Effects of coagulation-sedimentation-filtration pretreatment on micropollutant abatement by the electro-peroxone process

Abstract

The electro-peroxone (EP) process has been considered an attractive alternative to conventional ozonation for micropollutant abatement in water treatment. However, how to integrate the EP process into the water treatment trains in water utilities has yet to be investigated. This study compared micropollutant abatement during the EP treatment of potable source water with and without pretreatment of biological oxidation, flocculation, sedimentation, and filtration. Results show that this pretreatment train removed 39% of dissolved organic carbon (DOC) and 28% of the UV254 absorbance of the raw water, leading to higher ozone (O3) stability in the treated water. By electrochemically generating hydrogen peroxide to accelerate O3 decomposition to hydroxyl radicals (•OH), the EP process considerably shortened the time required for ozone depletion and micropollutant abatement during the treatment of both the raw and pretreated water to ∼1 min, compared to ∼3 and 7.5 min during conventional ozonation of the raw and treated water, respectively. For the same specific ozone dose of 1 mg O3 mg−1 DOC (corresponding to 4.3 and 2.8 mg O3 L−1 for the raw and treated water, respectively), the abatement efficiencies of micropollutants with moderate and low ozone reactivity were increased by ∼10–15%, while the energy consumption for micropollutant abatement was decreased by ∼24–56% during the EP treatment of the treated water than the raw water. These results indicate that partial removal of DOC and ammonia from the raw water by the pretreatment train has a beneficial effect on enhancing micropollutant abatement and reducing energy consumption of the EP process. Therefore, it is more cost-effective to integrate the EP process after the pretreatment train in water utilities for micropollutant abatement.