Abstract
Supplying drinking water in Al-Dewanyia city to meet Iraqi Drinking Water Guidelines is a challenge as source waters contain high concentrations of Natural Organic Matter (NOM) that often exceed 12 mg/L Dissolved Organic Carbon (DOC). The US EPA indicates that enhanced coagulation is the best available technology to control DOC in drinking water treatment plants. A water director of Al-Qadissiya has used enhanced coagulation at Al-Dewanyia Water Treatment Plants (WTP’s) in Iraq since 2004 to improve water quality in the distribution system. NOM reduction has led to treated water with a lower chlorine demand allowing a greater residual penetration enabling improved bacteriological compliance. Since the cost of DOC (and Disinfection by-product DBPs) determination was high, it was decided to study the traditional analysis of COD as a surrogate measure to detect the organic constituents in raw water and the extent to which optimized coagulation with ferric chloride can increase COD removal. The water samples studied belonged to Al-Dewanyia River. For samples the observed values of COD removal by coagulation at lower pH (about 1-1.5 pH values less than the regular pH (5.8 ~ 8.5)) were about 85-95 percent without making water turbidity unacceptable. In order to determine the effects of organic content on coagulation, The results indicated that a modified coagulation process without need to much increasing the amount of coagulant can be developed for these water samples.