砷對人類是眾所週知之致癌物，近年為因應法規標準之低砷濃度規定(<10 μg L-1)及日漸覺醒對砷毒害之意識，對原水中砷之有效去除技術的發展被廣泛討論。本研究目的在於探討以傳統前氯後混凝之技術搭配後續薄膜進行地下水原水中砷之去除效能評估。並發展膠羽膜離反應器，以機動性極高之模組，提升實場對砷之去除效能。結果顯示對砷之去除率以前氧化(NaOCl) + 混凝(FeCl3) > 單獨混凝(FeCl3) >單獨氧化。混凝加藥量提升，砂濾除砷效果增加，但亦伴隨濾床反沖洗頻率之增加。搭配薄膜，則發現膜槽之膠羽累積，有助於對砷之吸附，且相較於砂濾，薄膜可在較低混凝劑量下達有效之除砷效果，並在砂濾床已發生阻塞之條件下，薄膜仍維持通量不衰減。此外膠羽薄膜反應器在膠羽添加後搭配良好之槽體攪拌混合，對砷有立即且顯著之去除效果。前加氯無論對傳統混凝或膠羽膜離反應器除砷，皆有助益。膠羽薄膜反應槽應用於含砷原水之處理具有顯著之效果，然由於膠羽有達吸附飽和而需定時更換之考量，建議可以作為機動性調度之處理單元，視原水水質之變化而調整進入此單元之必要性；或作為保險單元，安裝於淨水程序之管末，以保障清水砷濃度低於法規標準。 Arsenic contamination in natural waters has become a worldwide issue since it is a well-known human carcinogen due to its toxicity. The maximum contaminant level of 10 μg L-1 arsenic for drinking water standard was established by WHO and USEPA as a strict guideline. Therefore, research and development on arsenic removal from natural raw waters has gained a lot of attention. In this study, the removal of arsenic from groundwater using pre-oxidation with NaOCl and hollow fiber microfiltration was investigated. The effect of coagulation using FeCl3 in combination with pre-oxidation and microfiltration on the removal efficiency of arsenic was also examined. Results showed that the removal efficiency of arsenic could be arranged in the following order: oxidation using NaOCl in combination with coagulation > coagulation alone > oxidation alone. In the sand filter, a higher dosage of coagulant applied would cause an increase in arsenic removal. However, this also leads to increase in the frequency of backwashing. The microfiltration unit provided better arsenic removal due to floc accumulation on the membrane that enhances arsenic adsorption. In addition, the microfiltration unit requires a lower dosage of coagulant and experiences lesser decline in flux in comparison to sand filtration. Membrane fouling by the microfiltration unit is prevented through a good tank mixing, which lifts and flushes away the floc film formed on the membrane. In general, the hollow fiber microfiltration unit can effectively remove arsenic from groundwater. However, due to floc formation and accumulation on the membrane that leads to the deterioration of membrane performance, replacing the microfiltration membrane is necessary. In addition, the properties and characteristics of the groundwater would also affect the frequency of changing the membrane unit. On the other hand, the microfiltration unit could be used as a tertiary treatment for drinking water, which could be installed at the end of the water purification process, in order to control the with arsenic concentration below the regulatory standards.
