Pilot Study of Coagulation-Direct Filtration for Low-Temperature and Low-Turbidity Source Water

A pilot study was carried out for direct filtration assisted with low-dose coagulation to treat low temperature and low turbidity reservoir water for drinking water. The impacts of filtration rate, gap between coagulation and filtration, coagulant dosage and filtering material were examined. The tested ranges were as following: filtration rate 4-10 m/h, gap between coagulation and filtration 1-5 min, coagulant dosage 4- 20 mg/L. The results show that direct filtration with low-dose coagulation was very effective in treating the low temperature and low turbidity source water. The optimal conditions were as following: PAC dose of 12 mg/L, filtration rate of 6 m/h, gap between coagulation and filtration of 3 min. The effluent turbidity was 0.5 NTU, COD was 2.4 mg/L, and the filtration cycle was 9 h. The coagulant dose was only 40% of that of conventional treatment.