畫 目 標 本 研 究 將 以 二 氧 化 氯 為 對 象, 探 討 其 做 為 飲 用 水 水 質 處 理 藥 劑 公 告 對 象 時 所 須 考 量 及 評 估 之 藥 劑 主 成 份 與 不 純 物 等 相 關 特 性, 以 提 供 環 保 署 對 飲 用 水 水 質 處 理 藥 劑 進 行 公 告 作 業 程 序 時 之 重 要 參 考 依 據 1-2

20 第 二 章 執 行 方 法 第 二 章 執 行 方 法 收 集 二 氧 化 氯 國 內 外 相 關 文 獻, 以 了 解 二 氧 化 氯 的 各 種 特 性 ; 參 考 歐 美 先 進 國 間 與 亞 洲 鄰 近 國 家 與 二 氧 化 氯 相 關 的 飲 用 水 水 質 規 範, 作 為 公 告 二 氧 化 氯 為 飲 用 水 添 加 藥 劑 之 參 考 ; 收 集 市 面 上 二 氧 化 氯 產 品 進 行 分 析 以 作 為 參 考 ; 配 合 環 保 署 列 席 相 關 會 議, 提 供 二 氧 化 氯 公 告 程 序 之 諮 詢 意 見 本 計 畫 所 包 含 之 工 作 內 容 條 列 如 下 : 1. 收 集 並 彙 整 國 內 外 有 關 二 氧 化 氯 製 造 成 份 特 性 保 存 使 用 反 應 分 析 消 毒 副 產 物 等 文 獻 與 研 究 報 告 資 料 2. 就 歐 美 等 先 進 國 家 中 已 使 用 二 氧 化 氯 於 飲 用 水 水 質 處 理 者, 收 集 其 對 處 理 藥 劑 使 用 上 之 相 關 規 範, 特 別 是 藥 劑 主 成 份 與 不 純 物 之 相 關 規 定 3. 針 對 二 氧 化 氯 做 為 飲 用 水 水 質 處 理 藥 劑 所 須 之 相 關 公 告 內 容 提 出 建 議, 包 括 藥 劑 中 英 文 名 稱 化 學 式 品 質 管 制 規 定 ( 不 純 物 項 目 及 其 含 量 ) 等 4. 二 氧 化 氯 純 度 及 其 不 純 物 之 檢 測 分 析 方 法 評 估 ( 包 括 以 真 實 商 品 3 件 進 行 分 析 及 評 估 ) 5. 邀 請 專 家 學 者 辦 理 二 次 研 商 會 議 ( 含 期 中 期 末 審 查 會 議 ) 6. 提 供 環 保 署 對 二 氧 化 氯 藥 劑 在 申 請 指 定 公 告 相 關 作 業 程 序 中 所 須 之 諮 詢 意 見, 並 列 席 相 關 會 議 以 提 供 協 助 7. 提 出 期 中 與 期 末 研 究 報 告 為 公 告 二 氧 化 氯 做 為 飲 用 水 水 質 處 理 所 使 用 之 藥 劑, 本 研 究 將 依 循 圖 2-1 所 列 之 作 業 流 程 來 執 行 相 關 工 作 項 目 2-1

21 以 二 氧 化 氯 做 為 飲 用 水 水 質 理 藥 劑 之 評 估 資 料 收 集 二 氧 化 氯 製 造 成 份 特 性 保 存 使 用 反 應 分 析 消 毒 副 產 物 等 相 關 文 獻 資 料 歐 美 等 先 進 國 家 之 使 用 相 關 規 範 國 內 既 有 之 相 關 規 範 研 擬 公 告 草 案 藥 劑 名 稱 ( 中 英 文 ) 化 學 式 最 大 添 加 劑 量 相 關 配 套 措 施 訂 定 最 大 殘 餘 量 並 納 入 飲 用 水 水 質 標 準 訂 定 消 毒 副 產 物 最 大 允 許 限 值 其 納 入 飲 用 水 水 質 標 準 增 訂 檢 測 分 析 方 法 市 售 商 品 檢 測 分 析 二 氧 化 氯 純 度 檢 測 方 法 評 估 不 純 物 檢 測 方 法 評 估 諮 詢 溝 通 座 談 會 專 家 學 者 諮 商 座 談 會 公 聽 會 公 告 飲 用 水 水 質 處 理 藥 劑 圖 2-1 公 告 二 氧 化 氯 作 為 飲 用 水 值 處 理 藥 劑 之 作 業 流 程 2-2

22 第 三 章 本 年 度 主 要 工 作 內 容 及 重 要 發 現 與 成 果 第 三 章 本 年 度 主 要 工 作 內 容 及 重 要 發 現 與 成 果 計 畫 針 對 二 氧 化 氯 國 內 外 相 關 文 獻 進 行 收 集 與 探 討, 分 別 就 二 氧 化 氯 的 基 本 特 性 在 淨 水 工 程 上 的 應 用 與 二 氧 化 氯 與 其 他 消 毒 劑 的 比 較 上 進 行 說 明 參 考 美 國 WHO 德 國 日 本 韓 國 的 飲 用 水 水 質 規 範 及 研 究, 並 依 據 期 中 報 告 會 議 與 諮 商 會 上 委 員 的 各 項 意 見, 建 議 公 告 二 氧 化 氯 限 制 於 氣 態, 並 建 議 最 大 添 加 劑 量 為 1.4 mg/l 添 加 後 最 高 殘 餘 濃 度 限 值 0.8 mg/l 及 添 加 後 亞 氯 酸 根 濃 度 限 值 1.0 mg/l 收 集 三 種 市 面 樣 品 進 行 分 析, 其 中 兩 種 屬 於 直 接 以 水 吸 收 二 氧 化 氯 之 藥 劑, 另 一 種 則 為 使 用 前 須 先 兩 種 藥 劑 混 合 混 合 藥 劑 含 較 高 濃 度 之 二 氧 化 氯, 但 也 伴 隨 著 不 純 物 的 問 題 3.1 二 氧 化 氯 的 基 本 性 質 二 氧 化 氯 的 結 構 與 物 化 特 性 二 氧 化 氯 (Chlorine Dioxide, ClO 2 ) 純 液 態 為 深 紅 色, 氣 態 時 呈 現 綠 黃 色, 帶 有 特 殊 的 漂 白 水 味 道, 比 氯 氣 更 具 刺 激 性 及 毒 性, 分 子 量 為 , 是 少 數 存 在 自 然 界 中 的 單 體 自 由 基 (monomeric free radicals) 物 質 ; 當 空 氣 中 二 氧 化 氯 含 量 達 mg/l 時, 一 般 人 就 會 察 覺, 而 濃 度 達 到 45 mg/l 時 即 會 對 嗅 覺 產 生 刺 激 性 (White, 1992) 二 氧 化 氯 的 結 構 式 可 能 有 下 列 三 種 形 式 同 時 並 存 :.. Cl.. O.. Ȯ..... O..... Cl. Ȯ Cl.. O... Ȯ.... 在 結 構 上 為 了 滿 足 八 隅 體 的 穩 定 狀 態, 氯 與 氧 原 子 會 搶 電 子 而 使 二 氧 化 氯 呈 現 不 穩 定 狀 態, 容 易 分 解 成 氧 氣 及 氯 氣 二 氧 化 氯 的 另 外 一 個 特 性 是 具 有 爆 炸 的 可 能 性 : 當 溫 度 上 升 或 較 長 時 間 曝 露 在 光 線 下, 或 與 某 些 有 機 物 接 觸 時 即 可 能 引 發 爆 炸, 尤 其 在 運 送 中 更 易 發 生 ; 因 此 輕 微 的 酸 化 (ph=6) 可 提 高 二 氧 化 氯 的 穩 定 性, 也 因 為 這 個 原 因 二 氧 化 氯 大 多 在 使 用 現 場 製 備, 並 以 水 溶 液 的 形 態 參 與 反 應 二 氧 化 氯 的 溶 解 度 極 大 且 性 質 亦 極 為 特 殊, 對 水 的 溶 解 度 大 約 是 氯 氣 的 5 倍, 於 mm-hg 分 壓 下, 對 水 的 溶 解 度 為 2.9 gclo 2 /1L H 2 O, 其 享 利 常 3-1

23 以 二 氧 化 氯 做 為 飲 用 水 水 質 理 藥 劑 之 評 估 數 為 1.0 mole/kg.bar; 二 氧 化 氯 雖 然 可 迅 速 溶 於 水 中, 但 極 大 部 分 是 以 分 子 型 態 存 在 於 水 中, 不 會 與 水 分 子 產 生 化 學 反 應 或 解 離 ; 因 此 只 要 將 少 量 的 空 氣 吹 入 水 溶 液 中, 便 可 將 二 氧 化 氯 自 水 中 趕 出 二 氧 化 氯 水 溶 液 亦 會 與 紫 外 線 產 生 光 化 學 分 解 效 應, 產 生 氯 酸 及 鹽 酸, 故 為 降 低 分 解 效 應, 二 氧 化 氯 溶 液 需 以 棕 色 瓶 貯 存, 並 置 於 無 光 照 射 的 冰 箱 中 低 溫 保 存 表 3-1 物 質 安 全 資 料 表 中 二 氧 化 氯 的 基 本 性 質 物 化 性 質 特 性 沸 點 11 熔 點 - 59 ph 值 酸 性 外 觀 紅 黃 色 氣 體 或 黃 綠 色 溶 液 氣 味 不 佳, 與 氯 及 硝 酸 相 似 比 重 ( 水 =1) 0 水 中 溶 解 度 安 定 性 可 溶 不 安 定 不 相 容 性 與 下 列 物 質 混 合 : 接 觸 會 引 燃 引 起 爆 轟 爆 炸 反 應 磷 硫 及 可 燃 性 物 質 氫 氣 一 氧 化 碳 丁 二 烯 甲 烷 及 乙 烯 等 3-2

24 第 三 章 本 年 度 主 要 工 作 內 容 及 重 要 發 現 與 成 果 二 氧 化 氯 的 製 造 方 法 二 氧 化 氯 因 為 性 質 不 穩 定, 因 此 大 多 在 使 用 現 場 製 造, 其 製 備 方 法 繁 多, 主 要 有 : 二 氧 化 硫 還 原 法 甲 醇 法 氯 離 子 還 原 法 酸 催 化 法 及 氯 氣 法 二 氧 化 氯 純 度 不 足 並 有 餘 氯 的 存 在, 將 於 淨 水 處 理 時 產 生 低 濃 度 的 三 鹵 甲 烷 (Bruce et al., 1999) 由 於 二 氧 化 氯 的 純 度 控 制 會 影 響 後 續 的 淨 水 處 理, 因 此 產 製 二 氧 化 氯 過 程 的 產 量 產 率 純 度 之 控 制 皆 是 應 用 二 氧 化 氯 於 淨 水 處 理 必 須 了 解 之 課 題 目 前 國 外 自 來 水 廠 大 都 採 用 氯 氣 法 製 造 二 氧 化 氯 ; 而 一 般 實 驗 室 則 主 要 採 用 酸 催 化 法 來 生 成 二 氧 化 氯 酸 製 法 ( 酸 催 化 法 ) (1) 以 硫 酸 為 酸 劑 10NaClO 2 +5H 2 SO 4 8ClO2+2HCl+5Na 2 SO 4 + 4H 2 O (3-1) 二 氧 化 氯 的 生 成 量 可 由 亞 氯 酸 鈉 的 純 度 濃 度, 酸 的 濃 度 及 反 應 時 的 ph 反 應 時 間 及 反 應 時 的 溫 度 決 定 本 法 理 論 上 並 不 生 成 氯 氣, 但 根 據 分 析 結 果 顯 示, 所 得 之 二 氧 化 氯 溶 液 內 含 4 7.5% 的 自 由 餘 氯 (APHA et al., 1995) (2) 以 鹽 酸 為 酸 劑 將 鹽 酸 加 入 亞 氯 酸 鈉 溶 液 中 產 生 二 氧 化 氯, 反 應 式 如 下 ; 5NaClO 2 + 4HCl 4ClO 2 + 5NaCl + 2H 2 O (3-2) 實 廠 應 用 時, 須 加 過 量 的 鹽 酸 方 能 達 到 較 佳 的 產 能 ; 通 常 鹽 酸 與 亞 氯 酸 鈉 的 重 量 比 接 近 1:1, 使 實 際 加 酸 量 達 理 論 加 酸 量 的 2.5 至 3 倍 此 外 二 氧 化 氯 的 生 成 濃 度 深 受 ph 值 影 響, 若 ph>1 則 反 應 速 率 會 減 緩 致 使 產 率 下 降 ; 研 究 報 告 亦 顯 示 酸 催 化 反 應 中 鹽 酸 比 硫 酸 更 能 提 高 二 氧 化 氯 的 產 率 並 減 低 餘 氯 的 產 生 (Masschelein, 1984) ph 控 制 技 術 (ph-adjusted method) 是 將 HCl 加 入 氯 溶 液 後 再 與 亞 氯 酸 鹽 反 應 的 技 術 在 酸 性 的 環 境 下, 抑 制 氯 溶 液 的 水 解 現 象, 反 應 式 如 下 : (Aieta et al., 1986) OCl - + H + HOCl and HOCl + HCl Cl 2 + H 2 O (3-3) 其 中 ph 值 需 維 持 在 23 之 間 ; 藉 由 ph 控 制 技 術 可 提 高 二 氧 化 氯 的 產 率 達 3-3

25 以 二 氧 化 氯 做 為 飲 用 水 水 質 理 藥 劑 之 評 估 90% 以 上 (Jordon, 1980), 此 外 反 應 若 在 高 濃 度 的 環 境 中 進 行, 而 且 反 應 中 氯 盡 量 以 HOCl 或 Cl 的 型 態 存 在, 皆 有 助 於 提 高 生 成 物 二 氧 化 氯 的 純 度 (Emmenegger,1967) 此 外 二 氧 化 氯 在 鹼 性 環 境 中 有 被 分 解 的 特 性, 反 應 式 如 下 所 示 : 2ClO 2 +2OH - H 2 O+ ClO ClO 3 (3-4) 故 ph 值 的 控 制 不 但 有 助 於 二 氧 化 氯 純 度 的 保 存 亦 能 減 少 無 機 性 消 毒 副 產 物 的 形 成 (Gordon et al., 1999) (3) 以 乙 酐 為 酸 劑 配 置 方 法 為 將 乙 酐 加 入 次 氯 酸 鈉 溶 液 中 混 合 反 應, 二 氧 化 氯 將 迅 速 生 成, 反 應 式 如 下 ; 4NaClO 2 + 2(CH 3 CO) 2 O + H 2 O NaClO 3 + NaCl +2CH 3 COOH+2CH 3 COONa+2ClO 2 (3-5) 此 法 優 點 為 快 速 簡 便 ; 又 二 氧 化 氯 是 本 反 應 中 唯 一 具 有 氧 化 能 力 的 產 物, 所 以 可 以 用 碘 滴 定 法 來 進 行 定 量 生 成 物 二 氧 化 氯 溶 液 中 含 有 雜 質 諸 如 Cl - acetic - acid ClO 3 等, 除 了 acetic acid 外, 其 他 雜 質 會 妨 礙 分 析 的 結 果 與 二 氧 化 氯 的 生 成 (Masschelein, 1984) 氯 溶 液 法 : 將 氯 氣 通 入 水 中 形 成 氯 溶 液 後, 再 與 次 氯 酸 根 離 子 液 反 應 形 成 二 氧 化 氯, 反 應 式 為 : 2NaClO 2 + Cl 2(aq) 2ClO 2 +2NaCl (3-6) 此 外 反 應 也 有 可 能 形 成 氯 酸 根 離 子 :(Masschelein, 1984) 2NaClO 2 + Cl 2(aq) +OH - NaClO 3 +HCl+Cl - (3-7) 2ClO 2 +HOCl+H 2 O 2ClO H + +HCl (3-8) 氯 氣 - 固 態 亞 氯 酸 鈉 法 2NaClO 2 + Cl 2(g) 2ClO 2 + 2NaCl (3-9) 理 論 上,2 莫 耳 的 亞 氯 酸 鈉 和 1 莫 耳 的 氯 氣 反 應 可 生 成 2 莫 耳 的 二 氧 化 氯, 但 實 際 上 無 法 達 到 ; 因 此 實 廠 在 操 作 時, 會 將 氯 氣 和 亞 氯 酸 鈉 的 加 藥 量 提 高 至 重 量 比 為 1:1, 以 提 升 二 氧 化 氯 產 能, 同 時 減 少 亞 氯 酸 鈉 殘 餘 量 3-4

26 第 三 章 本 年 度 主 要 工 作 內 容 及 重 要 發 現 與 成 果 氯 酸 根 離 子 還 原 法 ( 雙 氧 水 製 法 ): 在 80 2M 硫 酸 3.4M 氯 酸 鈉 3.2M 硫 酸 鈉 的 環 境 下, 過 氧 化 氫 會 與 氯 酸 根 離 子 反 應 形 成 二 氧 化 氯, 反 應 式 為 : H 2 O 2 +2H + +2ClO - 3 2ClO 2 +2H 2 O+O 2 (3-10) 惟 反 應 進 行 時, 生 成 物 二 氧 化 氯 會 再 與 過 氧 化 氫 反 應, 而 發 生 二 氧 化 氯 損 失 的 情 況, 二 氧 化 氯 的 消 耗 量 佔 生 成 量 大 約 在 0.8%~1.5% 之 間, 反 應 式 為 : H 2 O 2 +2ClO 2 2HClO 2 +O 2 (3-11) 美 國 環 保 署 最 終 的 目 標 便 是 希 望 二 氧 化 氯 產 量 達 到 95%, 而 餘 氯 量 小 於 5 % 綜 合 上 述, 目 前 所 提 出 產 製 二 氧 化 氯 的 方 法 經 整 理 如 表 3-2 (EPA Guidance Manual, 1999) 3-5

27 以 二 氧 化 氯 做 為 飲 用 水 水 質 理 藥 劑 之 評 估 表 3-2 二 氧 化 氯 產 製 型 態 一 覽 表 (EPA Guidance Manual, 1999) 產 製 型 態 備 註 產 物 特 性 酸 製 法 : 5 ClO HCl 4 ClO 2 + ClO 3 在 酸 性 環 境 中 反 應 可 能 產 生 氯 酸 根 離 子 ; 反 應 速 率 緩 慢, 需 要 與 進 料 幫 浦 連 結 產 量 限 制 :25-30 lb/day 最 大 有 效 產 率 約 80% 氯 溶 液 - 亞 氯 酸 鈉 : Cl 2 + H 2 O [HOCl/HCl] [HOCl/HCl]+NaClO 2 ClO 2 +H/OCl - +ClO - 3 +NaOH 氯 溶 液 - 亞 氯 酸 鈉 ( 循 環 式 ) 或 FRENCH LOOP TM : 2HOCl + 2 NaClO 2 2 ClO 2 + Cl 2 +2 NaOH 飽 和 液 氯 在 與 亞 氯 酸 鈉 混 和 前 需 先 經 過 再 循 環 反 應 槽 氯 氣 - 亞 氯 酸 鈉 溶 液 ( 真 空 式 ): NaClO 2(aq) + Cl 2(g) ClO 2(aq) 氣 氯 與 25% 亞 氯 酸 鈉 溶 液 經 注 射 器 注 入 反 應 槽 氣 氯 - 固 態 亞 氯 酸 鈉 : NaClO 2(s) + Cl 2(g) ClO 2 + NaCl 電 化 學 法 : ClO - 2 ClO 2 + e - 氯 酸 根 離 子 還 原 法 : 2NaClO 3 +H 2 O 2 +H 2 SO 4 2ClO 2 +NaSO 4 +H 2 O+O 2 在 酸 性 環 境 中 反 應 可 能 產 生 氯 酸 根 離 子 ; 反 應 速 率 稍 慢, 需 加 過 量 的 氯 和 酸 與 氫 氧 化 鈉 中 和 流 出 液 呈 酸 性 (ph ) 產 量 限 制 :1000 lb/day 最 大 有 效 產 率 約 80-92% 需 加 過 量 的 氯 和 酸 與 氫 氧 化 鈉 中 和 最 大 有 效 濃 度 3g/L, 產 量 限 制 :1000 lb/day, 最 大 有 效 產 率 約 92-98%, 餘 氯 量 10% 流 出 液 具 高 腐 蝕 性, 幫 浦 與 反 應 槽 需 做 水 位 校 正 在 中 性 環 境 中 反 應, 反 應 速 度 快 速 需 維 持 內 壓 至 少 40psig 反 應 速 度 快 速 氯 氣 經 氮 氣 或 濾 後 空 氣 稀 釋 再 參 與 反 應, 可 產 生 8% 二 氧 化 氯 蒸 汽 電 解 25% 亞 氯 酸 鈉 溶 液 在 酸 性 環 境 中 反 應 產 量 lb/day 流 出 液 呈 中 性 低 餘 氯 產 生 量 (<2%) 最 大 有 效 產 率 約 95-99% 最 大 有 效 產 率 約 >99% 總 產 量 >10000 lb/day 使 用 濃 縮 的 過 氧 化 氫 及 硫 酸 3-6

28 第 三 章 本 年 度 主 要 工 作 內 容 及 重 要 發 現 與 成 果 實 驗 室 常 用 二 氧 化 氯 製 備 方 法 及 分 析 方 法 二 氧 化 氯 的 生 成 實 驗 根 據 Standard Methods for the Examination of Water and Wastewater(19th Edition) 4500-ClO 2 B 方 法, 以 酸 生 成 法 來 製 造 所 需 的 二 氧 化 氯, 生 成 的 裝 置 如 圖 3-1 所 示 首 先 將 反 應 瓶 ( 溶 有 10 g 的 NaClO 2 於 750 ml 去 離 子 水 中 ) 裝 有 10 %, 20 ml 濃 硫 酸 的 滴 定 管 裝 有 1L 飽 和 NaClO 2 溶 液 的 去 氯 瓶 及 含 有 1.5 L 純 水 的 吸 收 瓶 串 聯 ; 而 後 整 個 系 統 通 以 和 緩 的 氮 氣, 使 產 生 平 緩 的 氣 泡 於 各 瓶 中, 再 將 裝 有 硫 酸 溶 液 的 滴 定 管 打 開 以 每 5 分 鐘 加 入 5 ml 的 速 度 進 行 二 氧 化 氯 生 成 反 應, 在 最 後 一 次 加 入 5 ml H 2 SO 4 溶 液 後 持 續 通 氣 約 半 小 時 即 完 成 試 驗 依 此 方 法 操 作 可 於 吸 收 瓶 中 生 成 250~600 mg/l 的 ClO 2 ; 最 後 將 所 生 成 的 二 氧 化 氯 溶 液 置 於 棕 色 瓶 內, 保 存 在 4 之 無 光 照 的 冰 箱 中 每 次 使 用 前 以 碘 滴 定 法 或 DPD 法 測 定 其 濃 度 3-7

29 以 二 氧 化 氯 做 為 飲 用 水 水 質 理 藥 劑 之 評 估 10% H SO 2 4 N 2 抽 氣 櫃 冰 浴 NaClO 2 曝 氣 石 反 應 瓶 圖 3-1 二 氧 化 氯 生 成 裝 置 去 氯 瓶 吸 收 瓶 3-8

30 第 三 章 本 年 度 主 要 工 作 內 容 及 重 要 發 現 與 成 果 二 氧 化 氯 的 分 析 實 驗 室 中 常 採 用 DPD 法 來 確 認 所 生 成 的 二 氧 化 氯 是 否 含 有 餘 氯, 而 後 每 次 使 用 前 再 用 碘 滴 定 法 來 測 定 二 氧 化 氯 溶 液 之 濃 度 DPD 法 測 定 方 法 如 圖 3-2 所 示 其 中 讀 數 A 乘 以 5 倍 即 為 二 氧 化 氯 溶 液 之 濃 度, 而 讀 數 A 即 為 自 由 餘 氯 的 濃 度 ; 當 B-5A=0 即 表 示 無 自 由 餘 氯 的 存 在 圖 3-2 以 DPD 法 測 定 自 由 餘 氯 步 驟 3-9

31 以 二 氧 化 氯 做 為 飲 用 水 水 質 理 藥 劑 之 評 估 碘 滴 定 法 1 分 析 藥 品 (1) 冰 醋 酸 (CH 3 COOH) (2) 碘 化 鉀 (KI) (3) 硫 代 硫 酸 鈉 (Na 2 S 2 O 3 ) 2 步 驟 (1) 取 適 量 水 樣, 加 入 5 ml 冰 醋 酸 溶 液 (2) 再 加 入 1 克 碘 化 鉀 (KI) 攪 拌 溶 解 (3) 將 溶 液 置 於 暗 處 反 應 5 分 鐘 (4) 以 0.025N 硫 代 硫 酸 鈉 (Na 2 S 2 O 3 ) 滴 定 至 淡 黃 色 後, 加 幾 滴 澱 粉 指 示 劑 後 再 滴 定 至 無 色 3 計 算 式 如 下 : mg-clo 2 /L = (A ± B) N /C 式 中 A: 硫 代 硫 酸 鈉 滴 定 量 (ml) B: 空 白 滴 定 量 (ml) N: 硫 代 硫 酸 鈉 當 量 強 度 C: 水 樣 體 積 (ml) 3-10

32 第 三 章 本 年 度 主 要 工 作 內 容 及 重 要 發 現 與 成 果 二 氧 化 氯 在 水 中 的 反 應 二 氧 化 氯 可 迅 速 溶 於 水 中, 但 大 部 分 不 與 水 分 子 發 生 化 學 反 應 及 水 解 效 應, 只 有 當 水 中 的 環 境 改 變, 才 會 影 響 二 氧 化 氯 在 水 中 的 反 應 : (1) 光 解 效 應 當 二 氧 化 氯 被 紫 外 光 (λ=360nm) 照 射 後, 會 在 水 中 發 生 一 連 串 的 光 化 學 反 應 (AWWARF, 1992) ClO 2 hν (ClO + O) cage (3-12) (ClO+ O) cage Cl + O2 (3-13) ClO + ClO 2 Cl 2 O 3 (3-14) Cl 2 O 3 + H 2 O ClO + ClO H + (3-15) Cl + Cl - Cl2 (3-16) Cl (or Cl - 2 ) + ClO 2 Cl2O 2 (3-17) Cl 2 O 2 + H 2 O Cl + ClO H + (3-18) O + O 2 O 3 (3-19) 若 僅 是 在 充 足 的 陽 光 下,ClO 2 仍 會 立 即 轉 變 成 ClO 2 - 或 HOCl 由 以 上 可 知, 光 線 對 ClO 2 影 響 是 很 大 的, 故 為 避 免 分 解, 應 將 其 儲 存 於 低 溫 陰 暗 處 (2) 解 離 作 用 二 氧 化 氯 在 水 中, 常 因 不 同 的 ph 而 有 不 同 的 反 應 當 二 氧 化 氯 在 酸 性 溶 液 中 時, 進 行 : ClO 2 + 4H + + 5e - Cl - + 2H 2 O E oxid = -1.95V (3-20) 而 在 鹼 性 溶 液 中, 則 為 ClO 2 + e - - E oxid =-1.16V (3-21) ClO2 式 為 : 上 式 中 所 產 生 的 ClO 2 - 亦 為 一 種 氧 化 劑, 但 氧 化 能 力 較 ClO 2 慢, 常 見 的 反 應 3-11

33 以 二 氧 化 氯 做 為 飲 用 水 水 質 理 藥 劑 之 評 估 ClO H + + 4e - Cl - + 2H 2 O (3-22) 另 外 二 氧 化 氯 在 水 溶 液 可 能 會 進 行 下 列 三 種 反 應 產 生 亞 氯 酸 鹽 氯 酸 鹽 及 氯 離 子 : (ph=6 8) (3-23) 2ClO 2 + H 2 O HClO2 + HClO 3 (ph=2 9) (3-24) 6ClO 2 + 3H 2 O 5HClO3 + HCl (3-25) 4HClO 2 2ClO2 + HCl + HClO 3 + H 2 O 由 以 上 種 種 的 反 應 可 知, 二 氧 化 氯 溶 於 水 之 後, 必 定 伴 隨 著 亞 氯 酸 鹽 (ClO 2 - ) 氯 酸 鹽 (ClO 3 - ) 及 氯 離 子 (Cl - ) 等 主 要 的 無 機 性 副 產 物 生 成 二 氧 化 氯 與 水 中 含 氯 物 種 之 交 互 反 應 在 不 同 的 反 應 條 件 與 濃 度 下, 不 同 的 含 氯 物 種 交 互 反 應 所 產 生 的 生 成 物 種 也 就 有 所 不 同 (Aieta et al., 1986) 若 水 體 中 同 時 有 二 氧 化 氯 氯 的 存 在, 則 可 能 有 以 下 的 反 應 發 生 : 1. Chlorine 與 ClO 2 的 反 應 : HOCl+ClO 2 +H 2 O 2ClO H + +HCl (3-26) 此 反 應 之 反 應 速 率 小, 所 以 ClO 3 - 生 成 緩 慢, 除 非 在 很 大 量 的 淨 水 處 理 系 統 中, 否 則 這 個 反 應 是 可 以 忽 略 的 (Gordon et al., 1972) 2. Chlorine 與 ClO 2 - 的 反 應 : 在 這 反 應 中 通 常 ClO 3 - 的 形 成 非 常 緩 慢, 惟 有 在 酸 性 的 環 境 中 (ph=5),clo 2 - 與 過 量 的 HOCl 反 應 才 會 形 成 ClO 3 - (Emmenegger, 1967) 在 Cl 2 與 ClO 2 - 的 反 應 中 另 有 產 生 中 間 產 物 Cl 2 O 2 的 反 應 機 制, 反 應 如 下 : Cl 2 + ClO 2 - Cl 2 O 2 +Cl - (3-27) 3-12

34 第 三 章 本 年 度 主 要 工 作 內 容 及 重 要 發 現 與 成 果 後 續 反 應 為 : Cl 2 O 2 2ClO 2 + Cl 2 (3-28) Cl 2 O 2 + ClO - 2 2ClO 2 + Cl - (3-29) 若 循 此 反 應 機 制, 當 初 始 反 應 物 (Cl 2 ClO - 2 ) 濃 度 過 低 或 含 氯 量 過 高 時 易 形 成 ClO - 3 (Gordon et al., 1999) 3. HOCl 與 OCl - 的 反 應 : 此 反 應 發 生 於 ph=5.8~6.5, 室 溫 下 氯 酸 根 離 子 的 生 成 反 應 速 率 緩 慢 (Aieta, 1985), 但 日 照 時 會 致 使 反 應 加 速 (Buxton, 1972) Gordon(2001) 亦 就 各 含 氯 物 種 之 交 互 反 應 情 形 彙 整 如 表 3-3 所 示 由 以 上 種 種 反 應 可 知, 只 要 ph 調 整 適 當 避 免 光 照 及 提 高 二 氧 化 氯 純 度, 便 可 有 效 抑 制 無 機 性 消 毒 副 產 物 的 產 生 3-13

35 以 二 氧 化 氯 做 為 飲 用 水 水 質 理 藥 劑 之 評 估 含 氯 物 種 反 應 描 述 表 3-3 含 氯 物 種 的 交 互 反 應 Gordon(2001) Cl - 1. 伴 隨 ClO 2 的 形 成 或 分 解 而 產 生 2. 在 反 應 中 能 扮 演 催 化 劑 的 角 色 HClO 2 +Cl - [HCl 2 O 2 - ] [HCl 2 O 2 - ]+Cl - ClO 2 +other products Cl 2 1. 與 ClO 2 - ( 或 HClO 2 ) 反 應 形 成 ClO 2 : Cl 2 +2ClO 2-2ClO2+2Cl - 2. 餘 氯 (Cl 2 /HOCl) 將 緩 慢 地 與 ClO 2 反 應 : Cl 2 +ClO 2 +H 2 O ClO 3 - +Cl - +2H + HOCl 與 ClO 2 - 反 應 形 成 ClO 2 : OCl - HOCl+2ClO 2-2ClO2+Cl - +OH - 與 ClO 2 - 反 應 形 成 ClO 3 - OCl-+ClO 2 - ClO 3 -+Cl- ClO 2 - /ClO 2 1. ClO 2 氧 化 反 應 :ClO 2 +substrate ClO 2 - ClO 3 - ClO 4-2. 酸 化 反 應 :5HClO 2 4ClO 2 +Cl - +H + +2H 2 O 3. 電 解 反 應 :ClO 2 - ClO 2 +e - 4. 水 解 反 應 :2ClO 2 +2OH - ClO 2 -+ClO 3 - +H 2 O 1. 形 成 ClO 2 之 前 驅 物 : 2ClO H++2Cl - 2ClO 2 +Cl 2 +2H 2 O 2ClO 3 - +H 2 SO 4 + H2O2 2ClO 2 +O 2 +SO H 2 O 2. 消 毒 副 產 物 : [Cl 2 O 2 ]+H 2 O ClO 3 - +Cl - +2H + ClO 2 - +HOCl ClO 3 - +Cl - +H + 1. 源 自 於 亞 氯 酸 鈉 中 的 不 純 物 2. 消 毒 副 產 物 3. 電 解 :ClO 3 - +H 2 O ClO H + +2e - 4. 高 度 酸 化 :8HClO 3 4HClO 4 +2H 2 O+3O 2 +2Cl

36 第 三 章 本 年 度 主 要 工 作 內 容 及 重 要 發 現 與 成 果 二 氧 化 氯 與 水 中 有 機 物 之 反 應 ClO 2 在 水 中 為 自 由 基 形 式, 容 易 進 行 單 電 子 氧 化 還 原 反 應, 在 酸 性 環 境 中 較 - 穩 定, 於 鹼 性 環 境 中 則 較 易 解 離 成 ClO 3 與 ClO - 2 ( 式 3-23) 二 氧 化 氯 是 一 種 具 高 度 選 擇 性 之 氧 化 劑, 容 易 親 近 有 機 物 帶 電 的 部 分, 進 行 親 電 子 氧 化 反 應, 同 時 將 本 身 還 原 為 亞 氯 酸 根 離 子 等 物 種 ; 且 二 氧 化 氯 不 易 分 解 有 機 物 中 之 碳 - 碳 單 鍵, 所 以 氧 化 有 機 物 之 礦 化 作 用 並 不 明 顯 (Gordon et al., 1995) 二 氧 化 氯 在 水 處 理 程 序 中 通 常 扮 演 氧 化 劑 而 非 鹵 化 劑 的 角 色, 常 被 認 為 與 O 3 同 樣 具 有 自 由 基 特 性, 兩 者 在 高 ph 環 境 下 會 解 離 成 氫 氧 自 由 基 (HO ), 再 與 有 機 物 反 應 生 成 具 有 奇 數 電 子 數 的 中 間 產 物 (intermediate) 後, 發 生 更 進 一 步 之 氧 化 作 用 不 過 有 關 ClO 2 與 有 機 物 在 水 中 反 應 的 報 告 並 不 很 多, 最 近 這 幾 年 更 是 寥 寥 可 數 ; 因 此 ClO 2 與 有 機 物 在 水 中 的 反 應 機 制 仍 不 確 定, 甚 至 可 以 用 不 很 清 楚 來 形 容 以 下 是 由 文 獻 中 所 摘 錄 有 關 ClO 2 與 有 機 物 在 水 中 的 反 應 (1) ClO 2 與 碳 氫 化 合 物 之 反 應 許 多 學 者 發 現 二 氧 化 氯 在 和 碳 氫 化 合 物 反 應 過 程 中 所 產 生 的 自 由 基 會 和 氧 氣 反 應, 並 伴 隨 著 自 由 基 的 循 環 作 電 子 的 轉 移 或 生 成 氫 氧 自 由 基 ( Ozawa and Kwan, 1984;Rav-Acha and Choshen, 1987) 文 獻 指 出 一 些 多 環 的 碳 氫 化 合 物 與 二 氧 化 氯 反 應 後 會 形 成 氯 化 衍 生 物 和 醌 類 ; 此 外, 含 雙 鍵 的 化 合 物 也 會 以 替 代 方 式 形 成 氯 醇 和 環 氧 化 物, 這 個 牽 涉 到 氧 原 子 的 轉 移 與 不 飽 和 雙 鍵 反 應 生 成 環 氧 化 物 的 替 代 機 制 已 被 Lindgren and Nilson (1975) 證 實 : ClO 2 + R 1 CH=CHR 2 ClO + R1HCOCHR 2 (3-30) 一 般 相 信 中 間 產 物 一 氧 化 氯 會 再 與 二 氧 化 氯 進 行 電 子 轉 移 反 應, 而 形 成 次 氯 酸 根 與 氯 酸 根 離 子, 此 機 制 可 能 為 二 氧 化 氯 與 有 機 物 反 應 過 程 中 含 氯 有 機 物 形 成 之 原 因 之 一 ; 而 反 應 中 所 形 成 的 HOCl 最 可 能 的 生 成 途 徑 是 由 ClO 2 與 不 飽 和 雙 鍵 3-15

37 以 二 氧 化 氯 做 為 飲 用 水 水 質 理 藥 劑 之 評 估 作 用 後 形 成 的 ROClO 再 進 行 水 解 而 生 成 (Lindgren, 1971) (2) ClO 2 與 酚 類 之 反 應 由 具 有 不 同 取 代 基 的 酚 類 化 合 物 與 ClO 2 反 應 之 研 究 得 知, 二 氧 化 氯 與 酚 作 用 後 的 產 物 包 括 氯 醌 氯 酚 苯 醌 一 氯 苯 醌 2,6- 二 氯 苯 醌 草 酸 和 丁 烯 二 酸 等 (Hoigne and Bader, 1982), 這 些 物 種 的 生 成 分 佈 決 定 於 二 氧 化 氯 與 酚 的 比 例 ; 當 酚 過 量 時, 氯 酚 類 化 合 物 為 主 要 產 物, 因 為 次 氯 酸 會 緩 慢 地 以 中 間 產 物 形 式 出 現 和 過 量 酚 反 應, 但 是 當 二 氧 化 氯 過 量 時, 則 苯 環 被 破 壞 並 進 行 氧 化 反 應, 生 成 對 - 苯 醌 草 酸 順 反 丁 烯 二 酸 等 最 終 產 物 ; 而 反 應 過 程 中 產 生 可 能 之 中 間 產 物 三 氯 酚 (Brueggeman et al., 1982) 在 酚 與 二 氧 化 氯 發 生 氧 化 反 應 後, 會 失 去 酚 環 上 的 對 位 取 代 基, 例 如 當 酚 反 應 成 醌 時, 對 位 的 -Cl -NO 2 -COOH 及 -CHO 會 消 失 (NAS, 1980;Carlson and Lin, 1985) 此 外,ClO 2 還 原 後 的 主 要 產 物 ClO 2 - 亦 可 與 α- 二 酮 醛 及 某 些 特 定 酚 類 快 速 反 應 ; 其 中 ClO 2 - 較 具 親 核 性 (Rosen-blatt, 1975), 與 醛 類 之 反 應 如 下 : RCHO+H + +3ClO 2 RCOO - +2ClO 2 +Cl - +H 2 O (3-31) 上 述 反 應 中 HOCl 為 可 能 之 中 間 產 物 (Lindgren, 1971;Lindgren and Nilson, 1973) 有 關 二 氧 化 氯 臭 氧 及 氯 氣 與 部 份 水 中 有 機 物 之 反 應, 整 理 如 表 3-4, 以 供 比 較 其 異 同 3-16

38 表 3-4 二 氧 化 氯 與 水 中 有 第 機 三 物 章 的 本 年 反 度 應 主 (Katz, 要 工 作 1992) 內 容 及 重 要 發 現 與 成 果 ClO 2 Cl 2 中 間 產 物 與 臭 氧 反 應 相 同, 另 有 酚 氯 酚 氯 醌 生 成 生 成 氯 酚 氯 化 物 ( 開 環 後 ) 開 環 後 生 成 物 與 臭 氧 反 應 相 非 氯 化 有 機 物 ( 芳 環 或 直 鏈 ) 同, 另 有 氯 化 脂 肪 族 生 成 氯 酚 氯 酚 多 氯 酚 鹵 化 非 鹵 化 脂 肪 族 直 鏈 化 合 物 苯 酸 苯 磺 酸 肉 桂 酸 與 ClO 2 不 其 他 芳 環 化 起 反 應 合 物 芳 環 行 氧 化 作 用 時, 會 脫 去 硝 基 非 鹵 化 多 環 羥 多 環 芳 香 族 氯 化 多 環 芳 香 族 可 能 與 ClO2 反 應 相 同 可 能 會 開 環 非 鹵 化 多 環 羥 二 苯 聯 胺 二 氯 化 多 環 芳 香 族 苯 胺 可 能 會 開 環, 但 較 臭 氧 反 應 慢 thianine 不 反 應 含 氮 雜 環 化 嘧 啶 等 環 狀 物 不 反 應, 取 代 基 被 合 物 氧 化, 但 非 氯 化 氯 化 物 氯 化 物 不 飽 和 脂 肪 氯 酮 氯 醇 氯 醇 酸 環 氧 化 合 物 鹼 性 環 境 下 形 成 環 氧 物 形 成 不 易 氧 化 的 酸 類 化 合 物 一 級 脂 肪 醛 不 飽 和 酸 ( 巴 豆 酸 順 丁 烯 二 酸 反 丁 烯 二 酸 ) 與 ClO2 不 反 應 二 級 醇 酮 類 乙 酸 ( 穩 定 物 種 ) 一 級 脂 肪 胺 不 反 應 二 級 脂 肪 胺 反 應 慢 三 級 脂 肪 胺 二 級 胺 醛 氯 仿 可 能 不 起 反 應 不 反 應 腐 植 酸 反 應 緩 慢 產 物 為 酚 三 鹵 甲 烷 糖 碳 水 化 合 環 上 的 取 代 基 被 氧 化 物 若 ClO 2 過 量, 則 進 行 開 環 作 用 三 鹵 甲 烷 前 純 ClO 2 ( 無 自 由 氯 ) 與 之 反 應 不 產 三 鹵 甲 烷 質 生 THMs 3-17

39 以 二 氧 化 氯 做 為 飲 用 水 水 質 理 藥 劑 之 評 估 3.2 二 氧 化 氯 在 淨 水 工 程 的 應 用 二 氧 化 氯 應 用 在 淨 水 工 程 的 實 場 上, 始 於 美 國 之 Niagara 水 廠 ( Aieta and Berg, 1986) 目 前 主 要 是 應 用 在 消 毒 控 制 臭 味 脫 色 去 除 藻 類 及 氧 化 水 中 鐵 錳 等 無 機 性 離 子 ; 近 年 來 更 利 用 二 氧 化 氯 當 作 前 處 理 之 氧 化 劑, 並 結 合 加 氯 程 序 來 改 變 有 機 物 的 分 子 大 小, 並 配 合 其 他 處 理 單 元 增 加 有 機 物 的 去 除 機 會 及 控 制 消 毒 副 產 物 的 生 成 現 將 二 氧 化 氯 在 淨 水 工 程 上 的 應 用 簡 述 如 下 (1) 消 毒 作 用 二 氧 化 氯 本 身 的 強 氧 化 力 可 破 壞 病 原 菌 對 蛋 白 質 的 合 成 蔡 氏 (1988) 指 出 當 二 氧 化 氯 濃 度 在 0.1mg/L 以 上, 消 毒 5 分 鐘 時 即 可 達 到 100% 之 消 毒 效 率 ; 許 氏 (1996) 也 從 實 驗 中 發 現 二 氧 化 氯 的 消 毒 效 率 極 佳, 當 淨 水 廠 以 正 常 的 加 藥 濃 度 1 mg/l 時, 在 很 短 的 時 間 內 即 可 達 到 99% 的 殺 菌 率, 且 實 驗 結 果 進 一 步 指 出 ph 值 對 二 氧 化 氯 在 消 毒 效 率 上 的 影 響 並 不 顯 著 (2) 臭 味 的 控 制 Akin et al. (1984) 以 ClO2 Cl 2 O 3 及 過 錳 酸 鉀 等 氧 化 劑 對 五 種 會 產 生 臭 味 和 色 度 的 化 合 物 進 行 氧 化 反 應, 這 五 種 化 合 物 包 括 TCA IPMP IBMP MIB geosmin, 其 中 某 些 物 質 在 幾 個 ng/l 即 有 很 高 初 嗅 數 ; 實 驗 結 果 指 出 ClO 2 對 這 五 種 化 合 物 的 臭 味 及 色 度 的 去 除 率 最 佳 (3) 鐵 錳 的 去 除 二 氧 化 氯 與 鐵 的 作 用 較 氯 氣 迅 速, 當 ph 值 大 於 7 時, 氧 化 較 完 全, 反 應 式 如 下 : ClO 2 +MnSO 4 +4NaOH MnO 2 +2NaClO 2 +Na 2 SO 4 +2H 2 O (3-32) 二 氧 化 氯 可 使 溶 解 態 的 二 價 鐵 轉 變 為 氫 氧 化 鐵, 在 形 成 膠 羽 後 以 沈 澱 過 濾 3-18

