Increased development in the Taihu LakeBasin of China has led to deterioration ofwater quality that is compounded by a rawwater algal content of ~3-5 x 10sup4/sup cells/mL.With their current approach of prechlorinationcombined with aluminum salt coagulantsto enhance the treatment process, treatmentfacilities find it difficult to meet the demandfor quality drinking water, especially duringperiods of algal blooms.Twelve stable composite coagulants wereprepared from aluminum sulfate (AS) and polydimethyl diallyl ammonium chloride (PDMDAAC)at formulations ranging from 0.55/5%to 3.99/20% AS/PDMDAAC. Jar test resultsindicated that compared with use of AS alone,the AS/PDMDAAC composite coagulantsprovided greater removal of chemical oxygendemand and free ammonia and demonstratedexcellent algae removal efficiencies. Furthermore,the enhanced coagulation process ofapplying composite coagulants could partlyreplace prechlorination and reduce the chlorinedoses added during the prechlorination anddisinfection processes, thus reducing healthrisks caused by excessive chlorine addition.Includes 29 references, tables, figures.