Fenton Preoxidation Combined With SBR Process To Treat Pesticide Wastewater

With the development of China’s pesticide production industry,the amount of pesticide wastewater that comes with it is also increasing.The complex pesticide production process leads to a large number of high-concentration organic wastewaters containing irritating odors,which are complex,highly toxic,very unstable in water quality,and difficult to biodegrade.If discharged directly into the water environment,they will cause serious water pollution.Therefore,it is urgent to study pesticide wastewater treatment technology with good degradation effect and stable performance.After the long-term research on an agrochemical plant in Jiangsu Province,combined with the existing sewage treatment process in the plant,the Fenton pre-oxidation combined with batch-type activated sludge process(SBR)was used to treat the wastewater of the agrochemical plant.In the experimental research data,some experimental conditions are summarized,which provides theoretical basis and practical guidance for the design and application of engineering.In this experiment,a one-year investigation was conducted on an agrochemical company in Jiangsu.The survey found that the company currently has 17 production workshops,producing more than 24 high-concentration wastewaters,and the wastewaters are doped with grease and floating materials,resulting in the increasing concentration of organic wastewater.The main characteristic pollutants in these wastewaters are chlorobenzene,toluene,nitrobenzene,methanol,COD,ammonia nitrogen and the like.For these different pollutants,it is necessary to carry out targeted wastewater collection and treatment,and use various measures such as multi-effect evaporation,concentration and desalting,Fenton oxidation,micro-electrolysis reduction,hydrolysis and acidification,etc.,and then through biological activated carbon process,treat sewage.The company has a large amount of wastewater,with high concentration and complex composition,which makes the treatment difficult and the treatment effect is unstable.The biochemical stage produces a large amount of foam,and the pH is continuously lowered,making it difficult to operate.In this experiment,the Fenton oxidation combined sequencing batch activated sludge process was selected to treat wastewater in the original process of the plant.In this experiment,the Fenton oxidation process was used to pretreat the high concentration pesticide wastewater.The dosage of H2O2,the reaction temperature,the ratio of FeSO4·7H2O to H2O2,the initial pH,the reaction time,the dosage method,and the coagulation were studied.The effects of various factors such as the dosage of the agent on the removal of COD from high-concentration wastewater were determined to determine the optimum conditions for the Fenton oxidation reaction.The experimental data showed that the optimal reaction conditions for Fenton oxidation were as follows:the ratio of FeSO4·7H2O to H2O2 was 20:1,the dosage of H2O2 was 18 g/L,the initial pH was between 3-3.34,and the action time was 80min,the reaction temperature is 30℃,the dosing method is a one-time dosing,the coagulant dosage is 7.359 g/L.After Fenton treatment,the COD in pesticide wastewater decreased from 4500 mg/L to 2553 mg/L,which greatly improved the biodegradability of pesticide wastewater,and provided favorable degradation conditions for subsequent deep biochemical treatment.After Fenton pre-oxidation,there are still a large number of pollutants in the wastewater,and the water quality indicators are far from meeting the comprehensive wastewater discharge standards.In order to meet the emission standards,the pretreated effluent is treated in depth.In this study,a sequencing batch activated sludge process was adopted as a biochemical measure for treating the wastewater.By acclimating the sludge,24 hours of domestication,and stable discharge was achieved.Then explore the effects of influent pH,dissolved oxygen,hydraulic retention time and other factors on the degradation of COD,and the best biochemical conditions were obtained.When the influent pH is about 7.5,the optimal dissolved oxygen is 6 mg/L,and the optimal hydraulic retention time is 24 h.Under the optimal conditions,after 28 cycles of operation,the effluent water quality COD was stable at 260 mg/L,and the wastewater COD degradation rate reached 91%.The final effluent water quality was stable and met the Integrated Wastewater Discharge Standard(GB8976-1996).