MIEX for removal of DBP precursors: Pilot‐plant findings

A 10‐gpm pilot plant was operated for four to five weeks at each of four US water treatment plants to evaluate the effectiveness of a magnetic ion exchange (MIEX) process for the removal of disinfection by‐product precursors. Variables examined were resin concentration, contact time, and regeneration frequency. Influent and effluent samples were taken on a regular basis and analyzed for ultraviolet (UV) absorbance at 254 nm, dissolved organic carbon (DOC), and bromide. Samples of the raw water and the MIEX‐treated water were also subjected to hydrophobic/hydrophilic fractionation, molecular size characterization, and chlorination under uniform formation conditions to determine the trihalomethane (THM) and haloacetic acid (HAA) formation potential before and after MIEX treatment. Results indicated that the resin removed substantial amounts of DOC and UV‐absorbing materials, except in one of the waters that had a high concentration of total dissolved solids and a low specific UV absorbance. The MIEX resin also removed bromide to some degree, depending on the presence of other competing anions in the raw water. Overall THM and HAA formation was decreased substantially as a result of MIEX treatment.