Enhanced coagulation for low-turbidity and micro-pollution reservoir water

Effective coagulation for low-turbidity, micro-pollution source water has long been a technical challenge in safe drinking water supply. This paper investigated the enhanced coagulation for typical low-turbidity, micro-pollution reservoir water (turbidity of 1.3 NTU, COD of 4 mg/L). The methods included coagulant comparison, dose optimization for coagulant aid, addition of Gaolin, and sludge recycle. The effluent turbidity, COD, and UV254 were monitored. The results show that the best coagulant was PAC with an optimal dose of 30 mg/L. PAM was a very effective coagulant aid and improved 25% turbidity reduction at a dose of 0.6 mg/L. Considering the cost, we proposed 0.05 mg/L PAM together with 20 mg/L PAC, and the total cost would be 0.031 RMB/t. Gaolin did not help coagulation for this type of source water. Sludge recycle was the most economic method and could reduce the coagulant dose to 5 mg/L. The best turbidity range for the mixture was 15-35 NTU.