Study on coagulation effects of PAC and PAFC on urban rainwater treatment

The coagulation tests for simulated urban rainwater were performed using PAC and PAFC respectively. The influences of coagulant type, dosage and pH of raw water on the coagulation effect were investigated. The results show that under the conditions of the fast stirring rate of 200 r/min(1 minute), the middle stirring rate of 150 r/min(5 minutes), low stirring rate of 50 r/min(15 minutes), the optimum dosage of PAC is 40ml/L, the optimum dosage of PAFC is 60ml/L. There is no significant difference in coagulation effect between PAC and PAFC. Taking cost into account, PAC was recommended. When the pH ranges from 6.5 to 7.5, the coagulation efficiency of PAC is better. When PAC dosage is 40mg/L and pH of raw water is 7.0, the removal rate of turbidity, ammonia nitrogen and CODcr was 98.14%, 18.05% and 47.46%, respectively.