Elimination of pesticide from high salinity wastewater by electrochlorination process: Active chlorine species and scale-up performance

Abstract

Active chlorine species-mediated electrochemical process is a promising strategy for refractory pollutants and ammonia removal in high salinity organic wastewater. Herein, we constructed an electrochlorination (E-Cl) process with the help of the high concentration of chloride ions (Cl−) in the wastewater to realize the efficient treatment of pesticide wastewater. The E-Cl process exhibited excellent chemical oxygen demand (COD, 86.43%) and atrazine (ATZ, 98.67%) removal efficiency for the actual pesticide wastewater since active chlorine species, including free chlorine and reactive chlorine species (RCS), and hydroxyl radical (•OH) were all in-situ produced during the electrolysis process. The quenching experiments indicated that the free chlorine was the primary oxidizing substance for the decomposition of ATZ, and the RCS and •OH mainly enhanced the mineralization of intermediate products. In addition, the inhibition mechanism of different background substances in the E-Cl process was different. The toxicity test and three-dimensional fluorescence spectrum all proved that the E-Cl process could effectively remove ATZ and other organic matter from the actual pesticide wastewater. Finally, an E-Cl pilot reactor was designed and the pilot-scale experiments showed that the COD and NH4+-N of the actual pesticide wastewater after the treatment of the E-Cl process were < 50 mg/L and < 1.5 mg/L, and the energy consumption (EC) was ∼4.98 kWh/m3. The successful treatment of actual pesticide wastewater by the E-Cl process suggests that this is a promising method for treating organic pollutants and ammonia under highly salinity conditions.