PAC/PDM复合混凝剂用于夏季太湖水混凝脱浊研究

Turbidity Removal of Summer High Algae Content Taihu Lake Raw Water Using Composite Coagulants of Polyaluminum Chloride and Polydimethyldiallylammonium Chloride

用特征粘度系列化的聚二甲基二烯丙基氯化铵（PDM）与聚合氯化铝（PAC）复合得到稳定的复合混凝剂,用于夏季高藻太湖水强化混凝脱浊处理.通过混凝烧杯实验,考察了无机/有机复合比例、PDM特征粘度对脱浊效果及絮团沉淀性能的影响.结果表明,对浊度为30-33 NTU,温度为28-30℃,藻含量为2.6×10^7个/L的太湖水,在与某市水厂混凝强度相近的搅拌强度下,当达到该水厂2NTU沉淀池出水的余浊标准时,PAC需7.00 mg/L的投加量,质量复合比例为5∶1、10∶1、20∶1的PAC（以Al2O3计）/PDM复合混凝剂所需PAC投加量随PDM特征粘度0.52、1.53、2.46 dL/g的增加分别为3.00-2.83 mg/L、3.50-3.49mg/L、5.37-4.67 mg/L,相对于PAC减少投加量57.14%-59.57%、50%-50.14%、23.29%-33.29%;作为深度处理的技术准备,当沉淀出水浊度要求提高至1NTU的情况下,复合药剂依然可发挥好的作用,PAC需10 mg/L的投加量,PAC（以Al2O3计）与PDM质量复合配比为20∶1、10∶1、5∶1的复合混凝剂需8.33-3.91 mg/L的投加量,能比PAC减少投加量16.7%-60.9%.可见,PDM明显提高了PAC的混凝脱浊效果与沉淀性能,且PAC/PDM质量复合配比越低,PDM特征粘度越高,脱浊效果与沉淀性能越好.

A series of stable composite coagulants was prepared using polyaluminum chloride（PAC） and polydimethyldiallylammonium chloride（PDM） with different intrinsic viscosity as raw materials.The enhanced coagulation processes of summer high algae content Taihu lake raw water by using the composite coagulants were reported in this paper.Jar tests were used to study the influences of the composite ratios of PAC to PDM and the intrinsic viscosity of PDM on the turbidity removal and precipitating performance.The results showed that for the summer Taihu raw water with temperature of 28-30℃ and turbidity of 30-33 NTU,algae content of 2.6×10^7cells/L.When 2NTU turbidity of supernatant from settlement tank was required according to the current process of potable water plant in Wuxi,the dosage of 7.00mg/L PAC was necessary,thePAC/PDM composite coagulants with the ratios（m/m） of 20∶1,10∶1,5∶1 only needed dosage ranges of 3.00-2.83mg/L,3.50-3.49mg/L,5.37-4.67mg/L with the increasing of PDM intrinsic viscosity from 0.52dL/g to 2.46dL/g.And compared with PAC only used,composite coagulants could decrease the PAC dose by 57.14%-59.57%,50%-50.14%,23.29%-33.29% correspondingly.When residual turbidity of 1 NTU was required,the dosage of 10mg/L were necessary for the treatment with PAC,composite coagulants with the ratios（m/m） of PAC to PDM of 20∶1,10∶1,5∶1 and the different intrinsic viscocity of PDM needed dosage of 8.33-3.91 mg/L, and could decrease the PAC dose by 16.7%-60.9%.Therefore,the efficiency turbidity removal and precipitating performance of composite coagulants were remarkably,and the lower the ratios of PAC to PDM and the higher the intrinsic viscosity of PDM,the higher efficiency of turbidity removal.