MIEX® treatment of an effluent-impacted stream

A case study was conducted to examine the effectiveness of the magnetic ion exchange (MIEX (R)) process in treating wastewater treatment plant (WWTP) effluent-impacted water and removing disinfection by-product (DBP) precursors. The WWTP effluent increased dissolved organic carbon (DOC), ultraviolet absorbance at 254 nm (UV254), anions, and DBP precursors at the discharge and downstream locations. During this study, the MIEX1 process reduced DOC by 42-47%, UV254 absorbance by 61-68%, and trihalomethane (THM) and haloacetic acid (HAA) formation potential (FP) by 50-70% at different downstream locations. On the other hand, only 10-15% halonitromethane (HNM) FP was reduced, and N-nitrosodimethylamine (NDMA) FP increased as a result of chloramination after MIEX treatment. Uniform formation condition (UFC) experiments showed that NDMA concentrations remained below 10 ng/L when chlorine or prechlorination was used for postdisinfection. However, the use of preformed chloramine resulted in 36 ng/L of NDMA formation. Because MIEX is capable of removing a substantial amount of THM and HAA precursors, it may allow the use of more chlorine for longer contact time, which can result in less NDMA formation.