Algae removal efficiencies of AS/PDMDAAC coagulants

Abstract

This research investigated the use of composite coagulants for enhanced coagulation of algae‐containing water from Taihu Lake in China. The composite coagulants comprised aluminum sulfate (AS) and poly dimethyl diallyl ammonium chloride (PDMDAAC) of different intrinsic viscosity values (0.55‐ .99 dL/g) and different mass percentages (5‐20%) in formulation. For algae‐containing water with a temperature of 29‐ 0oC and algal content of .52 × 104 cells/mL, algae removal rates of 81.11% and 85.89‐90.5 %, respectively, were realized using AS at a dose of 7.78 mg/L and AS/PDMDAAC at formulations of 0.55/5‐ .99/20% and doses of 6.55‐ .54 mg/L when 2‐ntu residual turbidity of effluent water after sedimentation was required. The removal rates of chemical oxygen demand and ammonia using AS/PDMDAAC in algae‐containing water were higher than those using AS alone. Composite coagulants could reduce required doses and decrease algal content in effluent water when 1‐ntu residual turbidity is required. When identical doses were used, 1.5 /10% AS/PDMDAAC outperformed AS combined with prechlorination.