Optimization Of Algae Removal And Turbidity Removal Process For Source Water Of South To North Water Transfer Project (Handan Section)

A waterworks in Handan city was introduced from the source water of Handan section of South to North Water Transfer Project.In order to solve the problem of algae pollution in the raw water and reduce the turbidity and algae in the effluent,a small-scale test device was designed to simulate the running water of the water plant.The algal and turbidity removal was improved by optimizing coagulation and filtration.The whole optimization experiment was divided into three parts:optimizing coagulation beaker test and optimizing coagulation process for algae removal.The experiment of turbidity removal and algae removal and turbidity removal by optimizing filtration process were carried out.In the test of coagulant stirring beaker,by selecting four different coagulants,the optimal coagulant is polyaluminum-ferric chloride,and the optimal dosage was 50mg/L.In the experiment of optimizing coagulation hydraulic parameters,the best G value and GT value of mixing agitation were found to be 345s^-1,41400,the best G value and GT value of flocculation agitation were respectively found to be 46s^-1,33120,and the removal rate of turbidity and chlorophyll a were 96.84%and 92.63%,respectively.Response surface methodology?RSM?was used to optimize the parameters affecting the coagulation process.The results showed that the dosage of coagulant had the most significant effect on algae removal and turbidity removal,and the interaction between coagulant dosage and mixing stirring speed was the most significant.The conditions were obtained by response surface methodology:the coagulant dosage was 48 mg/L,the mixing stirring speed was 318r/min,and the flocculation stirring time was 12 min The removal rates of chlorophyll a and chlorophyll a were respectively 97.01%and 93.04%.In the optimized coagulation pilot test,the optimal hydraulic retention time?HRT?was found by adjusting the flow rate and comparing the algae removal and turbidity removal effect under different working conditions.The test results show that the best effect of algae removal and turbidity removal is achieved when the inlet flow rate is 54L/h,the mechanical flocculation pool peace flow sedimentation tank hydraulic retention time,respectively for 20 min,120 min,the process of algal turbidity removal effect was best.The average value of effluent turbidity of sedimentation tank was 0.207 NTU,the average turbidity removal rate was 94.53%,the average chlorophyll-a content in the effluent of sedimentation tank was 0.44mg/m³,and the average chlorophyll-a removal rate was 89.97%.Continuous detection of the residual aluminum content in the effluent of the sedimentation tank shows that the average residual aluminum content is 0.151 mg/L.In the experiment of exploring the influence of p H on residual aluminum,it is concluded that when the raw water p H is 7.5,the residual aluminum content in the effluent is obviously reduced to 0.121mg/L.In the pilot test of optimizing the filtration process,the parameters of the filter column filter were optimized,and the algae removal and turbidity removal effects under different working conditions were compared and analyzed.The best working condition of algae removal and turbidity removal by filtration process was found out,so as to ensure the turbidity of the effluent and the best algal treatment effect and ensure the residual aluminum content in the water to reach the standard and ensure the safety of water supply.It was concluded that when L/d₁₀ was 1200 and filtration rate was 8m/h,the average turbidity of filtered effluent was 0.108 NTU,and the average turbidity removal rate of filter was 50.68%.The average content of chlorophyll-a in effluent was 0.21 mg/m³,and the removal rate of chlorophyll-a was 52.27%.Under the optimized coagulation filtration conditions,the turbidity removal rate was97.33%,the chlorophyll-a removal rate was 95.74%,and the average residual aluminum content after filtration was 0.133 mg/L.