Treatment Effects of A-F/PDM Composite Coagulants to Taihu Lake Prechlorinated Algae-Containing Water in Winter

Abstract

The series of stable A-F/PDM composite coagulants prepared by combining polydiallyldimethylammonium chloride (PDM) with the composite (A-F) of aluminum sulfate (AS) and ferric chloride (FeCl3) were used to research the treatment effects to Taihu Lake prechlorinated algae-containing water in winter. The composite coagulants were tested by jar tests for the effects of mass percents (5%~20%) and intrinsic viscosity values (0.55~3.99dL/g) of PDM on algae- and turbidity-removal efficiencies. The results show that when the residual turbidity of supernatant after sedimentation reaches the control standard of 2 NTU, the dosages of A-F and A-F/PDM (0.55/5%~3.99/20%) are 4.52 mg/L and 4.27~2.52 mg/L respectively, and the algae-removal rates are 90.1% and 92.0%~96.3% respectively. When the dosages are 4.52 mg/L, the algae-removal rates are 90.1% and 92.5%~99.0% respectively, and the residual turbidities are 2.00 NTU and 1.76~0.60 NTU respectively. Therefore, using A-F/PDM composite coagulants can enhance evidently the treatment effect of A-F to Taihu Lake prechlorinated algae-containing water in winter.