40 第 三 章 本 年 度 主 要 工 作 內 容 及 重 要 發 現 與 成 果 法 去 除 ; 若 Fe 2+ 與 Mn 2+ 以 有 機 錯 合 物 形 式 存 在, 二 氧 化 氯 仍 可 將 其 氧 化 後 配 合 混 凝 膠 凝 處 理 後 去 除 (Masschelein, 1979) 前 述 操 作 條 件 在 ph 值 大 於 7 時 效 果 較 佳, 而 以 ph 值 8 9 最 適 合, 反 應 如 下 : ClO 2 + FeO + NaOH + H 2 O Fe (OH) 3 + NaClO 2 (3-33) (4) 消 毒 副 產 物 生 成 控 制 ClO 2 在 酸 性 溶 液 中 較 在 鹼 性 溶 液 中 穩 定, 處 於 高 ph 的 水 環 境 中 會 解 離 生 成 氫 氧 自 由 基, 與 有 機 物 產 生 中 間 產 物 之 後 再 發 生 氧 化 作 用 Rav-Acha(1984) 以 Kinneret 原 水 為 實 驗 對 象 之 研 究 中 指 出 在 添 加 2 mg/l Cl 2 之 前 先 以 ClO 2 預 處 理 2 - 小 時 後, 其 THMs 產 生 量 較 單 獨 使 用 Cl 2 處 理 時 減 少 60%; 並 且 產 生 之 ClO 2 濃 度 比 單 獨 使 用 ClO 2 時 減 少 90% 此 現 象 與 Narkis 於 1995 年 探 討 結 合 ClO 2 與 Cl 2 對 消 毒 效 率 之 影 響 中 的 結 果 相 當 類 似 Gordon(2001) 指 出, 大 多 數 無 機 消 毒 副 產 物 是 源 自 於 生 成 ClO 2 的 產 製 過 程 中, 因 此 提 高 製 備 過 程 中 的 產 物 純 度 才 是 減 少 無 機 消 毒 副 產 物 的 最 佳 方 法 3-19

41 以 二 氧 化 氯 做 為 飲 用 水 水 質 理 藥 劑 之 評 估 3.3 二 氧 化 氯 與 其 他 消 毒 劑 的 比 較 由 於 加 氯 消 毒 所 衍 生 出 來 的 消 毒 副 產 物 的 問 題, 已 使 得 許 多 國 家 積 極 尋 找 其 他 替 代 消 毒 劑, 但 由 於 所 使 用 的 消 毒 劑 不 同, 所 誘 發 產 生 的 消 毒 副 產 物 種 類 與 濃 度 亦 有 所 差 異 在 替 代 消 毒 劑 中 目 前 較 常 用 的 有 二 氧 化 氯 臭 氧 及 氯 胺 等 來 作 為 加 氯 消 毒 的 替 代 消 毒 劑, 表 3-5 列 出 各 類 消 毒 劑 可 能 為 衍 生 出 來 的 DBPs, 而 表 3-6 則 是 常 見 的 替 代 消 毒 劑 優 缺 點 之 比 較 (1) 二 氧 化 氯 二 氧 化 氯 具 強 氧 化 性, 其 氧 化 能 力 約 為 氯 之 2.5 倍, 因 此 在 歐 洲 許 多 國 家 利 用 二 氧 化 氯 在 淨 水 程 序 中 早 已 行 之 有 年 使 用 二 氧 化 氯 作 為 替 代 消 毒 劑 主 要 基 於 以 下 幾 個 理 由 ( Katz et al., 1994; Susan, 1995): 消 毒 能 力 強, 有 效 ph 的 範 圍 廣 具 殘 餘 的 消 毒 能 力, 能 持 續 存 於 配 水 系 統 中 除 可 控 制 臭 味 外, 亦 可 去 除 鐵 錳 僅 需 加 入 少 量 之 二 氧 化 氯 和 較 短 接 觸 時 間 即 可 達 到 和 一 般 加 氯 相 同 之 消 毒 效 果 僅 會 產 生 少 量 對 人 體 健 康 有 害 的 THMs 二 氧 化 氯 在 淨 水 過 程 中, 具 有 抑 制 致 癌 物 THMs 產 生, 不 形 成 氯 酚 及 氯 胺 及 氧 化 殺 菌 力 較 氯 為 強 等 特 性 Narkis N. (1995) 研 究 顯 示, 以 ClO 2 進 行 原 水 之 消 毒 氧 化 處 理 時, 可 有 效 降 低 THMs 的 生 成 雖 然 臭 氧 之 殺 菌 力 與 氧 化 力 皆 優 於 二 氧 化 氯, 但 除 非 發 生 光 解 反 應, 二 氧 化 氯 不 會 如 臭 氧 般 氧 化 溴 離 子 形 成 溴 酸 根 離 子 (Hoigne et al., 1994); 二 氧 化 氯 氧 化 有 機 物 也 不 會 產 生 酮 類 等 有 機 物 臭 氧 化 所 產 生 之 消 毒 副 產 物 (Weinberg et al., 1993) 與 氯 相 較, 二 氧 化 氯 並 不 與 氨 氮 或 氨 反 應, 但 會 氧 化 亞 硝 酸 根 離 子 變 為 硝 酸 根 離 子, 而 且 純 二 氧 化 氯 不 與 有 機 物 行 親 電 子 取 代 反 應, 所 以 氧 化 反 應 後 所 3-20

42 第 三 章 本 年 度 主 要 工 作 內 容 及 重 要 發 現 與 成 果 產 生 的 鹵 化 消 毒 副 產 物 較 氯 氧 化 反 應 為 少 (2) 氯 胺 (Chloramine) 氯 氨 為 氯 與 氨 同 時 存 在 於 水 中 發 生 反 應 而 產 生, 主 要 有 一 氯 胺 (NH 2 Cl) 二 氯 胺 (NHCl 2 ) 三 氯 胺 (NHCl 3 ); 其 中, 以 NH 2 Cl 最 具 消 毒 能 力 Stevens et al. (1976) 曾 於 實 驗 室 內, 以 Ohio River 河 水 比 較 氯 與 氯 胺 在 不 同 接 觸 時 間 內 對 有 機 物 氯 化 的 情 形, 結 果 發 現 在 72 小 時 後, 加 氯 的 水 樣 形 成 了 160μg/L 的 THMs, 而 加 氯 胺 者, 僅 形 成 16μg/L THMs 使 用 氯 胺 為 消 毒 劑 最 主 要 的 優 點 為 具 有 持 久 之 殘 餘 消 毒 能 力 及 產 生 少 量 THMs; 但 對 Giardia cysts 及 病 毒 去 除 能 力 極 低, 且 在 水 中 已 被 証 實 對 腎 透 析 之 病 患 具 高 危 害 性 現 今 各 國 極 少 以 氯 胺 作 為 主 要 之 消 毒 劑 3-21

43 以 二 氧 化 氯 做 為 飲 用 水 水 質 理 藥 劑 之 評 估 表 3-5 各 類 消 毒 劑 可 能 衍 生 之 消 毒 副 產 物 (Craun et al., 1994) Item Species Disinfectants Organic DBPs THMs CHCl 3 HOCl, NH 2 Cl CHBrCl 2 HOCl, NH 2 Cl CHBr 2 Cl HOCl, NH 2 Cl CHBr 3 HOCl, NH 2 Cl, O 3 HAAs CH 2 ClCOOH HOCl, NH 2 Cl CHCl 2 COOH HOCl, NH 2 Cl CCl 3 COOH HOCl, NH 2 Cl CH 2 BrCOOH HOCl, NH 2 Cl, O 3 CHBr 2 COOH HOCl, NH 2 Cl, O 3 CBr 3 COOH HOCl, NH 2 Cl CHBrCOOH HOCl, NH 2 Cl CBr 2 ClCOOH HOCl, NH 2 Cl CBrCl 2 COOH HOCl, NH 2 Cl HANs CCl 3 CN HOCl, NH 2 Cl CHCl 2 CN HOCl, NH 2 Cl CHBrClCN HOCl, NH 2 Cl CHBr 2 CN HOCl, NH 2 Cl,O 3 HKs CHCl 2 COCH 3 HOCl CCl 3 COCH 3 HOCl Inorganic DBPs Chlorite - ClO 2 ClO 2 Chlorate - ClO 3 ClO 2, HOCl Bromate BrO 3 - O

44 第 三 章 本 年 度 主 要 工 作 內 容 及 重 要 發 現 與 成 果 表 3-6 各 種 消 毒 劑 之 優 缺 點 ( 張, 1996) 消 毒 劑 種 類 優 點 缺 點 二 氧 化 氯 氯 臭 氧 氯 胺 會 產 生 若 干 有 害 之 副 產 物 效 果 佳 USEPA 之 推 薦 劑 量 太 低 而 不 具 殺 相 對 費 用 較 低 菌 力 通 常 不 產 生 THMs 必 須 在 現 場 製 造 效 果 佳 且 已 被 廣 泛 的 使 用 產 生 有 害 之 消 毒 副 產 物 應 用 面 廣 做 為 輔 助 消 毒 劑 時, 其 操 作 條 件 和 費 用 便 宜 為 防 止 管 材 腐 蝕 而 控 制 ph 值 互 可 同 時 適 用 為 主 要 與 輔 助 之 消 毒 相 衝 突 劑 效 果 極 佳 至 今 被 証 實 產 生 最 少 之 有 害 副 產 需 要 輔 助 消 毒 劑 物 相 對 費 用 較 高 增 強 慢 速 砂 濾 及 GAC 濾 器 之 效 因 臭 氧 需 在 現 場 製 造 故 需 較 複 雜 果 之 操 作 技 巧 具 有 在 同 一 步 驟 進 行 氧 化 及 消 毒 之 功 能 會 產 生 若 干 有 害 之 副 產 物 對 細 菌 具 輕 度 之 去 除 效 果 且 能 夠 對 進 行 腎 透 析 之 患 者 具 有 毒 性 維 持 長 時 間 之 殺 菌 力 僅 被 推 薦 為 輔 助 消 毒 劑 且 對 病 毒 通 常 不 產 生 THMs 及 Giardia cyst 類 不 具 去 除 能 力 3-23

45 以 二 氧 化 氯 做 為 飲 用 水 水 質 理 藥 劑 之 評 估 (3) 臭 氧 (Ozone, O 3 ) 使 用 臭 氧 做 為 消 毒 劑, 最 主 要 目 的 在 於 以 臭 氧 氧 化 水 中 可 能 生 成 鹵 化 消 毒 副 產 物 之 有 機 物, 以 減 少 DBPs 之 生 成 Singer(1989) 對 美 國 境 內 數 個 以 臭 氧 作 為 前 氧 化 劑 的 淨 水 廠 做 過 研 究, 結 果 發 現 預 臭 氧 處 理 對 原 水 中 TOC 值 的 影 響 不 大, 但 會 改 變 有 機 物 的 組 成 而 達 到 去 除 色 度 與 降 低 UV 吸 收 值 的 效 果 ; 一 般 而 言 臭 氧 在 正 常 使 用 劑 量 下 可 降 低 THMFP 10~15%, 且 可 抑 制 溴 仿 的 形 成 然 而 預 臭 氧 處 理 有 時 反 而 會 增 加 三 鹵 甲 烷 的 生 成 潛 能, 比 如 將 原 本 非 前 驅 物 的 poly-substituted methyl-benzenes 氧 化 為 屬 於 前 驅 物 的 甲 基 酮 類, 但 對 於 原 本 是 前 驅 物 之 芳 香 族 類 ( 如 resorcinol), 經 氧 化 後 則 可 變 為 斷 鏈 (ring cleavage) 的 非 前 驅 物 產 物, 而 使 生 成 潛 能 降 低 ( 顧, 1996) 臭 氧 分 子 的 反 應 具 有 高 度 的 選 擇 性, 以 碳 氫 化 合 物 為 例, 臭 氧 分 子 只 會 與 具 有 不 飽 合 鍵 的 分 子 作 用 並 產 生 酮 類 或 醛 類, 對 於 飽 和 碳 氫 化 合 物 幾 乎 不 反 應 ; 氫 氧 自 由 基 的 反 應 則 是 快 速 而 且 沒 有 選 擇 性, 對 所 有 的 有 機 分 子 都 具 有 很 高 的 氧 化 能 力, 但 對 於 分 子 反 應 或 自 由 基 反 應 何 者 比 較 重 要, 則 視 水 質 而 定 ( 邱, 1996) 3-24

46 第 三 章 本 年 度 主 要 工 作 內 容 及 重 要 發 現 與 成 果 3.4 相 關 法 令 國 內 相 關 法 令 二 氧 化 氯 之 現 行 規 範 僅 在 環 境 衛 生 用 藥 及 食 品 添 加 殺 菌 劑 兩 方 面 有 所 提 及 ; 依 據 環 境 用 藥 管 理 法 第 五 十 二 條 環 保 署 毒 管 處 於 中 華 民 國 九 十 二 年 八 月 五 日 公 告 二 氧 化 氯 為 單 一 有 效 成 分 且 濃 度 在 百 分 之 六 以 下 之 環 境 衛 生 用 殺 菌 劑 為 不 列 管 環 境 用 藥, 不 適 用 環 境 用 藥 管 理 法 之 規 定 ; 於 食 品 添 加 物 使 用 範 圍 及 限 量 暨 規 格 標 準 中 的 第 二 類 殺 菌 劑 中 規 範 二 氧 化 氯 可 使 用 於 飲 用 水 及 食 品 用 水 ; 用 量 以 殘 留 有 效 氯 符 合 飲 用 水 標 準 為 度 依 據 飲 用 水 管 理 條 例 ( 九 十 二 年 一 月 八 日 公 告 ) 第 十 三 條 規 定 : 飲 用 水 水 質 處 理 所 使 用 之 藥 劑, 以 經 中 央 主 管 機 關 指 定 公 告 者 為 限 ; 而 藥 劑 公 告 依 據 為 公 告 飲 用 水 管 理 條 例 第 十 三 條 飲 用 水 水 質 處 理 所 使 用 之 藥 劑 ( 八 十 七 年 三 月 三 十 一 日 ) 與 飲 用 水 水 質 處 理 藥 劑 申 請 指 定 公 告 作 業 要 點 ( 八 十 七 年 三 月 三 十 日 ) ; 目 前 公 告 的 飲 用 水 水 質 處 理 藥 劑 有 臭 氧 硫 酸 鋁 聚 氯 化 鋁 氯 化 鐵 氫 氧 化 鈉 氫 氧 化 鈣 液 氯 次 氯 酸 鈉 次 氯 酸 鈣 氯 化 石 灰 高 錳 酸 鉀 硫 酸 磷 酸 氫 二 鈉 磷 酸 二 氫 鈉 聚 磷 酸 鈉 三 聚 磷 酸 鈉 聚 丙 烯 醯 胺 聚 氯 化 己 二 烯 二 甲 基 胺 與 氯 甲 基 一 氧 三 環 二 甲 基 胺 聚 合 物 共 十 九 種 國 外 相 關 規 範 目 前 美 國 環 保 署 規 範, 二 氧 化 氯 在 水 中 的 最 大 消 毒 劑 容 許 殘 餘 限 值 (Maximum Residual Disinfectant Level ) 為 0.8 mg/l, 且 規 範 其 無 機 消 毒 副 產 物 亞 氯 酸 根 離 子 在 水 中 的 最 大 容 許 量 (Maximum Contaminant Level) 為 1.0 mg/l 在 USEPA Guidance Manual-Alternative Disinfectants and Oxidants 中 建 議 二 氧 化 氯 的 添 加 使 用 量 不 超 過 1.4 mg/l, 以 避 免 二 氧 化 氯 亞 氯 酸 根 與 氯 酸 根 的 濃 度 總 和 超 過 1.0 mg/l; 世 界 衛 生 組 織 並 未 對 二 氧 化 氯 的 殘 留 濃 度 提 出 建 議 值, 主 要 是 原 因 3-25

47 以 二 氧 化 氯 做 為 飲 用 水 水 質 理 藥 劑 之 評 估 是 認 為 二 氧 化 氯 會 快 速 的 分 解, 故 改 針 對 飲 用 水 中 氯 酸 鹽 與 亞 氯 酸 鹽 殘 留 量 規 範, 規 範 值 皆 為 0.7 mg/l; 德 國 對 於 使 用 二 氧 化 氯 為 消 毒 劑, 規 範 最 大 添 加 量 (Maximum addition) 為 0.4 mg/l, 處 理 後 限 值 (Limit value after treatment) 為 0.2 mg/l, 較 USEPA 低 非 常 多, 主 要 是 因 為 German Drinking Water Act 中 規 範 消 毒 劑 在 必 須 時 才 添 加, 且 消 毒 被 視 為 是 飲 用 水 處 理 的 最 後 步 驟, 故 規 範 值 相 當 的 低 ; 日 本 水 道 協 會 與 韓 國 未 對 二 氧 化 氯 殘 留 濃 度 值 規 範 飲 用 水 水 質 處 理 的 藥 劑 主 要 有 混 凝 劑 抗 腐 蝕 劑 嗅 味 去 除 劑 消 毒 劑 軟 化 劑 及 預 防 性 藥 劑 等 分 類, 針 對 飲 用 水 水 質 處 理 藥 劑 的 內 容 說 明 主 要 針 對 四 個 項 目 : 性 狀 : 本 部 分 將 說 明 藥 劑 的 外 觀 顏 色 成 分 及 特 性 藥 劑 需 求 : 本 部 分 將 針 對 各 項 藥 劑 的 物 理 性 質 化 學 性 質 水 不 溶 性 物 質 等 需 求 分 別 說 明 特 殊 不 純 物 規 定 : 本 部 分 將 提 供 Water Chemicals Codex 中, 對 飲 用 水 處 理 藥 劑 所 建 議 之 不 純 物 最 高 含 量 (Recommended maximum impurity content, RMIC) 另 外, 國 內 有 使 用 之 藥 劑 部 分 將 根 據 行 政 院 環 保 署 所 公 告 之 飲 用 水 水 質 標 準 及 美 國 環 保 署 (USEPA) 出 版 之 Water Chemicals Codex 或 ANSI/NSF60 中 建 議 之 最 高 添 加 劑 量, 訂 定 單 一 管 制 標 準, 提 出 符 合 國 內 用 藥 標 準 之 RMIC 值, 以 供 參 考 製 造 與 應 用 : 將 針 對 各 項 藥 劑 的 製 造 方 法 及 用 途 加 以 說 明 3-26

48 第 三 章 本 年 度 主 要 工 作 內 容 及 重 要 發 現 與 成 果 表 3-7 為 國 外 相 關 規 範 之 限 值 彙 整 國 家 ClO 2 加 藥 ClO 2 最 大 ClO 2 - 最 ClO 3 - 最 量 上 限 值 容 許 殘 留 量 大 容 許 量 大 容 許 量 (mg/l) (mg/l) (mg/l) (mg/l) 美 國 _ WHO 德 國 _ 中 國 大 陸 0.7 _ 日 本 韓 國 3-27

49 以 二 氧 化 氯 做 為 飲 用 水 水 質 理 藥 劑 之 評 估 3.5 公 告 建 議 目 前 就 二 氧 化 氯 之 藥 劑 成 分 規 範 參 考 了 中 央 標 準 局 公 告 之 中 國 國 家 標 準 (CNS) 美 國 AWWA 公 告 之 AWWA Standards, 皆 未 對 二 氧 化 氯 藥 劑 規 範 美 國 環 保 署 在 EPA Guidance Manual-Alternative Disinfectants and Oxidants 中 詳 細 的 討 論 了 二 氧 化 氯 的 相 關 特 性 現 有 商 業 二 氧 化 氯 產 生 器 二 氧 化 氯 的 使 用 時 機 消 毒 能 力 的 探 討 及 消 毒 副 產 物 ; 世 界 衛 生 組 織 Concise International Chemical Assessment Document 37 CHLORINE DIOXIDE (GAS) 中 對 於 氣 態 的 二 氧 化 氯 有 深 入 的 研 究 報 告, 主 要 針 對 其 物 化 特 性 毒 性 暴 露 危 險 與 風 險 評 估 等 各 方 面 二 氧 化 氯 在 飲 用 水 中 的 規 範, 美 國 環 保 署 規 範 的 消 毒 劑 殘 餘 限 值 為 0.8 mg/l, 並 建 議 二 氧 化 氯 的 添 加 使 用 量 不 超 過 1.4 mg/l, 以 避 免 二 氧 化 氯 亞 氯 酸 根 與 氯 酸 根 的 濃 度 總 和 超 過 1.0 mg/l; 而 世 界 衛 生 組 織 則 未 有 二 氧 化 氯 的 殘 餘 濃 度 建 議 值, 主 要 是 因 為 二 氧 化 氯 會 快 速 的 分 解, 故 認 為 針 對 飲 用 水 中 亞 氯 酸 鹽 含 量 來 規 範 較 為 適 當 ; 德 國 因 將 消 毒 劑 當 作 必 要 才 添 加 且 置 於 飲 用 水 處 理 最 後 單 元, 故 規 範 二 氧 化 氯 殘 餘 限 值 為 0.2 mg/l, 且 訂 最 大 添 加 量 為 0.4 mg/l 亞 氯 酸 鹽 的 規 範 部 分,USEPA 定 訂 為 1.0 mg/l WHO 規 範 為 0.7 mg/l 而 德 國 規 範 限 值 為 0.2 mg/l, 主 要 是 與 其 規 範 之 二 氧 化 氯 添 加 量 及 殘 餘 量 配 合 而 訂 定 因 二 氧 化 氯 氣 體 的 不 安 定 性, 所 收 集 到 的 資 料 大 都 建 議 二 氧 化 氯 的 生 成 以 現 地 製 造 較 為 安 全 且 方 便 使 用 以 產 生 二 氧 化 氯 氣 體 直 接 導 入 欲 處 理 水 體 中 的 方 式, 或 是 先 將 二 氧 化 氯 氣 體 溶 入 水 中 再 行 應 用, 可 免 去 不 純 物 的 問 題 ; 若 以 成 品 二 氧 化 氯 藥 劑 或 是 混 合 反 應 生 成 二 氧 化 氯 之 藥 劑, 則 需 考 慮 其 不 純 物 之 問 題, 且 可 能 須 對 其 合 成 二 氧 化 氯 的 各 種 成 份 藥 劑 皆 進 行 規 範 此 外, 二 氧 化 氯 合 成 時 可 能 伴 隨 生 成 亞 氯 酸 根 與 氯 酸 根 等 的 無 機 副 產 物, 因 而 造 成 其 他 可 能 的 風 險 飲 用 水 中 的 水 質 處 理 添 加 藥 劑 攸 關 飲 用 水 水 質, 故 宜 避 免 其 他 可 能 之 危 害 風 險, 因 此 建 議 公 告 二 氧 化 氯 限 制 於 氣 態, 並 建 議 最 大 添 加 劑 量 為 1.4 mg/l, 另 將 3-28

50 第 三 章 本 年 度 主 要 工 作 內 容 及 重 要 發 現 與 成 果 添 加 後 最 高 殘 餘 濃 度 限 值 0.8 mg/l 及 添 加 後 亞 氯 酸 根 濃 度 限 值 1.0 mg/l 增 訂 于 飲 用 水 水 質 標 準 中, 並 以 處 理 後 之 清 水 做 為 檢 測 對 象 3-29

51 以 二 氧 化 氯 做 為 飲 用 水 水 質 理 藥 劑 之 評 估 3.6 市 售 樣 品 分 析 針 對 計 劃 需 求 收 集 了 三 家 廠 商 的 市 售 真 實 樣 品 來 進 行 分 析, 以 瞭 解 前 述 所 訂 定 二 氧 化 氯 純 度 與 不 純 物 檢 測 方 法 之 可 應 用 性 三 家 商 品 分 別 以 A B C 代 號 加 以 表 示 分 析 方 法 分 析 對 象 主 要 分 為 金 屬 離 子 與 含 氯 物 種 兩 類, 金 屬 離 子 分 析 方 法 參 考 環 境 檢 驗 所 公 告 之 水 質 檢 測 方 法, 詳 列 於 表 3-8 表 3-8 金 屬 離 子 分 析 方 法 鎘 鉻 銅 鐵 錳 鉛 鋅 汞 砷 硒 其 他 金 屬 火 燄 式 原 子 吸 收 光 譜 法 (NIEA W306.52A) 冷 蒸 氣 原 子 吸 收 光 譜 法 (NIEA W330.51A) 自 動 化 連 續 流 動 式 氫 化 物 原 子 吸 收 光 譜 法 (NIEA B) 自 動 化 連 續 流 動 式 氫 化 物 原 子 吸 收 光 譜 法 (NIEA B) 火 燄 式 原 子 吸 收 光 譜 法 含 氯 物 種 的 部 份 主 要 分 析 項 目 有 : 二 氧 化 氯 自 由 餘 氯 總 氯 亞 氯 酸 根 及 氯 酸 根, 二 氧 化 氯 自 由 餘 氯 及 總 氯 是 利 用 DPD 法 配 合 光 譜 儀 來 分 析, 亞 氯 酸 根 及 氯 酸 根 則 利 用 離 子 層 析 儀 (IC) 來 進 行 分 析, 分 析 方 法 及 儀 器 簡 介 如 下 : DPD 光 譜 法 : 使 用 AQUALYTIC R 光 譜 儀 系 統 的 PC MultiDirect, 出 場 校 正 日 期 為 2000/10/20, 配 合 DPD 與 glycine 的 錠 劑 來 進 行 分 析, 方 法 依 據 Standard Methods for 3-30

52 第 三 章 本 年 度 主 要 工 作 內 容 及 重 要 發 現 與 成 果 the Examination of Water and Wastewater(19th Edition) 4500-ClO 2 D, 分 析 範 圍 0.05~11 mg/l ClO 2 離 子 層 析 (IC): 使 用 Metrohm 790 personal IC 搭 配 TRANSGENOMIC ICSep AN1SC (250mm 4.6mm) 進 行 分 析, 以 微 電 導 度 計 作 為 偵 測 器 將 層 析 後 的 陰 離 子 定 量 本 計 劃 所 收 集 到 的 三 家 二 氧 化 氯 產 品 濃 度 都 很 高, 故 分 析 時 必 須 以 稀 釋 方 式 進 行 分 析 實 驗 中 以 10 倍 稀 釋 的 方 式 進 行 各 樣 品 的 稀 釋 序 列, 最 後 三 種 樣 品 皆 以 100 倍 的 稀 釋 倍 數 來 進 行 分 析, 故 最 後 結 果 之 有 效 位 數 僅 至 個 位 數 亞 氯 酸 根 及 氯 酸 根 的 分 析 結 果 因 氯 鹽 的 含 量 過 高 造 成 干 擾 且 亞 氯 酸 根 及 氯 酸 根 的 濃 度 相 當 低, 導 致 分 析 結 果 皆 低 於 偵 測 極 限, 故 於 後 續 中 不 列 出 此 兩 物 種 分 析 結 果 分 析 結 果 A 產 品 一 組 有 a b 兩 瓶 藥 劑, 使 用 前 需 兩 劑 稀 釋 混 合, 其 中 a 劑 主 要 成 分 為 5 ± 0.2% 的 二 氧 化 氯 水 溶 液 ;b 劑 主 要 成 分 為 醋 酸 就 該 公 司 提 供 之 資 料,a b 劑 與 純 水 以 1:1:18 混 合 可 得 到 2500 ppm 的 二 氧 化 氯 分 析 結 果 如 表 3-9 表 3-9 二 氧 化 氯 A 產 品 分 析 結 果 分 析 項 目 A 產 品 鎘 Cd 鉻 Cr 銅 Cu 鐵 Fe 錳 Mn 鋅 ND Zn 鉛 Pb 鈣 Ca 硒 Ce 鎂 Mg (mg/l) 鉀 K (mg/l) 鈉 Na (mg/l) 4.58 砷 As (mg/l) 汞 Hg (mg/l) 二 氧 化 氯 ClO 2 (mg/l) 360 自 由 餘 氯 (mg/l) 50 結 合 餘 氯 (mg/l) ND 總 氯 (mg/l) 1000 B 產 品 就 該 公 司 提 供 資 料 為 電 解 法 生 成 之 二 氧 化 氯 直 接 以 水 吸 收, 產 品 濃 度 為 500 ppm 該 公 司 提 供 市 售 成 品, 故 進 行 部 分 金 屬 不 純 物 分 析, 而 未 檢 送 檢 測 3-31

53 以 二 氧 化 氯 做 為 飲 用 水 水 質 理 藥 劑 之 評 估 公 司 分 析 砷 汞 硒 樣 品 分 析 結 果 如 表 3-10 表 3-10 二 氧 化 氯 B 產 品 分 析 結 果 分 析 項 目 B 產 品 鎘 Cd 鉻 Cr 銅 Cu 錳 Mn 鋅 Zn ND 鐵 Fe (mg/l) 鉛 Pb (mg/l) 鈣 Ca (mg/l) 鎂 Mg (mg/l) 鉀 K (mg/l) 鈉 Na (mg/l) 5.09 二 氧 化 氯 ClO 2 (mg/l) 10 自 由 餘 氯 (mg/l) 302 結 合 餘 氯 (mg/l) ND 總 氯 (mg/l) 317 該 公 司 的 二 氧 化 氯 產 品 利 用 電 解 法 製 成, 以 純 水 為 吸 收 水 體, 吸 收 二 氧 化 氯 氣 體 至 飽 和 再 行 利 用 (25 飽 和 濃 度 約 為 3000 mg/l), 因 樣 品 係 以 純 水 吸 收 二 氧 化 氯, 故 不 需 進 行 不 純 物 分 析, 僅 分 析 二 氧 化 氯 與 其 他 含 氯 相 關 物 種 該 公 司 樣 品 分 為 兩 種, 一 種 直 接 以 水 吸 收 至 飽 和, 另 一 種 則 利 用 10% 的 NaOH 來 進 行 去 氯 的 純 化 樣 品 分 析 結 果 如 表

54 表 3-11 二 氧 化 氯 C 產 第 三 品 章 分 本 析 年 結 度 果 主 要 工 作 內 容 及 重 要 發 現 與 成 果 分 析 項 目 C 產 品 直 接 吸 收 二 氧 化 氯 經 10%NaOH 再 吸 收 二 氧 化 氯 ClO 2 (mg/l) 自 由 餘 氯 (mg/l) 結 合 餘 氯 (mg/l) ND ND 總 氯 (mg/l) 就 分 析 結 果 討 論 如 下 : 三 家 公 司 的 樣 品 因 氯 鹽 的 含 量 過 高 造 成 干 擾 且 亞 氯 酸 根 及 氯 酸 根 的 濃 度 相 當 低, 導 致 分 析 結 果 皆 低 於 偵 測 極 限, 故 針 對 亞 氯 酸 根 及 氯 酸 根 的 分 析 方 式 須 加 以 改 進 研 究, 以 避 免 其 他 干 擾 影 響 分 析 三 家 公 司 樣 品 二 氧 化 氯 的 分 析 結 果 皆 遠 低 於 廠 商 所 告 知 的 濃 度 值, 推 測 原 因 應 與 二 氧 化 氯 本 身 特 性 有 關, 二 氧 化 氯 易 溶 於 水 中, 且 在 水 中 以 分 子 態 存 在, 且 也 容 易 由 水 中 趕 出, 三 家 樣 品 在 收 集 裝 瓶 存 放 運 送 過 程 都 有 所 耗 損, 加 上 分 析 方 法 並 無 法 直 接 分 析 高 濃 度 樣 品, 需 經 過 多 次 稀 釋 步 驟 才 能 夠 分 析, 造 成 最 後 分 析 出 的 樣 品 濃 度 都 相 當 低, 故 若 欲 將 二 氧 化 氯 應 用 於 飲 用 水 消 毒 上, 現 場 製 造 是 必 須 的 分 析 出 結 果 二 氧 化 氯 濃 度 最 高 的 是 A 公 司 的 產 品, 可 能 是 因 為 該 產 品 是 於 使 用 前 才 活 化, 所 以 減 少 了 其 他 過 程 的 耗 損, 分 析 後 的 濃 度 仍 僅 有 360 mg/l, 但 總 氯 高 達 1000 mg/l, 且 活 化 後 外 觀 呈 現 深 黃 色, 故 可 能 尚 含 有 其 他 含 氯 物 種 A 公 司 的 產 品 含 有 部 分 的 重 金 屬, 可 能 與 製 程 或 包 裝 有 關 C 公 司 的 產 品 經 10%NaOH 再 吸 收, 明 顯 降 低 了 自 由 有 效 氯 與 總 氯 量, 故 二 氧 化 氯 升 成 後 再 淨 化 之 步 驟 可 提 高 二 氧 化 氯 之 純 度 3-33

55 第 四 章 主 要 意 見 及 未 來 或 後 續 執 行 建 議 第 四 章 主 要 意 見 及 未 來 或 後 續 執 行 建 議 二 氧 化 氯 是 相 當 具 有 潛 力 的 消 毒 劑, 但 應 用 上 需 注 意 其 特 性 建 議 公 告 二 氧 化 氯 限 制 於 氣 態, 並 建 議 最 大 添 加 劑 量 為 1.4 mg/l 而 添 加 後 最 高 殘 餘 濃 度 限 值 0.8 mg/l 及 添 加 後 亞 氯 酸 根 濃 度 限 值 1.0 mg/l 可 增 列 在 飲 用 水 水 質 標 準 中 建 議 後 續 可 針 對 二 氧 化 氯 的 使 用 再 進 行 研 究, 且 建 議 將 二 氧 化 氯 及 其 無 機 副 產 物 納 入 飲 用 水 水 質 標 準 中 以 及 公 告 分 析 方 法 4.1 結 論 1. 二 氧 化 氯 是 一 種 有 效 的 消 毒 劑, 空 氣 中 濃 度 超 過 10% 有 爆 炸 的 危 險, 但 溶 解 於 水 中 卻 相 當 安 定, 溶 解 度 近 3g/L, 且 溶 解 於 水 中 大 都 以 分 子 態 存 在, 故 ph 操 作 範 圍 較 廣 2. 二 氧 化 氯 的 製 造 方 法 非 常 多, 應 用 上 建 議 現 地 製 造, 常 見 的 有 酸 製 法 氯 溶 液 法 氯 氣 - 固 態 亞 氯 酸 鈉 法 氯 酸 根 離 子 還 原 法 及 電 解 法, 以 USEPA 所 公 佈 的 資 料, 生 成 的 二 氧 化 氯 濃 度 都 可 達 80% 以 上 3. 二 氧 化 氯 溶 解 於 水 中 相 當 安 定, 但 會 發 生 光 解 反 應 ; 且 因 二 氧 化 氯 氧 化 力 相 當 大, 故 會 與 水 中 其 他 含 氯 物 種 及 有 機 物 發 生 反 應, 而 生 成 無 機 副 產 物 亞 氯 酸 根 及 氯 酸 根, 其 中 亞 氯 酸 根 有 較 大 毒 性 4. 二 氧 化 氯 可 用 於 消 毒 之 外, 還 可 應 用 於 臭 味 的 消 除 與 鐵 錳 的 去 除 上, 且 生 成 較 少 的 有 機 消 毒 副 產 物 5. 基 於 二 氧 化 氯 水 溶 液 中 不 純 物 管 制 上 的 困 難 與 不 確 定 性, 更 為 了 確 保 添 加 二 氧 化 氯 時 對 飲 用 水 水 質 安 全 的 掌 握, 建 議 公 告 二 氧 化 氯 限 制 於 氣 態, 並 建 議 依 美 國 環 保 署 的 規 範 訂 定 最 大 添 加 劑 量 為 1.4 mg/l, 而 添 加 後 最 高 殘 餘 濃 度 限 值 0.8 mg/l 及 添 加 後 亞 氯 酸 根 濃 度 限 值 1.0 mg/l( 亦 依 據 美 國 環 保 署 訂 定 的 規 範 ) 則 應 增 列 入 飲 用 水 水 質 標 準 中, 並 以 處 理 後 之 清 水 做 為 檢 測 對 象 4-1

56 以 二 氧 化 氯 做 為 飲 用 水 水 質 理 藥 劑 之 評 估 4.2 建 議 1. 本 計 劃 是 針 對 公 告 二 氧 化 氯 做 為 飲 用 水 水 質 處 理 藥 劑 進 行 之 報 告, 著 重 在 其 物 化 特 性 以 及 國 內 外 相 關 文 獻 之 收 集, 建 議 後 續 可 針 對 二 氧 化 氯 實 際 消 毒 利 用 上 之 研 究 2. 二 氧 化 氯 消 毒 會 伴 隨 產 生 無 機 副 產 物 亞 氯 酸 根 及 氯 酸 根, 目 前 僅 建 議 於 公 告 中 加 入 二 氧 化 氯 添 加 量 之 規 範, 建 議 環 保 署 另 考 慮 將 二 氧 化 氯 與 亞 氯 酸 根 的 殘 留 值 規 範 加 入 飲 用 水 水 質 標 準 中 3. 目 前 國 內 並 未 對 二 氧 化 氯 的 分 析 方 法 進 行 公 告, 建 議 可 參 考 Standard Methods for the Examination of Water and Wastewater, 且 亦 建 議 同 時 公 告 亞 氯 酸 鹽 與 氯 酸 鹽 之 分 析 方 法 4. 對 于 二 氧 化 氯 做 為 公 告 之 飲 用 水 水 質 處 理 藥 劑 後, 建 議 環 保 署 規 範 使 用 單 位 應 申 報 水 處 理 量 藥 劑 添 加 量 等 相 關 使 用 記 錄, 以 利 監 督 管 理 之 掌 控, 確 保 飲 用 水 水 質 之 安 全 4-2

57 參 考 文 獻 邱 創 汎, (1996). 臭 氧 殺 菌 相 關 問 題 之 探 討. 中 華 民 國 自 來 水 協 會 會 刊. 第 15 卷, 第 三 期, 第 頁 李 慶 毅, (1997). 以 二 氧 化 氯 為 替 代 消 毒 劑 時 小 分 子 有 機 物 之 反 應 探 討. 碩 士 論 文, 國 立 中 興 大 學 環 境 工 程 學 研 究 所, 台 中 市, 台 灣 施 宜 珍, (1996). 以 二 氧 化 氯 為 替 代 消 毒 劑 時 其 副 產 物 生 成 與 控 制 之 研 究. 碩 士 論 文, 國 立 中 興 大 學 環 境 工 程 學 研 究 所, 台 中 市, 台 灣 許 勝 聖, (1996). 以 二 氧 化 氯 為 替 代 消 毒 劑 時 其 生 成 控 制 及 消 毒 效 率 之 研 究. 碩 士 論 文, 國 立 中 興 大 學 環 境 工 程 學 研 究 所, 台 中 市, 台 灣 陳 建 璋, (1997). 腐 植 酸 對 二 氧 化 氯 消 毒 反 應 其 副 產 物 生 成 之 研 究. 碩 士 論 文, 國 立 中 興 大 學 環 境 工 程 學 研 究 所, 台 中 市, 台 灣 張 怡 怡, (1996). 飲 用 水 中 無 機 物 微 生 物 及 濁 度 管 制 項 目 及 管 制 標 準 之 合 理 性 分 析. EPA-85-J , 行 政 院 環 境 保 護 署 委 託 研 究 報 告. 台 北 醫 學 院 47

58 張 禎 祐,(2000), 以 二 氧 化 氯 為 替 代 消 毒 劑 之 副 產 物 生 成 與 控 制 研 究, 博 士 論 文, 中 興 大 學 環 境 工 程 研 究 所 台 中 市, 台 灣. 蔡 清 讚, (1988). 醫 院 廢 水 中 微 生 物 之 消 毒 之 懸 浮 固 體 中 之 消 毒 動 力 學. 博 士 論 文, 國 立 台 灣 大 學 土 木 工 程 學 研 究 所, 台 北 市, 台 灣 顧 洋, (1996). 臭 氧 處 理 在 淨 水 工 程 上 之 應 用. 中 華 民 國 自 來 水 協 會 會 刊. 第 15 卷, 第 三 期, 第 頁 Aieta, E.M. and J.D. Berg, (1986). A Review of Chlorine Dioxide in Drinking Water Treatment. J. AWWA. Vol.78, No.6, pp Akin, E.W., J.C. Hoff and J.G. LippHoff, S. Lalezary, M. Pirbazari and M.J. McGuire, (1984). Oxidation of Taste and Odor Compounds. AWWA Ann. Conf., Dallas, Texas. APHA, AWWA, WPCF, (1995), Standard methods for the examination of water and wastewater, 19th ed. AWWA Research Foundation, (1992), Use of alternative disinfectants, chlorination by-products: production and control, pp Bruce, W.L., A.H. Robert, C.H. Robert, (1999), Complementary uses of 48

59 chlorine dioxide and ozone for drinking water treatment, Ozone Science & Engineering, Vol. 21, pp Buxton, G.V. and M.S. Subhani,(1972), Radiation Chemistry and Photo-Chemistry of Aqueous Solution of Hypochlorite Ion. Jour. Chem. Soc. Faraday Ⅱ, 958 Brueggeman, E., J.E. Wajon, C.W.R. Wade and E.P. Burrows, (1982). Analysis of Unquenched Mixures of Chlorine Dioxide and Phenols by Reversed-Phase Highperformance Liquid Chromatography. J. Chromatogr. Vol.237, pp Craun, G.F., R.J. Bull, R. M. Clark, J. Doull, W. Grabow, G.M.Marsh, D.A. Okun, S. Regli, M.D. Sobsey, J.M., Symons.,(1994), Balancing chemical and microbial risks of drinking water disinfection, partⅠ benefits and potential risks, J. Water SRT-Aqua, Vol. 43, pp Carlson, R. M. and S. Lin, (1985). Characterization of the Products from the Reaction of Hydroxybenzoic and Hydroxycinnamic Acids with Aqueous Solutions of Chlorine, Chlorine Dioxide, and Chloramine. In Water Chlorination: Chemistry, Environmental Impact and Health Effects. Vol.5, pp Emmenegger, F.and G..Gordon,(1967), The rapid interaction between 49

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62 Environment Impact of Oxychlorine Compounds. Ann Arbor Science. Ann Anbor, MI. NAS (US National Academy of Sciences), (1980). Drinking Water and Health. Vol.2, National Academy Press, Washington, DC. Narkis, N., (1995). Disinfection of Efficients by Combnations of Chlorine Dioxide Dioxide and Chlorine. Water Sci. Technol. Vol.31, No.5, pp Ozawa, T. and T. Kwan, (1984). Electron Spin Resonance Studies on the Reactive Character of Chlorine Dioxide (ClO2) Radical in Aqueous Solution. Chem Pharm Bull. Vol.32, pp Rav-Acha, C. and E. Choshen, (1987). Aqueous Reactions of Chlorine Dioxide with Hydrocarbons. Environ. Sci. Technol. Vol.21, pp Rav-Acha, C., (1984). Disinfection of Drinking Water Rich in Bromide with Chlorine and Chlorine Dioxide, while Minimizing the Formation of Undesirable By-Products. Water Res. Vol.17, pp Rosen-blatt, D.H., (1975). Chlorine and Oxychlorine Species Reactivity with Organic Substances. In J. D. Johnson, Ed. Disinfection: Water and Wastewater. Ann Arbor Science. Ann Arbor, MI. pp Singer, P.C., (1989). Complying with Trihalomethane Reduction 52

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64 54

65 公 告 草 案 中 華 民 國 九 十 五 年 月 日 主 旨 : 公 告 二 氧 化 氯 為 飲 用 水 水 質 處 理 藥 劑 草 案 依 據 : 飲 用 水 管 理 條 例 第 十 三 條 公 告 事 項 : 一 藥 劑 編 號 : 二 二 藥 劑 名 稱 : ( 一 ) 中 文 名 稱 : 氣 態 二 氧 化 氯 ( 二 ) 英 文 名 稱 : Gaseous Chlorine Dioxide 三 化 學 式 : ClO2 四 最 大 添 加 劑 量 : 1.4 mg/l 五 其 他 事 項 依 本 署 公 告 之 飲 用 水 水 質 處 理 藥 劑 一 般 規 定 事 項 辦 理

66 附 表 公 告 二 氧 化 氯 為 飲 用 水 水 質 處 理 藥 劑 二 氧 化 氯 一 藥 劑 編 號 : 二 二 藥 劑 名 稱 : 中 文 名 稱 : 氣 態 二 氧 化 氯 英 文 名 稱 :Gaseous Chlorine Dioxide 三 化 學 式 :ClO 2 四 最 大 添 加 劑 量 :1.4 mg/l; 最 大 殘 餘 量 :0.8 mg/l; 亞 氯 酸 根 濃 度 限 值 :1.0 mg/l

