强化混凝对低浊含藻水污染控制研究

Pollution Control in Low Algal Turbidity Water Using Enhanced Coagulation

针对水源地夏季藻类暴发现象,探究了单独投加聚合氯化铝(PAC)、辅助投加高岭土为助凝剂,以及高锰酸钾(KMnO_(4))预氧化强化混凝3种工艺对稳定生长期内不同藻细胞浓度的低浊含藻水中OD_(680)、UV_(254)、DOC和浊度的去除效果。结果表明,当藻细胞密度为105个/mL时,辅助投加高岭土提高初始浊度至10 NTU后投加10 mg/L PAC对OD_(680)、UV_(254)、DOC的去除效果最佳,分别为96.8%、52.0%、55.1%,且沉淀30 min后出水浊度小于1 NTU;当藻细胞密度为106个/mL时,采用KMnO_(4)预氧化(1.2 mg/L,1.5 h)强化混凝可有效降低PAC投加量(4 mg/L),对OD_(680)、UV_(254)、DOC的去除效果最佳,分别为97.5%、39.3%、25.4%,且沉淀30 min后出水浊度仍小于1 NTU。扫描电镜(SEM)结果显示,预氧化对藻细胞的损伤较小,外壳出现轻微变化,混凝后对藻细胞的包裹性更强。对于实际低浊含藻水源水,KMnO_(4)预氧化强化混凝工艺对藻类、有机物和浊度的去除效果最优,同时在出水浊度达标情况下可以大幅减少混凝剂使用量。

Frequent algae blooms in lakes and reservoirs during summer has seriously impaired the safe-ty of drinking water sources in recent years.In this study,polyaluminium chloride(PAC)was selected as the coagulant,and we compared the efficacy and mechanism of three treatment processes.Treatment effectiveness was assessed by measuring the OD_(680),UV_(254),DOC and turbidity in low algal turbidity water with different algae concentrations and raw water from water treatment plants.The three treatments in-cluded:PAC(10 g/L),PAC with kaolin as a coagulant aid,and enhanced coagulation using pre-oxidation with potassium permanganate(KMnO_(4),1.2 mg/L).Trials were run on simulated source water,including two algal cell concentrations(105 cells/mL,106 cells/mL)tested during the stable growth period and three levels of turbidity(10,15,20 NTU).With PAC alone,at an algal cell concentration of 105 cells/mL and a turbidity level of 10 NTU,the decreases in OD_(680),UV_(254) and DOC were 78.6%,54.7%,40.1%.When kaolin was added to the same system,the OD_(680),UV_(254) and DOC decreased 96.8%,52.0%and 55.1%,and the turbidity of the effluent was<1 NTU after 30 min.At an algal cell concentration of 106 cells/mL,KMnO_(4) pre-oxidation(1.2 mg/L,1.5 h)enhanced coagulation with a decrease in PAC dos-age(4 mg/L),and the OD_(680),UV_(254) and DOC were reduced by 97.5%,39.3%and 25.4%.After 30 min,the turbidity of the effluent was still<1 NTU.Based on scanning electron microscope(SEM)imagery,pre-oxidation caused little damage to the algal cells.Only slight changes were observed on the outer mem-brane,and encapsulation of algal cells was stronger after coagulation.With raw water from the treatment plant,KMnO_(4) pre-oxidation enhanced coagulation and gave the highest reductions in algae,organic mat-ter and turbidity.Further,it allows for a significant reduction in coagulant dosage while ensuring that the turbidity of treated water meets the standard.