Evaluation of temperature impacts on drinking water treatment efficacy of magnetic ion exchange and enhanced coagulation

Magnetic ion exchange (MIEX^®) is an emerging technology for disinfection by-product (DBP) precursor removal in the drinking water industry. Although recent research has demonstrated that this technology is capable of achieving excellent natural organic matter (NOM) removal, there is paucity of published research showing the efficacy of ion exchange (IX) technology in cold water conditions. The overall objective of this research was to evaluate at bench-scale the potential impact of cold water operating conditions on enhanced coagulation with alum, MIEX^® and a combination of MIEX® and low dose alum. All three treatments were evaluated at 1 and 20 °C with settled water quality compared in terms of turbidity, UV254, dissolved organic carbon (DOC), specific UV absorbance (SUVA), trihalomethane formation potential (THMFP) and haloacetic acid formation potential (HAAFP). The results of the study showed that all three technologies evaluated were significantly impacted by cold water operating conditions in terms of turbidity removal, and UV254 removal was significantly reduced in both the MIEX^® and MIEX^®-Alum processes. However, treatment of the surface water with the combined process resulted in the highest removal of DBP precursor material and lowest THMFP and HAAFP concentrations at both temperatures compared to the individual unit operations.