67 二 氧 化 氯 (Chlorine Dioxide) 1. 性 狀 分 子 式 ClO 2 分 子 量 黃 綠 色 氣 體, 若 純 液 態 存 在 時 為 深 紅 色, 具 有 刺 激 性 的 味 道, 當 空 氣 中 二 氧 化 氯 濃 度 達 14~17 mg/l 時 一 般 人 就 會 察 覺, 濃 度 達 45 mg/l 時 即 對 嗅 覺 產 生 刺 激 性, 空 氣 中 濃 度 超 過 10% 遇 火 星 就 有 爆 炸 性 的 危 險, 壓 縮 儲 存 亦 有 爆 炸 的 危 險 性 二 氧 化 氯 對 水 的 溶 解 度 相 當 高, 在 11 時 對 水 的 溶 解 度 約 氯 氣 的 10 倍,25 對 水 的 溶 解 度 可 達 2.9 g ClO 2 /L H 2 O 二 氧 化 氯 水 溶 液 呈 黃 綠 色, 具 有 刺 激 性 的 味 道 二 氧 化 氯 雖 氧 化 力 很 強, 但 在 陰 涼 避 光 及 密 封 條 件 下 的 水 溶 液 中 相 當 穩 定 二 氧 化 氯 在 水 中 多 以 分 子 狀 態 存 在, 受 到 紫 外 光 照 會 產 生 光 化 學 分 解 效 應, 生 成 氯 酸 及 鹽 酸 2. 藥 劑 需 求 2.1 物 理 性 質 : 需 於 現 場 製 造 產 生 二 氧 化 氯 氣 體, 直 接 引 入 水 流 中, 或 先 將 二 氧 化 氯 氣 體 通 入 溶 解 於 水 中, 再 進 行 運 用 二 氧 化 氯 水 溶 液 需 儲 存 於 棕 色 瓶 中, 冷 藏 並 密 閉 以 避 免 氣 體 逸 散 2.2 化 學 性 質 : 現 場 製 造 應 避 免 長 時 間 照 光 及 高 溫 環 境 3. 特 殊 不 純 物 規 定 二 氧 化 氯 製 造 同 時 亦 可 能 產 生 氯 氣, 故 使 用 二 氧 化 氯 氣 體 作 為 消 毒 劑, 控 制 添 加 量 需 符 合 飲 用 水 水 質 標 準 之 自 由 有 效 餘 氯 (Free Residual Chlorine) 限 值 範 圍 0.2~1.0 mg/l 4. 製 造 與 應 用 可 利 用 化 學 法 電 化 學 法 或 其 他 方 式 配 合 特 殊 設 備 現 場 製 造, 適 用 於 漂 白 殺 菌 除 臭 除 味 及 氧 化 金 屬 物 質

68 以 二 氧 化 氯 做 為 飲 用 水 水 質 處 理 藥 劑 之 評 估 期 中 報 告 委 員 意 見 答 覆 委 員 審 查 意 見 意 見 回 覆 ( 一 ) 曾 四 恭 教 授 1. 本 計 畫 主 要 工 作 項 目 除 相 關 文 獻 研 1. 謝 謝 委 員 的 意 見, 在 期 末 報 告 中 會 討 外, 為 ClO 2 使 用 上 之 相 關 規 範, 針 對 二 氧 化 氯 的 特 性 再 加 以 說 明 特 別 是 藥 劑 主 要 成 分 與 不 純 物 之 相 2. 就 目 前 所 了 解 市 面 上 的 產 品, 以 酸 關 規 定, 建 議 能 在 章 節 中 加 以 說 明 製 法 與 電 解 法 的 成 品 最 多, 酸 製 法 2. ClO 2 之 製 造 方 法 多, 建 議 能 針 對 目 的 純 度 較 差 ; 目 前 規 劃 公 告 氣 態 二 前 市 場 採 用 之 製 造 方 法 加 以 說 明, 氧 化 氯, 故 不 需 針 對 不 純 物 部 分 進 尤 其 在 製 造 過 程 可 能 產 生 之 副 產 物 行 規 範 及 不 純 物, 可 作 為 公 告 ClO 2 不 純 物 3. 謝 謝 委 員 的 意 見, 在 期 末 報 各 時 會 之 依 據 將 兩 部 分 的 製 造 方 法 統 一 後 重 新 排 3. 表 3-2 所 提 出 之 ClO 2 製 造 方 法 與 列 P7-9 頁 之 製 造 方 法 部 份 有 不 太 一 4. 公 告 項 目 中 將 會 加 入 二 氧 化 氯 添 加 致, 建 議 能 統 一 說 明 後 亞 氯 酸 根 的 最 大 殘 餘 劑 量, 並 建 4. ClO 2 主 藥 劑 之 不 純 物 為 來 自 製 造 過 議 將 亞 氯 酸 根 規 範 於 飲 用 水 水 質 標 程 及 消 毒 反 應 產 物, 故 宜 以 這 二 方 準 中 面 加 以 討 論 可 能 之 不 純 物, 宜 考 慮 5. 二 氧 化 氯 製 造 方 法 相 當 多, 且 新 方 ClO ClO 3 之 毒 性 問 題 法 仍 不 斷 研 發, 故 不 考 慮 就 製 造 方 5. 由 於 不 純 物 與 製 造 方 法 有 關, 能 否 法 進 行 規 範 考 慮 公 告 內 容 包 括 製 造 方 法 ( 二 ) 李 國 欽 博 士 1. 以 RMIC=MCL/(MD*SF) 來 計 算 不 1. 若 以 二 氧 化 氯 作 為 消 毒 劑, 因 二 氧 純 物 之 可 允 許 含 量, 似 應 再 考 慮 其 化 氯 的 添 加 量 並 不 高, 故 以 RMIC 是 否 合 理 計 算 不 純 物 並 不 適 當, 且 目 前 公 告 2. 以 氣 體 直 接 加 入 水 體, 問 題 較 少, 規 劃 氣 態 二 氧 化 氯, 故 針 對 不 純 物 為 利 以 後 的 推 薦 參 數, 建 議 比 較 各 部 分 已 經 刪 去 氣 態 產 生 方 法 之 成 本 2. 謝 謝 委 員 的 意 見, 目 前 已 經 朝 此 方 3. 市 售 三 件 成 品 不 純 物 之 分 析 似 應 擴 向 進 行 大 範 圍 作 比 較 完 全 之 篩 選 3. 因 市 售 成 品 的 收 集 不 易, 會 盡 量 收 集 各 種 不 同 方 式 製 成 的 二 氧 化 氯 成 品 進 行 分 析 ( 三 ) 黃 志 彬 教 授 1. 報 告 中 對 二 氧 化 氯 製 造 方 法 之 說 明 1. 謝 謝 委 員 的 意 見, 會 就 兩 部 分 的 資

69 與 表 3-2 EPA 之 手 冊 有 多 處 差 異, 建 議 依 表 3-2 內 之 各 種 方 法 重 新 整 理 節 之 內 容 2. 液 態 ClO 2 亦 有 在 現 場 製 造, 一 般 採 用 酸 催 化 法, 此 為 最 普 遍 的 方 法, 但 此 方 法 使 用 之 藥 劑 亞 氯 酸 鈉 並 未 公 告 為 飲 用 水 藥 劑, 此 可 能 造 成 ClO 2 公 告 後, 自 來 水 事 業 單 位 仍 無 法 使 用 此 藥 劑, 或 造 成 某 些 產 品 無 法 應 用 引 起 困 擾 3. 建 議 收 集 市 面 上 現 有 商 品 三 件 時 注 意 注 意 其 製 造 方 法, 盡 量 涵 蓋 不 同 之 製 造 方 法 ( 尤 其 是 電 解 法 ) 4. 請 注 意 不 同 製 造 方 法 ( 現 場 或 商 品 ) 之 ClO 2 成 分 之 比 例 ( 四 ) 台 灣 省 自 來 水 股 份 有 限 公 司 吳 美 惠 經 理 1. 淨 水 場 使 用 二 氧 化 氯 時 如 何 避 免 工 安 問 題 及 如 何 處 理 工 安 問 題 2. 若 以 藥 劑 混 合 方 式 產 生 二 氧 化 氯 所 使 用 的 藥 劑 是 否 都 為 公 告 的 飲 用 水 水 質 處 理 藥 劑 3. 淨 水 場 使 用 二 氧 化 氯 可 能 會 產 生 無 機 性 副 產 物 如 氯 酸 鹽 亞 氯 酸 鹽 等 這 些 是 否 在 水 質 標 準 中 也 要 增 列 ( 五 ) 台 北 自 來 水 事 業 處 1. 末 端 使 用 如 何 控 制 ClO ClO 3 如 何 控 制 加 藥 量 及 線 上 偵 測 器 如 何 自 動 監 測 2. 若 二 氧 化 氯 公 告 為 飲 用 水 水 質 處 理 藥 劑, 應 針 對 二 氧 化 氯 本 身 之 安 全 及 使 用 上 安 全 問 題 作 考 量 料 進 行 重 新 排 列 並 加 以 修 改 潤 飾 2. 飲 用 水 添 加 藥 劑 攸 關 重 大, 故 公 告 宜 較 為 嚴 謹, 目 前 規 劃 公 告 氣 態 二 氧 化 氯, 較 不 受 製 造 方 法 限 制, 且 避 免 伴 隨 生 成 之 無 機 副 產 物 3. 謝 謝 委 員 的 意 見, 我 們 會 盡 量 收 集 各 種 不 同 方 式 製 成 的 二 氧 化 氯 成 品 進 行 分 析 4. 謝 謝 委 員 的 意 見, 我 們 會 對 各 式 售 產 品 進 行 成 分 分 析 1. 二 氧 化 氯 與 液 氯 皆 為 消 毒 藥 劑, 操 作 者 需 具 有 毒 性 化 學 物 質 操 作 人 員 執 照 2. 目 前 規 劃 公 告 氣 態 二 氧 化 氯, 較 不 受 製 造 方 法 限 制, 且 避 免 伴 隨 生 成 之 無 機 副 產 物 3. 謝 謝 委 員 的 意 見, 會 建 議 在 飲 用 水 水 質 標 準 中 增 列 二 氧 化 氯 氯 酸 鹽 及 亞 氯 酸 鹽 1. 此 部 份 建 議 參 考 美 國 環 保 署 Guidance Manual Alternative Disinfectants and Oxidant 中 針 對 CT value 來 進 行 規 劃 設 計, 在 不 超 過 最 大 添 加 量 的 限 制 下, 控 制 最 佳 的 加 藥 量 2. 二 氧 化 氯 與 液 氯 皆 為 消 毒 藥 劑, 操 作 者 需 具 有 毒 性 化 學 物 質 操 作 人 員 執 照

70 以 二 氧 化 氯 做 為 飲 用 水 水 質 處 理 藥 劑 之 評 估 諮 商 會 意 見 答 覆 李 委 員 錦 地 : 委 員 審 查 意 見 1. 對 於 美 國 環 保 署 與 德 國 最 大 添 加 量 及 處 理 後 限 制 值, 其 訂 定 背 景 及 理 由 似 須 再 加 以 了 解 及 詳 析 2. 公 告 時 似 可 以 最 大 添 加 量 及 處 理 後 限 制 值 二 項 曾 委 員 四 恭 : 1. 建 議 公 告 之 項 目 : (1) ClO 2 以 何 種 產 品 作 為 消 毒 用 劑, 因 關 係 到 不 純 物 污 染 問 題, 以 及 消 毒 劑 內 之 ClO 2 佔 總 氯 量 之 %, 例 如 80% 以 上 (2) 最 大 添 加 劑 量 : 原 則 上 添 加 量 - - 越 低, 產 生 ClO 2 及 ClO 3 副 產 物 之 殘 留 越 低, 但 加 量 太 低, 是 否 會 影 響 殺 菌 之 效 率, 請 提 供 相 關 數 據 (3) 最 大 消 毒 劑 殘 留 量 : 例 如 美 國 EPA 規 定 小 於 0.8 mg/l 2. 各 國 公 告 之 限 值 不 同, 宜 了 解 其 評 估 基 準 之 來 源 張 委 員 怡 怡 : 1. 同 意 公 告 ClO 2 處 理 藥 劑 2. 應 一 並 公 告 ClO 2 ClO - 2 (chlorite) ClO - 3 (chlorate) 定 量 方 法 及 增 加 飲 用 水 水 質 標 準 (Residual ClO 2,DBPs) 意 見 回 覆 1. 根 據 美 國 環 保 署 的 資 料, 其 最 大 添 加 量 與 最 大 消 毒 劑 殘 餘 量 的 訂 定 是 為 了 避 免 產 生 過 量 的 亞 氯 酸 鹽 ; 二 氧 化 氯 添 加 量 超 過 1.4 mg/l 時, 可 能 會 導 致 水 中 二 氧 化 氯 亞 氯 酸 根 與 氯 酸 根 的 總 量 超 過 1.0 mg/l 2. 謝 謝 委 員 的 意 見, 參 考 各 方 面 的 資 料 與 各 委 員 的 意 見 後, 將 二 氧 化 氯 最 大 添 加 劑 量 訂 為 1.4 mg/l; 最 高 殘 餘 劑 量 訂 為 0.8 mg/l 1. (1) 參 考 各 方 面 的 資 料 與 各 委 員 的 意 見 後, 目 前 規 劃 公 告 氣 態 二 氧 化 氯, 以 避 免 不 純 物 產 生 的 問 題 ; (2) 消 毒 效 率 的 部 分 建 議 參 考 美 國 環 保 署 Guidance Manual Alternative Disinfectants and Oxidant 中 針 對 CT value 來 進 行 規 劃 設 計, 就 不 同 的 原 水 來 源 進 行 所 需 最 低 濃 度 的 規 劃 ; (3) 公 告 項 目 已 加 上 最 高 殘 餘 劑 量 0.8 mg/l 2. 就 目 前 所 收 集 到 各 國 資 訊, 以 美 國 環 保 署 與 世 界 衛 生 組 織 所 獲 得 的 訂 定 標 準 資 訊 最 為 完 整, 故 現 公 告 將 二 氧 化 氯 最 大 添 加 劑 量 訂 為 1.4 mg/l; 最 高 殘 餘 劑 量 訂 為 0.8 mg/l 1. 謝 謝 委 員 的 意 見, 公 告 內 容 會 依 各 委 員 意 見 進 行 修 正 2. 謝 謝 委 員 的 意 見, 公 告 項 目 中 將 加 入 二 氧 化 氯 的 最 大 添 加 劑 量 與 最 高

71 3. 確 認 二 氧 化 氯 性 狀 : 對 水 的 溶 解 度 3.01g/L H 2 O?(WHO 資 料 ) 4. 建 議 ClO 2 的 使 用 管 理, 應 規 範 使 用 者 提 出 申 報 ( 如 高 分 子 助 凝 劑 ) USEPA 建 議 在 高 濃 度 TOC 時 機 使 用, 並 注 意 嗅 味 閥 值 0.4mg/L 若 水 廠 使 用 此 消 毒 劑, 應 有 能 力 作 現 場 自 行 檢 驗, 確 保 安 全 5. 建 議 公 告 項 目 之 最 大 添 加 量 及 殘 餘 量 應 有 更 充 足 的 說 明 理 由, 並 對 80 % 定 義 明 確 彭 委 員 福 佐 : 1. 在 台 灣 二 氧 化 氯 品 質 管 制 應 依 採 用 何 種 方 法 製 程 來 決 定, 因 不 同 方 法 製 成 其 品 質 會 有 不 同, 如 資 料 顯 示 酸 製 法 其 品 質 為 80%; 若 是 液 氯 - 亞 氯 酸 鈉 法 其 品 質 約 80~92%; 液 氯 - 亞 氯 酸 鈉 法 ( 循 環 式 ) 品 質 為 92~98% 2. 已 公 告 飲 用 水 處 理 藥 劑 中 品 質 管 制 都 有 列 不 純 物 質 項 目 及 品 質, 此 報 告 也 請 列 出 3. 最 大 添 加 量 為 1.4mg/L, 由 報 告 中 得 知 是 美 國 用 在 surface water;table 中 含 ClO 2 ClO 2 及 ClO - 3, 而 ClO 2 最 大 添 加 量 為 1.0mg/L, 其 中 也 考 量 ClO 2 在 空 氣 中 會 很 快 分 解 約 >10 %, 台 灣 地 區 為 亞 熱 帶 氣 候, 在 使 用 時 可 能 分 解 到 空 氣 中 的 量 會 比 歐 美 高, 故 需 實 際 評 估 後 再 訂 定 而 且 氯 對 地 球 臭 氧 層 的 影 響 也 一 並 考 慮 殘 餘 劑 量, 並 規 範 添 加 後 亞 氯 酸 根 殘 餘 量,ClO 2 ClO ClO 3 定 量 方 法 及 增 加 飲 用 水 水 質 標 準 的 部 份 將 會 建 請 環 保 署 與 環 檢 所 3. 就 我 們 所 收 集 到 的 資 料, 在 20 下 二 氧 化 氯 對 水 的 溶 解 度 約 為 3.0 g/l, 而 25 時 約 為 2.9 g/l 4. 根 據 標 準 方 法 中 的 二 氧 化 氯 分 析 方 法, 二 氧 化 氯 應 可 現 場 檢 測 5. 參 考 各 方 面 的 資 料 與 各 委 員 的 意 見 後, 將 二 氧 化 氯 最 大 添 加 劑 量 訂 為 1.4 mg/l; 最 高 殘 餘 劑 量 訂 為 0.8 mg/l 根 據 會 中 各 委 員 建 議 的 方 向, 公 告 項 目 針 對 氣 態 二 氧 化 氯, 以 避 免 副 產 物 亞 氯 酸 根 與 氯 酸 根, 故 刪 除 原 先 設 定 80% 之 純 度 1. 根 據 會 中 各 委 員 建 議 的 方 向, 公 告 項 目 針 對 氣 態 二 氧 化 氯, 以 去 除 副 產 物 亞 氯 酸 根 與 氯 酸 根 2. 目 前 規 劃 公 告 氣 態 二 氧 化 氯, 以 避 免 不 純 物 的 問 題 3. 該 表 中 提 到 二 氧 化 氯 在 空 氣 中 濃 度 超 過 10% 會 有 爆 炸 的 危 險 ; 而 二 氧 化 氯 添 加 量 超 過 1.4 mg/l 時, 可 能 會 導 致 水 中 二 氧 化 氯 亞 氯 酸 根 與 氯 酸 根 的 總 量 超 過 1.0 mg/l, 故 依 據 此 訂 定 最 大 添 加 量 二 氧 化 氯 在 水 中 很 安 定, 且 水 溶 解 度 相 當 大, 除 非 主 動 曝 氣, 否 則 應 不 會 大 量 逸 散 到 空 氣 中 4. 參 考 世 界 衛 生 組 織 的 報 告 是 針 對 製 造 場 所 進 行 研 究, 應 用 於 給 水 消 毒 時 世 界 衛 生 組 織 則 改 為 規 範 亞 氯 酸 根 濃 度 0.7 mg/l

72 4. 由 WHO CICADs 報 告 得 知 職 業 性 暴 露 到 氣 態 二 氧 化 氯 是 在 製 造 過 程 中 發 生, 且 是 從 吸 入 方 式 進 入 人 體 在 美 國 其 八 小 時 日 時 量 平 均 容 許 濃 度 (TWA) 為 0.1ppm(0.28 mg/m 3 ) 及 15 分 鐘 容 許 濃 度 為 0.3ppm(0.84 mg/m 3 ), 對 呼 吸 到 影 響 其 NOAEL 為 1ppm(2.8mg/m 3 ), 依 毒 性 等 級 言 是 劇 毒 性 由 IPCs 資 料 而 言, 二 氧 化 氯 於 飲 用 水 其 oral tolerable daily intake 為 30μg/kg 由 以 上 資 料 可 知 其 最 大 添 加 劑 量 為 1.4mg/L 是 否 太 高 台 灣 省 自 來 水 公 司 吳 美 惠 經 理 1. 二 氧 化 氯 品 質 管 制 規 範 為 何 只 訂 80 % 以 上? 能 詳 細 敘 述 如 何 計 算, 以 便 採 購 的 依 循 2. 操 作 人 員 使 用 二 氧 化 氯 是 否 和 液 氯 一 樣 要 有 毒 性 化 學 物 質 操 作 人 員 執 照? 3. 二 氧 化 氯 發 生 器 有 沒 有 設 備 規 範 及 安 全 措 施? 台 北 市 自 來 水 事 業 處 1. 二 氧 化 氣 之 產 生 過 程 會 因 反 應 條 件 之 不 同, 致 副 產 物 chlorite 及 chlorate 產 生 過 量 之 狀 況, 而 對 人 體 健 康 產 生 危 害, 故 產 率 (yield) 是 否 應 嚴 格 限 制 ( 例 :95% 以 上 ) 2. 後 端 之 消 毒 副 產 物 以 最 大 添 加 量 規 範 是 否 恰 當, 考 量 原 水 水 質 變 化 狀 況 添 加 目 的 淨 水 流 程 添 加 地 點 及 可 能 之 消 毒 副 產 物 控 制 策 略 ( 如 使 用 活 性 碳 去 除 chlorite), 以 規 範 自 來 水 中 消 毒 副 產 物 chlorite 及 chlorate 之 含 量 較 為 合 理, 且 易 於 管 制 執 行 1. 參 考 各 方 面 的 資 料 與 各 委 員 的 意 見 後, 公 告 項 目 針 對 氣 態 二 氧 化 氯, 以 避 免 副 產 物 亞 氯 酸 根 與 氯 酸 根, 故 刪 除 原 先 設 定 80% 之 純 度 2. 二 氧 化 氯 與 液 氯 都 屬 於 消 毒 劑, 且 都 為 毒 性 物 質, 故 操 作 者 需 具 有 毒 性 化 學 物 質 操 作 人 員 執 照 3. 就 目 前 所 收 集 的 資 料 並 未 對 二 氧 化 氯 產 生 器 進 行 規 範 1. 謝 謝 委 員 的 意 見, 參 考 各 方 面 的 資 料 與 各 委 員 的 意 見 後, 公 告 項 目 針 對 氣 態 二 氧 化 氯, 以 避 免 副 產 物 亞 氯 酸 根 與 氯 酸 根, 故 刪 除 原 先 設 定 80% 之 純 度 2. 參 考 各 方 面 的 資 料 與 各 委 員 的 意 見 後, 公 告 項 目 將 針 對 二 氧 化 氯 之 最 大 添 加 量 最 高 殘 餘 劑 量 與 二 氧 化 氯 添 加 後 亞 氯 酸 根 殘 餘 劑 量 進 行 公 告

73 衛 生 署 食 品 衛 生 處 1. 現 行 食 品 添 加 物 使 用 範 圍 及 限 量 規 定, 已 將 二 氧 化 氯 列 為 准 用 殺 菌 劑, 可 以 使 用 於 飲 用 水 及 食 品 用 水 之 殺 菌 處 理 該 規 定 係 於 82 年 訂 定, 較 為 簡 略 本 次 環 保 署 公 告 相 關 資 料, 可 供 為 本 署 日 後 研 究 相 關 規 定 參 考 1. 希 望 本 報 告 能 作 為 貴 署 之 參 考

74 以 二 氧 化 氯 做 為 飲 用 水 水 質 處 理 藥 劑 之 評 估 期 末 報 告 委 員 意 見 答 覆 委 員 審 查 意 見 ( 一 ) 蔣 本 基 教 授 1. 請 參 考 環 保 署 研 究 報 告 中 研 訂 飲 用 水 水 質 處 理 藥 劑 執 行 作 業 流 程 並 納 入 本 研 究 之 執 行 方 法 2. 將 國 外 資 料 經 驗 彙 整 成 章 節 列 表 表 示 之, 特 別 強 調 USEPA,AWWA 及 NSF 三 單 位 之 互 補 圖 關 係 值 得 國 人 借 鏡 3. 提 出 二 氧 化 氯 化 學 藥 劑 頒 佈 草 案 內 容 及 相 配 套 措 施 或 技 術 規 範 (1) ClO2 - / ClO3 - DBPS( 管 制 值 )(2) 不 純 物 (3) 勞 工 安 全 (4) 檢 驗 分 析 (5) 總 加 藥 量 (MAX. Dose) 4. 瞭 解 國 內 ClO2 製 造 廠 商 之 生 產 技 術 方 法 產 量 及 產 品 之 QA/QC 檢 驗 方 法 不 純 物 及 上 述 勞 安 問 題 5. 建 議 環 保 署 未 來 如 何 監 督 管 理 本 化 學 藥 劑 以 維 持 飲 用 水 安 全 ( 消 毒 效 率 與 DBPS) 意 見 回 覆 1. 已 參 考 環 保 署 研 究 報 告 研 訂 飲 用 水 水 質 處 理 藥 劑 執 行 作 業 流 程, 並 據 以 研 擬 第 二 章 執 行 方 法 中 圖 2-1 之 作 業 流 程 圖 2. 已 將 國 外 相 關 規 範 中 之 限 值 彙 整 成 節 表 3-7, 應 以 供 比 較 與 參 考 至 於 美 國 印 A AWWA 及 NSF 三 單 位 在 訂 定 相 關 建 議 指 南 規 範 與 標 準 之 角 色 扮 演 方 面, 與 國 內 訂 定 規 範 標 準 之 做 法 及 方 式 有 所 差 異, 可 供 環 保 署 未 來 訂 定 相 關 規 範 與 標 準 之 參 卓 3. 對 于 公 告 內 容 所 須 之 最 大 加 藥 量, - 已 納 入 草 案 中 ; 消 毒 副 產 物 ClO 2 與 - ClO 3 之 管 制 值, 建 議 依 循 美 國 的 標 準, 納 入 增 列 之 飲 用 水 水 質 標 準 中 ; 因 公 告 草 案 建 議 二 氧 化 氯 須 以 氣 態 型 式 添 加, 因 此 不 會 有 不 純 物 之 相 關 規 定 ; 檢 驗 分 析 部 份 亦 建 議 由 環 保 署 增 列 美 國 之 標 準 檢 驗 方 法 ( 以 上 內 容 均 已 納 入 3.5 節 公 告 建 議 及 4.1 節 結 論 中 ) 至 於 勞 工 安 全 部 份, 依 據 諮 商 會 議 中 環 保 署 與 專 家 學 者 之 共 識, 宜 由 未 來 使 用 單 位 ( 自 來 水 公 司 ) 自 行 訂 定 相 關 之 操 作 規 範, 本 研 究 亦 提 供 美 國 環 保 署 提 出 之 指 南 手 冊 等 技 術 內 容 供 參 考 ( 詳 附 錄 十 二 ) 4. 限 于 經 費 及 執 行 內 容 之 範 疇, 本 研 究 僅 對 市 售 真 實 商 品 三 件 進 行 二 氧 化 氯 純 度 及 其 不 純 物 之 檢 測 分 析 方

75 ( 二 ) 曾 四 恭 教 授 1. 本 報 告 依 各 種 文 獻 資 料 之 分 析 結 果, 建 議 二 氧 化 氯 應 用 在 飲 用 水 的 公 告 規 範 為 :(1)ClO2 之 使 用 限 於 氣 態 ClO2 (2) 最 大 添 加 劑 量 為 1.4 mg/l (3) 最 高 殘 餘 濃 度 限 值 0.8 mg/l (4) 添 加 後 亞 氯 酸 根 濃 度 限 值 1.0 mg/l 原 則 上 贊 成 此 項 規 範 建 議 再 補 充 說 明 這 些 規 範 之 依 據 ( 分 項 說 明 ) 2. 最 大 ClO2 添 加 量, 加 入 水 中 後 之 ClO2 殘 餘 溶 液 及 亞 氯 酸 根 之 質 量 平 衡, 請 再 說 明 以 了 解 規 範 中 ClO2 與 副 產 物 間 濃 度 之 合 理 性 法 加 以 評 估, 至 于 ClO2 製 造 上 之 生 產 技 術 方 法 產 量 及 產 品 之 QA/QC 等, 僅 進 行 相 關 文 獻 收 集 (3.1.2 節 與 節 附 錄 九 附 錄 十 一 附 錄 十 二 附 錄 十 三 ) 以 供 參 考 5. 對 于 未 來 ClO 2 成 會 公 告 之 飲 用 水 水 質 處 理 藥 劑 後, 環 保 署 將 針 對 處 理 後 之 清 水 進 行 檢 測, 以 確 定 是 否 符 合 建 議 增 列 之 ClO2 與 - ClO2 最 大 殘 留 限 值 飲 用 水 水 質 標 準 ( 如 4.1 節 結 論 所 述 ); 至 於 ClO 2 最 大 添 加 劑 量 之 管 制 方 面, 雖 有 公 告 草 案 中 所 列 之 規 範, 惟 查 核 不 易, 須 由 使 用 單 位 ( 自 來 水 公 司 ) 自 行 依 此 加 以 管 控, 必 要 時, 可 採 申 報 方 式 做 為 環 保 署 監 督 管 理 的 方 式 之 一 ( 如 4.2 節 建 議 中 所 述 ) 1. 已 依 委 員 意 見 修 正 公 告 草 案 之 內 容, 並 將 規 範 依 據 在 3.5 節 公 告 建 議 及 4.1 結 論 中 加 以 說 明 - 2. ClO 2 與 ClO 2 之 分 子 量 均 為 g/mole, 而 ClO 3 之 分 子 量 為 83.5g/mole, 對 于 ClO2 最 大 添 加 劑 量 不 超 過 1.4mg/L( 可 換 算 為 2.074*10-5 M), 依 質 量 平 衡, 最 多 可 分 別 產 生 1.4mg/L 1.4mg/L 1.73mg/L 之 ClO 2 ClO - 2 ClO - 3 ( 均 為 2.074*10-5 M); 惟 所 添 加 之 ClO 2 在 消 毒 反 應 中 會 產 生 各 種 可 能 的 化 學 反 應, 其 產 物 亦 可 能 包 括 殘 留 之 ClO 2 及 ClO - 2 ClO3 - Cl - 及 其 他 的 含 氯 物 種 美 國 環 保 署 在 考 量 個 別 物 種 的 安 全 殘 留 量, 分 別 訂 定 ClO 2 - 與 ClO 2 的 最 大 殘 留 限 值 為 0.8mg/L( 可 換 算 為 1.185*10-5 M) 及 1.0 mg/l( 可 換 算 為 1.48*10-5 M), 因

76 ( 三 ) 張 怡 怡 教 授 1. 確 認 市 售 液 態 ClO2 及 前 驅 物 藥 劑 品 質 相 關 分 析 數 據 (P.3-29 以 後 缺 ) 之 品 保 / 品 管 措 施 及 成 效 2. 建 議 對 工 作 內 容 2(3.4.2 節 ) 能 補 充 ClO2 不 純 物 的 發 生 濃 度 計 算 說 明 ( 如 : 高 鹼 度 反 映 時 間 影 響 ClO2 -,ClO3 - 及 自 解 現 象 ) 3. 公 告 氣 態 二 氧 化 氯 草 案 中 (1) 最 大 殘 餘 量 應 在 飲 用 水 水 值 標 準 中 規 範 (2) 亞 氯 酸 根 在 氣 態 中 ClO2 同 時 產 生, 則 在 藥 劑 中 不 純 物 含 量 規 範 ; 若 在 加 入 水 中 後 受 ph 反 應 時 間 水 質 影 響, 而 在 水 中 生 成, 則 在 飲 用 水 水 質 標 準 中 規 範 宜 在 報 告 中 詳 加 說 明 討 論 ClO2 4. 國 外 淨 水 場 使 用 情 形 是 否 可 以 補 充 文 獻, 略 做 說 明 5. 建 議 環 保 署 規 範 場 所 使 用 非 氯 消 毒 劑, 應 申 報 並 提 供 藥 劑 添 加 濃 度 使 用 記 錄 ( 四 ) 黃 志 彬 教 授 1. 二 氧 化 氯 是 否 可 有 效 去 除 有 機 物, 可 在 報 告 中 清 楚 表 達, 因 為 在 P.3-15 第 四 段 載 明 ClO2 不 易 分 解 有 兩 種 物 種 的 殘 留 量 會 呈 現 彼 此 消 長 的 互 動 關 係, 因 此 兩 者 的 最 大 殘 留 限 值 濃 度 和 與 ClO 2 最 大 添 加 劑 量 濃 度 間 不 會 呈 現 質 量 平 衡 的 關 係 1. P.3-29 以 後 所 缺 之 部 份 內 容 已 補 正 ; 對 市 售 商 品 之 成 份 分 析 均 依 據 環 保 署 公 告 方 法 或 參 考 美 國 之 標 準 檢 驗 方 法, 詳 如 節 中 及 表 3-8 所 示 2. 有 關 不 純 物 發 生 濃 度 與 ClO 2 添 加 濃 度 之 相 關 性, 同 曾 四 恭 教 授 意 見 2 答 覆 說 明 3. 已 依 委 員 意 見 修 正 公 告 草 案 內 容, - ClO 2 與 ClO 2 最 大 殘 留 限 值 已 建 議 納 入 增 列 之 飲 用 水 水 質 標 準 中, 檢 測 點 則 建 議 設 定 為 處 理 後 之 清 水 水 質, 對 反 應 時 間 及 其 他 水 質 參 數 ( 如 PH 值 ) 影 響 即 無 需 再 加 以 界 定 ( 詳 3.5 節 ) 4. 本 計 畫 主 要 係 針 對 國 外 機 關 規 範 與 標 準 進 行 資 料 收 集 與 彙 整, 以 協 助 研 擬 公 告 草 案 內 容, 國 外 淨 水 場 實 際 使 用 ClO 2 之 相 關 數 據, 因 無 法 收 集 到 較 完 整 並 具 代 表 性 之 統 計 數 據, 故 未 在 報 告 中 進 行 陳 述 ; 惟 根 據 美 國 環 保 署 1998 年 的 資 料 顯 示, 以 二 氧 化 氯 做 為 消 毒 劑 之 淨 水 場,ClO 2 添 加 劑 量 大 多 分 怖 于 ~2mg/L, 殘 留 之 ClO 2 與 ClO 3 - 平 均 為 0.24 與 0.2mg/L 5. 已 納 入 4.2 節 建 議 中, 可 供 環 保 署 參 考 1. 已 修 正 3.2 節 之 內 容, 以 避 免 前 後 文 字 上 的 差 異 引 起 誤 解 2. 因 ClO 2 最 大 添 加 劑 量 1.4mg/L 是 依

77 機 物 C-C 鍵, 因 此 礦 化 不 明 顯, 而 在 P.3-18 載 明 結 合 加 氯 程 序 可 增 加 有 機 物 的 去 除 可 能 會 引 起 誤 解, 請 作 可 能 之 調 整 2. 請 討 論 高 濃 度 氣 態 ClO2 注 入 少 量 水 中 ( 自 來 水 ) 是 否 會 產 生 較 高 濃 度 副 產 物 或 其 他 副 產 物? 並 可 收 集 相 關 文 獻 提 供 相 關 訊 息 3. 建 議 在 報 告 適 當 章 節 提 供 使 用 氣 態 ClO2 之 相 關 工 安 注 意 事 項 4. 公 告 方 法 中 註 明 最 大 添 加 劑 量 1.4 mg/l, 在 執 行 上 可 能 會 有 問 題, 除 了 現 場 操 控 不 易 外, 亦 不 易 由 內 部 / 外 部 管 控, 其 中 最 大 環 節 在 於 水 廠 進 注 量 是 可 變 的 ( 五 ) 林 財 富 教 授 1. 本 計 畫 資 料 收 集 豐 富, 在 少 量 經 費 下 及 短 時 間 內 完 成, 值 得 參 考 2. 建 議 補 充 執 行 市 售 樣 品 分 析 時, 檢 驗 項 目 之 背 景 參 考 方 法 比 較 標 準 ( 如 不 純 物 與 其 他 藥 劑 之 比 較 ) 來 源 3. 建 議 能 補 充 說 明 目 前 使 用 二 氧 化 氯 的 國 外 水 廠, 其 亞 氯 酸 鹽 氯 酸 鹽 的 濃 度 範 圍 4. P.3-23 倒 數 第 二 行 Giardia cysts 應 拆 成 二 字 5. 二 氧 化 氯 如 擬 在 水 廠 以 氣 態 先 行 溶 解 再 稀 釋 的 方 式, 進 行 加 藥, 此 時 濃 度 會 很 高, 若 在 密 閉 空 間 中 有 無 造 成 空 氣 中 濃 度 上 升 之 疑 慮? 建 議 提 供 二 氧 化 氯 的 亨 利 定 律 常 數, 以 供 後 續 估 算 的 依 據 ( 六 ) 彭 福 佐 副 教 授 1. 製 造 二 氧 化 氯 較 符 合 自 來 水 公 司 成 本 效 應 2. 用 氣 態 方 式 產 生 氣 態 二 氧 化 氯 時 會 據 處 理 水 量 來 換 算 出 添 加 劑 量, 以 符 合 此 一 上 限 值 規 範, 故 在 正 常 操 作 狀 況 下, 應 不 致 于 發 生 處 理 水 中 呈 現 過 高 濃 度 ClO 2 的 情 形 ; 惟 若 氣 態 ClO 2 是 以 高 濃 度 先 注 入 少 量 水 中 以 促 使 溶 解 吸 收, 再 以 稀 釋 方 式 加 入 處 理 水 中, 則 可 能 發 生 高 濃 度 副 產 物 的 生 成 機 會, 此 一 部 份 已 建 議 在 一 飲 用 水 水 質 標 準 中 增 列 ClO 2 及 - ClO 2 最 大 殘 留 容 許 濃 度 來 加 以 規 範 ( 詳 3.5 節 ) 3. 有 關 氣 態 ClO 2 之 相 關 工 安 問 題, 同 蔣 本 基 教 授 意 見 3 之 答 覆 說 明 4. 同 上 述 意 見 2 之 答 覆 說 明 1. 謝 謝 委 員 的 肯 定 2. 已 於 節 與 節 中 補 充 說 明 3. 同 張 怡 怡 教 授 意 見 4 之 答 覆 說 明 4. 已 依 委 員 意 見 修 正 5. 同 黃 志 彬 委 員 意 見 2 之 答 覆 說 明 ; 另 補 充 二 氧 化 氯 之 享 利 常 數 於 節 中, 以 提 供 後 續 估 算 上 的 依 據 1. 受 限 于 本 研 究 之 經 費 與 研 究 內 容 範 疇, 未 對 二 氧 化 氯 生 產 製 造 方 式 進 行 經 濟 分 析 與 評 估 ; 惟 各 種 二 氧 化

78 產 生 氯 氣 故 不 純 物 須 列 出 3. 公 告 草 案 請 依 環 保 署 公 告 方 式 撰 寫 4. 美 國 考 量 現 場 產 生 二 氧 化 氯 時 會 產 生 爆 炸 請 於 報 告 中 略 述 5. 參 考 文 獻 請 統 一 撰 寫 6. 二 氧 化 氯 屬 劇 毒 物 質 在 實 際 操 作 時 需 考 慮 工 安 問 題 也 請 於 報 告 中 述 說 氯 之 產 製 型 態 己 彙 整 于 表 3-2, 可 供 後 續 經 濟 評 估 之 參 考 2. 同 蔣 本 基 教 授 意 見 3 之 答 覆 說 明 3. 已 依 委 員 意 見, 研 擬 建 議 公 告 草 案 內 容 ( 詳 附 錄 一 ) 4. 已 納 入 3.3 節 之 內 容 中 5. 已 依 委 員 意 見 修 正 為 統 一 之 格 式 6. 同 蔣 本 基 教 授 意 見 3 之 答 覆 說 明

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91 行 年 行 令 行 年 行 六 令 行 年 令 六 理 例 例 例 落 數 六 六 濾 落 數 理 度 數 度 度 1

92 行 行 年 行 年 行 殺 靈 丹 拉 拉 利 拉 靈 2

93 硫 類 離 度 量 ~ 離 度 數 連 理 不 離 度 數 六 ~ 來 易 來 暴 度 度 列 度 度 度 度 度 數 來 易 來 理 理 理 度 理 來 易 來 暴 度 列 ~ 六 理 理 行 行 3

94 National Primary Drinking Water Standards OC OC R IOC IOC IOC OC IOC OC OC IOC R DBP IOC OC OC D MCL or TT1 Potential health effects from Common sources of Contaminant (mg/l)2 exposure above the MCL contaminant in drinking water Acrylamide TT8 Nervous system or blood problems; Added to water during sewage/wastewater increased risk of cancer treatment Alachlor Eye, liver, kidney or spleen problems; Runoff from herbicide used on Alpha particles 15 picocuries per Liter (pci/l) anemia; increased risk of cancer Increased risk of cancer Antimony Increase in blood cholesterol; decrease in blood sugar Arsenic Asbestos (fibers >10 micrometers) as of 1/23/06 7 million fibers per Liter (MFL) Skin damage or problems with circulatory systems, and may have increased risk of getting cancer Increased risk of developing benign intestinal polyps row crops Erosion of natural deposits of certain minerals that are radioactive and may emit a form of radiation known as alpha radiation Discharge from petroleum refineries; fire retardants; ceramics; electronics; solder Erosion of natural deposits; runoff from orchards, runoff from glass & electronics production wastes Decay of asbestos cement in water mains; erosion of natural deposits Atrazine Cardiovascular system or reproductive problems Runoff from herbicide used on row crops Barium 2 Increase in blood pressure Discharge of drilling wastes; discharge from metal refineries; erosion of natural deposits Benzene Anemia; decrease in blood platelets; increased risk of cancer Benzo(a)pyrene (PAHs) Reproductive difficulties; increased risk of cancer Discharge from factories; leaching from gas storage tanks and landfills Leaching from linings of water storage tanks and distribution lines Beryllium Intestinal lesions Discharge from metal refineries and coal-burning factories; discharge from electrical, aerospace, and defense industries Beta particles and photon emitters 4 millirems per year Increased risk of cancer Decay of natural and man-made deposits of certain minerals that are radioactive and may emit forms of radiation known as photons and beta radiation Bromate Increased risk of cancer Byproduct of drinking water disinfection Cadmium Kidney damage Corrosion of galvanized pipes; erosion of natural deposits; discharge from metal refineries; runoff from waste batteries and paints Carbofuran 0.04 Problems with blood, nervous system, or reproductive system Leaching of soil fumigant used on rice and alfalfa Carbon tetrachloride Liver problems; increased risk of cancer Discharge from chemical plants and other industrial activities Chloramines (as Cl2) MRDL=4.01 Eye/nose irritation; stomach discomfort, Water additive used to control anemia microbes Public Health Goal zero zero zero MFL zero zero zero zero zero MRDLG=41 LEGEND D Dinsinfectant IOC Inorganic Chemical OC Organic Chemical DBP Disinfection Byproduct M Microorganism R Radionuclides 1

95 OC D D DBP OC IOC IOC M IOC OC OC OC OC OC OC OC OC OC OC OC OC OC OC OC Contaminant MCL or TT1 Potential health effects from Common sources of (mg/l)2 exposure above the MCL contaminant in drinking water Chlordane Liver or nervous system problems; increased Residue of banned termiticide risk of cancer Chlorine (as Cl2) MRDL=4.01 Eye/nose irritation; stomach discomfort Water additive used to control microbes Chlorine dioxide (as ClO2) MRDL=0.81 Anemia; infants & young children: nervous Water additive used to control system effects microbes Chlorite 1.0 Anemia; infants & young children: nervous Byproduct of drinking water system effects disinfection Chlorobenzene 0.1 Liver or kidney problems Discharge from chemical and agricultural chemical factories Chromium (total) 0.1 Allergic dermatitis Discharge from steel and pulp mills; erosion of natural deposits Copper TT7; Short term exposure: Gastrointestinal Corrosion of household plumbing Action distress. Long term exposure: Liver or kidney systems; erosion of natural Level = damage. People with Wilson s Disease deposits 1.3 should consult their personal doctor if the amount of copper in their water exceeds the action level Cryptosporidium TT3 Gastrointestinal illness (e.g., diarrhea, Human and animal fecal waste vomiting, cramps) Cyanide (as free cyanide) 0.2 Nerve damage or thyroid problems Discharge from steel/metal factories; discharge from plastic and fertilizer factories 2,4-D 0.07 Kidney, liver, or adrenal gland problems Runoff from herbicide used on row crops Dalapon 0.2 Minor kidney changes Runoff from herbicide used on 1,2-Dibromo-3-chloropropa ne (DBCP) Reproductive difficulties; increased risk of cancer rights of way Runoff/leaching from soil fumigant used on soybeans, cotton, pineapples, and orchards o-dichlorobenzene 0.6 Liver, kidney, or circulatory system problems Discharge from industrial chemical factories p-dichlorobenzene Anemia; liver, kidney or spleen damage; Discharge from industrial changes in blood chemical factories 1,2-Dichloroethane Increased risk of cancer Discharge from industrial chemical factories 1,1-Dichloroethylene Liver problems Discharge from industrial chemical factories cis-1,2-dichloroethylene 0.07 Liver problems Discharge from industrial chemical factories trans-1,2-dichloroethylene 0.1 Liver problems Discharge from industrial chemical factories Dichloromethane Liver problems; increased risk of cancer Discharge from drug and chemical factories 1,2-Dichloropropane Increased risk of cancer Discharge from industrial chemical factories Di(2-ethylhexyl) adipate 0.4 Weight loss, live problems, or possible Discharge from chemical reproductive difficulties factories Di(2-ethylhexyl) phthalate Reproductive difficulties; liver problems; Discharge from rubber and increased risk of cancer chemical factories Dinoseb Reproductive difficulties Runoff from herbicide used on soybeans and vegetables Dioxin (2,3,7,8-TCDD) Reproductive difficulties; increased risk of cancer Emissions from waste incineration and other combustion; discharge from chemical factories Public Health Goal zero MRDLG=41 MRDLG=0.81 OC Diquat 0.02 Cataracts Runoff from herbicide use 0.02 OC Endothall 0.1 Stomach and intestinal problems Runoff from herbicide use 0.1 LEGEND zero zero zero zero zero 0.4 zero zero D Dinsinfectant IOC Inorganic Chemical OC Organic Chemical DBP Disinfection Byproduct M Microorganism R Radionuclides 2

