Research And Application Of Physicochemical And Biochemical Combined Process In The Treatment Of Pesticide Intermediate Wastewater

Pesticide wastewater is a general term for wastewater generated during the production and use of pesticides.The wastewater usually contains a large amount of refractory organic matter and has strong biological toxicity.For the treatment of this type of wastewater,conventional wastewater treatment methods are often ineffective.This paper studies the production wastewater of a pesticide factory in Jiangxi.According to the characteristics of the wastewater,the combined process of"air flotation+Fenton+ABR+two-stage A/O+Fenton+coagulation sedimentation"is used to treat the wastewater.The operating results show that the physicochemical,biochemical combination The process can effectively treat this waste water,and the effluent reaches the management standard of the sewage treatment plant in the local park.This paper studies the pretreatment effects of two advanced oxidation methods,persulfate oxidation and Fenton oxidation,on high-concentration wastewater.Experiments have shown that Fenton oxidation has the effect of COD_Crremoval,biodegradability improvement and treatment costs for the high-concentration wastewater.It is better than the persulfate oxidation method,and the optimal reaction conditions have been determined.And through biochemical experiments to explore the effect of anaerobic and aerobic reaction on the treatment of wastewater after pretreatment,the Fenton oxidation advanced treatment of the wastewater was carried out,and the start-up and debugging of ABR（Anaerobic Baffled Reactor）and two-stage A/O biochemical process,as well as stable operation Circumstances,draw the following conclusions:（1）The test results show that the optimal reaction conditions for using Fe²⁺activated potassium persulfate to treat high-concentration wastewater are:potassium persulfate concentration 20mmol/L,FeSO₄·7H₂O dosage 4 g/L,p H=7,reaction time1.5 h.The COD_Cr removal rate under this condition is 35.4%,and the biodegradability（B/C）of high-concentration wastewater has been increased from 0.025 to 0.268;the optimal reaction conditions for Fenton oxidation method to treat high-concentration wastewater are:H₂O₂ dosage 10 ml/L,FeSO₄·7H₂O The dosage is 10 g/L,p H=3,and the reaction time is 2 h.The COD_Cr removal rate under this condition was 38.3%,and the B/C value of high-concentration wastewater was increased from 0.025 to 0.306.（2）The biochemical test results show that when the volumetric load is 2kg COD/（m³·d）,the COD_Cr removal rate of anaerobic biochemical treatment reaches more than 50%.After 10 days of domestication,the time of one domestication cycle of aerobic sludge was shortened from 72 h to 32 h,and the removal rate of COD_Cr was54%,and the removal rate of NH₃-N was 57.32%.（3）The optimal reaction conditions for the advanced treatment of biochemical wastewater by Fenton oxidation method are:H₂O₂ dosage 2 ml/L,FeSO₄·7H₂O dosage1.5 g/L,p H=3,and reaction time 1.5 h.The removal rate of COD_Cr under this condition is 47.2%.（4）The treatment effect of the ABR reactor is stable after 90 days of start-up and domestication,and the COD_Cr removal rate reaches 51%during the stable operation period.（5）The removal rate of COD_Cr by two-stage A/O is 79.22%,and the removal rate of NH₃-N has reached 78.4%.After the advanced treatment of"Fenton+coagulation and sedimentation",the effluent stably reaches the standard of the wastewater treatment plant in the park,that is,COD_Cr is less than 500 mg/L,NH₃-N is less than 35 mg/L.