Removal of Natural Organic Matter from Water by Enhanced Coagulation

Abstract

Natural Organic Matter (NOM) is found in all surface, ground and soil waters. The presence of NOM causes many problems in drinking water treatment processes. Minimization of the disinfection by-products (DBPs) precursors or effective removal of NOM has emerged as a critical issue in the production of high quality drinking water from surface water. Enhanced coagulation is currently proposed as well as new process alternatives for the better removal of NOM. This study investigated the effects of different coagulants on the levels of organic matter removal. Three types of inorganic coagulants (ferric chloride, alum and polyaluminum chloride) and two types of flocculant (cationic and anionic polyelectrolytes) were used during experiments. The removal efficiency of NOM in terms of UV₂₅₄ and DOC increased with the dosage of coagulants increasing. Removal efficiencies of 43.2-66.6% and 55.4-83.4% were obtained for DOC and UV₂₅₄, respectively. The results of jar test which was conducted for determining the optimum coagulation conditions, indicated that maximum UV₂₅₄ and DOC removals were achieved with 80 mg/L FeCl₃ and 0.05 mg/L anionic polyelectrolyte at pH 5.25. THM levels of five different distribution system sampling points and THMFP were also determined in raw water. The amount of THM within distribution system varied from 18.2 µg/L to 70.2 µg/L, while the amount of raw water THMFP was found as a 98.7 µg/L.