96 Contaminant MCL or TT1 Potential health effects from Common sources of Public (mg/l)2 exposure above the MCL contaminant in drinking water Health Goal OC Endrin Liver problems Residue of banned insecticide Epichlorohydrin TT8 Increased cancer risk, and over a long period Discharge from industrial zero OC of time, stomach problems chemical factories; an impurity of some water treatment chemicals OC Ethylbenzene 0.7 Liver or kidneys problems Discharge from petroleum 0.7 refineries OC Ethylene dibromide Problems with liver, stomach, reproductive Discharge from petroleum zero system, or kidneys; increased risk of cancer refineries Fluoride 4.0 Bone disease (pain and tenderness of the Water additive which promotes 4.0 IOC bones); Children may get mottled teeth strong teeth; erosion of natural deposits; discharge from fertilizer and aluminum factories M Giardia lamblia TT3 Gastrointestinal illness (e.g., diarrhea, Human and animal fecal waste zero vomiting, cramps) OC Glyphosate 0.7 Kidney problems; reproductive difficulties Runoff from herbicide use 0.7 DBP Haloacetic acids (HAA5) Increased risk of cancer Byproduct of drinking water disinfection n/a6 OC Heptachlor Liver damage; increased risk of cancer Residue of banned termiticide zero OC Heptachlor epoxide Liver damage; increased risk of cancer Breakdown of heptachlor zero Heterotrophic plate count TT3 n/a (HPC) M OC OC IOC M OC IOC OC IOC IOC HPC has no health effects; it is an analytic method used to measure the variety of bacteria that are common in water. The lower the concentration of bacteria in drinking water, the better maintained the water system is. Hexachlorobenzene Liver or kidney problems; reproductive difficulties; increased risk of cancer Hexachlorocyclopentadien e Lead HPC measures a range of bacteria that are naturally present in the environment Discharge from metal refineries and agricultural chemical factories 0.05 Kidney or stomach problems Discharge from chemical factories TT7; Infants and children: Delays in physical or Action mental development; children could show Level = slight deficits in attention span and learning abilities; Adults: Kidney problems; high blood Corrosion of household plumbing systems; erosion of natural deposits pressure Legionella TT3 Legionnaire s Disease, a type of pneumonia Found naturally in water; multiplies in heating systems Lindane Liver or kidney problems Runoff/leaching from insecticide used on cattle, lumber, gardens Mercury (inorganic) Kidney damage Erosion of natural deposits; discharge from refineries and factories; runoff from landfills and croplands Methoxychlor 0.04 Reproductive difficulties Runoff/leaching from insecticide used on fruits, vegetables, alfalfa, livestock Nitrate (measured as Nitrogen) Nitrite (measured as Nitrogen) 10 Infants below the age of six months who drink water containing nitrate in excess of the MCL could become seriously ill and, if untreated, may die. Symptoms include shortness of breath and blue-baby syndrome. 1 Infants below the age of six months who drink water containing nitrite in excess of the MCL could become seriously ill and, if untreated, may die. Symptoms include shortness of breath and blue-baby syndrome. Runoff from fertilizer use; leaching from septic tanks, sewage; erosion of natural deposits Runoff from fertilizer use; leaching from septic tanks, sewage; erosion of natural deposits zero 0.05 zero zero LEGEND D Dinsinfectant IOC Inorganic Chemical OC Organic Chemical DBP Disinfection Byproduct M Microorganism R Radionuclides 3

97 OC OC OC Contaminant MCL or TT1 Potential health effects from Common sources of (mg/l)2 exposure above the MCL contaminant in drinking water Oxamyl (Vydate) 0.2 Slight nervous system effects Runoff/leaching from insecticide used on apples, potatoes, and tomatoes Pentachlorophenol Liver or kidney problems; increased cancer Discharge from wood preserving risk factories Public Health Goal 0.2 OC Picloram 0.5 Liver problems Herbicide runoff 0.5 Polychlorinated biphenyls Runoff from landfills; discharge of zero (PCBs) waste chemicals R IOC M Skin changes; thymus gland problems; immune deficiencies; reproductive or nervous system difficulties; increased risk of cancer Radium 226 and Radium 228 (combined) Selenium 0.05 Hair or fingernail loss; numbness in fingers or toes; circulatory problems 5 pci/l Increased risk of cancer Erosion of natural deposits zero Discharge from petroleum refineries; erosion of natural deposits; discharge from mines OC Simazine Problems with blood Herbicide runoff OC Styrene 0.1 Liver, kidney, or circulatory system problems Discharge from rubber and plastic 0.1 factories; leaching from landfills OC Tetrachloroethylene Liver problems; increased risk of cancer Discharge from factories and dry zero cleaners Thallium Hair loss; changes in blood; kidney, intestine, Leaching from ore-processing IOC or liver problems sites; discharge from electronics, glass, and drug factories OC Toluene 1 Nervous system, kidney, or liver problems Discharge from petroleum 1 factories Total Coliforms (including zero fecal coliform and E. coli) DBP Total Trihalomethanes (TTHMs) 5.0%4 Not a health threat in itself; it is used to indicate whether other potentially harmful bacteria may be present after 12/31/03 Liver, kidney or central nervous system problems; increased risk of cancer Coliforms are naturally present in the environment as well as feces; fecal coliforms and E. coli only come from human and animal fecal waste. Byproduct of drinking water disinfection OC Toxaphene Kidney, liver, or thyroid problems; increased Runoff/leaching from insecticide zero risk of cancer used on cotton and cattle OC 2,4,5-TP (Silvex) 0.05 Liver problems Residue of banned herbicide 0.05 OC 1,2,4-Trichlorobenzene 0.07 Changes in adrenal glands Discharge from textile finishing 0.07 factories OC 1,1,1-Trichloroethane 0.2 Liver, nervous system, or circulatory Discharge from metal degreasing 0.20 problems sites and other factories OC 1,1,2-Trichloroethane Liver, kidney, or immune system problems Discharge from industrial chemical factories OC Trichloroethylene Liver problems; increased risk of cancer Discharge from metal degreasing zero sites and other factories Turbidity TT3 Turbidity is a measure of the cloudiness of Soil runoff n/a water. It is used to indicate water quality and filtration effectiveness (e.g., whether disease-causing organisms are present). M Higher turbidity levels are often associated with higher levels of disease-causing micro-organisms such as viruses, parasites and some bacteria. These organisms can cause symptoms such as nausea, cramps, diarrhea, and associated headaches. R LEGEND Uranium 30 ug/l as of 12/08/03 Increased risk of cancer, kidney toxicity Erosion of natural deposits zero zero 0.05 n/a6 D Dinsinfectant IOC Inorganic Chemical OC Organic Chemical DBP Disinfection Byproduct M Microorganism R Radionuclides 4

98 OC M OC Contaminant MCL or TT1 Potential health effects from Common sources of (mg/l)2 exposure above the MCL contaminant in drinking water Vinyl chloride Increased risk of cancer Leaching from PVC pipes; discharge from plastic factories Viruses (enteric) TT3 Gastrointestinal illness (e.g., diarrhea, Human and animal fecal waste vomiting, cramps) Xylenes (total) 10 Nervous system damage Discharge from petroleum factories; discharge from chemical factories Public Health Goal zero zero 10 NOTES 1 Definitions Maximum Contaminant Level Goal (MCLG) The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety and are non-enforceable public health goals. Maximum Contaminant Level (MCL) The highest level of a contaminant that is allowed in drinking water. MCLs are set as close to MCLGs as feasible using the best available treatment technology and taking cost into consideration. MCLs are enforceable standards. Maximum Residual Disinfectant Level Goal (MRDLG) The level of a drinking water disinfectant below which there is no known or expected risk to health. MRDLGs do not reflect the benefits of the use of disinfectants to control microbial contaminants. Maximum Residual Disinfectant Level (MRDL) The highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial contaminants. Treatment Technique (TT) A required process intended to reduce the level of a contaminant in drinking water. 2 Units are in milligrams per liter (mg/l) unless otherwise noted. Milligrams per liter are equivalent to parts per million (ppm). 3 EPA s surface water treatment rules require systems using surface water or ground water under the direct influence of surface water to (1) disinfect their water, and (2) filter their water or meet criteria for avoiding filtration so that the following contaminants are controlled at the following levels: Cryptosporidium (as of 1/1/02 for systems serving >10,000 and 1/14/05 for systems serving <10,000) 99% removal. Giardia lamblia: 99.9% removal/inactivation Viruses: 99.99% removal/inactivation Legionella: No limit, but EPA believes that if Giardia and viruses are removed/inactivated, Legionella will also be controlled. Turbidity: At no time can turbidity (cloudiness of water) go above 5 nephelolometric turbidity units (NTU); systems that filter must ensure that the turbidity go no higher than 1 NTU (0.5 NTU for conventional or direct filtration) in at least 95% of the daily samples in any month. As of January 1, 2002, for systems servicing >10,000, and January 14, 2005, for systems servicing <10,000, turbidity may never exceed 1 NTU, and must not exceed 0.3 NTU in 95% of daily samples in any month. HPC: No more than 500 bacterial colonies per milliliter Long Term 1 Enhanced Surface Water Treatment (Effective Date: January 14, 2005); Surface water systems or (GWUDI) systems serving fewer than 10,000 people must comply with the applicable Long Term 1 Enhanced Surface Water Treatment Rule provisions (e.g. turbidity standards, individual filter monitoring, Cryptosporidium removal requirements, updated watershed control requirements for unfiltered systems). Filter Backwash Recycling: The Filter Backwash Recycling Rule requires systems that recycle to return specific recycle flows through all processes of the system s existing conventional or direct filtration system or at an alternate location approved by the state. 4 No more than 5.0% samples total coliform-positive in a month. (For water systems that collect fewer than 40 routine samples per month, no more than one sample can be total coliform-positive per month.) Every sample that has total coliform must be analyzed for either fecal coliforms or E. coli if two consecutive TC-positive samples, and one is also positive for E. coli fecal coliforms, system has an acute MCL violation. 5 Fecal coliform and E. coli are bacteria whose presence indicates that the water may be contaminated with human or animal wastes. Disease-causing microbes (pathogens) in these wastes can cause diarrhea, cramps, nausea, headaches, or other symptoms. These pathogens may pose a special health risk for infants, young children, and people with severely compromised immune systems. 6 Although there is no collective MCLG for this contaminant group, there are individual MCLGs for some of the individual contaminants: Haloacetic acids: dichloroacetic acid (zero); trichloroacetic acid (0.3 mg/l) Trihalomethanes: bromodichloromethane (zero); bromoform (zero); dibromochloromethane (0.06 mg/l) 7 Lead and copper are regulated by a Treatment Technique that requires systems to control the corrosiveness of their water. If more than 10% of tap water samples exceed the action level, water systems must take additional steps. For copper, the action level is 1.3 mg/l, and for lead is mg/l. 8 Each water system must certify, in writing, to the state (using third-party or manufacturers certification) that when it uses acrylamide and/or epichlorohydrin to treat water, the combination (or product) of dose and monomer level does not exceed the levels specified, as follows: Acrylamide = 0.05% dosed at 1 mg/l (or equivalent); Epichlorohydrin = 0.01% dosed at 20 mg/l (or equivalent). LEGEND D Dinsinfectant IOC Inorganic Chemical OC Organic Chemical DBP Disinfection Byproduct M Microorganism R Radionuclides 5

99 National Secondary Drinking Water Standards National Secondary Drinking Water Standards are non-enforceable guidelines regulating contaminants that may cause cosmetic effects (such as skin or tooth discoloration) or aesthetic effects (such as taste, odor, or color) in drinking water. EPA recommends secondary standards to water systems but does not require systems to comply. However, states may choose to adopt them as enforceable standards. Aluminum Chloride Color Copper Corrosivity Fluoride Foaming Agents Iron Manganese Odor Contaminant 0.05 to 0.2 mg/l 250 mg/l 15 (color units) 1.0 mg/l noncorrosive 2.0 mg/l 0.5 mg/l 0.3 mg/l 0.05 mg/l ph Silver Sulfate Total Dissolved Solids Zinc 3 threshold odor number 0.10 mg/l 250 mg/l 500 mg/l 5 mg/l Secondary Standard Office of Water (4606M) EPA 816-F June

100 ANNEX 4 Chemical summary tables Table A4.1 Chemicals excluded from guideline value derivation Chemical Reason for exclusion Amitraz Degrades rapidly in the environment and is not expected to occur at measurable concentrations in drinking-water supplies Beryllium Unlikely to occur in drinking-water Chlorobenzilate Unlikely to occur in drinking-water Chlorothalonil Unlikely to occur in drinking-water Cypermethrin Unlikely to occur in drinking-water Diazinon Unlikely to occur in drinking-water Dinoseb Unlikely to occur in drinking-water Ethylene thiourea Unlikely to occur in drinking-water Fenamiphos Unlikely to occur in drinking-water Formothion Unlikely to occur in drinking-water Hexachlorocyclohexanes Unlikely to occur in drinking-water (mixed isomers) MCPB Unlikely to occur in drinking-water Methamidophos Unlikely to occur in drinking-water Methomyl Unlikely to occur in drinking-water Mirex Unlikely to occur in drinking-water Monocrotophos Has been withdrawn from use in many countries and is unlikely to occur in drinking-water Oxamyl Unlikely to occur in drinking-water Phorate Unlikely to occur in drinking-water Propoxur Unlikely to occur in drinking-water Pyridate Not persistent and only rarely found in drinking-water Quintozene Unlikely to occur in drinking-water Toxaphene Unlikely to occur in drinking-water Triazophos Unlikely to occur in drinking-water Tributyltin oxide Unlikely to occur in drinking-water Trichlorfon Unlikely to occur in drinking-water 488

101 ANNEX 4. CHEMICAL SUMMARY TABLES Table A4.2 Chemicals for which guideline values have not been established Chemical Reason for not establishing a guideline value Aluminium Owing to limitations in the animal data as a model for humans and the uncertainty surrounding the human data, a health-based guideline value cannot be derived; however, practicable levels based on optimization of the coagulation process in drinking-water plants using aluminium-based coagulants are derived: 0.1 mg/litre or less in large water treatment facilities, and 0.2 mg/litre or less in small facilities Ammonia Occurs in drinking-water at concentrations well below those at which toxic effects may occur Asbestos No consistent evidence that ingested asbestos is hazardous to health Bentazone Occurs in drinking-water at concentrations well below those at which toxic effects may occur Bromochloroacetate Available data inadequate to permit derivation of health-based guideline value Bromochloroacetonitrile Available data inadequate to permit derivation of health-based guideline value Chloride Not of health concern at levels found in drinking-water a Chlorine dioxide Guideline value not established because of the rapid breakdown of chlorine dioxide and because the chlorite provisional guideline value is adequately protective for potential toxicity from chlorine dioxide Chloroacetones Available data inadequate to permit derivation of health-based guideline values for any of the chloroacetones Chlorophenol, 2- Available data inadequate to permit derivation of health-based guideline value Chloropicrin Available data inadequate to permit derivation of health-based guideline value Dialkyltins Available data inadequate to permit derivation of health-based guideline values for any of the dialkyltins Dibromoacetate Available data inadequate to permit derivation of health-based guideline value Dichloramine Available data inadequate to permit derivation of health-based guideline value Dichlorobenzene, 1,3- Toxicological data are insufficient to permit derivation of health-based guideline value Dichloroethane, 1,1- Very limited database on toxicity and carcinogenicity Dichlorophenol, 2,4- Available data inadequate to permit derivation of health-based guideline value Dichloropropane, 1,3- Data insufficient to permit derivation of health-based guideline value Di(2-ethylhexyl)adipate Occurs in drinking-water at concentrations well below those at which toxic effects may occur Diquat Rarely found in drinking-water, but may be used as an aquatic herbicide for the control of free-floating and submerged aquatic weeds in ponds, lakes and irrigation ditches Endosulfan Occurs in drinking-water at concentrations well below those at which toxic effects may occur Fenitrothion Occurs in drinking-water at concentrations well below those at which toxic effects may occur Fluoranthene Occurs in drinking-water at concentrations well below those at which toxic effects may occur Glyphosate and AMPA Occurs in drinking-water at concentrations well below those at which toxic effects may occur Hardness Not of health concern at levels found in drinking-water a Heptachlor and Occurs in drinking-water at concentrations well below those at which heptachlor epoxide toxic effects may occur continued 489

102 GUIDELINES FOR DRINKING-WATER QUALITY Table A4.2 Continued Chemical Hexachlorobenzene Hydrogen sulfide Inorganic tin Iodine Iron Malathion Methyl parathion Monobromoacetate Monochlorobenzene MX Parathion Permethrin ph Phenylphenol, 2- and its sodium salt Propanil Silver Sodium Sulfate Total dissolved solids (TDS) Trichloramine Trichloroacetonitrile Trichlorobenzenes (total) Trichloroethane, 1,1,1- Zinc Reason for not establishing a guideline value Occurs in drinking-water at concentrations well below those at which toxic effects may occur Not of health concern at levels found in drinking-water a Occurs in drinking-water at concentrations well below those at which toxic effects may occur Available data inadequate to permit derivation of health-based guideline value, and lifetime exposure to iodine through water disinfection is unlikely Not of health concern at concentrations normally observed in drinking-water, and taste and appearance of water are affected below the health-based value Occurs in drinking-water at concentrations well below those at which toxic effects may occur Occurs in drinking-water at concentrations well below those at which toxic effects may occur Available data inadequate to permit derivation of health-based guideline value Occurs in drinking-water at concentrations well below those at which toxic effects may occur, and health-based value would far exceed lowest reported taste and odour threshold Occurs in drinking-water at concentrations well below those at which toxic effects may occur Occurs in drinking-water at concentrations well below those at which toxic effects may occur Occurs in drinking-water at concentrations well below those at which toxic effects may occur Not of health concern at levels found in drinking-water b Occurs in drinking-water at concentrations well below those at which toxic effects may occur Readily transformed into metabolites that are more toxic; a guideline value for the parent compound is considered inappropriate, and there are inadequate data to enable the derivation of guideline values for the metabolites Available data inadequate to permit derivation of health-based guideline value Not of health concern at levels found in drinking-water a Not of health concern at levels found in drinking-water a Not of health concern at levels found in drinking-water a Available data inadequate to permit derivation of health-based guideline value Available data inadequate to permit derivation of health-based guideline value Occurs in drinking-water at concentrations well below those at which toxic effects may occur, and health-based value would exceed lowest reported odour threshold Occurs in drinking-water at concentrations well below those at which toxic effects may occur Not of health concern at concentrations normally observed in drinking-water a a b May affect acceptability of drinking-water (see chapter 10). An important operational water quality parameter. 490

103 ANNEX 4. CHEMICAL SUMMARY TABLES Table A4.3 Guideline values for chemicals that are of health significance in drinking-water Guideline value a Chemical (mg/litre) Remarks Acrylamide b Alachlor 0.02 b Aldicarb 0.01 Applies to aldicarb sulfoxide and aldicarb sulfone Aldrin and dieldrin For combined aldrin plus dieldrin Antimony 0.02 Arsenic 0.01 (P) Atrazine Barium 0.7 Benzene 0.01 b Benzo[a]pyrene b Boron 0.5 (T) Bromate 0.01 b (A, T) Bromodichloromethane 0.06 b Bromoform 0.1 Cadmium Carbofuran Carbon tetrachloride Chloral hydrate 0.01 (P) (trichloroacetaldehyde) Chlorate 0.7 (D) Chlordane Chlorine 5 (C) For effective disinfection, there should be a residual concentration of free chlorine of 0.5 mg/litre after at least 30 min contact time at ph <8.0 Chlorite 0.7 (D) Chloroform 0.2 Chlorotoluron 0.03 Chlorpyrifos 0.03 Chromium 0.05 (P) For total chromium Copper 2 Staining of laundry and sanitary ware may occur below guideline value Cyanazine Cyanide 0.07 Cyanogen chloride 0.07 For cyanide as total cyanogenic compounds 2,4-D (2,4-dichlorophenoxyacetic 0.03 Applies to free acid acid) 2,4-DB 0.09 DDT and metabolites Di(2-ethylhexyl)phthalate Dibromoacetonitrile 0.07 Dibromochloromethane 0.1 1,2-Dibromo-3-chloropropane b 1,2-Dibromoethane b (P) Dichloroacetate 0.05 (T, D) Dichloroacetonitrile 0.02 (P) Dichlorobenzene, 1,2-1 (C) continued 491

104 GUIDELINES FOR DRINKING-WATER QUALITY Table A4.3 Continued Guideline value Chemical (mg/litre) Remarks Dichlorobenzene, 1,4-0.3 (C) Dichloroethane, 1, b Dichloroethene, 1, Dichloroethene, 1, Dichloromethane ,2-Dichloropropane (1,2-DCP) 0.04 (P) 1,3-Dichloropropene 0.02 b Dichlorprop 0.1 Dimethoate Edetic acid (EDTA) 0.6 Applies to the free acid Endrin Epichlorohydrin (P) Ethylbenzene 0.3 (C) Fenoprop Fluoride 1.5 Volume of water consumed and intake from other sources should be considered when setting national standards Formaldehyde 0.9 Hexachlorobutadiene Isoproturon Lead 0.01 Lindane Manganese 0.4 (C) MCPA Mecoprop 0.01 Mercury For total mercury (inorganic plus organic) Methoxychlor 0.02 Metolachlor 0.01 Microcystin-LR (P) For total microcystin-lr (free plus cellbound) Molinate Molybdenum 0.07 Monochloramine 3 Monochloroacetate 0.02 Nickel 0.02 (P) Nitrate (as NO - 3 ) 50 Short-term exposure Nitrilotriacetic acid (NTA) 0.2 Nitrite (as NO - 2 ) 3 Short-term exposure 0.2 (P) Long-term exposure Pendimethalin 0.02 Pentachlorophenol b (P) Pyriproxyfen 0.3 Selenium 0.01 Simazine Styrene 0.02 (C) 2,4,5-T Terbuthylazine Tetrachloroethene 0.04 Toluene 0.7 (C) 492

105 ANNEX 4. CHEMICAL SUMMARY TABLES Table A4.3 Continued Guideline value Chemical (mg/litre) Remarks Trichloroacetate 0.2 Trichloroethene 0.07 (P) Trichlorophenol, 2,4,6-0.2 b (C) Trifluralin 0.02 Trihalomethanes The sum of the ratio of the concentration of each to its respective guideline value should not exceed 1 Uranium (P, T) Only chemical aspects of uranium addressed Vinyl chloride b Xylenes 0.5 (C) a b P = provisional guideline value, as there is evidence of a hazard, but the available information on health effects is limited; T = provisional guideline value because calculated guideline value is below the level that can be achieved through practical treatment methods, source protection, etc.; A = provisional guideline value because calculated guideline value is below the achievable quantification level; D = provisional guideline value because disinfection is likely to result in the guideline value being exceeded; C = concentrations of the substance at or below the healthbased guideline value may affect the appearance, taste or odour of the water, leading to consumer complaints. For substances that are considered to be carcinogenic, the guideline value is the concentration in drinking-water associated with an upper-bound excess lifetime cancer risk of 10-5 (one additional cancer per of the population ingesting drinking-water containing the substance at the guideline value for 70 years). Concentrations associated with upper-bound estimated excess lifetime cancer risks of 10-4 and 10-6 can be calculated by multiplying and dividing, respectively, the guideline value by

106 7.Supply of Drinking Water with Clean and Safe Ministry of Health, Labour and Welfare in Japan is established the drinking water quality standards of 46 items to keep up the supply of drinking water with clean and safe(table 1). To respond to the standards, all the water utilities have fully introduced the works of improvement of water treatment facilities as well as introduction of necessity operation management. On the other hand, the water quality laboratory of water utilities is periodically conducting in order to measure for water quality whether tap water meets the standards perfectly by these measures or not. Table 1. Water Quality Standards of Drinking Water In case of exceeding concentration of the standards, it is necessary to clarify the causative factors and take measures against prevention. In regard to prevention measures, the modification of operation management of the treatment plant is in the case a good solution or construction and improvement of facilities for water purification plant are also another ways. Water utilities are continuously required constant efforts to clear 100 per cent for drinking water standards to supply clear and safe tap water. 1)Items Relating to the Comfortableness of Water Quality and Monitoring As the items of supplement for the drinking water quality standards, two types of guideline were established and water utilities are carrying a proper monitoring after the new drinking water standards, if it is necessary. One is the guideline value for the " Items Relating to the Comfortableness of Water Quality" (thirteen items such as 2-

107 Methylisoborneol etc.) aiming at higher quality water corresponding to the public needs. The other one is the guideline values for the "Items Relating Monitoring" (thirtyfive items such as Dioxin etc.) to ensure the safety of drinking water even in future. In addition the pesticides consisting of 26 items that may be used at the golf course are also monitoring appropriately, if it is necessary. 2)Revision of Drinking Water Quality Standards and Improvement of the Facilities of Water Supply Drinking water quality standards of water supply is always renewing by introducing of the latest scientific approach, such as toxicity information, etc. Water works facilities are strongly requested to match the new drinking water quality standards to supply good quality and safe tap water even in future ages.

108 WATER AND WASTEWATER DISINFECTION National Report from Germany Dr. B. Wricke, TZW General Observations The German Drinking Water Act only calls for a disinfection of drinking water when it is necessary. The microbiological requirements on drinking water ought to be guaranteed by the protection of the raw water sources, the treatment of the water and by disinfection, which is regarded to be the last safety step. There is no requirement to have a disinfectant residual in the distribution system. Drinking water which is treated out of protected groundwater, will be not disinfected in the most cases. That is because it does already meet the bacteriological requirements and of the low regrowth potential. Surface water will be treated generally before disinfection. In this process, bank filtration is well common using river water for raw water source. In the most cases the source protection and the treatment process allow to work with very low or without disinfectant residual in the distribution systems. More then 50 % of the drinking water in Germany is not being disinfected. In the last ten years, the drinking water disinfection practice in Germany was influenced by the very low THM level of 10 µg/l (see table 1), by the results of the UV disinfection research and in the last few years by the discussion of the protozoa problem. In order to guarantee the low THM level, waterworks used the following strategies: - optimisation of the treatment technology to increase of the DOC removal efficiency - change from chlorine to chlorine dioxide or UV radiation - renunciation of disinfection if it was not necessary. UV radiation is becoming a more and more accepted alternative to conventional chemical disinfection. As a result of researches carried out from 1987 till 1993, it had been shown, that the UV disinfection is safe, if the UV systems were being tested by using a biodosimetric test and UV sensors will be used for the control of the radiation. Resulting of the tests, certified systems are available nowadays. The discussion of the protozoa problem showed the limits of the chemical disinfection. Therefor the requirements on the treatment process increased. Protozoa should be removed before of the disinfection step using floc-filtration or membrane filtration. Water sources The following raw water sources are used for drinking water treatment in Germany. The data is from the BGW statistics of the year Groundwater 64 % Spring Water 9 % Surface Water 27 % Incl. Bankfiltrate Regulations and Standards Associated with Disinfection of Water In German water practice, disinfection is defined as the use of chemical and physical disinfection methods. The German Drinking Water Regulation permits chlorine, chlorine dioxide and ozone for disinfection. It also defines maximum addition and standards after

109 treatment for the disinfectants itself as well as for disinfection by-products. Table 1 gives an overview. Table 1: Disinfectants and DBP according the German Drinking Water Regulation Disinfectant Minimum value after treatment (mg/l) Maximum addition (mg/l) Limit value after treatment (mg/l) Chlorine * 0.3* Free chlorine 0.01* THM Chlorine dioxide Chlorine dioxide Chlorite Ozone Ozone THM * Maximum addition of chlorine may be increased to 6 mg/l, limits after treatment are then 0.6 mg/l free chlorine and mg/l THM, if the microbiological standards cannot be obtained otherwise or if ammonia temporarily interferes with disinfection The UV radiation is allowed to use for water disinfection, too. The radiation exposure should be above 400 J/m² considering photoreactivation. Only certified UV systems should be used. The properties of UV systems for drinking water disinfection are defined in the DVGW standard W294 as well as the testing and monitoring procedures. Membrane filtration may be used as a treatment step for the removal of pathogens and other micro-organism, too. Since it is not necessary to disinfect the water with chemicals or with UV radiation if the drinking water meets the microbiological requirements, it is possible to use the membrane filtration itself. Application Points and Doses for Disinfectants There are no regulations for the disinfection application points. However since 1990 it is not allowed to use chlorine as well as chlorine dioxide for oxidation within the treatment process. That s why it is common, that the disinfection application point for these chemicals is being located in the end of the treatment process. Ozone is being used for oxidation as well as for disinfection during the treatment process. Only when the DOC is very low it will be used as the last step. Normally ozonation is being followed by a biofiltration and a safety disinfection. The allowed disinfectant doses and the required residual concentrations after the treatment, are given in table 1. In practice the doses are chosen as low as possible. The contact time for chlorine and chlorine dioxide should be 30 minutes. Disinfection Technologies The following disinfection chemicals and technologies being employed in Germany: 1.hypochlorite liquor 2.chlorine gas 3.chlorine dioxide

110 4.UV radiation Chloramination is not allowed. Disinfectant residuals The allowed minimum and maximum levels of disinfectant residuals are given in table 1. To control the disinfection it is required to measure the residual concentration after the treatment. There is no level of disinfectant required in the distribution system. Pathogens and Surrogate Microorganisms The German Drinking Water Regulation requires the monitoring of the drinking water by using the fecal indicators Escherichia coli, coliforms and fecal streptococci. They should not be detectable in 100 ml. In addition, the regulation demands that the heterotrophic plate counts (HPC) at 20 C and 36 C incubation temperature should not exceed a guidance value of 100 colony forming units (CFU)/mL. Disinfection of Wastewater Wastewater disinfection is not a general objective in German wastewater treatment plants. At present, there are only a few treatment plants applying disinfection of the effluent. These plants discharge into sensitive areas, i.e. recreational and bathing waters. Therefore, the most important regulation is the EU bathing water directive. The technique used for disinfection purpose is UV radiation. Membrane filtration is another method considered for the reduction of pathogens but yet not applied in full-scale.

111 Drinking water test item and water quality standard Drinking water test item and water quality standards Water quality standard of each country Classification Test items Standard Microbe Harm Inorganic matter for health Disinfection and disinfection by products Harm matter for health Aesthetic effective matter Total Colony Counts 100CFU/mL below Total Coliforms No/100mL Yersinia No/ L E.coli/Fecal Coliforms No/100mL Lead 0.05 /L below Fluoride 1.5 /L below Arsenic 0.05 /L below Selenium 0.01 /L below Mercury /L below Cyanide 0.01 /L below Chromium(as Cr(VI)) 0.05 /L below Ammonium Nitrogen 0.5 /L below Nitrate Nitrogen 10 /L below Cadmium /L below Boron 0.3 /L below Free residual chlorine 4.0 /L below THMs 0.1 /L below Chloroform 0.08 /L below Chloralhydrate 0.03 /L below Dibromoacetonitril 0.1 /L below Dichloroacetonitril 0.09 /L below Trichloroacetonitril /L below Haloacetic acids 0.1 /L below Phenol /L below Diazinon 0.02 /L below Parathion 0.06 /L below Fenitrothion 0.04 /L below Carbaryl 0.07 /L below Trichloroethane 0.1 /L below PCE 0.01 /L below TCE 0.03 /L below Dichloro methane 0.02 /L below Benzene 0.01 /L below Toluene 0.7 /L below Ethyl Benzene 0.3 /L below Xylene 0.5 /L below Dichloroethylene 0.03 /L below Carbon tetrachloride /L below Dibromochloropropane /L below Hardness 300 /L below Consumption of KMnO4 10 /L below Odor Odorless Taste Tasteless Copper 1 /L below Color 5degree below Alkyl Benzene Sulfate( ABS) 0.5 /L below ph Zinc 1 /L below

112 Chlorine ion 250 /L below Total solids 500 /L below Iron 0.3 /L below Manganese 0.3 /L below Turbidity 1NTUbelow Sulfate 200 /L below Aluminium 0.2 /L below

113 4. CHLORINE DIOXIDE Since the beginning of the twentieth century, when it was first used at a spa in Ostend, Belgium, chlorine dioxide has been known as a powerful disinfectant of water. During the 1950s, it was introduced more generally as a drinking water disinfectant since it provided less organoleptic hindering than chlorine. Approximately 700 to 900 public water systems use chlorine dioxide to treat potable water (Hoehn, 1992). Today, the major uses of chlorine dioxide are: CT disinfection credit; Preoxidant to control tastes and odor; Control of iron and manganese; and Control of hydrogen sulfide and phenolic compounds. 4.1 Chlorine Dioxide Chemistry Oxidation Potential The metabolism of microorganisms and consequently their ability to survive and propagate are influenced by the oxidation reduction potential (ORP) of the medium in which it lives (USEPA, 1996). Chlorine dioxide (ClO 2 ) is a neutral compound of chlorine in the +IV oxidation state. It disinfects by oxidation; however, it does not chlorinate. It is a relatively small, volatile, and highly energetic molecule, and a free radical even while in dilute aqueous solutions. At high concentrations, it reacts violently with reducing agents. However, it is stable in dilute solution in a closed container in the absence of light (AWWA, 1990). Chlorine dioxide functions as a highly selective oxidant due to its unique, one-electron transfer mechanism where it is reduced to chlorite (ClO 2 - ) (Hoehn et al., 1996). The pka for the chlorite ion, chlorous acid equilibrium, is extremely low at ph 1.8. This is remarkably different from the hypochlorous acid/hypochlorite base ion pair equilibrium found near neutrality, and indicates the chlorite ion will exist as the dominant species in drinking water. The oxidation reduction of some key reactions are (CRC, 1990): ClO 2(aq) + e - = ClO 2 - E = 0.954V Other important half reactions are: ClO H 2 O +4e - = Cl - + 4OH - E = 0.76V ClO H 2 O + 2e - = ClO OH - E = 0.33V ClO H + + e - = ClO 2 + H 2 O E = 1.152V April EPA Guidance Manual Alternative Disinfectants and Oxidants

114 4. CHLORINE DIOXIDE In drinking water, chlorite (ClO 2 - ) is the predominant reaction endproduct, with approximately 50 to 70 percent of the chlorine dioxide converted to chlorite and 30 percent to chlorate (ClO 3 - ) and chloride (Cl - ) (Werdehoff and Singer, 1987). 4.2 Generation Introduction One of the most important physical properties of chlorine dioxide is its high solubility in water, particularly in chilled water. In contrast to the hydrolysis of chlorine gas in water, chlorine dioxide in water does not hydrolyze to any appreciable extent but remains in solution as a dissolved gas (Aieta and Berg, 1986). It is approximately 10 times more soluble than chlorine (above 11 C), while it is extremely volatile and can be easily removed from dilute aqueous solutions with minimal aeration or recarbonation with carbon dioxide (e.g. softening plants). Above 11 to 12 C, the free radical is found in gaseous form. This characteristic may affect chlorine dioxide's effectiveness when batching solutions and plumbing appropriate injection points. Other concerns are the increased difficulty in analyzing for specific compounds in the presence of many interfering compounds/residual longevity and volatility of gaseous compounds. In the gaseous form, the free radicals also react slowly with water. The reaction rate is 7 to 10 million times slower than that of the hydrolysis rate for chlorine gas (Gates, 1989). Chlorine dioxide cannot be compressed or stored commercially as a gas because it is explosive under pressure. Therefore, it is never shipped. Chlorine dioxide is considered explosive at higher concentrations which exceed 10 percent by volume in air, and its ignition temperature is about 130 C (266 F) at partial pressures (National Safety Council Data Sheet 525 ClO 2, 1967). Strong aqueous solutions of chlorine dioxide will release gaseous chlorine dioxide into a closed atmosphere above the solution at levels that may exceed critical concentrations. Some newer generators produce a continuous supply of dilute gaseous chlorine dioxide in the range of 100 to 300 mm-hg (abs) rather than in an aqueous solution (National Safety Council, 1997). For potable water treatment processes, aqueous solutions between 0.1 and 0.5 percent are common from a number of current generation technologies. Most commercial generators use sodium chlorite (NaClO 2 ) as the common precursor feedstock chemical to generate chlorine dioxide for drinking water application. Recently, production of chlorine dioxide from sodium chlorate (NaClO 3 ) has been introduced as a generation method where in NaClO 3 is reduced by a mixture of concentrated hydrogen peroxide (H 2 O 2 ) and concentrated sulfuric acid (H 2 SO 4 ). Chlorate-based systems have traditionally been used in pulp and paper applications, but have recently been tested full-scale at two U.S. municipal water treatment plants. This is an emerging technology in the drinking water field and is not discussed in this guidance manual. EPA Guidance Manual 4-2 April 1999 Alternative Disinfectants and Oxidants

115 4. CHLORINE DIOXIDE Chlorine Dioxide Purity Chlorine dioxide generators are operated to obtain the maximum production (yield) of chlorine dioxide, while minimizing free chlorine or other residual oxidant formation. The specified yield for chlorine dioxide generators is typically greater than 95 percent. In addition, the measurable excess chlorine should be less than 2 percent by weight in the generator effluent. Generator yield is defined as (Gordon et al., 1990): Yield [ ClO ] = [ ] [ ] ( )[ ] ClO + ClO + ClO Where: [ ClO 2 ] [ ClO ] 2 [ ClO ] = Chlorine dioxide concentration, mg/l. = Chlorite concentration, mg/l. = Chlorate concentration, mg/l. = Molecular weight ratio of ClO - 2 to ClO - 3. Since any chlorite ion fed to the generator may result in the formation of ClO 2, ClO 2 -, or ClO 3 -, the purity of the resultant mixture can be calculated using the concentrations of each of the species from appropriate analytical measurements. The determination of purity requires neither flow measurement, mass recoveries, nor manufacturer-based methods to determine production yield, theoretical yield, efficiency, or conversion for any precursor feedstock. This approach does not require flow measurements that can introduce up to 5 percent error in the calculations. Utilities that use chlorine dioxide should measure excess chlorine (as FAC) in the generator effluent in addition to the ClO 2 - related species. FAC may appear as false ClO 2 residuals for CT purposes, or result in the formation of chlorinated DBPs if high, relative to the ClO 2 level in the generated mixture. Excess chlorine is defined as: Excess Cl [Cl ] = 2 [ClO ] [ClO ] ( 67.45) [ClO ] Where: = stoichiometric and molecular weight ratio of Cl 2 to ClO - 2. ( ) The following represents a summarily simpler equation that substantially resolves the problems of different equipment-specific calibration methods, chlorine-contaminated ClO 2, or low efficiency conversion of either chlorite- or chlorate-based precursor material. 100 April EPA Guidance Manual Alternative Disinfectants and Oxidants

116 4. CHLORINE DIOXIDE [ClO ] Purity = [ClO 2 ] + [FAC] + [ClO 2 ] + [ClO 3 ] This practical (weight-based) calculation permits a variety of approved analytical methods (discussed in section 4.6) to be used to assess generator performance on unbiased scientific principles, rather than non-standardized manufacturer specifications Methods of Generating Chlorine Dioxide For potable water application, chlorine dioxide is generated from sodium chlorite solutions. The principal generation reactions that occur in the majority of generators have been known for a long time. Chlorine dioxide can be formed by sodium chlorite reacting with gaseous chlorine (Cl 2(g) ), hypochlorous acid (HOCl), or hydrochloric acid (HCl). The reactions are: 2NaClO 2 + Cl 2(g) = 2ClO 2(g) + 2NaCl 2NaClO 2 + HOCl = 2ClO 2(g) + NaCl + NaOH 5NaClO 2 + 4HCl = 4ClO 2(g) + 5NaCl + 2H 2 O [1a] [1b] [1c] Reactions [1a], [1b], and [1c] explain how generators can differ even though the same feedstock chemicals are used, and why some should be ph controlled and others are not so dependent on low ph. In most commercial generators, there may be more than one reaction taking place. For example, the formation and action of hypochlorous acid as an intermediate (formed in aqueous solutions of chlorine) often obscures the overall reaction for chlorine dioxide production. Table 4-1 provides information on some types of available commercial generators. Conventional systems react sodium chlorite with either acid, aqueous chlorine, or gaseous chlorine. Emergent technologies identified in Table 4-1 include electrochemical systems, a solid chlorite inert matrix (flow-through gaseous chlorine) and a chlorate-based emerging technology that uses concentrated hydrogen peroxide and sulfuric acid. EPA Guidance Manual 4-4 April 1999 Alternative Disinfectants and Oxidants

117 4. CHLORINE DIOXIDE Table 4-1. Commercial Chlorine Dioxide Generators GENERATOR TYPE ACID-CHLORITE: (Direct Acid System) AQUEOUS CHLORINE- CHLORITE: (Cl2 gas ejectors with chemical pumps for liquids or booster pump for ejector water). RECYCLED AQUEOUS CHLORINE OR "FRENCH LOOP" (Saturated Cl2 solution via a recycling loop prior to mixing with chlorite solution.) GASEOUS CHLORINE- CHLORITE (Gaseous Cl2 and 25% solution of sodium chlorite; pulled by ejector into the reaction column.) GASEOUS CHLORINE- SOLIDS CHLORITE MATRIX (Humidified Cl2 gas is pulled or pumped through a stable matrix containing solid sodium chlorite.) ELECTROCHEMICAL (Continuous generation of ClO2 from 25% chlorite solution recycled through electrolyte cell) MAIN REACTIONS Reactants, byproducts, key reactions, and chemistry notes 4HCl + 5NaClO2 4ClO2(aq) + ClO3 - Low ph ClO3 - possible Slow reaction rates Cl2 + H2O [HOCl / HCl] [HOCl/HCl] + NaClO2 ClO2(g) + H/OCl - + NaOH + ClO3 - Low ph ClO3 - possible Relatively slow reaction rates 2HOCl + 2NaClO2 2ClO2 + Cl2 + 2NaOH Excess Cl2 or HCl needed due to NaOH formed. Cl2(g) + NaClO2(aq) ClO2(aq) Neutral ph Rapid reaction Potential scaling in reactor under vacuum due to hardness of feedstock. Cl2(g) + NaClO2(s) ClO2(g) + NaCl Rapid reaction rate New technology NaClO2(aq) ClO2(aq) + e - New technology ACID/PEROXIDE/CHLORIDE 2NaClO3 + H2O2 + H2SO4 2ClO2 + O2 + NaSO4 + H20 Source: Adapted from Gates, SPECIAL ATTRIBUTES Chemical feed pump interlocks required. Production limit ~ lb/day. Maximum yield at ~80% efficiency. Excess Cl2 or acid to neutralize NaOH. Production rates limited to ~ 1000 lb/day. High conversion but yield only 80-92% More corrosive effluent due to low ph (~ ). Three chemical systems pump HCl, hypochlorite, chlorite, and dilution water to reaction chamber. Concentration of ~3 g/l required for maximum efficiency. Production rate limited to ~ 1000 lb/day. Yield of 92-98% with ~10% excess Cl2 reported. Highly corrosive to pumps; draw-down calibration needed. Maturation tank required after mixing. Production rates 5-120,000 lb/day. Ejector-based, with no pumps. Motive water is dilution water. Near neutral ph effluent. No excess Cl2. Turndown rated at 5-10X with yield of 95-99%. Less than 2% excess Cl2. Highly calibrated flow meters with min. line pressure ~ 40 psig needed. Cl2 gas diluted with N2 or filtered air to produce ~8% gaseous ClO2 stream. Infinite turndown is possible with >99% yield. Maximum rate to ~1200 lb/day per column; ganged to >10,000 lb/day. Counter-current chilled water stream accepts gaseous ClO2 from production cell after it diffuses across the gas permeable membrane. Small one-pass system requires precise flow for power requirements (Coulombs law). Uses concentrated H2O2 and H2SO4. Downscaled version; Foam binding; Low ph Commercial Generators The conventional chlorine-chlorite solution method generates chlorine dioxide in a two-step process. First, chlorine gas is reacted with water to form hypochlorous acid and hydrochloric acid. These April EPA Guidance Manual Alternative Disinfectants and Oxidants

