Study On The Treatment Of Three Kinds Of Pesticide Production Wastewater

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 this article, a pesticide factory production wastewater of Jiang Xi Province is our investigative object. The pesticide factory production wastewater has three different kinds of production wastewater. There are thiophanate methyl production wastewater(pH = 3～4 , COD = 8000～12000mg/L , SS = 160mg/L, BOD = 1600mg/L), methomyl production wastewater(pH = 6～7 , COD = 80000～110000mg/L, SS=280mg/L, BOD=2800mg/L) and methyl isocyanate production wastewater(pH = 3～4 , COD = 8000～12000mg/L, SS = 160mg/L , BOD = 1600mg/L).A pretreatment and biochemical treatment combined process is made according to the characteristic of pesticide production wastewater which has high concentration , high salinity and high toxicity characteristics. The key of design of the treatment of pesticide production wastewater lies in the pretreatment process.The method of Chemical precipitation by copper chloride is used as the technology of treatment of thiophanate methyl production wastewater. After sedimentation, the COD value decreases from 6500～10500mg/L to 2800～5000mg/L. The way of pyrolysis is used as the technology of treatment of methomyl production wastewater. After pyrolysis, the COD value decreases from 81000～110000mg/L to 32000～58000mg/L.The means of alkaline hydrolysis is used as the technology of treatment of methyl isocyanate production wastewater. After alkaline hydrolysis, the COD value decreases from 2000～3200mg/L to 900～1500mg/L.By first pretreatment, three kinds of wastewater are collected. Treated by Fenton reagent, the COD value decreases from 1200～5600mg/L to 600～3700mg/L.Through the above pretreatment, the biodegradability of the wastewater improves. Because of high salinity, wastewater must be diluted to certain concentration. The COD of effluent can reach the first class of wastewater discharge standard when the wastewater following pretreatment is diluted in certain proportion and treated by biochemical method.Now, the process has been put in project after several pilot-scale tests. The running results show that the water quality of effluent meets the first level criteria of the Integrated Wastewater Discharge Standard (GB8978—1996) . It can be foreseen that this new process is suitable to the efficient treatment of refractory organic wastewater.