The Coagulation of Humic Substances by Means of Aluminum Salts

Abstract

Mechanisms for the removal of humic substances from water by coagulation with aluminum salts were studied by means of conventional jar test procedures. Independent variables were the type and concentration of humic substance, the type and concentration of aluminum coagulant, and pH. Removal of humic substances was determined by measuring total organic carbon or by direct ultraviolet spectroscopy. Under some experimental conditions the humic substances were directly precipitated by soluble aluminum species; under other conditions they were removed by adsorption on Al(OH) 3 (s). Polyaluminum chloride, an unconventional coagulant in the United States, is a promising alternative to alum for removing humic substances from some water supplies.