118 4. CHLORINE DIOXIDE acids then react with sodium chlorite to form chlorine dioxide. The ratio of sodium chlorite to hypochlorous acid should be carefully controlled. Insufficient chlorine feed will result in a large amount of unreacted chlorite. Excess chlorine feed may result in the formation of chlorate ion, which is an oxidation product of chlorine dioxide and not currently regulated. Acid-Chlorite Solution - Chlorine dioxide can be generated in direct-acidification generators by acidification of sodium chlorite solution. Several stoichiometric reactions have been reported for such processes (Gordon et al., 1972). When chlorine dioxide is generated in this way, hydrochloric acid is generally preferred (Reaction [1c]). Aqueous Chlorine-Chlorite Solution - Chlorite ion (from dissolved sodium chlorite) will react with hydrochloric acid and hypochlorous acid to form chlorine dioxide in these systems, commonly referred to as conventional systems (Reaction [1b]): Figure 4-1 shows a typical chlorine dioxide generator using aqueous chlorine-chlorite solution (Demers and Renner, 1992). If chlorine gas and chlorite ion are allowed to react under ideal conditions (not usually formed in aqueous chlorine type systems), the resulting ph of the effluent may be close to 7. To fully utilize sodium chlorite solution, the more expensive of the two ingredients, excess chlorine is often used. This approach lowers the ph and drives the reaction further toward completion. The reaction is faster than the acid-chlorite solution method, but much slower than the other commercial methods described in the following discussion. Recycled Aqueous Chlorine or French Loop - In this aqueous chlorine design, shown in Figure 4-2, chlorine gas is injected into a continuously circulating water loop. This eliminates the need for a great excess of Cl 2 gas to be fed to the generator since the molecular chlorine will dissolve in the feed water, and thus maintain a low ph level of the feed water. Loop-based generators keep chlorine at or above saturation levels. The low ph condition results in high yields of chlorine dioxide (greater than 95 percent at design production rate) (Thompson, 1989). Chlorine in the generator effluent may react with chlorine dioxide to form chlorate if allowed to stand in batch storage too long. The French Loop type of generator is more difficult to operate due to system start-up and control of sodium chlorite feed rate (meter pump), chlorine feed rate (rotameter), and the recirculating loop (pump). Newer designs incorporate a second batching tank for continuous aqueous chlorine storage, thus removing many of these startup or recycling difficulties. Gaseous Chlorine-Chlorite Solution - Sodium chlorite solution can be vaporized and reacted under vacuum with molecular gaseous chlorine. This process uses undiluted reactants and is much more rapid than chlorine solution:chlorite solution methods (Pitochelli, 1995). Production rates are more easily scaled up, and some installed systems have reported producing more than 60,000 pounds per day. EPA Guidance Manual 4-6 April 1999 Alternative Disinfectants and Oxidants

119 4. CHLORINE DIOXIDE Control Box Chlorine Dioxide Solution Sight Glass Check Valve ph Sensor Low Vacuum Switch Ejector 25% Active Sodium Chlorite Solution Tank Level Switch Rate Control Valve Chlorine Flowmeter Pressure Regulator Water Flowmeter Bypass Line Solenoid Valve Restrictor Vacuum Regulator with Loss of Chlorine Switch Vent Chlorine Gas Water Inlet Source: Demers and Renner, Figure 4-1. Conventional Chlorine Dioxide Generator When Using Chlorine-Chlorite Method The acid-sodium hypochlorite-sodium chlorite method of generating chlorine dioxide is used when chlorine gas is not available. First, sodium hypochlorite is combined with hydrochloric or another acid to form hypochlorous acid. Sodium chlorite is then added to this reaction mixture to produce chlorine dioxide ph Effects on Chlorine Dioxide Generation If hypochlorous acid is formed, one of the byproducts of its reaction with sodium chlorite in solution is sodium hydroxide. Since sodium hydroxide is also a common stabilizer of sodium chlorite feedstock, the resulting ph of the mixture can be too high. A high ph slows the formation of chlorine dioxide and impels less efficient chlorate-forming reactions. This is the same process in which chlorite and hypochlorite ions react in drinking water to form chlorate ion. This neutralizing effect of caustic may be influenced by different stabilities used in each of the types and sources of April EPA Guidance Manual Alternative Disinfectants and Oxidants

120 4. CHLORINE DIOXIDE sodium chlorite which are approved for use in drinking water under AWWA Standard B (AWWA, 1995). Chlorine Dioxide Solution Sight Glass Control Box ph Sensor Check Valve Chlorine Dioxide Wall Cabinet Water Flowmeter Flow Switch Pressure Regulator Solenoid Valve Bypass Line Restrictor Level Switch Level Switch Level Switch 25% Active Sodium Chlorite Solution Tank 10% Active Sodium Chlorite Solution Tank Acid Tank Water Inlet Source: Demers and Renner, Figure 4-2. Chlorine Dioxide Generation Using Recycled Aqueous Chlorine Method In very low ph aqueous chlorine solutions, chlorous acid (and not the chlorite ion) may be directly oxidized to chlorine dioxide as shown in reaction [1d]. At this low ph, gaseous chlorine remains "dissolved" in the water at concentrations higher than the normal occurrence, and allows reaction [1a] to proceed. 2HClO 2 + HOCl = HCl + H 2 O + 2ClO 2 [1d] Chlorate Byproduct Formation One of the most undesirable byproducts in generators is the chlorate ion (ClO 3 - ). Chlorate production is possible through reactions with the intermediate dimer, {Cl 2 O 2 }. Rather than the chlorite ion being simply "converted" to chlorine dioxide, reactions [1a] through [1d] can result in the supposed formation of the unstable, unsymmetrical intermediate dimer, {Cl 2 O 2 } or {Cl - -ClO 2 } as shown in reaction [2] (Emmenegger and Gordon, 1967). Cl 2 + ClO 2 - = {Cl-ClO 2 } + Cl - [2] EPA Guidance Manual 4-8 April 1999 Alternative Disinfectants and Oxidants

121 4. CHLORINE DIOXIDE In some generators that operate with relatively low initial reactant concentrations, a significant amount of chlorate is formed by reactions with {Cl 2 O 2 }, as shown in reactions [3a], [3b], and [3c]. {Cl 2 O 2 } + H 2 O = ClO Cl - + 2H + {Cl 2 O 2 } + HOCl = ClO Cl - + H + {Cl 2 O 2 } + 3HOCl + H 2 O = 2ClO H + + 3Cl - [3a] [3b] [3c] Highly acidic (ph <3) reaction mixtures force the degradation of {Cl 2 O 2 } to chlorate rather than chlorine dioxide, as well as the direct oxidation of chlorite to chlorate. The overall reactions that describe chlorate ion formation are: ClO HOCl = ClO Cl - + H + [4a] and ClO Cl 2 + H 2 O = ClO Cl - + H + [4b] The following conditions may also produce the chlorate ion: Excessively high ratios of Cl 2 gas:clo 2 -. Presence of high concentrations of free chlorine at low ph in aqueous solutions. Dilute chlorite solutions held at low ph. Base-catalyzed disproportionation of chlorine dioxide at high ph values (ph >11). Reaction mixtures that are highly acidic (ph <3). An excess of hypochlorous acid will directly oxidize chlorite ions to chlorate ions rather than to chlorine dioxide (independent of the rapid formation of the {Cl 2 O 2 } intermediate) Generator Design As hypochlorous acid is formed under acidic conditions, the lowering of optimal concentrations of precursor reactants will also increase chlorate levels in the generator by promoting reaction [3b]. Therefore, if weak precursor feed stocks or high amounts of dilution water are added to the generator, chlorate will be more prevalent (according to reaction [3a]). These limitations explain why generators most often use ~25 percent chlorite solutions and gaseous (or near-saturated aqueous) chlorine. Higher strength solutions of sodium chlorite (e.g., 37 percent) also are more susceptible to crystallization or stratification at ambient temperatures as high as 25 C(78 F). Due to these dilution effects, some systems function best as "intermittent batch" generators, (that produce high concentrations of chlorine dioxide) rather than as "continuous" generators (that produce lower concentrations (< 1g/L) of chlorine dioxide). The stored solutions are pumped or injected from April EPA Guidance Manual Alternative Disinfectants and Oxidants

122 4. CHLORINE DIOXIDE the storage tank. Cycling frequently avoids long-term (over 24 hour periods) storage of the generated solution. Chlorine loop-type systems can obtain high conversion rates if excess chlorine is always present. Excess chlorine permits the molecular chlorine reaction mechanism (described above) to proceed. The low ph of the mixture also minimizes the contribution of OH - formed via equation [1b] by neutralizing it. These solutions may still be contaminated with excess chlorine needed to drive the conversion of chlorite ion, but not to the same degree as found in simple aqueous chlorine systems when operated under dilute conditions. Chlorine-loop generators run best at high capacity since the chlorite ion is most available in this production mode. Conventional or acid-enhanced generators produce chlorine dioxide through the intermediate {Cl 2 O 2 } as long as relatively high concentrations of reactants (~above g/l) are maintained in the reaction chamber prior to dilution. Vapor-phase, recycled loop, and solid chlorite-type generators that minimize dilute aqueous reaction conditions can obtain high efficiencies by preventing any chlorite ion from reacting in the "slower" steps described above. This is accomplished by establishing conditions that force the immediate reaction between chlorite ions and gas-phase or molecular chlorine at a rate hundreds of times faster than the Cl 2 hydrolysis in water. This essentially minimizes the impact of competitive chlorine hydrolysis or acidification on the dominant [ClO 2 - :Cl 2 gas] mechanism, and prevents the chlorite ion reacting with hypochlorous acid directly. In all generators, large excess amounts of Cl 2 may result in the over-oxidization of chlorite and directly form chlorate in aqueous solution (reaction [4b]). Precursor chemical feed rates for the generators should always be adjusted to chart settings supplied with generators, notably with the continuous flow, direct gas injection systems. Re-calibration of these systems is sometimes needed on-site if feed stock sodium chlorite is not of the correct strength, or if pre-calibrated flow devices have been replaced. If aqueous chlorine solutions are mixed with sodium chlorite feed stock solutions, the following mechanisms are dominant, which may affect the formation rates of chlorine dioxide: Chlorine gas reacts with water to form hypochlorous and hydrochloric acids, rather than directly with chlorite to form chlorine dioxide. (Water and chlorite both compete for the Cl 2 molecule simultaneously) (see equations [4.1a-c] and Section 6.1.1). Chlorate ion is formed (reactions [3a], [3b], and [3c]). Only 4 moles of chlorine dioxide are obtained from 5 moles of sodium chlorite via direct acidification (reaction [1c]). This may become important at low ph and high chloride ion levels. The practical side of all of this is that different generators operate under different optimal conditions. For example, reactor columns should not be continuously flooded with excess water in vapor-phase systems. It is the main reason why dry chlorite-based generator reactor columns should not get wet. Over-dilution of the precursor reactants themselves will lower conversion efficiencies due to the EPA Guidance Manual 4-10 April 1999 Alternative Disinfectants and Oxidants

123 4. CHLORINE DIOXIDE favored formation of chlorate over chlorine dioxide. Batch-type generation should always be carried out at maximal ClO 2 concentration with appropriate adjustments at the pump (located downstream of the reactor at the batch tank) for dosage or flow. Changes in chlorine dioxide concentrations in the batch tanks would then be minimized, and pump calibration does not need to include a broad range of chlorine dioxide levels. For the newer gas chlorine generators using dry sodium chlorite in an inert matrix, small amounts of humidifying water in the mixture do not interfere significantly with the simple gaseous Cl 2 :ClO 2 - reaction. These small traces of water allow for continuous exposure of ClO 2 - on the inert surfaces within the reactor column. Chlorine dioxide generators are relatively simple mixing chambers. The reactors are frequently filled with media (Teflon chips, ceramic or raschig rings) to generate hydraulic turbulence for mixing. A sample petcock valve on the discharge side of the generator is desirable to allow for monitoring of the generation process. The Recommended Standards for Water Works (GLUMRB, 1992) and drinking water design textbooks such as Unit Processes in Drinking Water Treatment by Masschelein (1992) are excellent sources for chlorine dioxide generation design criteria and application Chemical Feed Systems Fiberglass Reinforced vinyl ester Plastic (FRP) or High Density Linear Polyethylene (HDLPE) tanks with no internal insulation or heat probes are recommended for bulk storage of 25 to 38 percent solution sodium chlorite. Nozzles should include truck unloading vents and local level and temperature indication. Transfer pumps should be centrifugal with 316 stainless steel, fiberglass, Hypalon, wetted Teflon parts, or epoxy resins. The pump should be sealless or equipped with double mechanical seals. The recommended piping material is CPVC, although vinyl ester or Teflon piping systems are acceptable. Carbon steel and stainless steel piping systems are not recommended. Depending upon system size, sodium chlorite can be purchased in 55-gallon drums, 275-gallon nonreturnable totes, or in bulk quantities. A 30-day storage supply of sodium chlorite can easily be met for most small systems by using 55-gallon drums. A 55-gallon drum weighs approximately 600 lbs. Equipment should be provided such that one person can easily handle a drum. All gaseous chlorine or hypochlorite solution-related plumbing should follow Chlorine Institute directives. Storage and chlorine dioxide systems typically include the following: Storage and feeding in a designated space. Use of non-combustible materials such as concrete for construction. Storage in clean, closed, non-translucent containers. Exposure to sunlight, UV light, or excessive heat will reduce product strength. April EPA Guidance Manual Alternative Disinfectants and Oxidants

124 4. CHLORINE DIOXIDE Avoid storage and handling of combustible or reactive materials, such as acids or organic materials, in the sodium chlorite area. Secondary containment for storage and handling areas to handle the worse case spill with sumps provided to facilitate recovery. A water supply near storage and handling areas for cleanup. Inert material should be used in contact with the strong oxidizing and/or acid solutions involved in chlorine dioxide systems. Storage tanks with vents to outside. Adequate ventilation and air monitoring. Gas masks and first aid kits outside of the chemical areas. Reactor with glass view ports if it is not made of transparent material. Flow monitoring on all chemical feed lines, dilution water lines, and chlorine dioxide solution lines. Dilution water should not be excessively hard in order to avoid calcium deposits and should be near neutral ph. On-site and frequent testing of chemical solution strengths should be practiced to achieve efficient process control. Air contact with chlorine dioxide solutions should be controlled to limit the potential for explosive concentrations possibly building up within the generator. Chlorine dioxide concentrations in air higher than 8 to 10 percent volume should be avoided. Two methods can be applied: operation under vacuum or storage under higher positive pressure (45 to 75 psig) to prevent buildup of gas-phase ClO 2 in the head space. Bulk storage (batch) tanks containing ClO 2 should be suitably vented to atmosphere. Sodium chlorite solution feed pumps are commonly diaphragm-metering pumps for liquid feed rate control. If centrifugal pumps are used, the only acceptable packing material is Teflon. If lubrication is needed, minimum quantities of fire-resistant lubricants should be used. Pump motors should be totally enclosed, fan-cooled (TEFC) with sealed-for-life bearings. Couplings should be of the greaseless type. Water lines for mechanical seals should have a pressure gauge and throttling valve on the outlet side. Visual means should be provided to verify adequate water flow. Each pump should include a calibration chamber. Pipes carrying sodium chlorite should be provided sufficient support to minimize risk of overstressing joints. Flexible connections to pumps should also be provided to minimize risk of vibration damage. Pipe should be sloped to drainage points and valved hose connections provided at strategic points for efficient flushing and draining. Service water for flushing feed lines should be introduced only through temporarily connected hoses protected by a backflow preventer. Service water lines should include check valves. Hose connections from service water lines should have a vent valve to release pressure before the hose is disconnected after use. EPA Guidance Manual 4-12 April 1999 Alternative Disinfectants and Oxidants

125 4. CHLORINE DIOXIDE Flows are frequently measured with magnetic flow meters, mass flow meters, or rotameters for precise control. Provisions should always be made for back-flow prevention. Sodium chlorite is extremely reactive, especially in the dry form, and care should be taken to protect against potentially explosive conditions. Chlorine dioxide solution concentrations below about 10 g/l will not produce sufficiently high vapor pressures to present an explosion hazard under most ambient conditions of temperature and pressure. In water treatment, chlorine dioxide solution concentrations rarely exceed 4 g/l for temperatures less than 40 C, and treatment levels generally range from 0.1 to 5.0 mg/l. If temperatures exceed 50 C, storage tanks should be suitably vented due to the higher levels of ClO 2 possible. As cold service/potable water is typically used as generator dilution water, these conditions are rarely encountered Generator Power Requirements Generator power requirements are similar to those for chlorination systems. For all generators (20 to 12,000 lb/day) power can be supplied from 120 VAC single phase, to 480 VAC three phase. Power demand will vary based upon make-up water pressure available to operate the venturi. Fractional horsepower metering pumps are required, based upon system configuration. 4.3 Primary Uses and Points of Application for Chlorine Dioxide The calculation of CT for chlorine dioxide is similar to other disinfectants, with accurate determinations of residual concentrations being a prerequisite for effective disinfection. Primary disinfectant credit is achieved by the residual concentration and the effective contact time. It has been found in practice that because of the volatile nature of the gas, chlorine dioxide works extremely well in plug flow reactors such as pipe lines. It can be easily removed from dilute aqueous solution by turbulent aeration in rapid mix tanks or purging in recarbonation basins. CT credits should not be expected through a filter because the likelihood that no residual remains in the filtered water (DeMers and Renner, 1992). For post CT disinfection credit, chlorine dioxide can be added before clearwells or transfer pipelines. Ample sampling points should be included to allow close monitoring of residual concentrations. It is well known that chlorine dioxide is commonly destroyed by UV in basins exposed to sunlight or bright fluorescent lights. Therefore, protective design elements should be incorporated if such exposure is anticipated Disinfection Before chlorine dioxide is selected for use as a primary disinfectant an oxidant demand study should be completed. Ideally, this study should consider the seasonal variations in water quality, temperature, and application points. Table 4-2 shows typical results for a single sample of a demand study completed on a surface water source. April EPA Guidance Manual Alternative Disinfectants and Oxidants

126 4. CHLORINE DIOXIDE The MRDL for chlorine dioxide is 0.8 mg/l and the MCL for chlorite is 1.0 mg/l per the D/DBP rule. This means that if the oxidant demand is greater than about 1.4 mg/l, chlorine dioxide may not be used as a disinfectant because the chlorite/chlorate ions byproduct, might exceed the maximum level allowed, unless inorganic byproducts (e.g., chlorite) are subsequently removed. There are numerous means to reduce excessive chlorite levels prior to chlorination in conventional water plants. Table 4-2. Surface Water Chlorine Dioxide Demand Study Results Dose (mg/l) Time (min) ClO2 (mg/l) ClO2 - (mg/l) ClO3 - (mg/l) Source: DeMers and Renner, Note: *Raw water sample, 23 C, 8.5 ph Typical dosages of chlorine dioxide used as a disinfectant in drinking water treatment range from 0.07 to 2.0 mg/l. For plants using chlorine dioxide, median concentrations of chlorite and chlorate were found to be 0.24 and 0.20 mg/l, respectively in an EPA survey (USEPA, 1998), the standard is 1.0 mg/l Taste and Odor Control A common application of chlorine dioxide in drinking water in the United States has been for control of tastes and odors associated with algae and decaying vegetation. Chlorine dioxide is also effective in destroying taste and odor producing phenolic compounds. The recommended location for application of chlorine dioxide for this purpose will depend on raw water quality, the type of treatment plant and any other purposes for chlorine dioxide addition. In conventional treatment plants, it is recommended that chlorine dioxide be added near the end of or following, the sedimentation basin. If the raw water turbidity is low (for example, less than 10 NTU), chlorine dioxide can be added at the beginning of the plant. Some utilities follow this practice because chlorine dioxide is effective in controlling algae growth in flocculation and sedimentation basins that are exposed to sunlight (DeMers and Renner, 1992). Such application during periods of darkness may be more successful for nuisance algae control Oxidation of Iron and Manganese Chlorine dioxide can be used to oxidize both iron and manganese. Chlorine dioxide reacts with the soluble forms of iron and manganese to form precipitates that can be removed through sedimentation and filtration. Chlorine dioxide reduces to chlorite ion in this reaction (Knocke et al., 1993). About 1.2 mg/l of chlorine dioxide is required to remove 1.0 mg/l of iron, and 2.5 mg/l of chlorine dioxide are required to remove 1.0 mg/l of manganese. For high concentrations of iron and manganese, the use of chlorine dioxide is limited to the 1.0 mg/l chlorite/chlorate ion byproduct, as EPA Guidance Manual 4-14 April 1999 Alternative Disinfectants and Oxidants

127 4. CHLORINE DIOXIDE described before. Ferrous iron may be added prior to conventional coagulation to chemically reduce chlorite ion (to chloride ion) and improve the overall flocculation process. 4.4 Pathogen Inactivation and Disinfection Efficacy For water treatment, chlorine dioxide has several advantages over chlorine and other disinfectants. In contrast to chlorine, chlorine dioxide remains in its molecular form in the ph range typically found in natural waters (Roberts et al., 1980). Chlorine dioxide is a strong oxidant and disinfectant. Its disinfection mechanisms are not well understood, but appear to vary by type of microorganism Inactivation Mechanisms Gross physical damage to bacterial cells or viral capsids has not been observed at the low concentrations of chlorine dioxide typically used to disinfect drinking water. Therefore, studies have focused primarily on two more subtle mechanisms that lead to the inactivation of microorganisms: determining specific chemical reactions between chlorine dioxide and biomolecules; and observing the effect chlorine dioxide has on physiological functions. In the first disinfection mechanism, chlorine dioxide reacts readily with amino acids cysteine, tryptophan, and tyrosine, but not with viral ribonucleic acid (RNA) (Noss et al., 1983; Olivier et al., 1985). From this research, it was concluded that chlorine dioxide inactivated viruses by altering the viral capsid proteins. However, chlorine dioxide reacts with poliovirus RNA and impairs RNA synthesis (Alvarez and O Brien, 1982). It has also been shown that chlorine dioxide reacts with free fatty acids (Ghandbari et al., 1983). At this time, it is unclear whether the primary mode of inactivation for chlorine dioxide lies in the peripheral structures or nucleic acids. Perhaps reactions in both regions contribute to pathogen inactivation. The second type of disinfection mechanism focuses on the effect of chlorine dioxide on physiological functions. It has been suggested that the primary mechanism for inactivation was the disruption of protein synthesis (Bernarde et al., 1967a). However, later studies reported the inhibition of protein synthesis may not be the primary inactivation mechanism (Roller et al., 1980). A more recent study reported that chlorine dioxide disrupted the permeability of the outer membrane (Aieta and Berg, 1986). The results of this study were supported by the findings of Olivieri et al. (1985) and Ghandbari et al. (1983), which found that the outer membrane proteins and lipids were sufficiently altered by chlorine dioxide to increase permeability Environmental Effects Studies have been performed to determine the effect of ph, temperature, and suspended matter on the disinfection efficiency of chlorine dioxide. Following is a summary of the effects these parameters have on pathogen inactivation. April EPA Guidance Manual Alternative Disinfectants and Oxidants

128 4. CHLORINE DIOXIDE ph In comparison to chlorine, studies have shown that ph has much less effect on pathogen inactivation for viruses and cysts with chlorine dioxide than with chlorine in the ph range of 6 to 8.5. Unlike chlorine, studies on chlorine dioxide have shown the degree of inactivation of poliovirus 1 (Scarpino et al., 1979) and Naegleria gruberi cysts (Chen et al., 1984) increase as the ph increases. The results of studies on E. coli inactivation are inconclusive. It has been found that the degree of inactivation by chlorine dioxide increases as ph increases (Bernarde et al., 1967a). However, an earlier study found that the bactericidal activity of chlorine dioxide was not affected by ph values in the range of 6.0 to 10.0 (Ridenour and Ingols, 1947). A recent study on Cryptosporidium found that inactivation of oocysts using chlorine dioxide occurred more rapidly at a ph of 8.0 than 6.0. At a similar CT value, the level of inactivation at ph of 8.0 was approximately twice that at a ph of 6.0 (Le Chevallier et al., 1997). Another study found that chlorine dioxide efficacy increases for Giardia inactivation at higher ph levels and that this may be the result of chemical or physical changes in Giardia cyst structure rather than ph effects on chlorine dioxide disproportionation (Liyanage et al., 1997). More research is needed to further clarify how ph impacts the effectiveness of chlorine dioxide Temperature Similar to chlorine, the disinfection efficiency of chlorine dioxide decreases as temperature decreases (Ridenour and Ingols, 1947). This finding is supported by the data from Chen et al. (1984) shown in Figure 4-3 for the inactivation of Naegleria gruberi cysts. The curve shows the CT required to achieve 99 percent inactivation for temperatures between 5 and 30 C. In a more recent study, LeChevallier et al. (1997) found that reducing the temperature from 20 C to 10 C reduced the disinfection effectiveness of chlorine dioxide on Cryptosporidium by 40 percent, which is similar to previous results for Giardia and viruses. Gregory et al. (1998) found that even under the most favorable conditions (i.e., at a ph of 8.5), required doses to achieve 2-log Cryptosporidium inactivation do not appear to be a feasible alternative, requiring doses of more than 3.0 mg/l with a 60 minute detention time. At neutral ph levels, the required doses may be more than 20 mg/l. EPA Guidance Manual 4-16 April 1999 Alternative Disinfectants and Oxidants

129 4. CHLORINE DIOXIDE CT Product (mg min/l) Temperature ( C) Figure 4-3. Effect of Temperature on N. Gruberi Cyst Inactivation at ph Suspended Matter Suspended matter and pathogen aggregation affect the disinfection efficiency of chlorine dioxide. Protection from chlorine dioxide inactivation due to bentonite was determined to be approximately 11 percent for turbidities equal to or less than 5 NTUs and 25 percent for turbidities between 5 and 17 NTUs (Chen et al., 1984). Laboratory studies of poliovirus 1 preparations containing mostly viral aggregates took 2.7 times longer to inactivate with chlorine dioxide than single state viruses (Brigano et al., 1978). Chen et al. (1984) also found that clumps of Naegleria gruberi cysts were more resistant to chlorine dioxide than unclumped cysts or clumps of smaller size Disinfection Efficacy Several investigations have been made to determine the germicidal efficiency of chlorine dioxide since its introduction in 1944, as a drinking water disinfectant. Most of the investigations were carried out as a comparison to chlorine; some studies have compared chlorine dioxide and ozone. Chloride dioxide is a more effective disinfectant than chlorine but is less effective than ozone Bacteria Inactivation Quantitative data were published as early as the 1940s demonstrating the efficacy of chlorine dioxide as a bactericide. In general, chlorine dioxide has been determined to be equal to or superior to chlorine on a mass-dose basis. It was demonstrated that even in the presence of suspended matter, April EPA Guidance Manual Alternative Disinfectants and Oxidants

130 4. CHLORINE DIOXIDE chlorine dioxide was effective against E. coli and Bacillus anthracoides at dosages in the range of 1 to 5 mg/l (Trakhtman, 1949). Ridenour and Armbruster (1949) reported that an orthotolidine arsenite (OTA) chlorine dioxide residual of less than 1 mg/l was effective against Eberthella typhosa, Shigella dysenteriae, and Salmonella paratyphi B. Under similar ph and temperature slightly greater OTA residuals were required for the inactivation of Pseudomonas aeruginosa and Staphylococcus aureus. Chlorine dioxide was shown to be more effective than chlorine at inactivating B. subtilis, B. mesentericus, and B. megatherium spores (Ridenour et al., 1949). Moreover, chlorine dioxide was shown to be just as effective or more effective than chlorine at inactivating Salmonella typhosa and S. paratyphi (Bedulivich et al., 1954). In the early 1960s several important contributions were made by Bernarde et al. (1967a and 1967b). Chlorine dioxide was found to be more effective than chlorine at disinfecting sewage effluent and the rate of inactivation was found to be rapid. A comprehensive investigation of chlorine dioxide as disinfectant was performed by Roberts et al. (1980). The investigation was performed using secondary effluents from three different wastewater treatment plants. One of the objectives was to determine the relationships between dosages and contact times and bactericidal efficiency. Dosages were compared for 2, 5, and 10 mg/l of chlorine dioxide and chlorine. The contact times selected were 5, 15 and 30 minutes. Results of the investigation are shown in Figure 4-4. As shown, chlorine dioxide demonstrated a more rapid coliform inactivation than chlorine at the shortest contact time of 5 minutes and higher concentrations. However, after 30 minutes of contact time, chlorine dioxide was equal or slightly less efficient than chlorine as a bactericide. Oliveri et al. (1984) studied the effectiveness of chlorine dioxide (and chlorine) residuals in inactivating total coliform and f2 coliphage virus in sewage introduced to a water distribution system. Initial chlorine dioxide residuals between 0.85 and 0.95 mg/l resulted in an average 2.8 log inactivation of the total coliform and an average 4.4-log inactivation of the f2 coliphage virus, over a contact time of 240 minutes. EPA Guidance Manual 4-18 April 1999 Alternative Disinfectants and Oxidants

131 4. CHLORINE DIOXIDE Source: Roberts et al., Figure 4-4. Comparison of Germicidal Efficiency of Chlorine Dioxide and Chlorine Protozoa Inactivation The disinfection efficiency of chlorine dioxide has been shown to be equal to or greater than chlorine for Giardia inactivation. Based on a 60 minute contact time, chlorine dioxide doses in the range of 1.5 to 2 mg/l are capable of providing a 3-log Giardia inactivation at 1 C to 25 C and phs of 6 and 9 (Hofmann et al., 1997). Depending on the temperature and ph, Cryptosporidium has been found to be 8 to 16 times more resistant to chlorine dioxide than Giardia (Hofmann et al., 1997). Although some Cryptosporidium oocysts remained viable, one group of researchers found that a 30-minute contact time with 0.22 mg/l chlorine dioxide could significantly reduce oocyst infectivity (Peeters et al., 1989). In contrast, other researchers have found that CT values in the range of 60 to 80 mg min/l were necessary to provide 1- to 1.5-log inactivation (Korich et al., 1990; Ransome et al., 1993). Finch et al. (1995) reported that the CT values for 1-log inactivation was in the range of 27 to 30 mg min/l. For 2-log inactivation, the CT value was approximately 40 mg min/l, and 70 mg min/l for 3-log inactivation. Finch et al. (1997) found 3-log inactivation of Cryptosporidium oocysts with initial chlorine dioxide residual concentrations of 2.7 and 3.3 mg/l for contact times of 120 minutes, at ph of 8.0 and a temperature of 22ºC. April EPA Guidance Manual Alternative Disinfectants and Oxidants

132 4. CHLORINE DIOXIDE Both Chen et al. (1985) and Sproul et al. (1983) have investigated the inactivation of Naegleria gruberi cysts by chlorine dioxide. Both studies concluded that chlorine dioxide is an excellent disinfectant against cysts and that chlorine dioxide is better than or equal to chlorine in terms of inactivation. Chlorine dioxide was found to be superior to chlorine at higher phs. However, the authors cautioned that the CT required for 2-log inactivation was much higher than normally employed for water treatment at that time Virus Inactivation Chlorine dioxide has been shown to be an effective viricide. Laboratory studies have shown that inactivation efficiency improves when viruses are in a single state rather than clumped. It was reported in 1946 that chlorine dioxide inactivated Poliomyelitis (Ridenour and Ingols, 1946). This investigation also showed that chlorine dioxide and free chlorine yielded similar results. Other studies have verified these findings for poliovirus 1 (Cronier et al., 1978) and Coxsackie virus A9 (Scarpino, 1979). At greater than neutral phs (where hypochlorite ion is the predominant species) chlorine dioxide has been found to be superior to chlorine in the inactivation of numerous viruses such as echovirus 7, coxsackie virus B3, and sendaivirus (Smith and McVey, 1973). Sobsey (1998) determined CT values based on a study of Hepatitis A virus, strain HM 175. The study found 4-log inactivation levels are obtainable at CT values of less than 35 at 5 C and less than 10 at a temperature of 25 C CT Values Chlorine dioxide is regarded as a strong disinfectant that is effective at inactivating bacterial, viral, and protozoan pathogens. CT values for Giardia and virus inactivation are shown in Figure 4-5 and Figure 4-6, respectively (AWWA, 1991). CT values shown in Figure 4-5 are based on disinfection studies using in vitro excystation of Giardia muris. Average CT values for 2 log removal were extrapolated using first order kinetics and multiplied by a safety factor of 1.5 to obtain the CT values for other log removal CT values. Due to the limited amount of data available at ph values other than 7, the same CT values are used for all phs. Because chlorine dioxide is more effective at a ph 9 than at a ph of 7, the CT values shown in Figure 4-5 are more conservative for higher phs than for lower phs. A lower safety factor was used to derive the CT values for chlorine dioxide than for ozone due to the fact that the chlorine dioxide values were derived from Giardia muris studies, which are more resistant than Giardia lamblia. EPA Guidance Manual 4-20 April 1999 Alternative Disinfectants and Oxidants

133 4. CHLORINE DIOXIDE log Inactivation log Inactivation 1.5-log Inactivation 2-log Inactivation CT Product (mg min/l) log Inactivation 3-log Inactivation Source: AWWA, Temperature ( C) Figure 4-5. CT Values for Inactivation of Giardia Cysts by Chlorine Dioxide CT values shown in Figure 4-6 were obtained by applying a safety factor 2 to the average CT values derived from the studies on hepatitis A virus, strain HM 175 (Sobsey, 1988). CT values at temperatures other than 5 C were derived by applying a twofold decrease for every 10 C increase in temperature. Figure 4-7 and Figure 4-8 show the relationship between CT products and log inactivation of Cryptosporidium at 20 and 10 C, respectively, and phs of 6 and 8. CT values shown in Figure 4-7 and Figure 4-8 indicate that oocysts were more rapidly inactivated at ph 8 than 6 and that temperature does impact the disinfection efficiency of chlorine dioxide. Reducing the temperature from 20 to 10 C reduced the disinfection effectiveness by 40 percent. Finch (1997) is studying Cryptosporidium inactivation under laboratory conditions using a variety of different disinfectants, one of which is chloride dioxide. April EPA Guidance Manual Alternative Disinfectants and Oxidants

134 4. CHLORINE DIOXIDE log Inactivation log Inactivation log Inactivation CT Va lu es (m g mi n/ L) Temperature ( C) Source: AWWA, Figure 4-6. CT Values for Inactivation of Viruses by Chlorine Dioxide 4.5 Chlorine Dioxide Disinfection Byproducts Byproducts from the use of chlorine dioxide include chlorite, chlorate, and organic DBPs. This section discusses the formation of these byproducts and methods to reduce or remove these DBPs. The use of chlorine dioxide aids in reducing the formation of TTHMs and HAAs by oxidizing precursors, and by allowing the point of chlorination to be moved farther downstream in the plant after coagulation, sedimentation, and filtration have reduced the quantity of NOM Production of Chlorite and Chlorate Chlorite and chlorate are produced in varying ratios as endproducts during chlorine dioxide treatment and subsequent degradation. The primary factors affecting the concentrations of chlorine dioxide, chlorite, and chlorate in finished drinking water involve: Dosage applied/oxidant demand ratio. Blending ratios of sodium chlorite and chlorine during the chlorine dioxide generation process. Exposure of water containing chlorine dioxide to sunlight. EPA Guidance Manual 4-22 April 1999 Alternative Disinfectants and Oxidants

135 4. CHLORINE DIOXIDE Log Inactivation CT Product (mg min/l) ph 6.0; 1.52 mg/l dose, 1.23 mg/l residual ph 6.0; 0.51 mg/l dose, 0.38 mg/l residual ph 8.0; 1.52 mg/l dose, 1.23 mg/l residual ph 8.0; 0.51 mg/l dose, 0.39 mg/l residual Source: LeChevallier et al., Figure 4-7. C. parvum Inactivation by Chlorine Dioxide at 20 C Log Inactivation ph 6.0; 1.52 mg/l dose, 1.23 mg/l residual ph 6.0; 0.51 mg/l dose, 0.39 mg/l residual CT Product (mg min/l) ph 8.0; 1.52 mg/l dose, 1.23 mg/l residual ph 8.0; 0.51 mg/l dose, 0.39 mg/l residual Source: LeChevallier et al., Figure 4-8. C. parvum Inactivation by Chlorine Dioxide at 10 C April EPA Guidance Manual Alternative Disinfectants and Oxidants

136 4. CHLORINE DIOXIDE Reactions between chlorine and chlorite if free chlorine is used for distribution system residual maintenance. Levels of chlorate in sodium chlorite feedstock. Incomplete reaction or non-stoichiometric addition of the sodium chlorite and chlorine reactants can result in unreacted chlorite in the chlorine dioxide feed stream. Dilute chlorine dioxide solutions are stable under low or zero oxidant-demand conditions. The quantity of chlorate produced during the chlorine dioxide generation process is greater with excess chlorine addition. Likewise, a low or high ph can increase the quantity of chlorate during the chlorine dioxide generation process. See Section 4.2, Generation, for a detailed discussion of the chemistry of chlorine dioxide generation. Numerous inorganic and biological materials found in raw water will react with chlorine dioxide (Noack and Doerr, 1977). Chloride (Cl - ) and chlorite (ClO 2 - ) ions are the dominant degradation species arising from these reactions, although chlorate (ClO 3 - ) can appear for a variety of reasons when chlorine dioxide is used (Gordon et al., 1990; Werdehoff and Singer, 1987). The immediate redox reactions with natural organic matter play the dominant role in decay of chlorine dioxide into chlorite in drinking water (Werdehoff and Singer, 1987). Chlorite ion is generally the primary product of chlorine dioxide reduction. The distribution of chlorite and chlorate is influenced by ph and sunlight. Approximately 50 to 70 percent of the chlorine dioxide consumed by oxidation reactions is converted to chlorite under conditions typical in water treatment (Rav-Acha et al., 1984; Werdehoff and Singer, 1987). The application of 2 mg/l chlorine dioxide is expected to produce 1 to 1.4 mg/l of chlorite (Singer, 1992). Chlorite is relatively stable in the presence of organic material but can be oxidized to chlorate by free chlorine if added as a secondary disinfectant (Singer and O Neil, 1987). ClO OCl - = ClO Cl - Chlorate is therefore produced through the reaction of residual chlorite and free chlorine during secondary disinfection. In addition, chlorine dioxide also disproportionates under highly alkaline conditions (ph>9) to chlorite and chlorate according to the following reaction: 2ClO 2 + 2OH - = ClO ClO H 2 O In water treatment processes that require high ph, such as softening, chlorine dioxide should be added after the ph has been lowered (Aieta et al., 1984). The occurrence of photochemical decomposition of chlorine dioxide can affect the ultimate concentrations of chlorine dioxide, chlorite, and chlorate in water treated with chlorine dioxide. Moreover, generally, sunlight may increase chlorate concentrations in uncovered storage basins containing water with chlorine dioxide residuals. Exposure to ultraviolet light will also change the potential reactions between chlorine dioxide and the bromide ion. EPA Guidance Manual 4-24 April 1999 Alternative Disinfectants and Oxidants

137 4. CHLORINE DIOXIDE Organic DBPs Produced by Chlorine Dioxide Chlorine dioxide generally produces few organic DBPs. However, Singer (1992) noted that the formation of non-halogenated organic byproducts of chlorine dioxide has not been adequately researched, and expected that chlorine dioxide will produce the same types of oxidation byproducts that are produced through ozonation. The application of chlorine dioxide does not produce THMs and produces only a small amount of total organic halide (TOX) (Werdehoff and Singer, 1987). A study was conducted in 1994 by Richardson et al., to identify semivolatile, organic DBPs produced by chlorine dioxide treatment in drinking water. Samples were taken from a pilot plant in Evansville, Indiana that included the following treatment variations: Aqueous chlorine dioxide; Aqueous chlorine dioxide, ferrous chloride, (FeCl 2 ), chlorine (Cl 2 ), and dual media filtration (sand and anthracite); Gaseous chlorine dioxide; and Gaseous chlorine dioxide, ferrous chloride (FeCl 2 ), chlorine (Cl 2 ), and dual media filtration (sand and anthracite). Using multispectral identification techniques, more than 40 different DBPs (many at sub-nanogram/l [ng/l] levels) were identified including carboxylic acids and maleic anhydrides isolated from XAD concentrates, some of which may be regulated in the Stage 2 DBPR. THMs were not found after chlorine dioxide was added to the water; however, THMs did show up during subsequent chlorination Chlorine Dioxide DBP Control Strategies EPA recommends that the total concentration of chlorine dioxide, chlorite, and chlorate be less than 1.0 mg/l as Cl 2 (USEPA, 1983). In addition, chlorine dioxide concentrations exceeding 0.4 to 0.5 mg/l contribute to taste and odor problems (AWWA, 1990). Due to these issues, the use of chlorine dioxide to provide a disinfectant residual is somewhat limited in moderate to high TOC water. In low oxidant-demand water, however, ClO 2 residuals may last several days. Once formed, chlorate is stable in finished drinking water. No known treatment exists for removing chlorate once it is formed. However, three strategies (Gallagher et al., 1994) that have been proven effective for chlorite removal are: Adding reduced-sulfur compounds such as sulfur dioxide and sodium sulfite (not recommended). Applying either granular activated carbon (GAC) or powdered activated carbon (PAC). Adding reduced iron salts, such as ferrous chloride and ferrous sulfate. April EPA Guidance Manual Alternative Disinfectants and Oxidants

138 4. CHLORINE DIOXIDE Chlorite removal from drinking water through sulfur dioxide and other sulfur-based reducing agents has been reported effective, but not desirable. A study of chlorite removal by sulfur dioxide indicates that a lower ph level yields higher chlorite removal, and chlorite removal efficiencies increase as the sulfur dioxide dose increases. Unfortunately, this removal process forms significant levels of chlorate when sulfur dioxide and metasulfite are utilized. Therefore, it is concluded that treatment with sulfur dioxide and metasulfite is not desirable for chlorite removal (Dixon and Lee, 1991). In addition, sodium thiosulfate results in effective chlorite reduction, but the degree of removal is highly dependent upon ph and contact time and relatively high dosages are required. Again, this application of sodium thiosulfate is not desirable because the required dosages are too high (Griese et al., 1991). The addition of ferrous iron in drinking water is effective for chlorite removal, with chloride the expected byproduct. Chlorite reduction occurs quickly in the ph range of 5 to 7, and complete reduction occurs within 3 to 5 seconds. Excess reduced iron remaining in solution reacts with dissolved oxygen at neutral ph, but under acidic conditions (ph < 6.5) the stability of the soluble iron can create aesthetic (staining) problems if excess iron is used. Special consideration should be given to ferrous iron dosage requirements so that the secondary MCL for iron is not exceeded (Knocke and Iatrou, 1993). Chlorite can be controlled by PAC at relatively high dosages (10 to 20 mg/l) and low phs (5.5 to 6.5). Unless PAC is used for other purposes, such as odor control, it requires large doses and is not cost effective. PAC brands can differ in their capacity to reduce chlorite. GAC can remove chlorite but breakthrough may occur relatively early. The removal of chlorite by GAC appears to be a result of adsorption and chemical reduction (Dixon and Lee, 1991). There is an initial high removal efficiency due to chlorite adsorption. As the adsorptive sites are occupied, chemical reduction on the GAC surface becomes the primary removal mechanism. This results in an initial high removal efficiency. Although chlorite levels exiting the GAC filters are low, the chlorate levels are high, most likely a result of reactions in the GAC filters between chlorite and free chlorine. According to studies, the capacity of GAC beds is low, and if free chlorine and chlorite ion are present in the GAC influent, chlorate ion will form. The most effective way to operate GAC for chlorite reduction and avoid chlorate is to minimize production run times and have no chlorine present in the filter. 4.6 Status of Analytical Methods In addition to the monitoring requirements that apply regardless of the disinfectant used, the DBPR requires that water systems that use chlorine dioxide for disinfection or oxidation must also monitor their system for chlorine dioxide and chlorite. EPA Guidance Manual 4-26 April 1999 Alternative Disinfectants and Oxidants

