Experimental Study On Tail Water Treatment Technology Of Pesticide Chemical Industry Park

Pesticide production tail water composition is complex,low C/N and high content of toxic and harmful substances,such wastewater discharge is large,and there are problems such as effluent instability,pollutant discharge does not meet standards.In order to solve the problems of high total nitrogen content,low C/N ratio and refractory organic compounds in the effluent from the sewage treatment plant of a pesticide chemical industrial park,this study established a combined water treatment process with biological treatment technology as the main technology and advanced oxidation technology as the advanced treatment,and carried out a pilot scale test of the effluent treatment.The operating parameters of the two deep processing technologies were optimized and the optimal process was determined.The nitrogen removal efficiency of sulfur autotrophic denitrification system and the relationship between the change of microbial community structure in the system and nitrogen removal efficiency were discussed.The main research results are as follows:The denitrification performance of the sulfur autotrophic denitrification system for tail water was studied.The system was operated in two phases,with room temperature of about 16℃and HRT of 22 h,The system was operated for 53 days under anaerobic conditions.The experimental results show that the average removal rate of NO₃^--N is87%and the average effluent concentration is 21 mg/L when the simulated wastewater is treated with NO₃^--N for 25 days.The average TN removal rate is 88%,and the average effluent concentration is 17 mg/L.The system has good nitrogen removal effect and stable operation,and the effluent COD of the system is 145 mg/L.The sulfur autotrophic denitrification system has no obvious degradation effect on the organic matter in the tail water,but has good removal effect on the nitrogen in the tail water.The degradation efficiency of organic matter in tail water by two advanced treatment technologies was investigated.The combined iron-carbon micro-electrolysis-Fenton oxidation process and persulfate catalytic oxidation process were selected,and the operating parameters were investigated.The experimental results show that when influent COD concentration is 145 mg/L,the combined process of iron carbon micro-electrolysis and Fenton oxidation,p H is 3,30%H₂O₂dosage is 1‰,reaction time is 2h,the COD removal efficiency is the best,the removal rate is 43%,the effluent COD concentration is 81 mg/L.When p H is 5,the ratio of Na₂S₂O₈/Fe SO₄·7H₂O is 0.8 and the reaction time is 1 h,the COD removal efficiency is the best,the removal rate is 57%,and the effluent COD concentration is 62 mg/L.Comprehensive comparison shows that both processes can effectively degrade organic matter in tail water,and persulfate catalytic oxidation system has better degradation effect.The synergistic effect of microbial community in the operation of sulfur autotrophic denitrification system was further revealed.Proteobacteria,Campilobacter and Bacteroidetes are the main bacterobacteria,among which Campilobacter is significantly increased during the operation of denitrification system,which is closely related to denitrification.Sulfurimonas and Thiobacillus are the typical bacteria existing in the system,and the bacteria in these two genera have the function of sulfur autotrophic denitrification.Thiobacillus is the dominant bacterium related to the autotrophic denitrification of sulfur,which plays an important role in the oxidation of inorganic sulfur and the reduction of nitrate.