AWWA JAW72294

Increased development in the Taihu Lake Basin of China has led to deterioration of water quality that is compounded by a raw water algal content of ~3-5 x 10⁴ cells/mL. With their current approach of prechlorination combined with aluminum salt coagulants to enhance the treatment process, treatment facilities find it difficult to meet the demand for quality drinking water, especially during periods of algal blooms. Twelve stable composite coagulants were prepared from aluminum sulfate (AS) and poly dimethyl diallyl ammonium chloride (PDMDAAC) at formulations ranging from 0.55/5% to 3.99/20% AS/PDMDAAC. Jar test results indicated that compared with use of AS alone, the AS/PDMDAAC composite coagulants provided greater removal of chemical oxygen demand and free ammonia and demonstrated excellent algae removal efficiencies. Furthermore, the enhanced coagulation process of applying composite coagulants could partly replace prechlorination and reduce the chlorine doses added during the prechlorination and disinfection processes, thus reducing health risks caused by excessive chlorine addition.

Includes 29 references, tables, figures.