加药量和水力搅拌速度对雨水混凝效果的影响

为降低分流制雨水中悬浮颗粒物及其他污染物浓度,减轻城市景观河道的水体富营养化程度,对取自泵站的雨水进行混凝沉淀工艺优化实验。以PAC为混凝剂,采用Zeta电位仪、激光粒度仪和iPDA在线监测技术对混凝过程进行监测,考察了混凝剂投加量和水力搅拌速度对絮体形成和分流制雨水处理效果的影响,结果表明,混凝剂投加量和混合水力搅拌速度直接影响絮体Zeta电位和聚沉特性;混合搅拌速度控制混凝反应速率,絮凝速度梯度影响絮体形成粒径。FI曲线特征参数对控制混凝工艺具有指导意义。PAC投加量为35 mg/L,混合阶段搅拌速度800 r/min,搅拌30 s,絮凝阶段采用150、108和60 r/min的转速各自搅拌5 min,沉后水中剩余颗粒总数最少,浊度、COD和总磷去除效果最佳。

Effect of coagulant dosage and hydraulic strirring speed on rainwater coagulation

Coagulation-sedimentation optimization tests of rainwater from pumping station were carried out in order to decrease the concentrations of suspended particles and other pollutants in rainwater of separated drainage system and alleviate the eutrophication of scenic river. Using PAC as coagulant, the effect of coagulant dosage and hydraulic sirring speed on formation of flocs and treatment effect of rainwater in separated drainage system were investigated by monitoring the coagulation process using zeta potential analyzer, laser particle analyzer and iPDA on-line monitoring technology. The results showed that the zeta potential of flocs and coagulation characteristics were directly affected by coagulant dosage and hydraulic stirring speed. Coagulation reaction rate was controlled by stirring speed. The diameter of the formed flocs was affected by flocculation velocity gradient. The feature parameter of FI curve was directive and significant for controlling coagulation process. The optimum conditions were obtained: coagulant dose of PAC was 35 mg/L, stirring speed during mixing stage was 800 r/min for 30 s, stirring speeds during flocculating stage were 150,108 and 60 r/min for 5 min respectively in turn. Under the optimum conditions, the total particles after sedimentation were the least, the best removal efficiency of turbidity, COD and total phosphorus were obtained.