Impact of fractional character on the coagulation of NOM

The current work investigates how the natural organic matter (NOM) fraction make-up of the raw water influences coagulation performance. Four characteristics organic fractions were separated based on their hydrophobicity. Results revealed that the hydrophilic non adsorbed fraction (HPINA) was least amenable to removal by conventional coagulation, attributed to a negligible charge density. Whereas the fulvic acid fraction (FAF) most readily resembled the bulk raw water operational characteristics in relation to coagulation, such as floc size, strength, settling velocity, iso electric point (IEP), generating small compact flocs and exerting the most influence on the charge balance of the system. The most notable exception is in relation to removal. A lower FAF removal was observed compared with the raw water, attributed in part to co-operation effects, as although studying isolated NOM fractions does provide some benefits, some of the synergistic effects may be lost. However, results demonstrate that simple fractionation, in terms of the hydrophobic/hydrophilic balance of the water, could provide a fast and effective method for improved understanding of coagulation performance. (c) 2006 Elsevier B.V. All rights reserved.