Research And Engineering Practice Of Wastewater Treatment In A Fine Chemical Enterprise In Lanzhou

The wastewater produced by a fine chemical enterprise in Lanzhou had the characteristics of complex organic pollutants,many refractory substances,high chroma,high toxicity and extremely low biodegradability.How to deal with this kind of wastewater efficiently and economically was of great significance.By analyzing the main components of high-concentration refractory fine chemical wastewater discharged from a fine chemical production enterprise in Lanzhou,The combined process of physicochemical pretreatment（iron-carbon micro-electrolysis,Fenton oxidation,coagulation and precipitation）+biochemical treatment（hydrolysis acidification,aerobic treatment）was proposed in a targeted manner.First of all,the laboratory parameters were optimized to the maximum extent,and the actual working conditions were debugged to realize the degradation of the wastewater and make it meet the discharge standard.Through experiments and debugging,the following conclusions could be drawn:The fine chemical wastewater treatment experiment was carried out with iron-carbon micro-electrolytic fillers,and the optimal parameters were determined by single factor experiment and orthogonal experiment:when pH=3,iron-carbon solid-liquid ratio 150g/L,and reaction time 120min,It can reach 27.2%that the rate of COD removal,with less iron-carbon filler investment and lower time cost.In the kinetic analysis,the second-order reaction kinetic equation could better reflect the appwerent kinetics of iron-carbon micro-electrolysis for refractory organic wastewater.The Fenton oxidation method was used for the treatment of fine chemical wastewater,and the optimal parameters were determined by single factor experiment and orthogonal experiment.The COD removal rate could reach 31%,when pH=4,the dosage of Fe²⁺was2.4g/L,the dosage of H₂O₂ was 15mL/L,and the reaction time was at 90min.The process of COD degradation by Fenton oxidative pretreatment was determined to be the second-order reaction kinetics,and the kinetic equation was established.In the kinetic analysis,the second-order reaction kinetic equation could better reflect the appwerent kinetics of Fenton oxidation of refractory organic wastewater.The type of coagulant and the optimal dosage of coagulant were determined by coagulation sedimentation experiment method:the removal rate of COD by polyaluminum chloride（PAC）was higher than that of polyaluminum sulfate（PAS）and polyferric sulfate（PFS）;when the dosage of PAC is equal to 90mg/L,it had the best effect on the removal rate of COD.Therefore,it was determined that PAC was the coagulant in the coagulation process,and the optimum dosage is 90 mg/L.In the actual debugging process,through the start-up and debugging of the iron-carbon micro-electrolysis-Fenton oxidation unit,it could be seen that the material of iron-carbon micro-electrolysis has a great influence on the wastewater treatment effect.Through the combined debugging of iron-carbon micro-electrolysis-Fenton oxidation-flocculation precipitation process,combined with economic factors,the comprehensive effect of adding only PAM to the effluent of iron-carbon micro-electrolysis is better than adding PAC or PAC and PAM.In the biochemical treatment stage,the advantages and disadvantages of different aerobic treatment processes were compwered and analyzed,and the removal effect and economic cost were mainly considered,and the biological contact oxidation method was finally selected as the aerobic treatment process.In summary,through the actual engineering verification,the COD removal rates of the hydrolysis acidification tank and the aerobic tank were 53.6%and 93%.If the comprehensive operation effect of physicochemical and biochemical system was mainly considered,the treatment effect of iron-carbon micro-electrolysis-Fenton oxidation reaction was better than that of iron-carbon micro-electrolysis and biochemical stage.The average removal rate of the micro-electrolysis-Fenton oxidation process was higher than the latter by 6.8%,but after the end of the biochemical reaction,the difference in the removal rate of COD between the two treatment methods is small.But from an economic point of view,the cost of iron-carbon micro-electrolysis-Fenton oxidation process was much higher than adding corn meal to the pool in iron-carbon micro-electrolysis and biochemical stage.The test results show that the pH value of the hydrolysis and acidification tank fluctuates slightly around 6.0,and the pH value of the outlet of the contact oxidation tank was stable in the range of 6.0～6.5.The dissolved oxygen in the hydrolysis and acidification tank was controlled at 0.2～0.3mg/L,and in the aerobic microbial culture,the dissolved oxygen was controlled between 2～4mg/L,so that the aerobic sludge in the sludge floc could obtain enough dissolved oxygen and good handling.After the combined process system runs stably,the effluent value was stable,the COD effluent concentration was always lower than 400mg/L,and the COD removal rate of the whole process was about 97%.The average BOD of effluent was 76.3mg/L,the average removal rate of BOD in raw water was 91.4%,the average concentration of NH₃-N in effluent was 27mg/L,and the average removal rate of NH₃-N was over 82%.By economic cost analyzing,the operating cost of fine chemical wastewater treatment was 22.72 yuan/ton.In the combined process,the effluent of each index was stable and in good operating state,and pollutants in fine chemical wastewater could be removed through the physical and chemical pretreatment and biochemical stages.This process could provide data reference and basis for the cost investment of projects with the same or similar water quality in the future.