Combination coagulation using multiple coagulants for low turbidity water treatment

摘要

Coagulation of low turbidity source water from Luan River using FeCl3 cannot get a satisfied treated water quality even increasing the coagulant dosage to as high as 60 mg/L.A composite inorganic macromolecule polymer-polyaluminum ferric chloride(PAFC)was selected and a combination coagulation using PAFC and FeCl3 was designed to improve the coagulation efficiency of Low turbidity source water.The coagulation performances of PAFC,FeCl3 and their combination were conducted.The optimization and economic analysis of the combination coagulation using PAFC and FeCl3 were carried out. Results show that the residual tUrbidity for the combination coagnlation using RAFC and FeCl3 are much lower than those for coagulation using single PAFC or FeCl3 under the same total coagulant dosage.The optimal efficiency of the combination coagulation was obtained under a total coagulant dosage of approximately 15-20 mg/L with a PAFC/FeCl3 mass ratio of 3:1 and a coagulation mode of dosing with PAFC followed by FeCl3 in a 5～20 S interval.Other parameters of UV254,COMMn,iron and alam in the treated water by the optimized combination coagulation are all much lower than those by the single PAFC or FeCl3 coagulation.