Hydrolytic Acidification-Two Stage EGSB-A/O Combined Process for Pesticide Wastewater Treatment

The wastewater produced by a chemical enterprise in Ningxia has the characteristics of high COD, high salt content, and high ammoniacal nitrogen. The biodegradability of the wastewater is poor due to presence of higher concentration of pollutant. The scale of first stage of treatment was 400m3/d. The wastewater of different characteristic was collected and treated separately. The combined process of "micro electrolysis + Fenton oxidation + coagulation precipitation + evaporation crystallization" was used to pretreat the wastewater containing high salt and high COD. The main process was "hydrolytic acidification + two-stage Expanded Granular Sludge Bed (EGSB) + two-stage advance Fenton oxidation (A/O)". The final concentrations of effluent COD, NH3-N and TDS are 376 mg/L, 34.74 mg/L, and 442 mg/L, and the removal rates are 99.9%, 81.3%, and 99.9%, respectively. The environmental, engineering and economical (3E) practices showed that the combined process has stable operation, strong impact resistance, and high reduction of COD in the effluent.