Study On Advanced Treatment Technology Of Coking Wastewater Biochemical Effluent

Coking wastewater is a large amount of high concentration organic wastewater produced in the process of coal to coke,gas purification and coking product recovery,which can not meet the discharge requirements through biochemical treatment.Biochemical effluent must be treated by physicochemical treatment to meet the discharge standards.Qianlishan wastewater treatment plant mainly undertakes the coking wastewater treatment of five coal coking plants in Qianlishan Industrial Park.The coking wastewater generated by the coal coking plant is pretreated and then sent to Qianlishan wastewater treatment plant for centralized treatment.Qianlishan sewage treatment plant mainly deals with coke dry quenching coking wastewater in industrial park.The treatment process is divided into biochemical treatment and advanced(reclaimed water reuse)section.The biochemical system adopts O1+A/O2 process,supplemented by air flotation,mixed reaction coagulation sedimentation and other physicochemical measures.After biochemical treatment,it is difficult to continue to reduce the concentration of organic matter,so the physicochemical advanced treatment is carried out after the secondary sedimentation tank to ensure that the effluent meets the discharge requirements of the discharge standard of pollutants for Coking Chemical Industry(GB 16171-2012).Therefore,in this study,coagulation,Fenton oxidation,iron carbon micro electrolysis,activated carbon adsorption and a variety of combined processes were used for advanced treatment of biochemical tail water.Through the comparison and selection of physicochemical treatment process of coking wastewater and the optimization of treatment conditions,the efficiency of physicochemical treatment is improved and the cost is effectively reduced.The results are as follows:(1)The results showed that the optimal dosage of PAC is 1400mg/L,the optimal dosage of CPAM is 8mg/L,the optimal p H is 5,and the optimal stirring time is 10min.Under the above optimal conditions,COD in the secondary sedimentation tank can be reduced to113.34mg/L,the removal rate is 65.87%,and the treatment cost is 2.1 yuan/m³;the optimal dosage of PFS is 800mg/L,the optimal p H is 7,the optimal dosage of CPAM is 0mg/L,and the optimal stirring time is 15min.Under the above optimal conditions,COD in the secondary sedimentation tank can be reduced to 104.22mg/L,the removal rate is 70.63%,and the treatment cost is 1.2 yuan/m³.(2)The results showed that the optimal treatment conditions for coking wastewater from secondary sedimentation tank by Fenton oxidation were as follows:Fe²⁺dosage:624.78mg/L;n(H₂O₂):n(Fe²⁺)dosage:6.06;initial p H:2.75.The technical analysis shows that under the optimal process conditions,the actual dosage of Fe SO4·7H₂O is 3.10g/L,the corresponding dosage of H₂O₂(30%)is 7.74ml/L,and the COD concentration of the experimental effluent is70-90mg/L,which can not meet the standard stably.The treatment cost of the process reaches9.29 yuan/T.(3)The results showed that the optimal treatment conditions were as follows:sponge iron dosage:304.0g/L;iron carbon ratio:4.15:1;initial p H:6.52;reaction time:152.8 min.Through technical and economic comparison,iron carbon micro electrolysis process has good removal effect in the initial stage of coking wastewater treatment,but with the increase of operation cycle,the effluent effect gradually becomes worse.When the operation cycle is more than 5cycles,the treatment effect of the system is gradually stable,the effluent COD is about100mg/L,and the treatment cost is 1.29 yuan/m³.(4)The coking wastewater from secondary sedimentation tank was treated by coagulation Fenton oxidation,and the treatment conditions were optimized by response surface methodology.The results showed that the optimal treatment conditions were as follows:Fe²⁺dosage:302.38mg/L;n(Fe²⁺):n(H₂O₂)ratio:1:6.84;initial p H:3.84;reaction time:125.84min.The COD can be reduced to 50-70mg/L by the combined process of coagulation and Fenton,and the treatment cost is 6.18 yuan/m³;the coking wastewater in the secondary sedimentation tank is treated by coagulation and iron carbon micro electrolysis,and the treatment conditions are optimized by response surface methodology.The optimal conditions of iron carbon micro electrolysis are as follows:sponge iron dosage:156.56g/L;initial p H:4.88;iron carbon ratio:3.6:1;reaction time:125.72min After the third cycle operation,the effluent COD concentration is about 40-50mg/L,which meets the discharge standard,and the treatment cost is 1.84 yuan/m³;on the basis of coagulation experiment,adding powdered activated carbon treatment,coagulant PAC and PFS combined with activated carbon have good treatment effect,and the COD removal rate is 8.8%when the dosage of PFS is 800mg/L and the dosage of activated carbon is 2g/L,,the COD removal rate is about 85%,COD concentration can be reduced to 50-60mg/L,reaching the discharge standard,and the treatment cost is 6.20yuan/m³.(5)On the basis of the optimal conditions of iron carbon micro electrolysis process,adding hydrogen peroxide,the results show that the dissolution amount of Fe²⁺is 363.47mg/L,when the reaction time is 60min,and adding H₂O₂ when the dissolution amount of Fe²⁺is maximum,the optimal dosage of H₂O₂ is 2ml/L and the optimal reaction time is 150min.The COD concentration of treated effluent is 30-40mg/L,which meets the discharge standard,and the treatment cost is 3.29 yuan/m³.(6)Through the comparison of technology and economy,the four processes of coagulation Fenton process,coagulation iron carbon micro electrolysis process,iron carbon micro electrolysis coupling Fenton process and coagulation activated carbon adsorption can meet the emission requirements.The cost of coagulation iron carbon micro electrolysis process is the lowest,followed by iron carbon micro electrolysis coupled with Fenton process,and the cost of coagulation Fenton process and coagulation activated carbon adsorption process is relatively high.