強化氧化混凝程序鋁水解物種對藻類衍生消毒副產物前質去穩定之影響

水庫水源發生藻華會為水廠帶來豐富的藻類有機物(Algogenic organic matter, AOM)，從而導致飲用水供應加氯過程產生消毒副產物(DBPs)。前氧化是一種很有用的方式去提高藻類去除效能，以利後續聚氯化鋁(Polyaluminum chloride, PACl)混凝進行最大限度地減少消毒副產物前質(precursors)。然而，鋁水解物種會嚴重影響DBP前質減少之效能。本研究旨在探討 NaOCl 和 ClO2 前氧化對兩種藻類(銅綠微囊藻(Microcystis aeruginosa)和小球藻(Chlorella sp)細胞降解之影響，以及AOM 之分子量(MW)分佈和相應的 DBP 生成潛能(DBPFP)。此外，進一步評估了具有不同鋁物種之PACl混凝劑，即包括具有71%聚合鋁(Alb)之PACl-H和具有51%單體鋁(Ala)之PACl-W，其對各種分子量之AOM和DBPFP降低之影響。研究結果顯示，在低混凝劑量下(1和2 mg/L as Al)，無論氧化劑種類為何，PACl-H混凝減少藻細胞數之能力均較PACl-W佳。然而，PACl-W混凝搭配ClO2前氧化，在高混凝劑量下(4 mg/L as Al）可有效減少藻細胞數(減少比例高達99.6%)。在銅綠微囊藻和小球藻懸浮液之DOC、UV 吸光度和螢光強度方面，PACl-H混凝搭配ClO2前氧化可顯著降低AOM濃度。此時，在提高氧化劑量後(4 mg/L as Cl2)，強化ClO2氧化在特定的分子量(MW)分佈中(10 kDa至大於100 kDa)表現出較佳的AOM 減少率。另一方面，主成份分析(Principal component analysis, PCA)推論已進一步顯示鹵化DBP生成與特定MW分佈(小於1 kDa至100 kDa)的類腐殖酸(Humic acid-like)和類可溶性微生物產物(SMP-like)物質相關密切。總而言之，前氧化程序採用NaOCl或ClO2強化氧化足以增強PACl-H混凝處理含藻水中DBP前質之最小化。

關鍵字

藻類；強化前氧化；混凝；消毒副產物

並列摘要

Algal blooming occurred in the water source from reservoirs often brings abundant algogenic organic matter (AOM) to water treatment plants, which causes disinfection by-products (DBPs) formation in chlorination process for drinking water supply. Pre-oxidation is a promising approach to improve the performance of algae removal and minimize the disinfection by-product precursors for subsequent coagulation with polyaluminum chloride (PACl). However, the effect of Al hydrates strongly influences the reduction of DBP precursors by coagulation. This study aimed to investigate the effect of NaOCl and ClO2 pre-oxidation on the cell degradation of two algae species, including Microcystis aeruginosa and Chlorella sp, and their AOM fraction changes based on molecular weight (MW) fractionation and the corresponding DBP formation potential. Besides, the effect of various PACl coagulant with different Al hydrates, namely PACl-H with 71% polymeric Al and PACl-W with 51% monomeric Al regarding fractionated AOM and DBP formation potential reduction was further evaluated. The result has shown that PACl-H coagulation outperforms the algal cells removal regardless of oxidant types at low coagulant dosage (1 and 2 mg/L as Al). However, PACl-W coagulation coupled with ClO2 oxidation is effective in cell reduction (up to 99.6%) at high coagulant dosage (4 mg/L as Al). Basically, PACl-H coagulation coupled with ClO2 oxidation performs the significant reduction of AOM in terms of DOC, UV absorbance, and fluorescent intensity for Microcystis aeruginosa and Chlorella sp suspensions. At such a condition, the intensified ClO2 oxidation exhibits higher AOM reduction in a specific MW distribution, ranging from 10 kDa to >100 kDa. In addition, the principal component analysis (PCA) inference has elaborated that halogenated DBPs are well correlated with humic acid-like and soluble microbial product-like substances in a specific MW distribution, ranging from <1 kDa-100 kDa. It is concluded that intensified pre-oxidation with NaOCl or ClO2 is sufficient to enhance the minimization of DBP precursors in algae-laden water treatment by PACl-H coagulation.

並列關鍵字

Algae ； Intensified pre-oxidation ； Coagulation ； Disinfection by-products

參考文獻

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強化氧化混凝程序鋁水解物種對藻類衍生消毒副產物前質去穩定之影響

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