Abstract
Chemical disinfection of surface waters has been proven effective in minimizing the risk of contamination by water-borne pathogens. However, surface waters contain natural organic matter (NOM) which, upon chemical disinfection, is readily converted into hazardous disinfection-by-products. Hence, NOM removal from these waters is critical. Chemical coagulation is a readily implementable technology to minimize these undesired side-effects by NOM removal. Herein, capabilities of ferric chloride (FeCl3) and polyaluminum chloride (PACl) as pre-treatment for NOM abatement from natural raw surface water have been benchmarked. Excitation-emission fluorescence matrix (EEM) spectroscopy characterization of NOM fractions demonstrated high removal efficiency. A two-level full factorial design was employed to analyze the effects of coagulant dosage and initial pH on the removal of turbidity, humic acid-like substances and fulvic acid-like substances from the raw water. Higher removal of ~77% NOM was attained with PACl than with FeCl3 (~72%). Optimization through response surface methodology showed that the initial pH—coagulant dosage interaction was significant in removing NOM and turbidity for both PACl and FeCl3. These results identify the opportunity for coagulation technologies to prevent and minimize disinfection-by-products formation through NOM removal.
Highlights
Natural organic matter (NOM) is a complex mixture of organic compounds consisting of aromatic, aliphatic, phenolic, and quinolic functional groups [1]
Disinfection by-products (DBPs) can be formed when NOM reacts with active chlorine species during the drinking water treatment process [3,4,5]
Coagulation treatment presents the most techno-economically viable option, and it is the most widely used in drinking water treatment plants worldwide
Summary
Natural organic matter (NOM) is a complex mixture of organic compounds consisting of aromatic, aliphatic, phenolic, and quinolic functional groups [1]. Trihalomethanes and haloacetic acids are two popular groups of halogenated. Minimizing NOM content prior to disinfection treatment can be identified as an urgent need to avoid DBP yield [7]. Different technologies such as photocatalysis [8], electrochemical treatments [9], the Fenton process [10], adsorption [11], ionic exchange [12] or coagulation [13] have been explored to remove NOM from drinking water sources prior to disinfection. Coagulation treatment presents the most techno-economically viable option, and it is the most widely used in drinking water treatment plants worldwide
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