Real herbicide wastewater treatment by combined means of electrocatalysis application and biological treatment

Abstract

In this study, the real herbicide wastewater was degraded by electrocatalysis oxidation followed by subsequent biological treatment. The influence of several process variables of electrocatalysis oxidation, such as current density, pH and electrode gap on chemical oxygen demand (COD) removal ratio, was investigated and the optimum conditions were determined. The results indicated that COD removal ratio reached 87.0%, and the COD decreased from 7519 mg L−1 to 980 mg L−1 after 120 min electrolysis under the degradation parameters of the current density of 4 a dm−2, pH value of 4 and the plate spacing of 1.0 cm. The electrocatalysis degradation of real herbicide wastewater followed pseudo-first-order kinetics. The BOD5/COD increased from 0.18 to 0.43 after 120 min electrolysis. Then, the biological contact oxidation process was performed on the effluent of the electrochemical process. The results showed that the final COD removal ratio reached 95.8% after biological contact oxidation on the following condition: hydraulic residence time was 12 h and the aeration quantity was 0.6 m3 h−1. Conclusively, it can be proved that electrocatalysis is feasible as a pre-treatment technology to treat real herbicide wastewater.