Study On Treatment Of Pesticide Wastewater With Coagulation-Oxidation-Anaerobic-BAF Process

The treatment of highly concentrated refractory wastewater is difficult all along because the wastewater has high concentration of organic matter and poor degradability. Pesticide production wastewater is a typic highly concentrated refractory wastewater because of its complicated components and high toxicity. The treatment of pesticide production wastewater always draws the attention of society. In pesticide’s production and purification process, a large amount of high COD concentrations, high-SS, chroma, high salinity and bio-inhibitory wastewater are discharged. According to the properties of such wastewater, we used Advanced oxidation-anaerobic-aerobic combined process to treat the nitrobenzene pesticide wastewater. Take COD, SS, chroma as the key indicators to the treatment effect on processing unit and combined process.Pretreatment section inspected the chlorine dioxide’s dosage, initial reaction pH, reaction time and other techniques and operating conditions. It was found that oxidation chlorine dioxide pesticide wastewater, the treatment had obvious effect, COD removal rate reached90%and above, there was a marked improvement in color which was from opalescent into colorless. Through several single factor experiments, it was identified that chlorine dioxide’s reagent dosage and optimal reaction conditions:chlorine dioxide dosage of20mL/L,, stirring for30minutes, static response for4hours.Anaerobic sewage sludge seeded anaerobic reactor and operated in a low organic load. Start-up period, COD volume loading increased from0.7kgCOD/(m3·d) to1.4kgCOD/(m3-d) above, and completed within one month. The biodegradability of effluent wastewater was significantly improved, meanwhile the COD and color decreased. During normal operation of reactor, study on the in-fluent COD, the effluent COD concentration and volume loading could be found reactor COD volumetric loading changed with the charge of COD concentration changes, the removal of COD had significantly positive correlation with COD volume loading. When influent COD>450mg/L, the effluent COD from an aerobic reactor was less than250mg/L and COD removal rate was above45per cent. When influent concentration was300mg/L, COD removal efficiency significantly decreased, the effluent COD was close to350mg/L, minimum removal was only15%to22%.When the HRT=12h, the effluent water quality through BAF aerobic degradation could meet the first discharge standard(GB21904-2008), effluent COD<11Omg/L, SS<50mg/L, color<50, PH=6-9.