Removal of Dissolved Organic Carbon by Coagulation With Iron Sulfate

Charge, solubility, and molecular‐size characteristics of dissolved organic carbon in raw and treated water from a Virginia reservoir were investigated to determine the types of organic compounds removed by ferric sulfate, coagulation, and settling. All three parameters influenced removal of dissolved organic carbon. Larger molecules were more readily precipitated than smaller ones. Ionic compounds were more effectively removed than neutral compounds. Hydrophilic and hydrophobic organics were preferentially removed over compounds of intermediate solubility. Two main groups of organic halide precursors were identified. Fulvic acids were the dominant precursors in raw water—they reacted rapidly with chlorine and had high specific yields, but were readily precipitated. Low‐molecular‐weight neutral compounds were the dominant precursor group remaining in treated waters. These molecules reacted more slowly with chlorine and had lower organohalide yields.