Pretreatment Of High Concentration Wastewater From Refractory Fine Chemical Manufacture

Fine chemical wastewater?FCW?is characterized by high concentration of organic matter,complex components,and high toxicity,and it is highly hazardous to the environment and human health.With this organic pollutants are mostly artificially synthesized,which is hard to recognize and degrade by microorganisms,the wastewater B/C value is extremely low,it is hard for the conventional biological process to mineralize all pollutants of FCW.Hence,appropriate physical and chemical pretreatment is the key to ensure the biochemical treatment effect of FCW.A fine chemical company is in Gansu province,and the main products include vidarabine,antioxidants UV-2908,UV-612 and other chemical products.The characteristics of the fine chemical production wastewater with a strong acidity,high pollutant concentration,extremely high sulphate concentration and poor biodegradability.Thus,this study chooses home and abroad the most economical and practical pretreatment technologies include iron carbonmicroelectrolysis?ICME?,Fentonoxidation?FO?andhydrolysis acidification?HA?process,which based on the analysis of the characteristics of wastewater quality.In this study,the optimal reaction conditions of ICME and FO pretreatment were determined through single-factor influence experiments and response surface optimization experiments,and the reaction kinetics were investigated.The advantages of ICME combined with FO process were investigated,the single-factor experiment was used to optimize the optimal process parameters of the synergistic process and the economics of the process were discussed.Based on this,use of UV and FTIR analysis methods to explore to remove pollutants mechanism in the single-process and synergistic process.Through acclimation of hydrolysis acidified sludge and enhanced hydrolysis acidification,the influencing factors and the best operating parameters of the enhanced hydrolysis acidification process?EHA?were investigated.The feasibility of aerobic biochemistry was verified by SBR reactor for the wastewater pretreated by the combined process of ICME-FO-EHA.Finally,a set of"ICME-FO-EHA"combination process was used to pretreat the wastewater.Research indicates:?1?Treatment of wastewater by ICME is carried out.Through studying and analyzing response surface methodology and single factor experiment,the four main influencing factors of reaction time,initial pH value,iron carbon mass ratio and iron carbon dosage were determined.The experimental results show that the ICME process can degrade wastewater without adjusting the pH.The optimum conditions of ICME were determined to be dosage of sponge iron was 31.68g/L,the mass ratio of iron to carbon was 0.9,and the reaction time was122min,respectively.The removal rate of COD_Crr was up to 30.40%under the optimal conditions.The degradation of COD_Cr method conforms to the secondary reaction kinetics dynamics,after level regression equation fitting of the equation is obtained for Y=28355.2638/?1+0.0038*t?,the correlation coefficient of fitting curve is R²=0.9579.ICME can effectively reduce the concentration of pollutants in the wastewater and improve the biodegradability of the wastewater.?2?Treatment of wastewater by FO is carried out.Through studying and analyzing response surface methodology and single factor experiment,the four main influencing factors of reaction time,initial pH value,H₂O₂ dosage,n?H₂O₂?:n(Fe²⁺),and H₂O₂ dosing frequency were determined.The response surface optimization analysis method was used to optimize the working conditions of Fenton oxidation technology for high concentration of difficult to degrade fine chemical wastewater.The optimal combination of factors was:initial pH was4.04,H₂O₂ dosage was 7.73 mL/L,n?H₂O₂?:n(Fe²⁺),was 11.69:1,the reaction time was 88minutes,and the H₂O₂ dosage was 4 times,respectively.The removal rate of COD_Cr in wastewater was up to 30.04%.The degradation of COD_Cr method conforms to the tertiary reaction kinetic dynamics,after level regression equation fitting of the equation is obtained for Y=33474.1591/?1+0.01267t?0.5,the correlation coefficient of fitting curve is R²=0.9973.?3?“ICME-FO synergistic process”was used to pretreat the wastewater.ICME system can provide a high concentration of Fe²⁺(Fe²⁺=1184.02mg/L)and suitable pH?pH=3.94?during 90 min reaction,and has the experimental conditions of co-treatment with Fenton oxidation.The results show that after the reaction of ICME 90 min,the H₂O₂ solution was added at a rate of 6 mL/L in the effluent,and the Fenton oxidation reaction time was 90 min,which the COD_Cr removal rate of the wastewater was 51.50%achieved by the synergistic process.At the same time,the B/C value of the wastewater was increased from 0.074 to 0.197.The collaborative process has improved the utilization of raw materials and reduced the cost of wastewater treatment compared to a single process.?4?The Ultraviolet spectroscopy?UV?and Fourier transform infrared spectroscopy?FTIR?was used to investigate the mechanism of contaminant removal by the synergistic process.Analysis of UV and FTIR in different systems of ICME process,the analysis shows that refractory organics in wastewater are effectively degraded,ICME pretreatment process is a synergistic effect of various physical and chemical treatment processes.The results of UV and FTIR analysis of wastewater before and after synergistic process showed that the hard-degradable organics such as double-bond unsaturated and cyclic aromatic organics in wastewater have been effectively degraded in ICME and FO systems,·OH can further Oxidative decompose the intermediate products produced by the ICME reaction.However,the effluent still contains aromatic compounds.?5?The enhanced hydrolytic acidification process was used to carry out of the effluent of the ICME-FO synergistic process.This study showed that the optimal combination of factors was carrier fill ratio 30%,HRT 12h,temperature 20?,respectively.The average COD_Crr removal rate was 15.47%and the average removal rate of sulfate ions was 39.06%by enhanced hydrolysis acidification process.Meanwhile,B/C ratio was enhanced form less than0.2 to over 0.3.?6?After wastewater was pretreated by the"ICME-FO-EHA"combination process,the COD_Crr removal rate of wastewater was up to 61.12%.Meanwhile,B/C ratio was enhanced to form less than 0.1 to over 0.3,which suggest that its biodegradability was improved.Furthermore,the aerobic biochemical exploration experiment results show the influent water quality is 1:1 after the pretreatment water is mixed with the domestic sewage,and after 96hours aeration aerobic biochemical treatment,making the effluent COD_Cr stabilized below"B-grade"indicator in“Wastewater quality standards for discharge to municipal sewers”[CJ343-2010],which is the effluent COD_Cr discharged to WWTP was limited below500mg/L.