Stability of particle flocs upon addition of natural organic matter under quiescent conditions

In this research, the influence of two natural organic polymers (polysaccharide and humic acid) on the stability of colloidal aggregates was examined. The primary objective of this research was to determine whether addition of organic matter to flee suspensions results in the fragmentation or stabilization of aggregates. A second objective was to determine how the size of aggregates and the composition of organic matter influence the floc breakup or stabilization process. It was found that the stability of aggregates depended on the type of organic material present as well as hoc size. For example, humic acid increased the stability of aggregates more effectively than polysaccharides of larger size. It was also found that the addition of humic acid or polysaccharide generally decreased the rate of coagulation of small aggregates but had less influence on large aggregates. In no case did the addition of polysaccharide or humic acid result in the fragmentation of particle aggregates. The existence of strong interparticle forces within flocs prevented aggregate breakup upon adsorption of natural organic polymers. The results presented here provide important new information regarding the influence of NOM on the behavior of particles in aquatic systems. (C) 2001 Elsevier Science Ltd. All rights reserved.