強化混凝-臭氧-薄膜處理提升過濾程序出水 溶解性有機物質之去除

Abstract

金門太湖為太湖淨水場之水源，水源中含高濃度之有機物質，無法有效地利用現有之傳統淨水程序去除，因此為提升太湖淨水場出水水質，本研究擬以混凝-薄膜-臭氧，進一步去除快濾單元出水之溶解性有機物質（Dissolved organic matter, DOM），以達我國飲用水水質4 mg TOC /L之標準。Lin（2014）以吸附混凝去除有機質，利用陶瓷膜，無沉澱直接過濾混凝膠羽，其出水DOC仍然高於4 mg TOC /L。本研究延續該實驗，今以原吸附混凝接續陶瓷膜過濾之淨水程序為基礎，再增加臭氧處理，觀察DOC之變化，利用優選反洗程序，延長陶瓷膜過濾使用時間，為解析有機組成之去除與殘留，本研究分析各流程殘餘有機物之親疏水性分布與分子量大小，提供金門太湖淨水場實際應用參考。 優選臭氧順序與劑量為：吸附混凝後以陶瓷膜過濾水中膠羽，再以0.8 mg ozone/ mg DOC之臭氧處理有機物質，此優選程序可將快濾出水由10.87 mg TOC /L降至1.57 mg TOC /L，結果可達我國飲用水水質4 mg TOC /L標準，為使陶瓷膜使用時間增長，反洗程序以每兩小時操作一次，優選反洗程序為三次物理反洗結合一次化學反洗，可將透膜壓差恢復至100%。吸附混凝可去除64%之疏水性有機物質及44%之親水性有機物質，臭氧處理後，疏水性有機物質去除率可達88 %，親水性有機物質去除率可達78 %。分子量大小分布之探討，經粉狀活性碳後，分子量介於3,000 – 300 Da有機物質有較高之去除率；混凝後，分子量介於30,000 – 3,000 Da有機物質有較高之去除率；臭氧對於分子量介於10,000 – 3,000 Da與1,000 – 300 Da有機物質有較高之去除率。

The removal of dissolved organic matter (DOM) by conventional treatment processes in drinking water treatment plants (DWTPs) has been ineffective in Tai-lake on Kinmen. In this study, various advanced treatments were tested for DOM removal. Combined the result by Lin., (2014), this year, Enhanced coagulation, Powdered activated carbon (PAC), ceramic membrane (CM), and ozone were used in various combinations to effect removal of DOM in the DWTP in Kinmen, Taiwan. The rapid sand filtration effluent from the Tai Lake DWTP of Kinmen, Taiwan with DOC of 10.87 mg/L was treated with poly aluminum chloride (PACL) as a coagulant and DOC reduction was measured by DOC and UV absorbance at 254 nm. The molecular size distribution (MSD) of DOM was investigated using gel filtration chromatography (GFC) and its hydrophilic/hydrophobic (HPI/HPO) characteristics using the DAX-8 resin. DOM removal efficiency was improved when EC and PAC were used prior to CM and ozone, resulting in removal of DOC from 10.87 to 1.57 mg TOC /L with corresponding decrease in UV254 from 0.087 to 0.013. The removal efficiencies for DOCHPO and DOCHPI were 88% and 79%, respectively. The PAC could adsorb more low molecular weight (MW) organic matter, and the high MW organic matter could be more efficiently removed by PACL as well as ozone. This process shows promise in improving DOM removal and the potential to increase compliance with the drinking water standard of Taiwan.