在淨水處理程序中，高含藻原水屬於難處理原水之一，因為藻類具有形狀多變、比重較輕及細胞密度小等特性，在混凝沉澱的過程中較不容易沉降去除，因而造成過濾單元阻塞、反沖洗及耗材更換的次數增加等問題。本研究評估自製之聚矽酸鐵(PSI)，對高含藻原水之混凝效果，試驗使用高含藻之原水進行瓶杯試驗，從中找出最適加藥量。進一步研究助沉劑之添加，對提升沉降去除效果之探討。研究中選擇鐵氧磁性顆粒與皂土進行試驗比較。其中鐵氧磁性顆粒具有磁性，在靜置的過程中，可藉由磁力加快顆粒的沉降速度。結果顯示PSI搭配助沉劑可有效去除藻類，而藉由鐵氧磁體與磁力，確實可明顯提升膠羽沉降速度，且鐵氧磁性顆粒的添加不會改變水中pH值，對水中之帶電特性影響也不大。本研究自製PSI之矽鐵比依照含藻原水帶負電的特性，矽鐵比配製比例為0.2:1，含藻原水加入過量的PSI會使原水產生色度，且藥劑會與含藻原水產生水和反應使濁度提高，經研究結果得到最適加藥量為10ppm。再者，本研究進一步評估鐵氧磁性顆粒自汙泥中回收再用之可行性，發現在經收集、?燒及清洗的過程後，在600℃的高溫下將使用過的鐵氧磁性顆粒進行?燒，可達87%的重量回收率，而經瓶杯試驗結果顯示，回收後之鐵氧磁性顆粒仍保有磁性及助沉的效用。 In the water treatment processes, raw water with higher algae content belongs to one of the most difficultly treated cases because the algae have the characteristics of shape changing, low specific gravity and cell density, etc. As a result, in the coagulating sedimentation process, it is hard to remove algae completely, hence blocking the filter unit and increasing times of back-washing and material replacement.This study evaluated efficacy of poly silicate iron (PSI) used in the coagulation of raw water with higher algae content. Via Jar Test, the optimum PSI dosage was estimated. At the silicon/iron molar ratio of 0.2 : 1, the optimal PSI dosage is 10 ppm. At a higher dosage, the water will exhibit brown color and the turbidity is higher. Moreover, co-settling agents (magnetic iron oxide and bentonite) for enhancing settlement efficiency were added and compared. The result showed that magnetic iron oxide can more effectively speed up the settling velocity.In conclusion, adding PSI and co-settling agent can effectively improve the removal of algae. Furthermore, addition of iron oxide magnetic particles has no noticeable effect on the pH values and electrical properties of water. Spent iron oxide particles were recycled. By calcining the spent iron oxide at 600℃, about 87 wt.% was recovered whilst the iron oxide still retained the magnetic and settlement-assisting ability.