139 4. CHLORINE DIOXIDE Chlorine Dioxide and Chlorite Analytical Methods For compliance monitoring for chlorine dioxide, systems must use one of the two methods specified in 40 CFR (c), including (1) DPD, Standard Method 4500-CLO 2 D, or (2) Amperometric Method II, Standard Method 4500-CLO 2 E. Where approved by the state, systems may also measure residual disinfectant concentrations for chlorine dioxide by using DPD colorimetric test kits. For compliance monitoring for chlorite, systems must use one of the three methods specified in 40 CFR (b), including (1) Amperometric Titration, Standard Method 4500-CLO 2 E, (2) Ion Chromatography, EPA Method 300.0, or (3) Ion Chromatography, EPA Method The regulations specify that Amperometric Titration may be used for routine daily monitoring of chlorite at the entrance to the distribution system, but that Ion Chromatography must be used for routine, monitoring of chlorate and monthly additional monitoring of chlorate in the distribution system. Details of these analytical procedures can be found in: - Standard Methods for the Examination of Water and Wastewater, 19 th Edition, American Public Health Association, Methods for the Determination of Inorganic Substances in Environmental Samples. USEPA EPA/600/R-93/ USEPA Method 300.1, Determination of Inorganic Anions in Drinking Water by Ion Chromatography, Revision 1.0. USEPA EPA/600/R-98/118. Table 4-3 summarizes the analytical methods approved for use for chlorine dioxide and chlorite and provides some background information for each method Chlorine Dioxide Monitoring for Systems Using Chlorine Dioxide For chlorine dioxide monitoring, community, non-transient non-community, and transient noncommunity water systems that use chlorine dioxide for disinfection or oxidation, are required to take daily samples at the entrance to the distribution system. For any daily sample that exceeds the chlorine dioxide MRDL of 0.8 mg/l, the system must take additional samples in the distribution system the following day at the locations specified in the DBPR, in addition to the daily sample required at the entrance to the distribution system. Additional sampling is to be performed in one of two ways, depending on the disinfectant that is used to maintain a disinfectant residual in the distribution system. If chlorine dioxide or chloramines are used to maintain a disinfectant residual, or if chlorine is used to maintain the residual and there are no disinfection addition points after the entrance to the distribution system (i.e., no booster chlorination), the system must take three samples as close to the first customer as possible, at intervals of at least six hours. If chlorine is used to maintain a disinfectant residual and there are one or more disinfection addition points after the entrance to the distribution system, the system must take one sample at each of the following locations: (1) as close to the first customer as possible, (2) in a location representative of average residence time, April EPA Guidance Manual Alternative Disinfectants and Oxidants

140 4. CHLORINE DIOXIDE and (3) as close to the end of the distribution system as possible (reflecting maximum residence time in the distribution system). Chlorine dioxide monitoring may not be reduced. If any daily sample taken at the entrance to the distribution system exceeds the MRDL, and on the following day one (or more) of the three samples taken in the distribution system exceed the MRDL, the system is in violation of the MRDL. The system must take immediate corrective action to lower the level of chlorine dioxide below the MRDL, and must notify the public of the acute violation pursuant to 40 CFR The system must also report to the State pursuant to 40 CFR If any two consecutive daily samples taken at the entrance to the distribution system exceed the MRDL, the system is also in violation of the MRDL and must notify the public of the non-acute violation pursuant to 40 CFR The system must also report to the State pursuant to 40 CFR Chlorite Monitoring for Systems Using Chlorine Dioxide For chlorite monitoring, community and non-transient non-community water systems that use chlorine dioxide for disinfection or oxidation are required to take daily samples at the entrance to the distribution system. For any daily sample that exceeds the chlorite MCL of 1.0 mg/l, the system must take additional samples in the distribution system the following day at the locations specified in the DBPR. These additional samples are to be collected at: (1) a location as close to the first customer as possible, (2) a location representative of average residence time, and (3) a location as close to the end of the distribution system as possible (reflecting maximum residence time in the distribution system). In addition, systems using chlorine dioxide must take a three-sample set each month in the distribution system similar to the three locations required if the chlorite MCL is exceeded in the sample collected at the entrance to the distribution system. Specifically, these three-sample sets are to be collected: (1) in a location near the first customer, (2) in a location representative of average residence time, and (3) at a location reflecting maximum residence time in the distribution system. Any additional routine sampling must be conducted in the same three-sample sets at the specified locations. This monthly sampling requirement may be reduced to quarterly after one year of monitoring where: (1) no individual chlorite sample taken in the distribution system has exceeded the MCL and (2) the system has not been required to conduct follow-up monitoring as a result of a daily sample collected at the entrance to the distribution system. These systems can remain on an annual schedule until either the daily sample or any of the three individual quarterly samples exceed the MCL, at which time, the system must revert to monthly monitoring. If the arithmetic average of any three-sample set exceeds the chlorite MCL of 1.0 mg/l, the system is in violation of the MCL and must notify the public pursuant to 40 CFR , in addition to reporting to the State pursuant to 40 CFR Operational Considerations As with all disinfectant selections, the primacy agency should be consulted when selecting disinfectants. Certain states have their own operational, maintenance, and monitoring requirements EPA Guidance Manual 4-28 April 1999 Alternative Disinfectants and Oxidants

141 4. CHLORINE DIOXIDE for the application of chlorine dioxide. California prohibits the use of chlorine dioxide in ground water systems, according to Merkle et al., Also, in Texas, the Texas Natural Resources Conservation Commission (TNRCC) requires the public water supply to sign a bilateral agreement which outlines a detailed operator qualifications requirement, testing methods, and procedures, monitoring locations, testing frequency and reporting procedures. The chlorine dioxide concentration leaving the water treatment plant must be less than 0.8 mg/l and the chlorite concentration in the distribution system must be less than 1.0 mg/l. State requirements must be reviewed to determine the cost-effectiveness of utilizing chlorine dioxide as part of the overall water treatment scheme. Analytical testing and reporting requirements may have significant labor and cost impacts. April EPA Guidance Manual Alternative Disinfectants and Oxidants

142 4. CHLORINE DIOXIDE Table 4-3. Analytical Methods for Chlorine Dioxide and Related Compounds DPD as Test Kits Colorimetric (SM-4500-ClO2 G) DPD-glycine Method Colorimetric (SM ClO2 D) DPD-FAS Titrimetric method (SM ClO2.D) 5-Step Amperometric Method 4500-ClO2.E Method Basis Interferences Limits Ion Chromatography (EPA Method or 300.1) Conductivity Two-step Amperometric Method 4500-ClO2.E Source: Gates, Notes: SM = Standard Methods Colored oxidation product. Use of color comparator is not recommended. Use instrument detection. Colored product, free Cl2 is masked with glycine as chloraminacetic acid. DPD color titration with standard FAS until red color is discharged. I - oxidation; ph control and gas purging steps. Skilled analyst needed. Must use AS9 column, ext. standards & suppression. I - Oxidation; ph control. Amendable to operator-based dosage control. Practical method Process Considerations Mn2 +, other Cl2, related oxidants. ClO2 - slowly; other oxidants. Iron, other oxidants. Suitable for ClO2 generated solution. Low levels not okay. No other oxidants. Chloramines, ClO2; OCl - & HOCL undetectable. Cu2+, Mn2+, NO2 - Accounts for free Cl2, NH2Cl, ClO2 - species. The basic components of chlorine dioxide generation systems include: Aqueous hypochlorite solution storage and feed system; Sodium chlorite storage and feed system; Acid storage and feed system (for Direct-Acidification generators); Chlorine storage and feed system; Chlorine dioxide generator; and Chlorine dioxide feed piping and dispersion equipment. > 0.1 mg/l > 0.1 mg/l > 0.1 mg/l ~ PQL ClO2 - : mg/l; ClO3 - at 0.5 mg/l ~ 0.05 mg/l > 0.1 mg/l, not ClO3 - Sodium chlorite storage and feed systems are basically liquid systems that consist of a storage tank(s) and solution feed pumps. Outside storage of 25 percent solutions (or greater) of sodium chlorite is not recommended in cold climates since stratification may occur below 4 C (40 F). Any ice formation may also damage the storage tanks. In some cases, storage might be separated into bulk tanks and smaller operational or day tanks that are filled periodically. Storage of dark drums for long periods in hot climates should be avoided since sodium chlorite decomposition will occur. In the storage area, light fixtures, switches, wiring, and conduit runs should be located to avoid the risk of sodium chlorite spilling on them. EPA Guidance Manual 4-30 April 1999 Alternative Disinfectants and Oxidants

143 4. CHLORINE DIOXIDE Generator Operation A manual chlorine dioxide feed system may be used where the chlorine dioxide dose remains fairly constant. The reagent chemicals are manually set for the desired chlorine dioxide capacity at a ratio of chemicals optimized for maximum chlorine dioxide yield. Some generating systems can produce 95 percent pure chlorine dioxide solutions at full design capacity, but purity can vary when the feed rate is changed. Turndown capacity may be limited by precision of the flow metering devices, typically 20 percent of rate capacity. Purity can vary when the feed rate is changed significantly. Feed water alkalinity, operating conditions, and ph also can affect yield. The ratio of reagent chemicals should be routinely adjusted for optimum operation. Chlorine dioxide generators can be provided with automated control to provide modulation of chlorine dioxide feed rates based upon changes in flow (flow paced) and chlorine dioxide demand (residual control). The automatic modulation of the generators to meet a demand setpoint varies with manufacturer. Generally, vacuum and combination systems are limited by the hydraulic requirements of the venturi and the optimum reaction conditions for chlorine dioxide generation. A chemical metering pump or injector system is then used with a batch production system to control the applied dose of chlorine dioxide Feed Chemicals Chlorine dioxide is generated when sodium chlorite is either oxidized or acidified, or both, under controlled ph and temperature conditions. Commonly, solutions of 25 percent active sodium chlorite or less are used in chlorine dioxide generators. The major safety concern for solutions of sodium chlorite is the unintentional and uncontrollable release of high levels of chlorine dioxide. Such levels may approach detonation or conflagration concentrations by accidental acidification. The feedstock acid used by some of the generators is only one source of accidental chemical acidification. Accidental mixing with large amounts of any reducing agent or oxidizable material (such as powdered activated carbon or flammable solvents) also represents a significant hazard. The AWWA Standard B (a) includes an outline of some of these materials (AWWA, 1995). Another concern when handling and storing sodium chlorite solutions is crystallization, which occurs as a result of lower temperatures and/or higher concentrations. Crystallization will plug pipelines, valves, and other equipment. Sodium chlorite solution should not be allowed to evaporate to a powder. If dried, this product becomes a fire hazard and can ignite in contact with combustible materials. A sodium chlorite fire may result in a steam explosion if too much water and inappropriate fire-fighting techniques are used to quench such a fire. As the temperature of burning sodium chlorite is around 2200 C, water quickly turns to steam. Because thermal breakdown products of sodium chlorite at high temperatures include molecular oxygen, appropriate techniques are required to correctly extinguish closed containers or large amounts of dry material that has been ignited. Stratification of sodium chlorite in holding tanks may also occur and would influence the chlorine dioxide yield. If stratification occurs in the bulk tank, sodium chlorite changes from high density to April EPA Guidance Manual Alternative Disinfectants and Oxidants

144 4. CHLORINE DIOXIDE low density as it is fed. The density will continue to change until the material is re-mixed. In stratified tanks, excess chlorite would be fed to the generator since the bottom of the tank will have denser material, and this material would have more chlorite than required. Similarly, the bulk tank would later discharge too little chlorite. Although infrequent, such stratification is not readily apparent and may likely remain unnoticed by operations unless the generator performance is evaluated frequently. If stratification or crystallization occurs in bulk delivery trucks, the entire content should be warmed prior to delivery so that the sodium chlorite is re-mixed. Operators should be aware of the possibility of stratification and crystallization during delivery conditions. Sodium chlorite is commercially available as a 38 percent or 25 percent solution. Chemical and physical properties are given in Table 4-4. Table 4-4. Properties of Sodium Chlorite as Commercially Available 38% Solution* 25% Solution* Sodium Chlorite, (%) NaClO Sodium Chloride, (%) NaCl Inert Ingredients, mixture of other sodium salts (%) Water (%) Appearance Slightly cloudy, pale Clear, pale yellow yellow 35 C (lb/gal), typical Crystallization Point ( C) 25-7 * Source: Vulcan Chemicals For systems handling the 38 percent solution, storage tanks, piping and pumps will require a heated enclosure, or heat tracing and insulation. The 25 percent solution may not require any special protection except in cold climates. The ideal production of 1.0 pound of chlorine dioxide requires 0.5 pounds of chlorine and 1.34 pounds of pure sodium chlorite. Chlorine gas is available as a nearly 100 percent pure chemical on a weight basis. Gas flow metering devices are typically limited to +/- 5 percent accuracy at full rated capacity. For example, a 100 pound per day flow tube would allow between 20 and 30 pounds of chlorine to flow if set at 25 pounds per day (i.e., 25 +/- 5 percent of maximum flow capacity). Sodium chlorite is supplied commercially as a pre-mixed aqueous solution of various strengths. The 25 percent solution is the most commonly used grade for potable water treatment. Pure chlorine dioxide solutions (very dark amber and oily in appearance) are very dangerous and are likely to detonate if exposed to oxidizable materials or vapors, or even to bright lights. They are extremely uncommon except perhaps in very specific laboratory setup systems using concentrated sodium chlorite and concentrated acid mixtures. Such laboratory generation methods are not EPA Guidance Manual 4-32 April 1999 Alternative Disinfectants and Oxidants

145 4. CHLORINE DIOXIDE recommended for the uninitiated laboratory analyst or operator. Inexperienced personnel should not mix strong acid and strong sodium chlorite solutions together unless they are familiar with the purgeable extraction methods for sodium chlorite and have a safely designed setup under a fume hood. 4.8 Summary Advantages and Disadvantages of Chlorine Dioxide Use The following list highlights selected advantages and disadvantages of using chlorine dioxide as a disinfection method for drinking water (Masschelein, 1992; DeMers and Renner, 1992, Gallagher et al., 1994). Because of the wide variation of system size, water quality, and dosages applied, some of these advantages and disadvantages may not apply to a particular system. Advantages Chlorine dioxide is more effective than chlorine and chloramines for inactivation of viruses, Cryptosporidium, and Giardia. Chlorine dioxide oxidizes iron, manganese, and sulfides. Chlorine dioxide may enhance the clarification process. Taste and odors resulting from algae and decaying vegetation, as well as phenolic compounds, are controlled by chlorine dioxide. Under proper generation conditions (i.e., no excess chlorine), halogen-substituted DBPs are not formed. Chlorine dioxide is easy to generate. Biocidal properties are not influenced by ph. Chlorine dioxide provides residuals. Disadvantages The chlorine dioxide process forms the specific byproducts chlorite and chlorate. Generator efficiency and optimization difficulty can cause excess chlorine to be fed at the application point, which can potentially form halogen-substitute DBPs. Costs associated with training, sampling, and laboratory testing for chlorite and chlorate are high. Equipment is typically rented, and the cost of the sodium chlorite is high. Measuring chlorine dioxide gas is explosive, so it must be generated on-site. Chlorine dioxide decomposes in sunlight. Chlorine dioxide must be made on-site. Can lead to production noxious odors in some systems. April EPA Guidance Manual Alternative Disinfectants and Oxidants

146 4. CHLORINE DIOXIDE Summary Table Table 4-5 summarizes considerations and descriptions for chlorine dioxide use. Table 4-5. Summary for Chlorine Dioxide Consideration Generation Primary Uses Inactivation Efficiency Byproducts Formation Point of Application Special Considerations Description Chlorine dioxide must be generated on-site. In most potable water applications, chlorine dioxide is generated as needed and directly educed or injected into a diluting stream. Generators are available that utilize sodium chlorite and a variety of feedstocks such as Cl2 gas, sodium hypochlorite, and sulfuric or hydrochloric acid. Small samples of generated solutions, up to 1 percent (10 g/l) chlorine dioxide can be safely stored if the solution is protected from light, chilled (<5 C), and has no unventilated headspace. Chlorine dioxide is utilized as a primary or secondary disinfectant, for taste and odor control, TTHM/HAA reduction, Fe and Mn control, color removal, sulfide and phenol destruction, and Zebra mussel control. Chlorine dioxide rapidly inactivates most microorganisms over a wide ph range. It is more effective than chlorine (for pathogens other than viruses) and is not ph dependent between ph 5-10, but is less effective than ozone. When added to water, chlorine dioxide reacts with many organic and inorganic compounds. The reactions produce chlorite and chlorate as endproducts (compounds that are suspected of causing hemolytic anemia and other health effects). Chlorate ion is formed predominantly in downstream reactions between residual chlorite and free chlorine when used as the distribution system disinfectant. Chlorine dioxide does not produce THMs. The use of chlorine dioxide aids in reducing the formation of TTHMs and HAAs by oxidizing precursors, and by allowing the point of chlorination to be moved farther downstream in the plant after coagulation, sedimentation, and filtration have reduced the quantity of NOM. In conventional treatment plants, chlorine dioxide used for oxidation is fed either in the raw water, in the sedimentation basins, or following sedimentation. To limit the oxidant demand, and therefore chlorine dioxide dose and the formation of chlorite, it is common to add chlorine dioxide following sedimentation. Concerns about possible taste and odor complaints have limited the use of chlorine dioxide to provide a disinfectant residual in the distribution system. Consequently, public water suppliers that are considering the use of chlorine dioxide for oxidation and primary disinfectant applications may want to consider chloramines for secondary disinfection. An oxidant demand study should be completed to determine an approximate chlorine dioxide dosage to obtain the required CT value as a disinfectant. In addition to the toxic effects of chlorine, chlorine dioxide gas is explosive at levels > 10% in air. The chlorine dioxide dosage cannot exceed 1.4 mg/l to limit the total combined concentration of ClO2, ClO2-, ClO3-, to a maximum of 1.0 mg/l. Under the proposed DBP regulations, the MRDL for chlorine dioxide is 0.8 mg/l and the MCL for chlorite is 1.0 mg/l. Regulations concerning the use of chlorine dioxide vary from state-to-state. EPA Guidance Manual 4-34 April 1999 Alternative Disinfectants and Oxidants

147 4. CHLORINE DIOXIDE 4.9 References 1. Aieta, E., and J.D.Berg A Review of Chlorine Dioxide in Drinking Water Treatment. J. AWWA. 78(6): Aieta, E.M., P.V. Roberts, and M. Hernandez Determination of Chlorine Dioxide, Chlorine and Chlorate in Water. J. AWWA. 76(1): Alvarez, M.E. and R.T. O Brien Mechanism of Inactivation of Poliovirus by Chlorine Dioxide and Iodine. Appl. Envir. Microbiol. 44: AWWA (American Water Works Association) AWWA Standard B303-95: Sodium Chlorite. 5. AWWA Guidance Manual for Compliance with the Filtration and Disinfection Requirements for Public Water Systems Using Surface Water Sources. 6. AWWA Water Quality and Treatment, fourth edition. McGraw-Hill, Inc., New York, NY. 7. Bedulivich, T.S., M.N. Svetlakova, and N.N. Trakhtman Use of Chlorine Dioxide in Purification of Water. Chemical Abstracts. 48: Bernarde, M.A., et al.1967a. Kinetics and Mechanism of Bacterial Disinfection by Chlorine Dioxide. J. Appl. Microbiol. 15(2): Bernarde, M.A., W.B. Snow, and V.P. Olivieri. 1967b. Chlorine Dioxide Disinfection Temperature Effects. J. Appl. Bacteriol. 30(1): Chen, Y.S.R., O.J. Sproul, and A.J. Rubin Inactivation of Naegleria gruberi Cysts by Chlorine Dioxide. Water Res. 19(6): Chen, Y.S.R., O.J. Sproul, and A.J. Rubin Inactivation of Naegleria Gruberi cysts by Chlorine Dioxide. EPA Grant R , Department of Civil Engineering, Ohio State University. 12. CRC Handbook of Chemistry and Physics D.L. Lide (editor), Seventy-first edition, CRC Press, Boca Raton, FL. 13. Cronier, S., et al Water Chlorination Environmental Impact and Health Effects, Vol. 2. R. L. Jolley, et al. (editors) Ann Arbor Science Publishers, Inc. Ann Arbor, MI. 14. Demers, L.D., and R. Renner Alternative Disinfectant Technologies for Small Drinking Water Systems. AWWARF, Denver, CO. April EPA Guidance Manual Alternative Disinfectants and Oxidants

148 4. CHLORINE DIOXIDE 15. Dixon, K.L. and R.G. Lee Disinfection By-Products Control: A Survey of American System Treatment Plants. Presented at AWWA Conference, Philadelphia, PA. 16. Emmenegger, F. and G. Gordon The Rapid Interaction Between Sodium Chlorite and Dissolved Chlorine. Inorg. Chem. 6(3): Finch, G.R., L.R. Liyanage, M. Belosevic, and L.L. Gyürek Effects of Chlorine Dioxide Preconditioning on Inactivation of Cryptosporidium by Free Chlorine and Monochloramine: Process Design Requirements. Proceedings 1996 Water Quality Technology Conference; Part II. Boston, MA. 18. Finch, G.R., L.R. Liyanage, and M. Belosevic Effect of Disinfectants and Cryptosporidium and Giardia. Third International Symposium on Chlorine Dioxide: Drinking Water, Process Water, and Wastewater Issues. 19. Gallagher, D.L., R.C. Hoehn, A.M. Dietrich Sources, Occurrence, and Control of Chlorine Dioxide By-Product Residuals in Drinking Water. AWWARF, Denver, CO. 20. Gates, D.J The Chlorine Dioxide Handbook; Water Disinfection Series. AWWA Publishing, Denver, CO. 21. Gates, D.J Chlorine Dioxide Generation Technology and Mythology. Conference proceedings, Advances in Water Analysis and Treatment, AWWA, Philadelphia, PA. 22. Ghandbari, E. H., et al Reactions of Chlorine and Chlorine Dioxide with Free Fatty Acids, Fatty Acid Esters, and Triglycerides. Water Chlorination: Environmental Impact and Health Effects, R. L. Jolley, et al. (editors), Lewis, Chelsea, MI. 23. Gordon, G., G.L. Emmert, and B. Bubnis Bromate Ion Formation in Water When Chlorine Dioxide is Photolyzed in the Presence of Bromide Ion. Conference proceedings, AWWA Water Quality Technology Conference, New Orleans, LA. 24. Gordon, G., et al Minimizing Chlorite Ion and Chlorate Ion in Water Treated with Chlorine Dioxide. J. AWWA. 82(4): Gordon, G., W.J. Cooper, R.G. Rice, and G.E. Pacey Disinfectant Residual Measurement Methods, AWWARF, Denver, CO. 26. Gordon, G., R.G. Kieffer, and D.H. Rosenblatt The Chemistry of Chlorine Dioxide. Progress in Organic Chemistry, vol. 15. S.J. Lippaer (editor). Wiley Interscience, New York, NY. 27. Great Lakes Upper Mississippi River Board of State Public Health (GLUMRB) and Environmental Managers Recommended Standards for Water Works, Health Research Inc., Albany, NY. EPA Guidance Manual 4-36 April 1999 Alternative Disinfectants and Oxidants

149 4. CHLORINE DIOXIDE 28. Gregory, D. and K. Carlson Applicability of Chlorine Dioxide for Cryptosporidium Inactivation. Proceedings 1998 Water Quality Technology Conference, San Diego, CA. 29. Griese, M.H., K. Hauser, M. Berkemeier, and G. Gordon Using Reducing Agents to Eliminate Chlorine Dioxide and Chlorite Ion Residuals in Drinking Water. J. AWWA. 83(5): Hoehn, R.C Chlorine Dioxide Use in Water Treatment: Key Issues. Conference proceedings, Chlorine Dioxide: Drinking Water Issues: Second International Symposium. Houston, TX. 31. Hoehn, R.C., A.A. Rosenblatt, and D.J. Gates Considerations for Chlorine Dioxide Treatment of Drinking Water. Conference proceedings, AWWA Water Quality Technology Conference, Boston, MA. 32. Hofman, R., R.C. Andrews, and Q. Ye Chlorite Formation When Disinfecting Drinking Water to Giardia Inactivation Requirements Using Chlorine Dioxide. Conference proceedings, ASCE/CSCE Conference, Edmonton, Alberta, July. 33. Knocke, W.R. and A. Iatrou Chlorite Ion Reduction by Ferrous Ion Addition. AWWARF, Denver, CO. 34. Korich, D.G., et al Effects of Ozone, Chlorine Dioxide, Chlorine, and Monochloramine on Cryptosporidium parvum oocyst Viability. Appl. Environ. Microbiol. 56: LeChevallier, M.W., et al Chlorine Dioxide for Control of Cryptosporidium and Disinfection Byproducts. Conference proceedings, 1996 AWWA Water Quality Technology Conference Part II, Boston, Massachusetts. 36. LeChevallier, M.W., et al Chlorine Dioxide for Control of Cryptosporidium and Disinfection Byproducts. Conference proceedings, AWWA Water Quality Technology Conference, Boston, Massachusetts. 37. Liyanage, L.R.J, et al Effects of Aqueous Chlorine and Oxychlorine Compounds on Cryptosporidium Parvum Oocysts. Environ. Sci. & Tech. 31(7): Masschelein, W.J Unit Processes in Drinking Water Treatment. Marcel Decker D.C., New York, Brussels, Hong Kong. 39. Merkle, J.C. and C.B. Reeverts Ground Water Treatment: What Are the States Doing Now? AWWARF, Denver, CO. 40. Noack, M.G. and R.L. Doerr Reactions of Chlorine, Chlorine Dioxide and Mixtures of Humic Acid: An Interim Report. Conference proceedings, Second Conference on the Environmental Impact of Water Chlorination. R.L. Jolley, H. Gorchev, and D. Heyward (editors), Gatlinburg, TN. April EPA Guidance Manual Alternative Disinfectants and Oxidants

150 4. CHLORINE DIOXIDE 41. Noss, C.I., W.H. Dennis, V.P. Olivieri Reactivity of Chlorine Dioxide with Nucleic Acids and Proteins. Water Chlorination: Environmental Impact and Health Effects. R. L. Jolley, et al. (editors), Lewis Publishers, Chelsea, MI. 42. Olivieri, V.P., et al Mode of Action of Chlorine Dioxide on Selected Viruses. Water Chlorination: Environmental Impact and Health Effects. R. L. Jolley, et al. (editors), Lewis, Chelsea, MI. 43. Olivieri, V.P., et al Stability and Effectiveness of Chlorine Disinfectants in Water Distribution Systems. USEPA, Cincinnati, OH. 44. Peeters, J. E. et al Effect of Disinfection of Drinking Water with Ozone or Chlorine Dioxide on Survival of Cryptosporidium parvum oocysts. Appl. Environ. Microbiol. r5: Pitochelli, A Chlorine Dioxide Generation Chemistry. Conference proceedings, Third International Symposium, Chlorine Dioxide: Drinking Water, Process Water, and Wastewater Issues. New Orleans, LA. 46. Ransome, M.E., T.N. Whitmore, and E.G. Carrington Effect of Disinfectants on the Viability of Cryptosporidium parvum Oocysts. Water Supply. 11(1): Rav-Acha, C., A. Serri, E. Choshen, B. Limoni Disinfection of Drinking Water Rich in Bromide with Chlorine and Chlorine Dioxide, While Minimizing the Formation of Undesirable Byproducts. Wat. Sci. Technol. 17: Richardson, S.D. et al Multispectral Identification of ClO 2 Disinfection Byproducts in Drinking Water. Environ. Sci. & Technol. 28(4): Ridenour, G.M. and E.H. Armbruster Bactericidal Effects of Chlorine Dioxide. J. AWWA. 41: Ridenour, G. M. and R.S. Ingols Bactericidal Properties of Chlorine Dioxide. J. AWWA Ridenour, G.M., and R.S. Ingols Inactivation of Poliomyelitis Virus by Free Chlorine. Amer. Public Health. 36: Ridenour, G.M., and R.S. Ingols, and E.H. Armbruster Sporicidal Properties of Chlorine Dioxide. Water & Sewage Works. 96(8): Roberts, P.V., E.M. Aieta, J.D. Berg, and B.M. Chow Chlorine Dioxide for Wastewater Disinfection: A Feasibility Evaluation. Stanford University Technical Report 251. October. EPA Guidance Manual 4-38 April 1999 Alternative Disinfectants and Oxidants

151 4. CHLORINE DIOXIDE 54. Roller, S. D. et al Mode of Bacterial Inactivation by Chlorine Dioxide. Water Res. 14: Singer, P.C Formation and Characterization of Disinfection Byproducts. Presented at the First International Conference on the Safety of Water Disinfection: Balancing Chemical and Microbial Risks. 56. Singer, P.C., and W.K. O Neil Technical Note: The Formation of Chlorate from the Reaction of Chlorine and Chlorite in Dilute Aqueous Solution. J. AWWA. 79(11): Smith, J. E., and J.L. McVey Virus Inactivation by Chlorine Dioxide and Its Application to Storm Water Overflow. Proceeding, ACS annual meeting. 13(2): Sobsey, M Detection and Chlorine Disinfection of Hepatitis A in Water. CR , EPA Quarterly Report, December. 59. Sproul, O. J. et al Comparison of Chlorine and Chlorine Dioxide for Inactivation of Amoebic Cyst. Envir. Technol. Letters. 4: Thompson, A.L Practical Considerations for Application of Chlorine Dioxide in Municipal Water Systems. Conference proceedings,, Chlorine Dioxide Workshop. AWWARF, CMA, EPA. Denver, CO. 61. Trakhtman, N.N Chlorine Dioxide in Water Disinfection. Chemical Abstracts. 43: USEPA (U.S. Environmental Protection Agency) Trihalomethanes in Drinking Water: Sampling, Analysis, Monitoring, and Compliance. EPA 570/ , August. 63. USEPA Effect of Particulates on Disinfection of Enteroviruses and Coliform Bacteria in Water by Chlorine Dioxide. EPA-600/ USEPA Effect of Particulates on Inactivation of Enteroviruses in Water by Chlorine Dioxide. EPA-600/ , Cincinnati, OH. 65. Werdehoff, K.S, and P.C. Singer Chlorine Dioxide Effects on THMFP, TOXFP and the Formation of Inorganic By-Products. J. AWWA. 79(9):107. April EPA Guidance Manual Alternative Disinfectants and Oxidants

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153 4. CHLORINE DIOXIDE 4. CHLORINE DIOXIDE CHLORINE DIOXIDE CHEMISTRY Oxidation Potential GENERATION Introduction Chlorine Dioxide Purity Methods of Generating Chlorine Dioxide Generator Design Chemical Feed Systems Generator Power Requirements PRIMARY USES AND POINTS OF APPLICATION FOR CHLORINE DIOXIDE Disinfection Taste and Odor Control Oxidation of Iron and Manganese PATHOGEN INACTIVATION AND DISINFECTION EFFICACY Inactivation Mechanisms Environmental Effects Disinfection Efficacy CHLORINE DIOXIDE DISINFECTION BYPRODUCTS Production of Chlorite and Chlorate Organic DBPs Produced by Chlorine Dioxide Chlorine Dioxide DBP Control Strategies STATUS OF ANALYTICAL METHODS Chlorine Dioxide and Chlorite Analytical Methods Chlorine Dioxide Monitoring for Systems Using Chlorine Dioxide Chlorite Monitoring for Systems Using Chlorine Dioxide OPERATIONAL CONSIDERATIONS Process Considerations Generator Operation Feed Chemicals SUMMARY Advantages and Disadvantages of Chlorine Dioxide Use Summary Table REFERENCES Table 4-1. Commercial Chlorine Dioxide Generators Table 4-2. Surface Water Chlorine Dioxide Demand Study Results Table 4-3. Analytical Methods for Chlorine Dioxide and Related Compounds Table 4-4. Properties of Sodium Chlorite as Commercially Available Table 4-5. Summary for Chlorine Dioxide Figure 4-1. Conventional Chlorine Dioxide Generator When Using Chlorine-Chlorite Method Figure 4-2. Chlorine Dioxide Generation Using Recycled Aqueous Chlorine Method Figure 4-3. Effect of Temperature on N. Gruberi Cyst Inactivation at ph Figure 4-4. Comparison of Germicidal Efficiency of Chlorine Dioxide and Chlorine Figure 4-5. CT Values for Inactivation of Giardia Cysts by Chlorine Dioxide Figure 4-6. CT Values for Inactivation of Viruses by Chlorine Dioxide Figure 4-7. C. parvum Inactivation by Chlorine Dioxide at 20 C Figure 4-8. C. parvum Inactivation by Chlorine Dioxide at 10 C April EPA Guidance Manual Alternative Disinfectants and Oxidants

154 This report contains the collective views of an international group of experts and does not necessarily represent the decisions or the stated policy of the United Nations Environment Programme, the International Labour Organization, or the World Health Organization. Concise International Chemical Assessment Document 37 CHLORINE DIOXIDE (GAS) Please note that the layout and pagination of this pdf file are not necessarily identical to those of the pinted copy First draft prepared by Dr Stuart Dobson, Institute of Terrestrial Ecology, Huntingdon, United Kingdom, and Mr Richard Cary, Health and Safety Executive, Liverpool, United Kingdom Published under the joint sponsorship of the United Nations Environment Programme, the International Labour Organization, and the World Health Organization, and produced within the framework of the Inter-Organization Programme for the Sound Management of Chemicals. World Health Organization Geneva, 2002

155 The International Programme on Chemical Safety (IPCS), established in 1980, is a joint venture of the United Nations Environment Programme (UNEP), the International Labour Organization (ILO), and the World Health Organization (WHO). The overall objectives of the IPCS are to establish the scientific basis for assessment of the risk to human health and the environment from exposure to chemicals, through international peer review processes, as a prerequisite for the promotion of chemical safety, and to provide technical assistance in strengthening national capacities for the sound management of chemicals. The Inter-Organization Programme for the Sound Management of Chemicals (IOMC) was established in 1995 by UNEP, ILO, the Food and Agriculture Organization of the United Nations, WHO, the United Nations Industrial Development Organization, the United Nations Institute for Training and Research, and the Organisation for Economic Co-operation and Development (Participating Organizations), following recommendations made by the 1992 UN Conference on Environment and Development to strengthen cooperation and increase coordination in the field of chemical safety. The purpose of the IOMC is to promote coordination of the policies and activities pursued by the Participating Organizations, jointly or separately, to achieve the sound management of chemicals in relation to human health and the environment. WHO Library Cataloguing-in-Publication Data Chlorine dioxide (gas). (Concise international chemical assessment document ; 37) 1.Chlorine compounds - toxicity 2.Oxides - toxicity 3.Risk assessment 4.Occupational exposure I.International Programme on Chemical Safety II.Series ISBN ISSN (NLM Classification: QD 181.C5) The World Health Organization welcomes requests for permission to reproduce or translate its publications, in part or in full. Applications and enquiries should be addressed to the Office of Publications, World Health Organization, Geneva, Switzerland, which will be glad to provide the latest information on any changes made to the text, plans for new editions, and reprints and translations already available. World Health Organization 2002 Publications of the World Health Organization enjoy copyright protection in accordance with the provisions of Protocol 2 of the Universal Copyright Convention. All rights reserved. The designations employed and the presentation of the material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the World Health Organization concerning the legal status of any country, territory, city, or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. The mention of specific companies or of certain manufacturers products does not imply that they are endorsed or recommended by the World Health Organization in preference to others of a similar nature that are not mentioned. Errors and omissions excepted, the names of proprietary products are distinguished by initial capital letters. The Federal Ministry for the Environment, Nature Conservation and Nuclear Safety, Germany, provided financial support for the printing of this publication. Printed by Wissenschaftliche Verlagsgesellschaft mbh, D Stuttgart 10

156 TABLE OF CONTENTS FOREWORD EXECUTIVE SUMMARY IDENTITY AND PHYSICAL/CHEMICAL PROPERTIES ANALYTICAL METHODS Workplace air monitoring Biological monitoring in humans SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE ENVIRONMENTAL TRANSPORT, DISTRIBUTION, AND TRANSFORMATION ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE Environmental levels Occupational exposure COMPARATIVE KINETICS AND METABOLISM IN LABORATORY ANIMALS AND HUMANS EFFECTS ON LABORATORY MAMMALS AND IN VITRO TEST SYSTEMS Single exposure Irritation and sensitization Short-term exposure Inhalation Oral Medium-term exposure Long-term exposure and carcinogenicity Genotoxicity and related end-points Studies in bacteria In vitro studies in mammalian systems In vivo studies in mammalian systems Studies in germ cells Other studies Reproductive toxicity Effects on fertility Developmental toxicity Immunological and neurological effects EFFECTS ON HUMANS Drinking-water studies EFFECTS ON OTHER ORGANISMS IN THE LABORATORY AND FIELD iii

157 Concise International Chemical Assessment Document EFFECTS EVALUATION Evaluation of health effects Hazard identification and dose response assessment Criteria for setting tolerable intakes/concentrations or guidance values for chlorine dioxide gas Sample risk characterization Evaluation of environmental effects PREVIOUS EVALUATIONS BY INTERNATIONAL BODIES REFERENCES APPENDIX 1 SOURCE DOCUMENT APPENDIX 2 CICAD PEER REVIEW APPENDIX 3 CICAD FINAL REVIEW BOARD INTERNATIONAL CHEMICAL SAFETY CARD RÉSUMÉ D ORIENTATION RESUMEN DE ORIENTACIÓN iv

158 Chlorine dioxide (gas) FOREWORD Concise International Chemical Assessment Documents (CICADs) are the latest in a family of publications from the International Programme on Chemical Safety (IPCS) a cooperative programme of the World Health Organization (WHO), the International Labour Organization (ILO), and the United Nations Environment Programme (UNEP). CICADs join the Environmental Health Criteria documents (EHCs) as authoritative documents on the risk assessment of chemicals. International Chemical Safety Cards on the relevant chemical(s) are attached at the end of the CICAD, to provide the reader with concise information on the protection of human health and on emergency action. They are produced in a separate peer-reviewed procedure at IPCS. They may be complemented by information from IPCS Poison Information Monographs (PIM), similarly produced separately from the CICAD process. CICADs are concise documents that provide summaries of the relevant scientific information concerning the potential effects of chemicals upon human health and/or the environment. They are based on selected national or regional evaluation documents or on existing EHCs. Before acceptance for publication as CICADs by IPCS, these documents undergo extensive peer review by internationally selected experts to ensure their completeness, accuracy in the way in which the original data are represented, and the validity of the conclusions drawn. The primary objective of CICADs is characterization of hazard and dose response from exposure to a chemical. CICADs are not a summary of all available data on a particular chemical; rather, they include only that information considered critical for characterization of the risk posed by the chemical. The critical studies are, however, presented in sufficient detail to support the conclusions drawn. For additional information, the reader should consult the identified source documents upon which the CICAD has been based. Risks to human health and the environment will vary considerably depending upon the type and extent of exposure. Responsible authorities are strongly encouraged to characterize risk on the basis of locally measured or predicted exposure scenarios. To assist the reader, examples of exposure estimation and risk characterization are provided in CICADs, whenever possible. These examples cannot be considered as representing all possible exposure situations, but are provided as guidance only. The reader is referred to EHC for advice on the derivation of health-based guidance values. While every effort is made to ensure that CICADs represent the current status of knowledge, new information is being developed constantly. Unless otherwise stated, CICADs are based on a search of the scientific literature to the date shown in the executive summary. In the event that a reader becomes aware of new information that would change the conclusions drawn in a CICAD, the reader is requested to contact IPCS to inform it of the new information. Procedures The flow chart shows the procedures followed to produce a CICAD. These procedures are designed to take advantage of the expertise that exists around the world expertise that is required to produce the highquality evaluations of toxicological, exposure, and other data that are necessary for assessing risks to human health and/or the environment. The IPCS Risk Assessment Steering Group advises the Co-ordinator, IPCS, on the selection of chemicals for an IPCS risk assessment, the appropriate form of the document (i.e., EHC or CICAD), and which institution bears the responsibility of the document production, as well as on the type and extent of the international peer review. The first draft is based on an existing national, regional, or international review. Authors of the first draft are usually, but not necessarily, from the institution that developed the original review. A standard outline has been developed to encourage consistency in form. The first draft undergoes primary review by IPCS and one or more experienced authors of criteria documents to ensure that it meets the specified criteria for CICADs. The draft is then sent to an international peer review by scientists known for their particular expertise and by scientists selected from an international roster compiled by IPCS through recommendations from IPCS national Contact Points and from IPCS Participating Institutions. Adequate time is allowed for the selected experts to undertake a thorough review. Authors are required to take reviewers comments into account and revise their draft, if necessary. The resulting second draft is submitted to a Final Review Board together with the reviewers comments. 1 International Programme on Chemical Safety (1994) Assessing human health risks of chemicals: derivation of guidance values for health-based exposure limits. Geneva, World Health Organization (Environmental Health Criteria 170). 1

159 Concise International Chemical Assessment Document 37 CICAD PREPARATION FLOW CHART SELECTION OF PRIORITY CHEMICAL SELECTION OF HIGH QUALITY NATIONAL/REGIONAL ASSESSMENT DOCUMENT(S) FIRST DRAFT PREPARED PRIMARY REVIEW BY IPCS (REVISIONS AS NECESSARY) REVIEW BY IPCS CONTACT POINTS/ SPECIALIZED EXPERTS REVIEW OF COMMENTS (PRODUCER/RESPONSIBLE OFFICER), PREPARATION OF SECOND DRAFT 1 FINAL REVIEW BOARD 2 FINAL DRAFT 3 EDITING APPROVAL BY DIRECTOR, IPCS PUBLICATION 1 Taking into account the comments from reviewers. 2 The second draft of documents is submitted to the Final Review Board together with the reviewers comments. 3 Includes any revisions requested by the Final Review Board. 2

160 Chlorine dioxide (gas) A consultative group may be necessary to advise on specific issues in the risk assessment document. The CICAD Final Review Board has several important functions: to ensure that each CICAD has been subjected to an appropriate and thorough peer review; to verify that the peer reviewers comments have been addressed appropriately; to provide guidance to those responsible for the preparation of CICADs on how to resolve any remaining issues if, in the opinion of the Board, the author has not adequately addressed all comments of the reviewers; and to approve CICADs as international assessments. Board members serve in their personal capacity, not as representatives of any organization, government, or industry. They are selected because of their expertise in human and environmental toxicology or because of their experience in the regulation of chemicals. Boards are chosen according to the range of expertise required for a meeting and the need for balanced geographic representation. Board members, authors, reviewers, consultants, and advisers who participate in the preparation of a CICAD are required to declare any real or potential conflict of interest in relation to the subjects under discussion at any stage of the process. Representatives of nongovernmental organizations may be invited to observe the proceedings of the Final Review Board. Observers may participate in Board discussions only at the invitation of the Chairperson, and they may not participate in the final decision-making process. 3

