Comparison between Magnetic Ion Exchange Resin and Coagulation for THM Precursors Removal

Abstract

Quality of water supply is always a crucial matter of concern, especially after Covid-19 pandemic. Chemical disinfection could lead to a health risk due to an exposure to carcinogenic disinfection by-products (DBPs) due to a reaction between dissolved organic matter (DOM) and chlorine-based disinfectant. This study investigates water treatment process for the removal of DOM from a raw water collected from U-tapao canal, Songkla province. Conventional poly-aluminum chloride coagulation was compared to magnetic ion exchange (MIEX) resin for its efficacy in DOM removal and reduction of DBPs formation. The raw water contained 2.31 mg/L of dissolved organic carbon (DOC), resulted in trihalomethane formation potential (THM-FP) of 349 µg/L under 24-hour chlorination. MIEX resin was more effective than coagulation at DOC removal. At its optimum dose, coagulation achieved 43% and 45% of DOC removal and THMs formation potential reduction, respectively. MIEX treatment alone removed 64% of DOC and thus reduced THMs formation potential by 63%. Coagulation treatment was effective at reduction of formation of chloroform but led to an increase in brominated THMs formation. MIEX treatment reduced formation of both chlorinated and brominated THMs effectively. MIEX pre-treatment prior to coagulation reduced coagulation demand and chlorine demand. DOM characterization using fluorescence excitation emission matrix revealed that coagulation showed preferential removal of humic-like substances, while MIEX resin was effective at removal of all DOM fractions.