Experimental Study On Enhanced Coagulation Treatment Of High Algae Water With Potassium Mono-persulfate

The impact of human activities has led to an increase in the eutrophication of global water bodies,and algae bloom in large numbers in spring and summer.The outbreak of algae makes the source water emit stench and odor.And in the conventional water treatment process of water plant,it is easy to block the filter to increase the operation load.The algae toxin and metabolites produced by certain algae seriously threat the hygiene and safety of human drinking water.In order to solve the problem of conventional water treatment technology by the large-scale propagation of algae in source water,and based on the premise of not adding new structure,not breaking algae cell structure,and guaranteeing the hygiene and safety of effluent,the conventional coagulation process is intensified by compound potassium mono-persulfate in this project.The effects of enhanced coagulation treatment of high algae water by compound potassium mono-persulfate?PMS?or the disinfector?PMSO?with PMS as the main component and the compound agent of poly-aluminum chloride was primarily studied in this project.The simulation experiment of the enhanced coagulation treatment of M.aeruginosa solution with PMS and poly-aluminum chloride composite agent showed that the addition of PMS increased the algae removal rate of poly-aluminum chloride after coagulation from48.6%to 97.1%,and the algal removal efficiency increased significantly.Through the analysis of the factors affecting the algal removal rate of compounded agents enhanced coagulation,it is concluded that the pH value and humic acid concentration among the main background components of the water had an obvious effect on the enhanced coagulation.The concentration of inorganic ions such as carbonate/bicarbonate(CO₃^2-/HCO₃^-)and chloride?Cl^-?did not affect the enhanced coagulation.The algae removal rate decreased with the increase of pH value,and the algae removal rate decreased with the increase of humic acid concentration.The addition of methanol and tert-butanol had no effect on the algal removal rate of enhanced coagulation,which indicated that PMS could deactivate algal cells by auto-oxidation.The experimental study on the release and degradation of microcystin from Microcystis aeruginosa solution by PMS showed that the microcystins released by Microcystis aeruginosa into water could be degraded quickly and efficiently,and the algae cells would not be broken.The solution of algal cells oxidized by PMS was completely broken by ultrasound.Comparing the microcysin contents in solutions made before and after the break,it can be observed that the substances in the M.aeruginosa cells was not released into water under PMS oxidation.PMS,as a gentle oxidizing agent,deactivated the algal cells but did not break the cellular structure,which guaranteeing the safety of process effluent.The contrast experiment between the enhance coagulations of PMSO and poly-aluminum chloride and of PMSO and poly-aluminum sulfate indicated that removal effect by the enhanced coagulation of PMSO and poly-aluminum chloride on the removal of algae and COD_Mnn was better.The on-site experiment of the enhanced coagulation treatment of the compound agent of PMSO and poly-aluminum chloride on the high-algae artificial lake indicated that the best compounding ratio of PMSO and poly-aluminum chloride was 1:3;under the condition with the best adding amount of 50mg/L,the algal removal rate could reach93.2%and the COD_Mnn removal rate could reach 61.0%.Compared with the single addition of50mg/L poly-aluminum chloride in conventional coagulation algae removal,the algae removal rate increased with 50.9%,and the COD_Mnn removal rate increased with 20.7%.The on-site experiment of the enhanced coagulation treatment of the compound agent of PMSO and poly-aluminum chloride on the high-algae reservoir water indicated that the best compounding ratio of PMSO and poly-aluminum chloride was 1:2;under the condition with the best adding amount of 40mg/L,the algal removal rate could reach 97.9%and the COD_Mnn removal rate could reach 38.8%.Compared with the single addition of 40mg/L poly-aluminum chloride in conventional coagulation algae removal,the algae removal rate increased with 54%,and the COD_Mnn removal rate increased with 17.1%.The results indicated that the application of the enhanced coagulation of potassium mono-persulfate on the actual water source also had an effective performance on the algae species in high-algae water.The addition of potassium mono-persulfate caused an obvious improvement on the conventional coagulation algae removal.The experimental study on enhanced coagulation treatment on reservoir water in different seasons showed that the algae removal rate of the enhanced coagulation and COD_Mnn removal rate both decreased with the increase of algae cell content in water.To maintain the and the removal rate of algae and COD_Mn,when the algae content increased,the compound ratio of PMSO and poly-aluminum chloride could be increased or the adding amount of the compound agent could be increased.