161 Concise International Chemical Assessment Document EXECUTIVE SUMMARY This CICAD on chlorine dioxide gas was based on a review of human health concerns (primarily occupational) prepared by the United Kingdom s Health and Safety Executive (Health and Safety Executive, 2000). This document focuses on exposures via routes relevant to occupational settings, principally related to the production of chlorine dioxide, but also contains environmental information. The health effects and environmental fate and effects of chlorine dioxide used in the treatment of drinking-water, together with those of halogenated organics produced by the interaction between the disinfectant and other materials present in the water, are covered in a recent Environmental Health Criteria document (IPCS, 2000) and are not dealt with in detail here. Data identified as of September 1998 were covered in the Health and Safety Executive review. A further literature search was performed up to January 1999 to identify any additional information published since this review was completed. Since no source document was available for environmental fate and effects, the primary literature was searched for relevant information. Information on the nature of the peer review and availability of the source document is presented in Appendix 1. Information on the peer review of this CICAD is presented in Appendix 2. This CICAD was approved as an international assessment at a meeting of the Final Review Board, held in Stockholm, Sweden, on May Participants at the Final Review Board meeting are presented in Appendix 3. The International Chemical Safety Card for chlorine dioxide (ICSC 0127), prepared by the International Programme on Chemical Safety (IPCS, 1993), has also been reproduced in this document. Chlorine dioxide (ClO 2, CAS No ) exists as a greenish yellow to orange gas at room temperature. Chlorine dioxide gas is explosive when its concentration in air exceeds 10% v/v. It is water soluble, and solutions are quite stable if kept cool and in the dark. It is marketed and transported as a stabilized aqueous solution, generally less than 1% w/v (more concentrated forms are explosive). Occupational exposure to chlorine dioxide gas may occur during its manufacture, in the paper and pulp bleaching industries, during charging of the aqueous solution into drums, and during its use as a sterilizing agent in hospitals, as a biocide in water treatment, and as an improving agent in flour. During manufacture and subsequent captive use of the gas, good process plant control is essential because of the explosive nature of the gas. Furthermore, once the gas is absorbed in water, it has a low volatility. For these reasons, inhalation exposure is anticipated to be minimal. Limited occupational exposure data are available in relation to the manufacture and uses of chlorine dioxide; the measured or estimated concentrations indicated that all personal airborne exposures (in the United Kingdom) were below 0.1 ppm (0.28 mg/m 3 ) 8-h time-weighted average (TWA) and 0.3 ppm (0.84 mg/m 3 ) 15-min reference period. The most common dermal exposure may arise from contact with aqueous solutions of up to 1% of the substance during preparation and use. It is predicted that dermal exposure from contact with the aqueous solution in occupational settings will range from 0.1 to 5 mg/cm 2 per day. Toxicokinetic data are limited, although it would seem unlikely that there would be any significant systemic absorption and distribution of intact chlorine dioxide by dermal or inhalation routes. It is possible that other derivatives, such as chlorate, chlorite, and chloride ions, could be absorbed and widely distributed. One study shows that chlorine (chemical form not characterized) derived from aqueous chlorine dioxide is absorbed by the oral route, with a wide distribution and rapid and extensive elimination. No clear information is available on the identity of metabolites, although breakdown products are likely to include, at least initially, chlorites, chlorates, and chloride ions. Given the reactive nature of chlorine dioxide, it seems likely that health effects would be restricted to local responses. There are no quantitative human data, but chlorine dioxide is very toxic by single inhalation exposure in rats. There were no mortalities following exposure to 16 ppm (45 mg/m 3 ) for 4 h, although pulmonary oedema and emphysema were seen in all animals exposed to ppm ( mg/m 3 ) chlorine dioxide, the incidence increasing in a dose-related manner. The calculated mean LC 50 was 32 ppm (90 mg/m 3 ). In another study, ocular discharge, nosebleeds, pulmonary oedema, and death occurred at 260 ppm (728 mg/m 3 ) for 2 h. Chlorine dioxide is toxic when administered in solution by a single oral dose to rats; at 40 and 80 mg/kg body weight, there were signs of corrosive activity in the stomach and gastrointestinal tract. The calculated oral LD 50 was 94 mg/kg body weight. Data on the eye and respiratory tract irritancy of chlorine dioxide gas are limited in extent. However, there is evidence for eye and respiratory tract irritation in humans associated with unknown airborne levels of chlorine dioxide gas. Severe eye and respiratory tract 4

162 Chlorine dioxide (gas) irritancy has been observed in rats exposed to 260 ppm (728 mg/m 3 ) for 2 h. There are no reports of skin sensitization or occupational asthma associated with chlorine dioxide. The quality of the available repeated inhalation exposure data in animals is generally poor, such that the information on dose response must be viewed with some caution. In addition, there is concern that the nasal tissues were not examined, although rhinorrhoea was reported in one study in rats at 15 ppm (42 mg/m 3 ), indicating that the nasal passages may be a target tissue for inhaled chlorine dioxide. Other rat studies indicated that no adverse effects were reported at 0.1 ppm (0.28 mg/m 3 ) for 5 h/day for 10 weeks or at 1 ppm (2.8 mg/m 3 ) for 2 7 h/day for 2 months. Lung damage, manifested by bronchitis, bronchiolitis, or small areas of haemorrhagic alveolitis, appears to develop at 2.5 ppm (7.0 mg/m 3 ) or more following repeated exposure for 7 h/day for 1 month and at 10 ppm (28 mg/m 3 ) or more for 15 min twice per day for 4 weeks, with dose-dependent severity. Mortalities occurred following exposure at 15 ppm (42 mg/m 3 ) for 15 min, 2 or 4 times per day, for 1 month. In the same exposure regime, there were no adverse effects reported (among the limited observations performed) at 5 ppm (14 mg/m 3 ). The results of repeated oral exposure studies in rats and primates are generally of limited design and/or quality but show no evidence of systemic toxicity associated with chlorine dioxide administered in the drinking-water or by gavage. There are no data in relation to chronic exposure to or carcinogenicity of chlorine dioxide gas. Studies in mammalian cells using aqueous solutions of chlorine dioxide indicate that chlorine dioxide is an in vitro mutagen. This activity was not expressed in well conducted studies in vivo in somatic or germ cells. However, given the generally reactive nature of this substance and the fact that positive results have been produced in vitro, there is cause for concern for local site-of-contact mutagenicity, although no studies have been conducted for this end-point. Oral exposure to chlorine dioxide at parentally toxic levels in rats does not impair fertility or development. This is consistent with the view that as chlorine dioxide is a reactive gas, it would be unlikely to reach the reproductive organs in significant amounts. The available measured occupational exposure data (in the United Kingdom) and the exposure levels predicted using the Estimation and Assessment of Substance Exposure model indicate a maximum likely exposure of 0.1 ppm (0.28 mg/m 3 ), 8-h TWA. Comparison of this exposure level with the no-observed-adverseeffect level (NOAEL), which is derived from very limited data, suggests that there is no cause for concern in relation to the development of irritation of the respiratory tract or of the eyes in workers occupationally exposed to chlorine dioxide. Insufficent data are available with which to conduct an environmental risk assessment. Chlorine dioxide would be degraded rapidly in the environment to yield chlorite and chlorate. The few ecotoxicity data available show that chlorine dioxide can be highly toxic to aquatic organisms; the lowest reported LC 50 for fish was 0.02 mg/litre. Chlorate, released in pulp mill wastewaters following use of chlorine dioxide, has been shown to cause major ecological effects on brackish water communities. Brown macroalgae (seaweeds) are particularly sensitive to chlorate following prolonged exposure. The threshold for effects is between 10 and 20 µg/litre. 2. IDENTITY AND PHYSICAL/CHEMICAL PROPERTIES Chlorine dioxide (ClO 2, Chemical Abstracts Service [CAS] No ), a free radical, exists as a greenish yellow to orange gas at room temperature with a characteristic pungent chlorine-like odour. Chlorine dioxide gas is strongly oxidizing; it is explosive in concentrations in excess of 10% v/v at atmospheric pressure and will easily be detonated by sunlight or heat (Budavari et al., 1996). Its melting point is!59 C, its boiling point is 11 C (at kpa), and its vapour density is 2.34 (air = 1). Owing to the difficulties in transportation associated with the explosive nature of aqueous solutions of chlorine dioxide, marketed products are usually stabilized by the addition of substances such as sodium hydrogen carbonate, which leads to the formation of an aqueous sodium chlorite solution rather than chlorine dioxide. However, chlorine dioxide is then generated at the site of intended use by a displacement reaction (such as by the addition of an acid). Its solubility in water is 3 g/litre at 20 C, and its specific gravity is (Budavari et al., 1996). Some of the more commonly used synonyms for chlorine dioxide include chlorine oxide, chlorine peroxide, chloroperoxyl, chlorine(iv) oxide, and chlorine dioxide hydrate. 5

163 Concise International Chemical Assessment Document 37 The chemical structure of chlorine dioxide is shown below: The conversion factor for chlorine dioxide in air at 20 C and kpa is 1 ppm = 2.8 mg/m 3. Additional physical/chemical properties are presented on the International Chemical Safety Card (ICSC 0127) reproduced in this document. At room temperature and pressure, the natural form of chlorine dioxide is a gas that is unstable, highly reactive (an oxidizing agent), and explosive. Consequently, very few toxicological studies are available that relate to the gaseous form. Some studies have been conducted via the oral route using aqueous solutions of chlorine dioxide. Several of these studies were conducted using stabilized aqueous chlorine dioxide, sometimes by maintaining a constant ph using sodium carbonate and sodium hydrogen carbonate. However, it is recognized that this would effectively lead to the formation of aqueous sodium chlorite (which can subsequently generate chlorine dioxide by acid displacement). These studies are felt to be less relevant than those using stabilized aqueous chlorine dioxide and are not summarized in this review. The reasons for this are that chlorine dioxide dissolves discretely in water (i.e., it does not dissociate into ions), forming a solution of around ph 5 or less, whereas an aqueous solution of sodium chlorite has a different, ionized composition and a ph of approximately 8. The explosive nature of this substance has limited the concentration of chlorine dioxide in aqueous solutions to a maximum of about 1% w/v. 3. ANALYTICAL METHODS 3.1 Workplace air monitoring The US Occupational Safety and Health Administration (OSHA) has published Method ID 202, Determination of chlorine dioxide in workplace atmospheres (Björkholm et al., 1990; OSHA, 1991; Hekmat et al., 1994). This describes a method for making personal exposure measurements of chlorine dioxide. Samples are collected by drawing air through a midget fritted glass bubbler, or impinger, containing 0.02% potassium iodide in a sodium carbonate/sodium bicarbonate buffer solution, at a flow rate of 0.5 litres/ min. Chlorine dioxide is trapped and converted to chlorite (ClO 2 ), which is subsequently measured by suppressed ion chromatography using a conductivity detector. The method has a reported detection limit of ppm (0.011 mg/m 3 ) for a 4-h sampling time and 0.06 ppm (0.17 mg/m 3 ) for a 15-min sampling time. However, it is recommended that a sampling time of less than 1 h be used in order to avoid possible negative interference from chlorine and acid gases. 3.2 Biological monitoring in humans Because of the rapid formation of chloride ions following absorption of chlorine dioxide and the high normal, physiological levels of chloride in biological fluids, biological monitoring cannot detect occupational exposure to chlorine dioxide. Hence, there are no published biological monitoring methods available for chlorine dioxide. 4. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE The most significant uses of chlorine dioxide worldwide appear to be in bleaching paper pulp and cellulose. However, owing to the nature of the source document of this CICAD (Health and Safety Executive, 2000), this section focuses mainly on the production of chlorine dioxide. Potential occupational exposure to chlorine dioxide gas may occur during its manufacture, during charging of the aqueous solution into drums, and during its use as a sterilizing agent in hospitals, as a biocide in water treatment, and as an improving agent in flour (Health and Safety Executive, 2000). There will also be potential exposure to aerosol if aqueous solutions of chlorine dioxide are agitated or splashed, such as may occur during the charging of drums. During manufacture and subsequent captive use of the gas, good process plant control is essential because of the explosive nature of the gas. Furthermore, once the gas is absorbed in water, it has a low volatility. For these reasons, inhalation exposure is anticipated to be minimal. Additional uses are reported in bleaching flour, leather, fats and oils, textiles, and beeswax; water purification and taste and odour control of water; cleaning and detanning leather; and manufacture of chlorate salts, oxidizing agents, bactericides, antiseptics, and deodorizers (Budavari et al., 1996). However, no exposure data are available for these uses. It is estimated that up to 1400 tonnes of aqueous chlorine dioxide are used per year in the United Kingdom 6

164 Chlorine dioxide (gas) (Health and Safety Executive, 2000). In North America (USA and Canada), the estimated production in 1980 was tonnes per year, and in 1990, it was around tonnes per year (Clayton & Clayton, 1994). In Sweden, approximately tonnes per year were manufactured (principally in pulp mills) in 1992 (Landner et al., 1995). Release to the environment is almost exclusively to the air. The US Toxic Release Inventory reports total releases of chlorine dioxide in 1996 at approximately 550 tonnes to the atmosphere, of which more than 98% was via stacks and the remainder fugitive air releases. The majority of reported releases were from use of chlorine dioxide in pulp bleaching, with the remainder in food processing. 5. ENVIRONMENTAL TRANSPORT, DISTRIBUTION, AND TRANSFORMATION Chlorine dioxide is readily volatilized from aqueous solution at between 10 C and 15 C (Budavari et al., 1996). It is quite stable in solution if kept cool, in the dark, and in a closed vessel. Chlorides in solution catalyse decomposition, even in the dark. Volatilized chlorine dioxide decomposes to chlorine and oxygen with noise, heat, flame, and a minor pressure wave at low concentrations; it decomposes explosively at >40 kpa partial pressure. At phs between 4.8 and 9.8, up to 50% of chlorine dioxide is hydrolysed to chlorite. A chlorite concentration of 0.72 mg/litre was obtained following treatment with chlorine dioxide at 1.5 mg/litre (Moore & Calabrese, 1980). Use of chlorine dioxide in pulp mills leads to the formation of chlorate. This is reduced to chloride in treatment plants, where present (Landner et al., 1995). 6. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE 6.1 Environmental levels No data are available on levels of chlorine dioxide in the environment. Chlorine dioxide would be degraded in the environment to yield chlorite and chlorate in water, so no water concentrations of chlorine dioxide are expected. However, almost all release is to the atmosphere, with decomposition to chlorine and oxygen. 6.2 Occupational exposure The main source of occupational exposure worldwide would appear to be from the paper and pulp industry. Limited data are available, although one review (Jappinen, 1987) quotes ranges in pulp bleaching of 0 2 ppm (0 5.6 mg/m 3 ) (from Ferris et al., 1967; measured data were from around 1958, although it was not clear if these were from personal monitoring or static samples) and more recent ( ) measurements by the Finnish Institute of Occupational Health of < ppm (< mg/m 3 ). Limited occupational exposure data were received from one manufacturer of the gas. The data indicated that all personal exposures during drum charging were below 0.1 ppm (0.28 mg/m 3 ) 8-h TWA and 0.3 ppm (0.84 mg/m 3 ) 15-min reference period (Health and Safety Executive, 2000). Limited occupational exposure data were also received from companies using the substance as a biocide in hot and cold water systems and as a sterilizing agent in hospitals. No data were received from firms using it for reducing foul smells and odours in water treatment. During its use as a sterilizing agent in hospitals, all occupational exposures were found to be well below 0.1 ppm (0.28 mg/m 3 ) 8-h TWA and less than 0.3 ppm (0.84 mg/m 3 ) 15-min reference period. During its use for treating and controlling Legionella, personal exposures and static sampling concentrations of the gas were found to be less than 0.03 ppm (0.084 mg/m 3 ) 8-h TWA. In all situations where the gas is produced in a closed plant with full containment, the Estimation and Assessment of Substance Exposure (EASE) model, version 2 (a knowledge-based computer system for predicting exposures in the absence of measured occupational exposure data), predicted inhalation exposure to the gas of between 0 and 0.1 ppm (0 and 0.28 mg/m 3 ). It is expected that the potential for inhalation exposure to chlorine dioxide gas will be greater from an aqueous solution that has been agitated or activated by the addition of an acid than during production. The gas is highly reactive, and there may be the potential for skin contact, particularly when the humidity is high and the gas is absorbed in the moisture and may settle on cold surfaces. In this situation, therefore, those without gloves may be exposed to the aqueous form. However, the most common dermal exposure may arise from contact with up to 1% aqueous solutions of the 7

165 Concise International Chemical Assessment Document 37 substance during preparation and use. The EASE model (refer to European Union Technical Guidance Document 1 ) predicts that dermal exposure from contact with the aqueous solution will vary from mg/cm 2 per day during drum charging and its use in water treatment to 1 5 mg/cm 2 per day during its use as a sterilizing agent in hospitals. 7. COMPARATIVE KINETICS AND METABOLISM IN LABORATORY ANIMALS AND HUMANS There are no data available regarding dermal or inhalation routes of exposure to the gaseous form of chlorine dioxide, although it would seem unlikely that there would be any significant systemic absorption and distribution of intact chlorine dioxide by these routes. It is possible that other derivatives, such as chlorate, chlorite, and chloride ions, could be absorbed and widely distributed. One study (Abdel-Rahman et al., 1980; also reported in Abdel-Rahman et al., 1982) shows that chlorine (chemical form not characterized) derived from aqueous chlorine dioxide is absorbed by the oral route, with a wide distribution and rapid and extensive elimination. In this study, groups of four rats received a single oral gavage dose of approximately 1.5 or 4.5 mg 36 ClO 2 /kg body weight. Blood samples were collected for up to 48 h post-administration, and at 72 h, animals were killed, with samples taken from kidneys, lungs, small intestine, liver, spleen, thymus, bone marrow, and testes. 36 Cl was found in all tissues except testes, skin, and the remaining carcass, although levels in these tissues each accounted for less than 1% of the administered dose. No clear information is available on the identity of metabolites, although breakdown products are likely to include, at least initially, chlorites, chlorates, and chloride ions. About 40% of the 36 Cl was recovered in urine, expired air, and faeces, although the urine accounted for most (about 30%). 8. EFFECTS ON LABORATORY MAMMALS AND IN VITRO TEST SYSTEMS 8.1 Single exposure Chlorine dioxide is very toxic by inhalation in rats. Groups of five male and five female rats were exposed, nose only, to 0, 16, 25, 38, or 46 ppm (0, 45, 70, 106, or 129 mg/m 3 ) chlorine dioxide gas for 4 h (Schorsch, ). There were no mortalities at 16 ppm (45 mg/m 3 ) or in controls. However, there were 3/5, 4/5, and 5/5 deaths among males and 5/5, 2/5, and 4/5 deaths among females at 25, 38, and 46 ppm (70, 106, and 129 mg/m 3 ), respectively. Clinical signs of toxicity included respiratory distress. Macroscopically, pulmonary oedema and emphysema were seen in all groups of chlorine dioxideexposed animals, with the incidence increasing in a doserelated manner (severity was not described). The calculated mean LC 50 was 32 ppm (90 mg/m 3 ). Ocular discharge, nosebleeds, pulmonary oedema, and death occurred in rats exposed to 260 ppm (728 mg/m 3 ) for 2 h (Dalhamn, 1957). In this study, no further exposure levels were used. Chlorine dioxide is toxic when administered in solution by the oral route to rats. Groups of five male and five female rats received a single oral gavage dose of 10, 20, or 40 ml aqueous 0.2% w/v chlorine dioxide/kg body weight (not 2%, as stated in the test reports) (Tos, ). However, as correctly stated, the administered doses corresponded to 20, 40, and 80 mg chlorine dioxide/kg body weight. Two males and two females receiving 80 mg chlorine dioxide/kg body weight died, and a further two males at 40 mg/kg body weight also died within 48 h of administration. There were no deaths at 20 mg/kg body weight. General clinical signs of toxicity were observed among all treated groups of animals; in addition, there were occasional observations of red nasal discharge. Macroscopically, at 40 and 80 mg/kg body weight only, animals showed signs of corrosive activity in the stomach and gastrointestinal tract. There were no other treatment-related macroscopic abnormalities. The calculated oral LD 50 was 94 mg/kg body weight. 1 Technical Guidance Document in support of the risk assessment directive (93/67/EEC) for substances notified in accordance with the requirements of Council Directive 67/548/EEC; published May Unpublished data, conducted according to Organisation for Economic Co-operation and Development (OECD) guidelines, in compliance with Good Laboratory Practice, and with quality assurance inspection. Peer-reviewed by European Union Member States as part of classification and labelling activity. 8

166 Chlorine dioxide (gas) Groups of five male Sprague-Dawley rats received approximately 0, 0.12, 0.24, or 0.48 mg aqueous chlorine dioxide/kg body weight by oral gavage (Abdel-Rahman et al., 1980). Samples of blood were taken at 15, 30, 60, and 120 min post-administration for analysis of glutathione and methaemoglobin levels and osmotic fragility; methaemoglobin formation was not observed, and the other parameters measured were only slightly affected, with no clear dose response relationship. 8.2 Irritation and sensitization The limited data available (Dalhamn, 1957; see section 8.1) indicate that chlorine dioxide is a respiratory tract irritant. In relation to skin irritation, there are no data on gaseous or aqueous forms of chlorine dioxide; in relation to eye irritation, the limited data from the single exposure study by Dalhamn (1957) (see section 8.1) indicate that ocular discharge may occur as a result of exposure to gaseous chlorine dioxide. There is no useful information regarding skin or respiratory tract sensitization in animals. 8.3 Short-term exposure Inhalation All of the studies reported in this section suffer from inadequacies in reporting detail and study design. In addition, a further brief and unconventional study by Dalhamn (1957) and another by Paulet & Desbrousses (1971) were not included due to evidence of concurrent infection or extremely poor reporting. Groups of five rats were exposed, whole body, to either 0 or about 0.1 ppm (0.28 mg/m 3, the approximate mean over 10 weeks, but with a range down to 0.05 ppm [0.14 mg/m 3 ] and up to 0.3 ppm [0.84 mg/m 3 ] on one occasion) chlorine dioxide gas (Dalhamn, 1957) for 5 h/day, 7 days/week, for 10 weeks. There were no deaths and no clinical signs of toxicity. Body weight gain was reduced by approximately 6% compared with controls. Histopathological examination showed no exposure-related effects on kidneys, liver, or lungs (which appear to have been the only organs studied) of treated animals. No further useful information was available. Overall, although investigations were limited, no adverse effects were observed in this study. However, no information was presented regarding nasal effects, and the nose could reasonably be anticipated to be a target tissue. Unknown numbers of rats and rabbits were exposed to 1, 2.5, 5, 10, or 15 ppm (2.8, 7.0, 14, 28, or 42 mg/m 3 ) chlorine dioxide gas for 2 7 h/day for 1 or 2 months (Paulet & Desbrousses, 1974). Reduced body weight, leukocytosis, and pulmonary lesions (bronchoalveolitis) were claimed for exposures to 5 or 10 ppm (14 or 28 mg/m 3 ). At 2.5 ppm (7.0 mg/m 3 ), 7 h/day for 1 month, the report indicated that there were small areas of haemorrhagic alveolitis in the lungs, and no effects were reported at 1 ppm (2.8 mg/m 3 ). No experimental data were presented, and there was no indication of the extent of investigations or if control animals were used. The reliability of these findings is limited by poor reporting. Groups of rats were exposed to 0, 5, 10, or 15 ppm (0, 14, 28, or 42 mg/m 3 ) chlorine dioxide gas for 15 min, 2 or 4 times per day, for 1 month (Paulet & Desbrousses, 1974). Investigations included body weight, haematology, and histopathological examination of lungs and liver only. At 5 and 10 ppm (14 and 28 mg/m 3 ), there were no mortalities and no oculo-nasal catarrh. At 15 ppm (42 mg/m 3 ), one animal in each exposure group died, and survivors were reported to have oculonasal catarrh with weeping mucus ; between weeks 2 and 4, animals showed a marked decrease in body weight. However, changes in other groups were not directly comparable with controls, as the group mean weights at the start of the study showed considerable variation. There were no clear effects on total red and white cell counts among any of the exposed groups. Histopathologically, for animals exposed twice per day to 15 ppm (42 mg/m 3 ), congestion of vessels and peribronchiolar infiltration were observed at 2 weeks. After 4 weeks, bronchitis, thickening of alveolar walls, oedematous alveolitis, catarrhal alveolitis, and bronchiopneumonitic nodules were additionally reported. For animals exposed 4 times per day, findings were similar, but more severe. At 10 ppm (28 mg/m 3 ), bronchitis, bronchiolitis, and alveolar irritation were less marked than at 15 ppm (42 mg/m 3 ), and at 5 ppm (14 mg/m 3 ), there were no signs of toxicity related to exposure. There were no effects seen in the liver. Investigations were limited in this study. For the effects that were reported, the degree of severity was not well described, nor was the incidence of findings. Given these limitations, it is difficult to draw many firm conclusions. However, this study indicates that repeated inhalation exposure to 10 ppm (28 mg/m 3 ) or more chlorine dioxide gas 15 min per occasion, 2 4 times per day, over a 4-week period resulted in respiratory tract lesions, with mortalities seen at 15 ppm (42 mg/m 3 ) Oral Oral studies are of limited value with respect to occupational considerations, as the inhalation and dermal routes would be expected to be the main routes of occupational exposure. Furthermore, as chlorine dioxide 9

167 Concise International Chemical Assessment Document 37 is a very reactive substance, most effects would be expected to be local, again making the oral studies of limited relevance in the occupational context. Many of these studies have focused on investigations of thyroid hormone levels, based on the hypothesis that chlorine dioxide could inhibit thyroid function by interacting with endogenous iodide. The following studies are summarized to help complete the toxicological profile for chlorine dioxide. In a study focusing on thyroid function, groups of 12 male Sprague-Dawley rats received 0, 100, or 200 mg/litre aqueous chlorine dioxide for 8 weeks (Harrington et al., 1986). Body weight gain was reported to be significantly decreased in treated animals, although no data were presented, and there was no indication of the magnitude of the effect. Apparently, there was also a reduction in water consumption thought to be related to unpalatability. There was no effect seen on radioactive iodide uptake in the thyroid (measured on completion of 8 weeks of treatment). Over the 8-week treatment period, T 4 levels showed a decrease among chlorine dioxideexposed animals compared with controls. However, given the limited extent of observations (for instance, no histopathology was reported) and the fact that changes in thyroid hormone levels were within the control range of values, it is not possible to draw any firm conclusions. Groups of African Green monkeys (Cercopithecus aethiops) received aqueous chlorine dioxide at concentrations of 30, 100, or 200 mg/litre in a rising-dose protocol (each step lasting days) in drinking-water for up to 8 weeks (Bercz et al., 1982). Due to impaired palatability leading to reduced water intake, the two highest concentrations were both equivalent to about 9 mg/kg body weight per day. Haematology and blood biochemistry investigations were performed (including T 4 levels). No histopathology was performed. At 200 mg/litre, erythema and ulceration of the oral mucosa and increased nasal mucous discharge were observed. However, due to signs of dehydration, treatment of this group was stopped after 1 week. The increased nasal mucous secretion may be due to de-gassing of chlorine dioxide from the solution with subsequent irritation of the nasal tract by the gas. The authors claimed that there was a significant reversible thyrotoxic effect after 4 weeks of administration of 100 mg chlorine dioxide/litre, but the few data did not clearly support this. Overall, at 200 mg/litre aqueous chlorine dioxide, there were clear indications of irritation of the oral cavity, leading to palatability problems. At concentrations of 100 mg/litre (approximately 9 mg/kg body weight per day) or less, there were no clear effects among these primates over an 8-week exposure period. Similarly, groups of female African Green monkeys received 100 mg/litre freshly prepared aqueous chlorine dioxide in drinking-water for up to 8 weeks (Harrington et al., 1986). Investigations were focused on thyroid hormone levels and some associated parameters, such as iodide uptake and oestradiol levels. Again, there were no consistent changes seen in iodide uptake or T 4 levels, and no other effects were remarked on. 8.4 Medium-term exposure Groups of 10 male and 10 female Sprague-Dawley rats received approximately 0, 2, 4, 6, or 12 mg/kg body weight per day and 0, 2, 5, 8, or 15 mg/kg body weight per day, respectively, of aqueous chlorine dioxide in drinking-water for 90 days (Daniel et al., 1990). Examinations included clinical observation, body weight, food and water consumption, pre-terminal haematology and blood biochemistry, a comprehensive range of organ weights, and extensive macroscopic and microscopic examinations. There were no treatment-related deaths or clinical signs of toxicity. Water consumption was reduced, in a dose-related manner, among all treated groups, but this was probably related to palatability. Related to this effect, there were reductions in body weight gain and food consumption at the highest exposure level. There were no toxicologically significant effects on haematology, blood biochemistry, or organ weights. The only target tissue that was identified was the nasal cavity, which showed an increased incidence of goblet cell hyperplasia, squamous metaplasia, and inflammatory responses. These effects may have arisen from the evolution of chlorine dioxide gas from the drinking-water. Groups of four male Sprague-Dawley rats received 0, 1, 10, 100, or 1000 mg chlorine dioxide/litre in drinkingwater for 4 months (Abdel-Rahman et al., 1980). Blood samples were taken at 2 and 4 months for analysis of glutathione and methaemoglobin levels and for determination of osmotic fragility and erythrocyte morphology (using electron microscopy). Overall, this study showed some indication of reduced glutathione levels (about 10 20% lower than controls), which may be associated with the reactive nature of chlorine dioxide and the formation of free radicals, and also some changes in haematology parameters (osmotic fragility, erythrocyte morphology). None of these changes displayed any clear dose response pattern. Hence, the toxicological significance of these findings is unclear. 10

168 Chlorine dioxide (gas) 8.5 Long-term exposure and carcinogenicity There are no chronic inhalation or dermal studies available, and no conventional carcinogenicity studies are available. Groups of 10 male Sprague-Dawley rats received 0, 1, 10, 100, or 1000 mg/litre freshly prepared aqueous chlorine dioxide in drinking-water for up to 12 months (Abdel-Rahman et al., 1981). No clear treatment-related changes in any of the measured parameters (water consumption, haematology, glutathione levels, tritiated thymidine incorporation in liver, kidney, testes, and small intestine) were observed. However, the interpretation is complicated by a marked decrease in actual body weight among all groups, including controls. No histopathological investigations were performed. Overall, no useful information can be gained from this report. 8.6 Genotoxicity and related end-points Studies in bacteria In a modified Ames test, 10, 100, and 1000 mg/litre of an aqueous extract from chlorine dioxide gas sterilization of a medical device was tested against Salmonella typhimurium TA1535 only, with and without S9 (Jeng & Woodworth, 1990). A negative result was obtained, although there are considerable doubts about whether or not the extract tested contained any chlorine dioxide. The same authors (Jeng & Woodworth, 1990) performed another Ames test again using only TA1535 apparently against 10, 100, and 1000 mg chlorine dioxide gas/litre with and without metabolic activation. No further details of the techniques used were reported, and, although a negative result was claimed, no details were recorded In vitro studies in mammalian systems In an unpublished but well conducted in vitro cytogenetics assay, Chinese hamster ovary cells were treated with 0, 2.5, 5, 10, 15, 30, or 60 µg 0.2% chlorine dioxide/ml in phosphate-buffered saline solution in the absence of metabolic activation and 0, 6, 13, 25, 50, or 75 µg/ml in the presence of metabolic activation (Ivett & Myhr, 1986). Cell toxicity was observed at 60 µg/ml (!S9), and there was an absence of mitotic cells at 30 µg/ml. At µg/ml, there was a marked doserelated, statistically significant increase in the number of metaphases with chromosome aberrations. In the presence of metabolic activation, cell toxicity and an absence of mitotic cells were observed at 75 µg/ml. A statistically significant increase in the number of metaphases with chromosome aberrations was noted at 50 µg/ml. In a mouse lymphoma forward mutation assay using the L5178Y TK +/ system, cells were treated with 0 65 µg chlorine dioxide/ml in phosphate-buffered saline in the presence and absence of metabolic activation (Cifone & Myhr, 1986). In the absence of metabolic activation, marked toxicity was observed at the highest concentration used, 37 µg/ml. The relative growth (compared with control cultures) at the next two concentrations (15 and 24 µg/ml) was 13 18%. There was a doserelated increase in mutant frequency. Similarly, in the presence of metabolic activation, marked toxicity was observed at the highest concentration, 65 µg/ml, and there was also a dose-related increase in mutant frequency, indicating positive results both with and without metabolic activation in this test system. An unpublished in vitro cell transformation assay is available in which BALB/3T3 cells were administered 0 6 µg aqueous chlorine dioxide/ml (Rundell & Myhr, 1986). The frequency of transformed foci was within the range of spontaneous transformations observed in historical controls, indicating a negative result In vivo studies in mammalian systems In a bone marrow cytogenetics assay, groups of five male and five female CD-1 mice received a single intraperitoneal injection of approximately 0, 2, 5, or 15 mg aqueous chlorine dioxide/kg body weight (Ivett & Myhr, 1984a). Bone marrow cells were analysed for chromosome aberrations at 6, 24, and 48 h. There were no clear effects on the mitotic index, but two males receiving approximately 15 mg chlorine dioxide/kg body weight died, and other signs of toxicity (poor grooming) were also observed at the highest dose level. There were no increases in the frequency of chromosome aberrations among treated animals at any of the sacrifice times when compared with controls. Groups of five male and five female CD-1 mice received five daily oral gavage doses of approximately 0, 5, 10, or 20 mg aqueous chlorine dioxide/kg body weight (Meier et al., 1985). Animals were killed 6 h after the last administration, and 1000 polychromatic erythrocytes from the bone marrow of each animal were analysed for micronucleus formation. In addition, groups of four male and four female CD-1 mice were used for analysis of chromosome aberrations from bone marrow samples. Animals were exposed to the same doses as above, either as a single administration or using a repeatedexposure regime. Following single exposure, animals were killed at 6, 24, and 48 h post-administration and 50 11

169 Concise International Chemical Assessment Document 37 metaphase cells taken from the bone marrow of each animal for analysis of chromosome aberrations. A negative result was obtained for micronucleus formation, and there were no increases in the number of structural or numerical chromosome aberrations (including an assessment of hyperploidy and polyploidy). Apparently, there were no overt signs of general toxicity. Groups of five male ICR mice received a single intraperitoneal injection of approximately 0, 9, 21, 28, or 39 mg aqueous chlorine dioxide/kg body weight (Ivett & Myhr, 1984b). Following subcutaneous implantation of bromodeoxyuridine and 26 h after chlorine dioxide administration, approximately 25 bone marrow metaphase cells from each animal were assessed for sister chromatid exchange. Shortly after administration of aqueous chlorine dioxide, all animals showed hyperactive behaviour. There were no significant increases in sister chromatid exchange among any of the chlorine dioxidetreated groups Studies in germ cells The only study available (an unpublished dominant lethal assay in rats; Moore & Myhr, 1984) employed the intraperitoneal route of administration using up to 20 mg aqueous chlorine dioxide/kg body weight. This study did not show any mutagenic effects on male germ cells, and the result does provide some reassurance, in that even at levels affecting fertility and producing mortality, no evidence of mutagenic activity is seen. However, in addition, the results of in vivo mutagenicity studies conducted using this exposure route showed no evidence for effects in the bone marrow; hence, effects in the germ cells would not be expected Other studies Positive results for chlorine dioxide were claimed in various test systems (e.g., Ames test, in vitro cytogenetics, in vivo bone marrow micronucleus, in vivo chromosome aberrations). However, in general, the conduct of these tests was poorly described, and it has subsequently emerged that aqueous sodium chlorite solutions were tested rather than chlorine dioxide (Ishidate et al., 1984; Hayashi et al., 1988; Fujie & Aoki, 1989). 8.7 Reproductive toxicity There are no studies available using chlorine dioxide gas. A number of studies are available using aqueous chlorine dioxide or preparations that generate chlorine dioxide Effects on fertility In a one-generation study, groups of 12 male Long-Evans rats received 0, 2.5, 5, or 10 mg/kg body weight per day of aqueous chlorine dioxide by oral gavage 7 days/week for 56 days prior to mating and throughout the 10-day mating period (Carlton et al., 1991). Similarly, groups of 24 females received aqueous chlorine dioxide for 14 days prior to mating and then throughout the mating, gestation, and lactation periods until weaning on day 21 of lactation. Examinations included pre-terminal blood samples for assessment of thyroid hormones T 3 and T 4 and weights and histopathological examination of male reproductive organs. Samples were also taken for analysis of sperm motility and morphology. Dams were observed for fertility, length of gestation, body weight gain, and any signs of behavioural abnormality. Pre-terminal blood samples were taken, and animals were examined macroscopically, with an additional microscopic evaluation of reproductive organs. Overall, this study did not demonstrate any impairment of reproductive function, and there were no signs of developmental effects among rats receiving up to 10 mg aqueous chlorine dioxide/kg body weight per day. Reduced male fertility (reduced number of pregnant females) was observed among males receiving a single intraperitoneal injection of 20 mg aqueous chlorine dioxide solution/kg body weight in a dominant lethal assay (see section 8.6.4; Moore & Myhr, 1984). However, as this dose level was also associated with high mortality, it is unlikely that this result indicates a specific effect on fertility. In addition, the parenteral route of exposure used makes the results of doubtful relevance to human health. Groups of 10 male mice received oral gavage doses of up to approximately 16 mg freshly prepared aqueous chlorine dioxide/kg body weight on each of 5 consecutive days (Meier et al., 1985). Animals were killed 1, 3, and 5 weeks after the last administration, and caudal epididymides were removed for analysis of 1000 sperm-heads from each animal. There were no differences seen in the percentage of abnormal sperm-heads at any time point Developmental toxicity Groups of female Sprague-Dawley rats received approximately 0, 0.07, 0.7, or 7 mg/kg body weight per day (assuming body weight of 300 g and water consumption of 20 ml/day) of aqueous chlorine dioxide in drinking-water (Suh et al., 1983). After approximately 10 weeks of exposure, females were mated with untreated males and continued to receive chlorine dioxide 12

170 Chlorine dioxide (gas) throughout gestation. On day 20 of gestation, the dams were killed, their uteri were removed and weighed, and fetuses were examined; half of the fetuses were examined for skeletal and half for visceral abnormalities. There were no clinical signs of toxicity and no exposure-related mortalities among the dams. There was a slight, but not statistically significant, reduction in body weight gain among dams at 0.7 and 7 mg/kg body weight per day during pregnancy (about 14% reduction compared with controls). There was a slight reduction in the mean number of implants per dam in the top two dose groups, which attained statistical significance among animals at 7 mg/kg body weight per day (10.3 per dam compared with 12.3 per dam in controls), with a similar change in the number of live fetuses. This may be related to maternal toxicity at these two exposure levels, as there was a slight reduction in body weight gain among dams. The incidence of litters with anomalous fetuses was unaffected by treatment (5/6, 4/6, 6/6, and 7/8 among animals receiving 0, 0.07, 0.7, and 7 mg/kg body weight per day, respectively). In a study aimed at assessing thyroid function in neonates exposed directly to aqueous chlorine dioxide or potentially exposed in utero, groups of Sprague-Dawley rat pups born to unexposed dams received 0 or 14 mg aqueous chlorine dioxide/kg body weight per day by oral gavage between days 5 and 20 post-partum (Orme et al., 1985). In addition, groups of females received 0, 2, 20, or 100 mg aqueous chlorine dioxide/litre in drinking-water from 2 weeks prior to mating until pups were weaned (day 21 postpartum). Observations included food and water consumption, body weight, the age of eye opening, and locomotor activity. Terminal blood samples were taken from dams and pups for analysis of thyroid hormones T 3 and T 4. No clear information was presented on the general health of the dams (although body weight was apparently unaffected), making it difficult to determine the significance of any developmental effects in pups. Limited data were presented on body weight effects, although reduced body weight gain was noted for the pups born to chlorine dioxide-exposed dams between days 14 and 21 postpartum (50% lower between days 14 and 21). Locomotor effects were slight, variable, and transient, and hence of doubtful importance. For the pups born to dams receiving chlorine dioxide, there were some changes in T 3 and T 4 values that attained statistical significance, but values fell within the range of concurrent control values, and there was a lack of an obvious dose response. Overall, no evidence for an effect on thyroid hormone status was obtained, and there was no clear evidence for developmental toxicity following oral exposure of neonates to chlorine dioxide or to offspring exposed in utero and via lactation. 8.8 Immunological and neurological effects There are no data specifically relating to immunological effects. In a study specifically designed to study effects on the brain, groups of neonatal Long-Evans rat pups received 0 or 14 mg aqueous chlorine dioxide/kg body weight per day by oral gavage on days 1 20 postpartum (Toth et al., 1990). Pups were killed 11, 21, and 35 days postpartum. Investigations included the following: forebrains were examined histopathologically from females killed on day 35; terminal blood samples were taken for analysis of T 3 and T 4 levels; and liver mitochondria were analysed for "-glycerophosphate dehydrogenase activity (this enzyme is reported by the authors to be an enzyme significantly decreased in hypothyroidism). In addition, protein synthesis in the forebrain, cerebellum, and olfactory bulbs was assessed by measuring the uptake of 14 C-leucine, and total DNA content in those areas of the brain was also measured. There were a large number of deaths (about 30% of all newborns) among the neonatal pups that were attributed to gavage errors. There was a slight reduction in body weight (7% reduction between days 11 and 35), and there were related reductions in tissue weights, total protein, and DNA content. There were no significant histopathological changes noted in the brain except a reduction in the number of dendritic spine counts in one region. There were no other significant changes. The authors attributed the change in dendritic spine counts and reductions in total DNA and protein content as being indicative of a specific neurotoxic effect. However, there is no reasonable evidence for this; only a small number of samples (4 6) were used for analysis of spine counts, there were no other histopathological abnormalities recorded, and no clinical signs of toxicity were reported. Overall, there were some slight signs of reduced body weight gain at 14 mg/kg body weight per day in these neonates, and it would seem likely that the slight changes in the brain were related to this. 9. EFFECTS ON HUMANS Very few data are available relating to single exposures in humans. From the reports that are available (Dalhamn, 1957; Gloemme & Lundgren, 1957; Kennedy et 13

171 Concise International Chemical Assessment Document 37 al., 1991; Salisbury et al., 1991; Anon, 1997), it would appear that single high-level exposures may lead to eye irritation, respiratory tract lesions, and possibly permanent impairment of lung function. However, the quality of the data available is poor, often involving mixed exposures with other irritant gases, such as chlorine or sulfur dioxide, and there is no dose response information. 9.1 Drinking-water studies As with animal studies using this route of administration, human studies using drinking-water administration are of limited value in relation to occupational considerations; the inhalation and dermal routes would be expected to be the main routes of exposure. The following studies are summarized to help complete the toxicological profile for chlorine dioxide. In a series of extensive human volunteer studies on water disinfectants, groups of 10 males received aqueous chlorine dioxide in drinking-water by a range of different protocols (a sequence of rising concentrations of up to around 0.34 mg/kg body weight over a 16-day period, approximately mg/kg body weight on every third day for 12 weeks, or approximately mg aqueous chlorine dioxide/kg body weight per day daily for 12 weeks) (Lubbers et al., 1982, 1984; Lubbers & Bianchine, 1984). Observations included physical examination (blood pressure, respiration rate, pulse, oral temperature, and electrocardiography), extensive blood biochemistry, haematology, and urinalysis, and the subjective recording of taste. There were no significant adverse effects recorded for any of the parameters measured. A prospective epidemiological survey was performed on a group of 197 people exposed to chlorine dioxide-treated drinking-water on a seasonal basis (Michael et al., 1981). Haematology and blood biochemistry samples were taken before and after a 12-week chlorine dioxide exposure period. Reliable quantification of exposure was almost impossible due to the difficulties associated with estimating water consumption and the rapid decay of aqueous chlorine dioxide. There were no significant changes as a result of chlorine dioxide exposure in any of the parameters recorded. In a retrospective study, hospital records relating to the morbidity and mortality of infants born between 1940 and 1955 were studied from a community in the USA (Tuthill et al., 1982). Tap water was treated with chlorine dioxide between 1944 and 1958, and comparisons were made with a nearby community, which, in part, used the same three hospital facilities and apparently did not receive chlorine dioxide-treated tap water. There were no clear demographic differences between the populations studied. A statistically significant increase in premature births was noted among members of the community that received chlorine dioxide-treated tap water. However, the identification of prematurity was on the basis of the physician s assessment, there were no objective measures, and the proportion of premature births differed markedly between hospitals. There were no other significant differences in the condition of neonates between the two communities. Due to the lack of information on the extent of chlorine dioxide exposure, the uncertainties attached to the diagnoses of prematurity at the hospitals, and lack of adequate consideration of confounding factors such as smoking and socioeconomic status, no conclusions can be drawn from this study. 10. EFFECTS ON OTHER ORGANISMS IN THE LABORATORY AND FIELD An EC 50 for inactivation of Cryptosporidium parvum, a protozoan parasite that can infect the digestive tract of humans and other warm-blooded animals, was measured at 1.3 mg/litre; parasite inactivation was monitored by infectivity (Korich et al., 1990). Spores of the giant kelp (Macrocystis pyrifera) were exposed to nominal concentrations of chlorine dioxide for 48 h at 15 C with constant illumination by cool fluorescent lamps. A no-observed-effect concentration (NOEC) was determined at 2.5 mg/litre, with lowest-observed-effect concentrations (LOECs) for germination and germ tube length at 25 and 250 mg/litre, respectively (Hose et al., 1989). Embryos of the purple sea urchin (Strongylocentrolus purpuratus) were exposed to nominal concentrations of chlorine dioxide at 15 C for 48 h. Abnormalities recorded included pre-hatch malformations, retarded development, post-hatch abnormalities, skeletal malformations, and gut malformations. The NOEC was determined at 25 mg/litre, with a LOEC for malformations at 250 mg/litre (Hose et al., 1989). Bluegill sunfish (Lepomis macrochirus) and fathead minnow (Pimephales promelas) 96-h LC 50 values were reported at 0.15 and mg/litre, respectively. Exposure was by release of chlorine dioxide stock solutions into the test medium for approximately 1 h in each 24 h (Wilde et al., 1983). 14

