Natural organic matter removal by coagulation during drinking water treatment: A review

Natural organic matter (NOM) is found in all surface, ground and soilwaters. An increase in the amount of NOM has been observed over the past 10-20 years in rawwater supplies in several areas, which has a significant effect on drinking water treatment. The presence of NOMcausesmany problems in drinkingwater and drinkingwater treatment processes, including (i) negative effect onwater quality by causing colour, taste and odor problems, (ii) increased coagulant and disinfectant doses (which in turn results in increased sludge volumes and production of harmful disinfection by-products), (iii) promoted biological growth in distribution system, and (iv) increased levels of complexed heavy metals and adsorbed organic pollutants.NOMcan be removed fromdrinking water by several treatment options, of which the most common and economically feasible processes are considered to be coagulation and flocculation followed by sedimentation/flotation and sand filtration. Most of the NOM can be removed by coagulation, although, the hydrophobic fraction and high molar mass compounds of NOM are removed more efficiently than hydrophilic fraction and the lowmolar mass compounds. Thus, enhanced and/or optimized coagulation, aswell as newprocess alternatives for the better removal of NOMby coagulation process has been suggested. In the present work, an overview of the recent research dealing with coagulation and flocculation in the removal of NOM from drinking water is presented.