Electrochemical-assisted hydrolysis/acidification-based processes as a cost-effective and efficient system for pesticide wastewater treatment

Abstract

Owing to the low biodegradation and highly recalcitrant nature of pesticide wastewater, the conventional anaerobic treatment process is often limited with low organic removal efficiency. In this study, based on the existing wastewater treatment system of a pesticide production company, a pilot-scale original combined system (hydrolysis/acidification-based processes) and a pilot-scale enhanced combined system (electrochemical-assisted hydrolysis/acidification-based processes) were designed and operated in parallel to explore the feasibility and economics of pesticide wastewater treatment. The average effluent BOD5/COD ratio in the electrochemical-assisted hydrolysis/acidification reactor increased from 0.19 ± 0.02 to 0.30 ± 0.05, which was 16.3% greater than that of the original hydrolytic/acidification reactor. In addition, the maximum difference in effluent COD between the two-stage anaerobic process and original up-flow anaerobic sludge blanket reactor reached 5696 mg/L. Meanwhile, the optimum compliance rates of COD and BOD5 in the biological contact oxidation pool of the enhanced combined system were 85.7% and 100.0%, respectively, which proved that most of the effluent could meet the reception standard of an urban wastewater treatment plant (COD ≤ 300 mg/L; BOD5 ≤ 250 mg/L). Although the investment cost of the enhanced combined system was slightly higher than that of the original combined system, the operating cost of the enhanced combined system can achieve a cost reduction rate of 14.1% with a payback period of 10 y.