近年來國內相繼發現食品及飲品中含有對人體造成危害的化學物質，在臺灣飲用水來源大多以台灣自來水公司 (台水公司) 淨水場經由加藥混凝等淨水單元淨化、消毒過後直接配送到各用戶端，然而在飲用水中殘留鋁對人體的影響亦造成國人疑慮的一環，世界各國亦相繼建立相關資料及訂定飲用水中殘留鋁含量標準或建議限值，因此臺灣亦積極建立飲用水中殘留鋁相關資料，並針對其問題進行改善，其中最直接的改善方式及是將原有之鋁系混凝劑改為其他混凝劑。本研究系將原硫酸鋁( Aluminum Sulfate，Al2(SO4)3‧18H2O )混凝劑更換為氯化鐵 ( Ferric Chloride，FeCl3‧6H2O )混凝劑進行實場試驗進行相關探討，比較兩混凝劑之適用性。 本研究係以潭頂淨水場作為研究對象，研究期間原水濁度均屬低濁度之原水，對此一低濁度進行加藥試驗。根據實場試驗結果，推論清水水中之殘留鋁主要是由添加硫酸鋁混凝劑所產生，在原水水中之鋁型態主要以顆粒性鋁為主，顆粒性鋁經混凝過濾便能去除，然而原淨水系統清水水中殘留鋁的型態主要以溶解性鋁存在，其溶解性鋁皆已超出0.2 ppm之限值，顯示了水中殘留鋁之來源以添加藥劑為主，反觀添加氯化鐵混凝劑能有效降低水中殘留鋁的問題，將水中殘留鋁降至0.2 ppm之限值，且經由過濾單元亦不會造成水中色的增加，原水水中總鐵濃度也能被減少；在低濁度原水混凝方面，氯化鐵混凝劑其混凝成效較硫酸鋁好，能快速產生膠羽，且產生之膠羽顆粒較大，沉降較快，對於原水水中濁度之去除成效顯著，在各方面之探討，若未將硫酸鋁混凝劑更換為氯化鐵混凝劑將水中殘留鋁降低是可行的。 Water treatment processes are adapted prior to distribution to ensure supply of safe drinking water. In recent years, however, drinking water has been identified to contain harmful chemicals such as aluminum that when ingested causes adverse effects to human health. Drinking water standards for aluminum have been implemented in other countries. Currently, Taiwan is establishing data on residual aluminum in drinking water and studies are underway for future inclusion of aluminum as a regulated parameter in the drinking water standards and in the end improve the quality of drinking water supplied to stakeholders.In Taiwan, purified water is supplied and distributed by Taiwan Water Corporation from their treatment plants which use coagulants for clarification. Aluminum sulfate is the standard coagulant used in most water treatment facilities, resulting to presence of increased residual aluminum in treated waters and creating health concerns among end users.In this research, comparative study was conducted on the efficiency of ferric chloride and aluminum sulfate for the removal of residual aluminum in treated waters. Raw water samples were collected at Tan-Din water purification plant and dosing curves were established for both coagulants using jar tests.Results revealed that although both coagulants exceeded the 0.2 mg/L residual aluminum standard value, aluminum sulfate when added to raw water form aluminum particulates that require further filtration. On the other hand, ferric chloride effectively reduced residual aluminum way below the 0.2 mg/L limit, and the aluminum is in soluble form thus filtration can be omitted. Raw water total iron concentration can also be reduced while low degree of turbidity can be achieved. Ferric chloride is an effective coagulant compared to aluminum sulfate in that it can generate floc quickly and form large aggregates for easy settling and produce remarkable results in lowering the degree of turbidity of raw water through effective removal of residual aluminum.
