COAGULATION AND DIRECT FILTRATION OF HUMIC SUBSTANCES WITH POLYETHYLENIMINE

A series of polyethylenimine polymers (cationic) with molecular weights from 600 to 50 000-100 000 was used in coagulation and direct filtration studies of humic acid at pH 5.5-6. Destabilization of humic acid is achieved where the optimum polymer dosage is independent of molecular weight; however, solid/liquid separation of floe in the jar tests is poor due to poor particle contact opportunities. The direct filtration of humic acid is an effective treatment process with continuous polymer feed. The filter aid dosage can be selected from jar tests as coagulation and filtration are analogous. Polymer dosages which produce under- and overdosing in the jar test also produce identical effects in direct filtration. Greater head loss was observed for direct filtration without flocculation. A brief flocculation period results in particle aggregation, an increase in the mean size of the particles being applied to the filter bed, and lower head loss development. © 1979, American Chemical Society. All rights reserved.