Coagulation aid effect of preoxidation for coagulation and sedimentation technology in reclaimed water treatment

Taking secondary effluent from urban sewage treatment plant as the research object,the effects of different preoxidants of ordinary coagulation sedimentation process and preoxidation-coagulation sedimentation process on reclaimed water treatment were compared.The results showed that,when using KMnO4 as preoxidant,the best treatment effect could be obtained under the follow condition: the KMnO4 dosage was 1.8 mg/L,the pH value of the raw water was 7-8.To reach the same turbidity removal efficiency,the flocculation and sedimen-tation time were 12 and 15 min shorter respectively,and the PAC dosage was decreased by 8 mg/L by the preoxidation-coagulation and sedimentation process in contrast with that by the ordinary coagulation sedimenta-tion process.Furthermore,the removal rate of turbidity could be increased by 15% with KMnO4 preoxidation under the optimal condition.It could be seen that,preoxidation could obviously accelerate the formation and sedimentation of flocs,increase the density of flocs,which showed a significant coagulation aid effect for the coagulation and sedimentation technology in reclaimed water treatment.