AWWA JAW17257

Polyaluminum chloride is an unconventional coagulant that will soon be introduced to the United States market. It is produced by partial hydrolysis of aluminum chloride and is thought to consist of stable cationic polymers of aluminum. This article describes a study whose primary goals were to compare poly- aluminum chloride (PACl) and alum as coagulants of clay-fulvic acid suspensions and to evaluate the effects of fulvic acid on these coagulation processes. The benefits of polyaluminum chloride relative to alum were investigated as a function of pH, raw water composition, and mixing conditions. Relative removal efficiencies; stoichiometries of the removal processes; sludge volume; settling velocities; and direct filtration are discussed for the two coagulants. Conditions are outlined that might indicate the effective use of polyaluminum chloride instead of alum. Includes 21 references, tables, figures.