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

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 NH 4 + -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/m 3 . 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. • The E -Cl process exhibited excellent oxidation performance for the actual pesticide wastewater. • The active species produced in the E-Cl process include free chlorine, RCS and • OH. • RCS and • OH enhanced the mineralization efficiency of intermediate products of ATZ. • The background substances showed different inhibition performances in the E-Cl process. • The pilot-scale experiments proved the feasibility and economy of the E-Cl process.