172 Chlorine dioxide (gas) The NOEC for survival of kelp bass (Paralabrax clathratus) eggs exposed to chlorine dioxide for 48 h at 20 C without aeration was 25 mg/litre (Hose et al., 1989). A major field incident occurred in Sweden in the early 1980s, when it was recorded that the bladderwrack (Fucus vesiculosus), the major component of brackish water communities in Sweden, had disappeared from an area of 12 km 2 (Lindvall & Alm, 1983). It was subsequently demonstrated in laboratory experiments and model ecosystems that chlorate was responsible (Rosemarin et al., 1985; Lehtinen et al., 1988). It was also shown that brown algae of many species are sensitive to chlorate, with a threshold concentration at around µg/litre for prolonged exposure (4 5 months) when exposure took place in nitrate-limited brackish water with a salinity of (Rosemarin et al., 1994). A requirement to treat wastewater from pulp mills to reduce chlorate (derived from use of chlorine dioxide) to chloride has diminished the problem (Landner et al., 1995). Data on the effects of chlorine dioxide on terrestrial organisms were not available. 11. EFFECTS EVALUATION 11.1 Evaluation of health effects Hazard identification and dose response assessment Toxicokinetic data are limited, although it would seem unlikely that there would be any significant systemic absorption and distribution of intact chlorine dioxide by dermal or inhalation routes. It is possible that other derivatives, such as chlorate, chlorite, and chloride ions, could be absorbed and widely distributed. One study shows that chlorine (chemical form not characterized) derived from aqueous chlorine dioxide is absorbed by the oral route, with a wide distribution and rapid and extensive elimination. No clear information is available on the identity of metabolites, although breakdown products are likely to include, at least initially, chlorites, chlorates, and chloride ions. Given the reactive nature of chlorine dioxide, it seems likely that health effects would be restricted to local responses. There are no quantitative human data, but chlorine dioxide is very toxic by single inhalation exposure in rats; there were no mortalities following exposure to 16 ppm (45 mg/m 3 ) for 4 h, although pulmonary oedema and emphysema were seen in all animals exposed to ppm ( mg/m 3 ) chlorine dioxide, the incidence increasing in a dose-related manner. The calculated mean LC 50 was 32 ppm (90 mg/m 3 ). In another study, ocular discharge, nosebleeds, pulmonary oedema, and death occured at 260 ppm (728 mg/m 3 ) for 2 h. Chlorine dioxide is toxic when administered in solution by a single oral dose to rats; at 40 and 80 mg/kg body weight, animals showed signs of corrosive activity in the stomach and gastrointestinal tract. The calculated oral LD 50 was 94 mg/kg body weight. Data on the eye and respiratory tract irritancy of chlorine dioxide gas are limited in extent. However, there is evidence for eye and respiratory tract irritation in humans associated with unknown airborne levels of chlorine dioxide gas. Severe eye and respiratory tract irritancy has been observed in rats exposed to 260 ppm (728 mg/m 3 ) for 2 h. There are no reports of skin sensitization or occupational asthma associated with chlorine dioxide. The quality of the available repeated inhalation exposure data in animals is generally poor, such that the information on dose response must be viewed with some caution. In addition, there is concern that the nasal tissues were not examined, although rhinorrhoea was reported in one study in rats at 15 ppm (42 mg/m 3 ), indicating that the nasal passages may be a target tissue for inhaled chlorine dioxide. Also in rats, no adverse effects were reported at 0.1 ppm (0.28 mg/m 3 ) for 5 h/day for 10 weeks or at 1 ppm (2.8 mg/m 3 ) for 2 7 h/day for 2 months. Lung damage, manifested by small areas of haemorrhagic alveolitis, appears to develop at 2.5 ppm (7.0 mg/m 3 ) or more following repeated exposure for 7 h/day for 1 month and at 10 ppm (28 mg/m 3 ) or more for 15 min twice per day for 4 weeks. Mortalities occurred following exposure at 15 ppm (42 mg/m 3 ) for 15 min, 2 or 4 times per day, for 1 month. In the same exposure regime, there were no adverse effects reported (among the limited observations performed) at 5 ppm (14 mg/m 3 ). Repeated oral exposure studies are available in humans and animals but are of very little relevance to occupational considerations and were generally of limited design and/or quality. The results show no consistent evidence of thyroid toxicity (which has been most extensively studied) or of other systemic toxicity associated with chlorine dioxide administered in the drinking-water or by gavage. There are no data available on the effects of repeated dermal exposure and no useful data in relation to chronic exposure or carcinogenicity. 15

173 Concise International Chemical Assessment Document 37 No conclusions can be drawn from genotoxicity studies of chlorine dioxide in bacteria because of limitations in reporting and/or study design. Studies in mammalian cells using aqueous solutions of chlorine dioxide indicate that it is an in vitro mutagen. This activity was not expressed in well conducted studies in vivo in somatic or germ cells. However, given the generally reactive nature of this substance and the fact that positive results have been produced in vitro, there is cause for concern for local site-of-contact mutagenicity, although no studies have been conducted for this end-point. Well conducted studies in rats have shown that oral exposure at parentally toxic levels does not impair fertility or development. This is consistent with the view that as chlorine dioxide is a reactive gas, it would be unlikely to reach the reproductive organs in significant amounts Criteria for setting tolerable intakes/ concentrations or guidance values for chlorine dioxide gas The main health effect in relation to occupational exposure to chlorine dioxide is irritation of the respiratory tract, skin, and eyes. There are no reliable quantitative human data. The animal studies are old and of poor quality, and no long-term studies are available; the likely target tissue, the nasal tract, was not investigated, and studies focused on the lungs. A NOAEL for respiratory tract effects of 1 ppm (2.8 mg/m 3 ) derived from inhalation studies in rats of up to a 2-month duration thus is based on very limited data Evaluation of environmental effects Insufficient data are available with which to conduct an environmental risk assessment. Chlorine dioxide would be degraded in the environment to yield chlorite and chlorate in water. However, almost all release is to the atmosphere, with decomposition to chlorine and oxygen. The few ecotoxicity data available show that chlorine dioxide can be highly toxic to aquatic organisms; the lowest reported LC 50 for fish was 0.02 mg/litre. Chlorate, released in pulp mill wastewaters following use of chlorine dioxide, has been shown to cause major ecological effects on brackish water communities. Brown macroalgae (seaweeds) are particularly sensitive to chlorate following prolonged exposure. The threshold for effects is between 10 and 20 µg/litre. 12. PREVIOUS EVALUATIONS BY INTERNATIONAL BODIES Previous evaluations on gaseous chlorine dioxide by other international bodies were not identified. IPCS, based on data on chlorite, proposed an oral tolerable daily intake of 30 µg/kg body weight per day for chlorine dioxide in drinking-water (IPCS, 2000). Information on international hazard classification and labelling is included in the International Chemical Safety Card (ICSC 0127) reproduced in this document Sample risk characterization The scenario chosen as an example is occupational exposure in the United Kingdom; the available measured occupational exposure data and the exposure levels predicted using the EASE model indicate a maximum likely exposure of 0.1 ppm (0.28 mg/m 3 ), 8-h TWA. In occupational settings, a pragmatic approach (so-called margin of safety ) may be used by comparison of NOAELs for the key end-point of concern with the exposure levels achieved under occupational conditions to help determine the adequacy of current practices in terms of protecting human health. Applying this approach for chlorine dioxide, comparison of the predicted exposure level with the NOAEL of 1 ppm (2.8 mg/m 3 ) suggests that there is no cause for concern in relation to the development of irritation of the respiratory tract and of the eyes in workers occupationally exposed to chlorine dioxide. 16

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Ishidate M Jr, Sofuni T, Yoshikawa K, Hayashi M, Nohmi T, Sawada M, Matsuoka A (1984) Primary mutagenicity screening of food additives currently used in Japan. Food and chemical toxicology, 22(8): Ivett J, Myhr B (1984a) Mutagenicity evaluation of chlorine dioxide in the mouse bone marrow cytogenetic assay. Kensington, MD, Litton Bionetics Inc. (Report No ). Ivett J, Myhr B (1984b) Mutagenicity evaluation of chlorine dioxide in the sister chromatid exchange assay in vivo in the bone marrow. Kensington, MD, Litton Bionetics Inc. (Report No ). Ivett J, Myhr B (1986) Mutagenicity evaluation of chlorine dioxide in an in vitro cytogenetic assay. Kensington, MD, Litton Bionetics Inc. (Report No ). Jappinen P (1987) Exposure to sulphur compounds, cancer incidence and mortality in the Finnish pulp and paper industry. Helsinki, University of Helsinki, Faculty of Medicine (academic dissertation). 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175 Concise International Chemical Assessment Document 37 Landner L, Grimvall A, Håkansson H, Sangfors O, Walterson E (1995) Chlorine and chlorinated compounds in Sweden. Survey on fluxes to and in the environment, pools in the environment and health and environmental risks. Solna, Swedish National Chemicals Inspectorate (KEMI Report 5/95). Lehtinen K-J, Notini M, Mattsson J, Landner L (1988) Disappearance of bladder-wrack (Fucus vesiculosus L.) in the Baltic Sea: relation to pulp-mill chlorate. Ambio, 17(6): Lindvall B, Alm A (1983) Status of the bladder-wrack community in the Svartö Ödängla archipelago and in 16 reference localities along the coast of the county of Kalmar. Kalmar, University of Kalmar (Contribution No. 5) (in Swedish) [cited in Landner et al., 1995]. Lubbers J, Bianchine J (1984) Effects of the acute rising dose administration of chlorine dioxide, chlorate and chlorite to normal healthy adult male volunteers. Journal of environmental pathology, toxicology and oncology, 5: Lubbers J, Chauan S, Bianchine J (1982) Controlled clinical evaluations of chlorine dioxide, chlorite and chlorate in man. Environmental health perspectives, 46: Lubbers J, Chauan S, Miller J, Bianchine J (1984) The effects of chronic administration of chlorine dioxide, chlorite and chlorate to normal healthy adult male volunteers. Journal of environmental pathology, toxicology and oncology, 5: Meier J, Bull R, Stober J, Cimino M (1985) Evaluation of chemicals used for drinking water disinfection for production of chromosomal damage and sperm-head abnormalities in mice. Environmental mutagenesis, 7: Michael G, Miday R, Bercz J, Miller R, Greathouse D, Kraemer D, Lucas J (1981) Chlorine dioxide water disinfection: a prospective epidemiology study. Archives of environmental health, 36(1): Moore G, Calabrese E (1980) The effects of chlorine dioxide and sodium chlorite on erthyrocytes of A/J and C57L/J mice. Journal of environmental pathology and toxicology, 4: Swedish Environmental Research Group (Report No. K5015:1) [cited in Landner et al., 1995]. Rosemarin A, Lehtinen K-J, Notini M, Mattsson J (1994) Effects of pulp mill chlorate on Baltic Sea algae. Environmental pollution, 85:3 13. Rundell J, Myhr B (1986) Evaluation of chlorine dioxide in the in vitro cell transformation of BALB/3T3 cells. Kensington, MD, Litton Bionetics Inc. (Report No ). Salisbury D, Enarson D, Chan-Yeung M, Kennedy S (1991) Firstaid reports of acute chlorine dioxide gassing among pulpmill workers as predictors of lung health consequences. American journal of industrial medicine, 20: Schorsch F (1995) Study of acute toxicity of chlorine dioxide administered to rats by vapour inhalation. Verneuil en Halatte, Institut National de l Environnement Industriel et des Risques (INERIS) (Report No ). Suh D, Abdel-Rahman M, Bull R (1983) Effect of chlorine dioxide and its metabolites in drinking water on fetal development in rats. Journal of applied toxicology, 3(2): Tos E (1995) Acute oral toxicity study in rats treated with the test article chlorine dioxide. Ivrea (Torino), Instituto di richerche biomediche (RBM) (Report No ). Toth G, Long R, Mills T, Smith M (1990) Effects of chlorine dioxide on the developing rat brain. Journal of toxicology and environmental health, 31: Tuthill R, Giusti R, Moore G, Calabrese E (1982) Health effects among newborns after prenatal exposure to ClO 2-disinfected drinking water. Environmental health perspectives, 46: Wilde E, Soracco R, Mayack L, Shealy R, Broadwell T, Steffen R (1983) Comparison of chlorine and chlorine dioxide toxicity to fathead minnows and bluegill. Water research, 17: Moore M, Myhr B (1984) Evaluation of chlorine dioxide in the mouse dominant lethal assay. Kensington, MD, Litton Bionetics Inc. (Report No ). Orme J, Taylor D, Laurie R, Bull R (1985) Effects of chlorine dioxide on thyroid function in neonatal rats. Journal of toxicology and environmental health, 15: OSHA (1991) Method ID 202. Determination of chlorine dioxide in workplace atmospheres. In: OSHA analytical methods manual, 2nd ed. Washington, DC, US Department of Labor, Occupational Safety and Health Administration ( Paulet G, Desbrousses S (1971) Sur la toxicologie du ClO 2. [On the toxicology of ClO 2.] Archives des maladies professionelles, 33: Paulet G, Desbrousses S (1974) Action du bioxyde de chlore sur le rat en exposition discontinue. [Effects of chlorine dioxide on the rat during discontinuous exposure.] Archives des maladies professionelles, 35(9): Rosemarin A, Lehtinen K-J, Notini M, Axelsson B, Mattsson J (1985) Effects of pulp mill chlorate on algae. Stockholm, 18

176 Chlorine dioxide (gas) APPENDIX 1 SOURCE DOCUMENT APPENDIX 2 CICAD PEER REVIEW Health and Safety Executive (2000) Chlorine dioxide risk assessment document EH72/14. Sudbury, Suffolk, HSE Books (ISBN ) The authors draft version is initially reviewed internally by a group of approximately 10 Health and Safety Executive experts, mainly toxicologists, but also involving other relevant disciplines, such as epidemiology and occupational hygiene. The toxicology section of the amended draft is then reviewed by toxicologists from the United Kingdom Department of Health. Subsequently, the entire criteria document is reviewed by a tripartite advisory committee to the United Kingdom Health and Safety Commission, the Working Group for the Assessment of Toxic Chemicals (WATCH). This committee comprises experts in toxicology and occupational health and hygiene from industry, trade unions, and academia. The members of the WATCH committee at the time of the peer review were: Mr S.R. Bailey (Independent Consultant) Professor J. Bridges (University of Surrey) Dr H. Cross (Trades Union Congress) Mr D. Farrer (Independent Consultant) Dr A. Fletcher (Trades Union Congress) Dr I.G. Guest (Chemical Industries Association) Dr A. Hay (Trades Union Congress) Dr L. Levy (Institute of Occupational Hygiene, Birmingham) Dr T. Mallet (Chemical Industries Association) Mr A. Moses (Independent Consultant) Dr R. Owen (Trades Union Congress) Mr J. Sanderson (Independent Consultant) The draft CICAD on chlorine dioxide gas was sent for review to institutions and organizations identified by IPCS after contact with IPCS national Contact Points and Participating Institutions, as well as to identified experts. Comments were received from: A. Aitio, World Health Organization, Switzerland M. Baril, Institut de Recherches en Santé et en Sécurité du Travail du Québec, Canada R. Benson, US Environmental Protection Agency, Region VIII, USA J. Dunnick, National Institute of Environmental Health Sciences, USA P. Edwards, Department of Health, United Kingdom Elf Atochem SA, France T. Fortoul, National University of Mexico, Mexico R. Hertel, Federal Institute for Health Protection of Consumers and Veterinary Medicine (BgVV), Germany G. Koennecker, Fraunhofer Institute of Toxicology and Aerosol Research, Germany Y. Patel, Office of Water, US Environmental Protection Agency, USA K. Savolainen, Finnish Institute of Occupational Health, Finland J. Sekizawa, National Institute of Health Sciences, Japan D. Willcocks, National Industrial Chemicals Notification and Assessment Scheme, Australia P. Yao, Chinese Academy of Preventive Medicine, People s Republic of China K. Ziegler-Skylakakis, GSF - National Research Center for Environment and Health, Germany 19

177 Concise International Chemical Assessment Document 37 APPENDIX 3 CICAD FINAL REVIEW BOARD Stockholm, Sweden, May 1999 Dr A. Poole (representing CEFIC), Dow Europe S.A., Horgen, Switzerland Dr K. Ziegler-Skylakakis, Institute for Toxicology, GSF - National Research Center for Environment and Health, Neuherberg, Oberschleissheim, Germany Members Mr H. Abadin, Agency for Toxic Substances and Disease Registry, Centers for Disease Control and Prevention, Atlanta, GA, USA Dr B. Åkesson, Department of Occupational and Environmental Health, University Hospital, Lund, Sweden Dr T. Berzins (Chairperson), National Chemicals Inspectorate (KEMI), Solna, Sweden Mr R. Cary, Health and Safety Executive, Bootle, Merseyside, United Kingdom Dr R.S. Chhabra, General Toxicology Group, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA Secretariat Dr A. Aitio, Programme for the Promotion of Chemical Safety, World Health Organization, Geneva, Switzerland Ms M. Godden, Health and Safety Executive, Bootle, United Kingdom Ms L. Regis, Programme for the Promotion of Chemical Safety, World Health Organization, Geneva, Switzerland Dr P. Toft, Division of Health and Environment, World Health Organization, Regional Office for the Americas/Pan American Sanitary Bureau, Washington, DC, USA Dr M. Younes, Programme for the Promotion of Chemical Safety, World Health Organization, Geneva, Switzerland Dr S. Dobson (Rapporteur), Institute of Terrestrial Ecology, Monks Wood, Abbots Ripton, Huntingdon, Cambridgeshire, United Kingdom Dr H. Gibb, National Center for Environmental Assessment, US Environmental Protection Agency, Washington, DC, USA Dr R.F. Hertel, Federal Institute for Health Protection of Consumers and Veterinary Medicine, Berlin, Germany Dr G. Koennecker, Chemical Risk Assessment, Fraunhofer Institute of Toxicology and Aerosol Research, Hanover, Germany Dr A. Nishikawa, Division of Pathology, National Institute of Health Sciences, Tokyo, Japan Professor K. Savolainen, Finnish Institute of Occupational Health, Helsinki, Finland Dr J. Sekizawa, Division of Chem-Bio Informatics, National Institute of Health Sciences, Tokyo, Japan Ms D. Willcocks (Vice-Chairperson), Chemical Assessment Division, National Occupational Health and Safety Commission (Worksafe Australia), Sydney, Australia Professor P. Yao, Institute of Occupational Medicine, Chinese Academy of Preventive Medicine, Ministry of Health, Beijing, People s Republic of China Observers Dr N. Drouot (representing ECETOC), Elf Atochem, DSE-P Industrial Toxicology Department, Paris, France Ms S. Karlsson, National Chemicals Inspectorate (KEMI), Solna, Sweden Dr A. Löf, National Institute of Working Life, Solna, Sweden 20

178 CHLORINE DIOXIDE 0127 October 1999 CAS No: RTECS No: FO EC No: Chlorine oxide Chlorine peroxide Chlorine(IV)oxide ClO 2 Molecular mass: 67.5 TYPES OF HAZARD/ EXPOSURE ACUTE HAZARDS/SYMPTOMS PREVENTION FIRST AID/FIRE FIGHTING FIRE Not combustible but enhances combustion of other substances. Many reactions may cause fire or explosion. NO contact with combustibles. In case of fire in the surroundings: water in large amounts, water spray. EXPLOSION Risk of fire and explosion: see Chemical Dangers. Closed system, ventilation, explosion-proof electrical equipment and lighting. Do NOT expose to friction or shock. In case of fire: keep drums, etc., cool by spraying with water. Combat fire from a sheltered position. EXPOSURE AVOID ALL CONTACT! IN ALL CASES CONSULT A DOCTOR! Inhalation Cough. Headache. Laboured breathing. Nausea. Shortness of breath. Sore throat. Symptoms may be delayed (see Notes). Closed system and ventilation. Fresh air, rest. Half-upright position. Refer for medical attention. Skin Redness. Pain. Protective gloves. Protective clothing. Eyes Redness. Pain. Safety goggles or eye protection in combination with breathing protection. First rinse with plenty of water, then remove contaminated clothes and rinse again. Refer for medical attention. First rinse with plenty of water for several minutes (remove contact lenses if easily possible), then take to a doctor. Ingestion SPILLAGE DISPOSAL Evacuate danger area! Consult an expert! Ventilation. Remove gas with fine water spray. (Extra personal protection: complete protective clothing including self-contained breathing apparatus). PACKAGING & LABELLING O Symbol T+ Symbol N Symbol R: S: (1/2-) /37/ EMERGENCY RESPONSE STORAGE Fireproof if in building. Separated from combustible and reducing substances. Cool. Keep in the dark. Ventilation along the floor. IPCS International Programme on Chemical Safety Prepared in the context of cooperation between the International Programme on Chemical Safety and the European Commission IPCS 2000 SEE IMPORTANT INFORMATION ON THE BACK.

179 0127 CHLORINE DIOXIDE IMPORTANT DATA Physical State; Appearance RED-YELLOW GAS, WITH PUNGENT ODOUR. Physical dangers The gas is heavier than air. Chemical dangers May explode on heating, on exposure to sunlight or if subjected to shock or sparks. The substance is a strong oxidant and reacts violently with combustible and reducing materials. Reacts violently with organics, phosphorus, potassium hydroxide and sulfur, causing fire and explosion hazard. Reacts with water producing hydrochloric acid and chloric acid. Occupational exposure limits TLV (as TWA): 0.1 ppm; (ACGIH 1999). TLV (as (STEL) ): 0.3 ppm; (ACGIH 1999). Routes of exposure The substance can be absorbed into the body by inhalation. Inhalation risk A harmful concentration of this gas in the air will be reached very quickly on loss of containment. Effects of short-term exposure The substance irritates severely the eyes, the skin and the respiratory tract. Inhalation of gas may cause lung oedema (see Notes). Exposure far above the OEL may result in death. The effects may be delayed. Medical observation is indicated. Effects of long-term or repeated exposure The substance may have effects on the lungs, resulting in chronic bronchitis. PHYSICAL PROPERTIES Boiling point: 11 C Melting point: -59 C Relative density (water = 1): 1.6 at 0 C (liquid) Solubility in water, g/100 ml at 20 C: 0.8 Vapour pressure, kpa at 20 C: 101 Relative vapour density (air = 1): 2.3 Explosive limits, vol% in air: 10 ENVIRONMENTAL DATA This substance may be hazardous to the environment; special attention should be given to water organisms. NOTES The symptoms of lung oedema often do not become manifest until a few hours have passed and they are aggravated by physical effort. Rest and medical observation are therefore essential. Immediate administration of an appropriate spray, by a doctor or a person authorized by him/her, should be considered. Rinse contaminated clothes (fire hazard) with plenty of water. ADDITIONAL INFORMATION LEGAL NOTICE Neither the EC nor the IPCS nor any person acting on behalf of the EC or the IPCS is responsible for the use which might be made of this information IPCS 2000

180 Chlorine dioxide (gas) RÉSUMÉ D ORIENTATION Ce CICAD consacré au dioxyde de chlore repose sur un bilan des problèmes sanitaires (principalement en milieu professionnel) préparé par le Health and Safety Executive du Royaume-Uni (Health and Safety Executive, 2000). Ce document vise principalement les voies d exposition à prendre en considération en milieu professionnel, principalement sur les lieux de production du dioxyde de chlore, mais contient également des informations relatives à l environnement. Les effets de ce composé sur la santé et son devenir dans l environnement, de même que les implications sanitaires de son utilisation pour traiter l eau de boisson comme d ailleurs celles d autres dérivés halogénés résultant de l interaction entre ce désinfectant et d autres produits présents dans l eau, étant traités dans un récent document de la série Critères d hygiène de l environnement (IPCS, 2000), il n en sera pas question dans ce qui suit en détail. La mise au point rédigée par le Health and Safety Executive repose sur une bibliographie arrêtée à septembre Un dépouillement complémentaire de la litterature à été effectué jusqu à janvier 1999 afin de recueillir toutes données supplémentaires publiées après l achèvement de cette étude. En l absence de documentation sur le devenir du composé et ses effets sur l environnement, on s est tourné vers les publications originales pour essayer de trouver des informations sur ce point. Des renseignements sur la nature de l examen par des pairs et sur les sources documentaires existantes sont données à l appendice 1. L appendice 2 contient des informations sur l examen par des pairs du présent CICAD. Ce CICAD a été approuvé en tant qu évaluation internationale lors de la réunion du Comité d évaluation finale qui s est tenue à Stockholm (Suède) du 25 au 28 mai La liste des participants à cette réunion figure à l appendice 3. La fiche internationale sur la sécurité chimique du dioxyde de chlore (ICSC No 0127) établie par le Programme international sur la sécurité chimique (IPCS, 1993) est également reproduite dans le présent CICAD. Le dioxyde de chlore (ClO 2, No CAS ) se présente à la température ambiante sous la forme d un gaz jaune verdâtre à orange. Ce gaz est explosif lorsque sa concentration dans l air dépasse 10 % en volume. Il est soluble dans l eau et ses solutions aqueuse sont assez stables si on les conserve au frais et à l abri de la lumière. Il est commercialisé et transporté en solution aqueuse stabilisée (généralement à moins de 1% p/v, car il y a risque d explosion à concentration plus élevée). Il peut y avoir exposition professionnelle au dioxyde de chlore lors de sa production, de son utilisation dans l industrie du papier comme agent de blanchiment, lors de la mise en fûts de la solution aqueuse et également lorsqu on l utilise comme agent stérilisant en milieu hospitalier, comme désinfectant pour le traitement de l eau ou pour l amélioration de la farine. Lors de la production ou de l utilisation ultérieure du dioxyde de chlore captif sous forme gazeuse, une surveillance adéquate des ateliers est essentielle du fait du caractère explosif de ce gaz. Il est à noter qu une fois le gaz en solution dans l eau, sa volatilité est faible et on peut donc penser que l exposition par la voie respiratoire est minime. Il existe quelques données relatives aux limites d exposition professionnelle sur les lieux de travail où l on produit ou utilise du dioxyde de chlore; les concentrations mesurées ou estimées indiquent que dans tous les cas, l exposition atmosphérique individuelle (au Royaume-Uni) est inférieure à 0,1 ppm (0,28 mg/m 3 ) en moyenne sur 8 h pondérée par rapport au temps et à 0,3 ppm (0,84 mg/m 3 ) sur la période de référence de 15 minutes. L exposition par voie cutanée la plus fréquente peut résulter d un contact avec des solutions aqueuses contenant jusqu à 1 % du composé lors de la préparation ou de l utilisation de ces solutions. On estime que sur les lieux de travail, l exposition par contact cutané avec des solutions aqueuses devrait se situer entre 0,1 et 5 mg/cm 2 par jour. Les données toxicocinétiques sont limitées mais il ne semble pas qu il puisse y avoir une absorption et une distribution de dioxyde de chlore inchangé dans l ensemble de l organisme par voie percutanée ou respiratoire. En revanche, il est possible que d autres dérivés tels que des chlorates, chlorites ou chlorures puissent être absorbés et se répartir largement dans l organisme. Selon une étude, du «chlore» (forme chimique non précisée) provenant de solutions aqueuses de dioxyde de chlore peut être absorbé par la voie orale et se répartir ensuite largement dans l organisme avant d en être rapidement et majoritairement éliminé. On ne possède pas d informations précises sur l identité des métabolites mais il est vraisemblable que les produits de dégradation consistent en chlorates, chlorites et chlorures, du moins dans un premier temps. Etant donné la réactivité du dioxyde de chlore, il est vraisemblable que ses effets soient purement locaux. On ne possède pas de données quantitatives concernant des sujets humains, mais une seule inhalation de dioxyde de chlore se révèle en tout cas très toxique pour le le rat. Après exposition à une concentration de 16 ppm de dioxyde de chlore (45 mg/m 3 ) pendant 4 h, il n y a pas eu de mortalité chez les animaux d expérience malgré la 23

181 Concise International Chemical Assessment Document 37 présence, aux concentrations de ppm (45 à 129 mg/m 3 ), d un oedème pulmonaire et d un emphysème dont l incidence augmentait avec la dose. Le calcul a donné une CL 50 moyenne de 32 ppm (90 mg/m 3 ). Dans une autre étude, on a observé un écoulement oculaire, des saignements de nez, un oedème pulmonaire puis la mort lors de l exposition d animaux à 260 ppm (728 mg/m 3 ) pendant 2 h. Chez le rat, l administration par voie orale d une seule dose d une solution de dioxyde de chlore se révèle toxique; aux concentrations de 40 et 80 mg/kg de poids corporel, on a constaté les signes d une activité corrosive au niveau de l estomac et des intestins. Le calcul de la DL 50 par voie orale a donné une valeur de 94 mg/kg de poids corporel. Les données relatives au pouvoir irritant du dioxyde de chlore pour les muqueuses oculaire et respiratoire sont en nombre limité. Toutefois, on a la preuve que le composé présent dans l air est irritant pour les voies respiratoires et la muqueuse oculaire sans que l on sache à quelle concentration. Chez des rats exposés pendant deux heures à la concentration de 260 ppm (728 mg/m 3 ), on a constaté uen forte irritation des yeux et des voies respiratoires. On ne signale pas de cas de sensibilisation cutanée ni d asthme d origine professionnelle qui soient liés à une exposition au dioxyde de chlore. Les données fournies par les études comportant une exposition répétée par la voie respiratoire sont généralement de qualité médiocre, aussi faut-il interpréter avec prudence les informations relatives à la relation dose-réponse. On peut d ailleurs se demander pourquoi les tissus des fosses nasales n ont pas été examinés, alors même qu il a été fait état de rhinorrhée lors d une étude sur le rat à la dose de 15 ppm (42 mg/m 3 ). Ces observations montrent bien que les fosses nasales pourraient constituer un tissu cible en cas d inhalation de dioxyde de chlore. D autres études sur le rat ne font état d aucun effet nocif à la concentration de 0,1 ppm (0,28 mg/m 3 ) lors d une exposition de 5 h par jour pendant 10 semaines, ni à la concentration de 1 ppm (2,8 mg/m 3 ) pendant 2 à 7 h par jour sur une durée de deux mois. Une exposition répétée à la concentration de 2,5 ppm (7,0 mg/m 3 ) ou davantage, 7 h par jour pendant 1 mois ou à 10 ppm (2,8 mg/m 3 ) ou davantage 15 min deux fois par jour pendant 4 semaines a entraîné une atteinte pulmonaire se traduisant par une bronchite, une bronchiolite et de petits foyers d hémorragie alvéolaire dont la gravité était fonction de la dose. A la concentration de 15 ppm (42 mg/m 3 ) pendant 15 min 2 à 4 fois par jour sur un mois, on a constaté une mortalité parmi les animaux. Dans les mêmes conditions d exposition, on n a constaté, parmi le nombre limité d observations effectuées, aucun effet nocif à la concentration de 5 ppm (14 mg/m 3 ). Les études d exposition par voie orale portant sur des rats ou des primates sont généralement limitées dans leur conception comme d ailleurs dans leur qualité, mais les résultats obtenus ne révèlent aucun signe de toxicité générale qui soit imputable au dioxyde de chlore administré aux animaux en solution dans leur eau de boisson ou par gavage. On ne possède aucune donnée sur l exposition chronique au dioxyde de chlore ni sur sa cancérogénicité éventuelle. Les études relatives à l action des solutions de dioxyde de chlore sur les cellules mammaliennes montrent que ce composé est mutagène in vitro. Des études in vivo bien conduites et portant sur des cellules somatiques ou germinales n ont en revanche pas permis de constater l expression de cette activité. Cependant, étant donné la réactivité du composé et du fait que les résultats obtenus in vitro sont positifs, on peut s inquiéter de la possibilité d effets mutagènes localisés au point de contact, bien qu aucune étude n ait porté sur ce type d effet toxique. L exposition au dioxyde de chlore à des doses toxiques pour les géniteurs n affecte ni la fécondité, ni le développement. Ce résultat s explique par la réactivité de ce gaz, qui ne lui permet pas de parvenir en quantité importante jusqu à l appareil reproducteur. Les mesures de l exposition professionnelle (au Royaume-Uni) et le calcul de l intensité de cette exposition au moyen du modèle d évaluation de l exposition utilisé, indiquent que l exposition professionnelle est vraisemblablement égale à 0,1 ppm (0,28 mg/m 3 ) au maximum, en moyenne pondérée par rapport au temps sur une durée de 8 h. Si l on compare ce chiffre à la valeur de la concentration sans effet nocif observable (NOAEL), qui a été établie à partir de données très limitées, on est amené à considérer qu il n y a aucune raison de s inquiéter d une quelconque action irritante pour les yeux et les voies respiratoires des travailleurs exposés au dioxyde de chlore. On ne possède pas suffisamment de données pour procéder à une évaluation du risque environnemental. Le dioxyde de chlore libéré dans l environnement y subirait rapidement une décomposition en chlorite et chlorate. Les quelques données écotoxicologiques disponibles montrent que le dioxyde de chlore peut être très toxique pour les organismes aquatiques; la valeur la plus faible de la CL 50 qui ait été publiée pour les poissons est de 0,02 mg/litre. On a montré que le chlorate déchargé dans les eaux résiduaires des industries du papier après blanchiment au dioxyde de chlore pouvait faire d important 24

182 Chlorine dioxide (gas) dégâts écologiques dans la faune et la flore des eaux saumâtres. Les macroalgues brunes marines sont particulièrement sensibles au chlorate en cas d exposition prolongée. Le seuil d apparition des effets est compris entre 10 et 20 µg/litre. 25

183 Concise International Chemical Assessment Document 37 RESUMEN DE ORIENTACIÓN Este CICAD sobre el dióxido de cloro gaseoso se basó en un examen de los problemas relativos a la salud humana (fundamentalmente profesionales) preparado por la Dirección de Salud y Seguridad del Reino Unido (Dirección de Salud y Seguridad, 2000). Este examen se centra en las vías de exposición de interés para el entorno ocupacional, principalmente en relación con la producción de dióxido de cloro, pero contiene también información sobre el medio ambiente. Los efectos en la salud y el destino y los efectos en el medio ambiente del dióxido de cloro utilizado en el tratamiento del agua potable, junto con los de los productos orgánicos halogenados producidos por la interacción entre el desinfectante y otros materiales presentes en el agua, figuran en un documento reciente de los Criterios de Salud Ambiental (IPCS, 2000) y no se abordan aquí con todo detalle. En el examen de la Dirección de Salud y Seguridad figuran los datos identificados hasta septiembre de Se realizó una búsqueda bibliográfica ulterior hasta enero de 1999 para localizar cualquier información nueva que se hubiera publicado desde la terminación del examen. Puesto que no se disponía de documentos originales sobre el destino y los efectos en el medio ambiente, se realizó una búsqueda bibliográfica para obtener más información. La información acerca del carácter del examen colegiado y la disponibilidad del documento original figura en el apéndice 1. La información sobre el examen colegiado de este CICAD aparece en el apéndice 2. Este CICAD se aprobó como evaluación internacional en una reunión de la Junta de Evaluación Final celebrada en Estocolmo (Suecia) del 25 al 28 de mayo de La lista de participantes en esta reunión figura en el apéndice 3. La Ficha internacional de seguridad química sobre el dióxido de cloro (ICSC 0127), preparada por el Programa Internacional de Seguridad de las Sustancias Químicas (IPCS, 1993), también se reproduce en el presente documento. El dióxido de cloro (ClO 2, CAS Nº ) existe en forma de gas de un color entre amarillo verdoso y naranja a temperatura ambiente. El dióxido de cloro gaseoso es explosivo cuando su concentración en el aire es superior al 10% v/v. Es soluble en agua y las soluciones son bastante estables si se mantienen en un lugar refrigerado y oscuro. Se comercializa y transporta como solución acuosa estabilizada, generalmente en una concentración inferior al 1% p/v (las formas más concentradas son explosivas). Se puede producir exposición ocupacional al dióxido de cloruro gaseoso durante su fabricación, en las industrias de blanqueo de papel y pasta, durante la carga de la solución acuosa en bidones y durante su utilización como agente esterilizante en hospitales, como biocida en el tratamiento del agua y como agente para la mejora de la harina. Durante la fabricación y el posterior uso del gas cautivo, es esencial un buen control de la instalación de elaboración, a causa del carácter explosivo del gas. Además, una vez que el gas se absorbe en el agua, tiene una volatilidad baja. Por estos motivos se prevé una exposición por inhalación mínima. Hay datos limitados sobre la exposición ocupacional en relación con la fabricación y las aplicaciones del dióxido de cloro; las concentraciones medidas o estimadas indicaron que toda la exposición personal a través del aire (en el Reino Unido) era inferior a 0,1 ppm (0,28 mg/m 3 ) en un promedio ponderado por el tiempo de ocho horas y de 0,3 ppm (0,84 mg/m 3 ) en un periodo de referencia de 15 minutos. La exposición más común puede producirse por contacto con soluciones acuosas de hasta un 1% de la sustancia durante su preparación y uso. Se estima que la exposición cutánea por contacto con la solución acuosa en el entorno del trabajo oscila entre 0,1 y 5 mg/cm 2 al día. Los datos sobre la toxicocinética son limitados, aunque parece poco probable que se produzca una absorción y distribución sistémica importante de dióxido de cloro intacto por vía cutánea o por inhalación. Es posible que otros derivados, como los iones clorato, clorito y cloruro, se puedan absorber y distribuir ampliamente. En un estudio se ha puesto de manifiesto que el «cloro» (forma química no caracterizada) derivado del dióxido de cloro acuoso se absorbe por vía oral, con una distribución amplia y una eliminación rápida e importante. No se dispone de información clara sobre la identidad de los metabolitos, aunque cabe suponer que los productos de degradación incluyen, por lo menos inicialmente, iones clorato, clorito y cloruro. Dado el carácter reactivo del dióxido de cloro, parece poco probable que los efectos en la salud se limiten a respuestas locales. No hay datos humanos cuantitativos, pero el dióxido de cloro es muy tóxico en una exposición única por inhalación en ratas. No se observó mortalidad tras la exposición a 16 ppm (45 mg/m 3 ) durante cuatro horas, aunque se detectaron edema y enfisema pulmonar en todos los animales expuestos a ppm ( mg/m 3 ) de dióxido de cloro, aumentando la incidencia en una manera dependiente de la dosis. La CL 50 media calculada fue de 32 ppm (90 mg/m 3 ). En otro estudio se produjo exudación ocular, hemorragia nasal, edema pulmonar y muerte a 260 ppm (728 mg/m 3 ) durante dos horas. El dióxido de cloro es tóxico cuando se administra en solución mediante una 26

184 Chlorine dioxide (gas) dosis oral única a ratas; con 40 y 80 mg/kg de peso corporal se detectaron signos de actividad corrosiva en el estómago y el tracto gastrointestinal. La DL 50 calculada por vía oral fue de 94 mg/kg de peso corporal. Los datos sobre el efecto irritante en los ojos y las vías respiratorias del dióxido de cloro gaseoso son limitados. Sin embargo, hay pruebas de dicho efecto en personas asociadas con niveles desconocidos de dióxido de cloro gaseoso en el aire. En ratas expuestas a 260 ppm (728 mg/m 3 ) durante dos horas se observó irritación grave de los ojos y las vías respiratorias. No se han notificado casos de sensibilización cutánea o asma ocupacional relacionados con el dióxido de cloro. La calidad de los datos disponibles sobre la exposición por inhalación repetida es generalmente escasa, por lo que la información sobre la relación dosisrespuesta se debe examinar con prudencia. Además, existe el problema de que no se examinó el tejido nasal, aunque en un estudio se notificó rinorrea en ratas con 15 ppm (42 mg/m 3 ), lo cual indica que el conducto nasal puede ser un tejido destinatario del dióxido de cloro inhalado. Otros estudios en ratas pusieron de manifiesto que no se encontraban efectos adversos con 0,1 ppm (0,28 mg/m 3 ) cinco horas/día durante 10 semanas o con 1 ppm (2,8 mg/m 3 ) 2-7 horas/día durante dos meses. Al parecer se producen lesiones pulmonares, en forma de bronquitis, bronquiolitis o pequeñas zonas de alveolitis hemorrágica, con 2,5 ppm (7,0 mg/m 3 ) o más tras una exposición repetida de siete horas/día durante un mes y con 10 ppm (28 mg/m 3 ) o más en 15 minutos dos veces al día durante 4 semanas, con una gravedad dependiente de la dosis. Se observó mortalidad con 15 ppm (42 mg/m 3 ) 15 minutos, dos o cuatro veces al día durante un mes. En el mismo régimen de exposición, no se observaron efectos adversos (entre las observaciones limitadas realizadas) con 5 ppm (14 mg/m 3 ). producido resultados positivos in vitro, esta sustancia suscita preocupación por la mutagenicidad local en el punto de contacto, aunque no se han realizado estudios sobre este efecto final. La exposición oral de ratas a niveles de dióxido de cloro tóxicos para las madres no afecta a la fecundidad o el desarrollo. Esto concuerda con la opinión de que, puesto que el dióxido de cloro es un gas reactivo, sería poco probable que llegara a los órganos reproductivos en cantidades significativas. Los datos disponibles de medición de la exposición ocupacional (en el Reino Unido) y los niveles de exposición pronosticados utilizando el modelo de estimación y evaluación de la exposición indican una exposición probablemente máxima de 0,1 ppm (0,28 mg/m 3 ) en una evaluación ponderada por el tiempo de ocho horas. La comparación de este nivel de exposición con la concentración sin efectos adversos observados (NOAEL), que se obtiene a partir de datos muy limitados, parece indicar que no hay motivo de preocupación en cuanto al efecto de irritación de las vías respiratorias y de los ojos de los trabajadores expuestos al dióxido de cloro en el lugar de trabajo. Los datos disponibles son insuficientes para realizar una evaluación del riesgo para el medio ambiente. El dióxido de cloro se degradaría rápidamente en el medio ambiente para producir clorito y clorato. Los pocos datos de ecotoxicidad disponibles ponen de manifiesto que el dióxido de cloro puede ser muy tóxico para los organismos acuáticos; la CL 50 más baja para los peces fue de 0,02 mg/l. Se ha demostrado que el clorato, liberado en las aguas residuales de las fábricas de pasta de papel tras la utilización de dióxido de cloro, tiene efectos ambientales importantes en las comunidades de aguas salobres. Las macroalgas pardas son particularmente sensibles al clorato tras una exposición prolongada. El umbral para los efectos es de µg/l. Los estudios de exposición repetida por vía oral en ratas y primates son en general de formulación y/o calidad limitados, pero sus resultados ponen de manifiesto que no hay pruebas de toxicidad sistémica asociada con el dióxido de cloro administrado en el agua de bebida o mediante sonda. No hay datos en relación con la exposición crónica o la carcinogenicidad del dióxido de cloro gaseoso. Los estudios realizados en células de mamíferos utilizando soluciones acuosas de dióxido de cloro indican que es mutágeno in vitro. Esta actividad no se expresó en estudios bien realizados in vivo en células somáticas o germinales. Sin embargo, dado su carácter generalmente reactivo y debido al hecho de que se han 27

185 THE CONCISE INTERNATIONAL CHEMICAL ASSESSMENT DOCUMENT SERIES Azodicarbonamide (No. 16, 1999) Barium and barium compounds (No. 33, 2001) Benzoic acid and sodium benzoate (No. 26, 2000) Benzyl butyl phthalate (No. 17, 1999) Beryllium and beryllium compounds (No. 32, 2001) Biphenyl (No. 6, 1999) 1,3-Butadiene: Human health aspects (No. 30, 2001) 2-Butoxyethanol (No. 10, 1998) Chloral hydrate (No. 25, 2000) Chlorinated naphthalenes (No. 34, 2001) Crystalline silica, Quartz (No. 24, 2000) Cumene (No. 18, 1999) 1,2-Diaminoethane (No. 15, 1999) 3,3'-Dichlorobenzidine (No. 2, 1998) 1,2-Dichloroethane (No. 1, 1998) 2,2-Dichloro-1,1,1-trifluoroethane (HCFC-123) (No. 23, 2000) N,N-Dimethylformamide (No. 31, 2001) Diphenylmethane diisocyanate (MDI) (No. 27, 2000) Ethylenediamine (No. 15, 1999) Ethylene glycol: environmental aspects (No. 22, 2000) 2-Furaldehyde (No. 21, 2000) HCFC-123 (No. 23, 2000) Limonene (No. 5, 1998) Manganese and its compounds (No. 12, 1999) Methyl and ethyl cyanoacrylates (No. 36, 2001) Methyl chloride (No. 28, 2000) Methyl methacrylate (No. 4, 1998) N-Methyl-2-pyrrolidone (No. 35, 2001) Mononitrophenols (No. 20, 2000) Phenylhydrazine (No. 19, 2000) N-Phenyl-1-naphthylamine (No. 9, 1998) 1,1,2,2-Tetrachloroethane (No. 3, 1998) 1,1,1,2-Tetrafluoroethane (No. 11, 1998) o-toluidine (No. 7, 1998) Tributyltin oxide (No. 14, 1999) Triglycidyl isocyanurate (No. 8, 1998) Triphenyltin compounds (No. 13, 1999) Vanadium pentoxide and other inorganic vanadium compounds (No. 29, 2001) To order further copies of monographs in this series, please contact Marketing and Dissemination, World Health Organization, 1211 Geneva 27, Switzerland (Fax No.: ;

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