高能效電混凝浮除技術分離 水中藍綠藻細胞之研究

水體中的高污染營養物質(如氮和磷酸鹽)會引發藍綠藻等藻類大量繁殖。這種微藻細胞造成了嚴重的水質問題，包括增加消毒副產物(disinfection by-products, DBPs)生成潛能，並降低水廠淨水處理效率。基於時間效率與經濟性考量，鋁電極之電混凝法已被證明是一種有效分離微藻細胞的方法。本研究中，一種新電混凝-絮凝-浮除(electrocoagulation-flocculation-flotation, EFF)系統被設計用於銅綠微囊藻(Microcystis aeruginosa, MA)細胞分離和削減藻類有機物(algogenic organic matter, AOM）。EFF實驗在不同的pH值 (pH 5、7、8)及電流密度(3、5、10 mA/cm2)進行，並分析鋁水解物種對其效能之影響。此外，本研究同時評估磷酸鹽濃度(5、10 mg/L-PO43-)在最適操作條件下對EFF效能之影響。另外，使用掃描電子顯微鏡和能量色散X射線光譜法進一步觀察膠羽特性與化學元素組成，以確認EFF對微藻細胞之去除機制。最後，分析EFF處理後之水樣之分子量分佈、DBPs生成潛能與能源使用效率。研究結果顯示，在pH 8和5 mA/cm2條件下進行的EFF可以達到95%的MA細胞分離和56%的AOM消減效率，類可溶性微生物產物(SMPL)和類芳香族蛋白(APL)物質是AOM削減之主要貢獻者。在一開始操作EFF時，約80%的單體鋁物種(Ala)轉化為聚合鋁物種(Alb)和膠體鋁物種(Alc)，此結果導致了強烈沉澱掃除與弱電性中和混凝機制主導了藻類細胞的分離。在相似的MA去除效率下，EFF的能量輸入需求(2.07×10-2 kWh/kg)較傳統電混凝-浮除(electro-coagulation-flotation, ECF)系統低63%。另一方面，10 mg/L-PO43-的存在會使細小和鬆散結構的絮狀物形成而降低EFF對藻類分離的性能。此外，EFF對低分子量化合物及DBPs前質削減並不明顯。然而，EFF可以通過提高電流密度克服高濃度磷酸鹽降低藻類分離效能之問題。因此，EFF是一個高能源效率之系統，其適用於分離含藻原水，並可同時進行磷之削減處理。

關鍵字

電混凝浮除；鋁水解物種；微藻；除磷

並列摘要

The high pollutant nutrients such as nitrogen and phosphate in water bodies can trigger algal blooms like microcell cyanobacteria. This microcell caused severe water quality problems, including increased disinfection by-products (DBPs) formation potential and reduced treatment efficiency while entering the water treatment plant. Alumina-based electrocoagulation has proved as a means of microcell separation due to its time effectiveness and economic aspect. In this study, a novel electrocoagulation-flocculation-flotation (EFF) system was designated toward Microcystis aeruginosa (MA) cells separation and algogenic organic matter (AOM) reduction. EFF performance on various pH (pH 5, 7, 8), CD (3, 5, 10 mA/cm2), and the effect of alumina hydrate investigations. In addition, the impact of phosphate concentrations (i.e., 5, 10 mg/L-PO43-) were evaluated. Further observation was carried out with scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS) to determine the mechanism of algae removal during EFF. In addition, fractionated molecular weight, DBP formation potential reduction, and energy input were further quantified. The results have shown that EFF performed at pH 8 and 5 mA/cm2 could achieve 95% of MA cells separation and 56% of AOM reduction, with soluble microbial product-like (SMPL) as the main contributors, accounting for 60%. The formation of dominant colloidal Al species (Alc) governs the EFF to promote cells and AOM destabilization by strong sweep flocculation along with weak charge neutralization by polymeric Al species (Alb). At such a conditions, EFF requires only 2.07×10-2 kWh/kg in energy input and serves energy saving ~63% less than that by traditional ECF at similar MA cells separation. On the other hand, the presence of 10 mg/L-PO43- could lower the performance of EFF toward MA cells separation and worsen the floc formation with delicate and loose structures. In addition, low molecular weight compounds remain with insignificant reduction of DBPs precursors after EFF treatment. Nevertheless, EFF can overcome the problem with insignificant performance at concentrated phosphate by increasing current density. It is concluded that EFF is a feasible system with an energy-efficient approach and applicable to the separation of algae-laden water simultaneously with dephosphorization.

並列關鍵字

Electrocoagulation-flotation ； alumina hydrates ； microalgae ； dephosphorization

參考文獻

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