Flocculation in presence of organic macromolecules of natural water and secondary effluents

Flocculation processes were studied in three types of water representing turbid natural surface water, controlled synthetic systems of reference clay minerals suspensions in the presence of humates and fulvates at various degrees of interactions, and municipal wastewater treatment plant effluents. These systems contain suspended and colloidal dispersed solids accompanied by organic substances in dissolved or colloidal form. The presence of organic anionic macromolecules and soluble organics in water affects flocculation processes by raising the flocculant demand appreciably and hence affects the final water quality. Extraction and elimination of the organics from natural suspended solids, and removal of soluble organics from effluents reduced the organic content, thus decreasing considerably the flocculant demand. The addition of the extracted and separated organics to pure clay dispersions increased accordingly the cationic polyelectrolyte flocculant demand. (C) 1997 IAWQ. Published by Elsevier Science Ltd.