Coagulation performance and membrane fouling of polyferric chloride/epichlorohydrin-dimethylamine in coagulation/ultrafiltration combined process

Polyferric chloride (PFC) and epichlorohydrin-dimethylamine (DAM-ECH) with different PFC (as Fe³⁺)/DAM-ECH mass ratios (MR) and dose methods were used in the treatment of humic acid-kaolin (HA-kaolin) simulated water under different pH conditions. Coagulation performance, floc characteristics and membrane fouling of PFC/DAM-ECH in coagulation-ultrafiltration (C-UF) process were investigated in this study. Results showed that the optimum coagulation performance was achieved when PFC dose was 15mg/L with PFC/DAM-ECH MR of 2:1 under pH6.0. Opposite adding sequence (DAM-ECH/PFC) would reduce UV₂₅₄ (ultraviolet adsorption at 254nm) and DOC (dissolved organic carbon) removal efficiency. Addition of DAM-ECH on the basis of PFC produced larger and stronger flocs with better regrowth ability. Proper dosage of DAM-ECH under certain coagulation condition could achieve the best coagulation performance and keep the UF membrane operating under a preferable status. Results of this study would be beneficial for application of composite coagulant PFC-DAM-ECH and DAM-ECH as coagulant aid in water treatment processes.