Response surface methodology(RSM) was applied for optimizing the enhanced coagulation process by preozonation for Taihu lake water.Based on single-factor experiments,three independent variables(ozone dosage,coagulant dosage and residence time) were selected as affecting factors and three dependent variables(chemical oxygen demand(CODMn) removal efficiency,turbidity removal efficiency and operating cost) as responses.An experimental design of three factors and three levels was arranged through Box-Benhnken design (BBD).According to the proposed quadratic models,maximalCODMnand turbidity removal efficiencies and minimal operating costs are obtained at following optimum condition:The ozone dosage,coagulant dosage and residence time are found to be 0.9 mg/L,35 mg/L and 17 min for aluminum sulfate(AS) and 0.9 mg/L,24 mg/L,and 17 min for polymerization aluminum chloride(PAC),respectively.
