Petrochemical Treatment Effect And Microbial Community Analysis Of MBBR Suspended Packing A/O Combined Process

With the acceleration of industrialization in our country,the pollution of industrial wastewater has been more and more serious.As a typical industrial wastewater,petrochemical wastewater has become the top priority in industrial wastewater treatment due to its large displacement,high toxicity,complex composition and difficult treatment.The composition of petrochemical wastewater fluctuates greatly and has to be treated according to actual working conditions.In order to solve the problems of a petrochemical wastewater treatment plant in Jiangsu that the ammonia nitrogen emission is not up to standard,the ability to resist impact load is weak,the aeration efficiency is low,and the energy consumption is high,this study takes the actual influent water of the plant as the treatment object.MBBR（moving-bed biofilm reactor）Suspended fillers are added on the basis of A/O（anoxic/aerobic）process,and the optimal treatment process conditions are determined by studying the operating parameters of the MBBR suspended filler+A/O process and the composition of the sludge microbial community structure.The composition and distribution of the microbial community under this process and its pollution reduction ability are characterized and analyzed to improve the treatment effect.Finally,the aeration hole shape of the tube aerator is optimized to clarify the hole shape with the best aeration effect through the simulation test.The optimally designed aerator provides a suitable DO concentration（dissolved oxygen concentration）for the survival of microorganisms.In addition,it can reduce energy consumption and improve aeration efficiency.Use single factor and orthogonal experiments to study the effects of HRT （hydraulic retention time）,DO concentration,sludge reflux ratio and filler addition ratio（volume ratio）on COD（chemical oxygen demand）,NH₃-N（ammonia nitrogen）,TN（total nitrogen）and TP（total phosphorus）removal rate in petrochemical wastewater.It is determined by a single factor and orthogonal experiment that the optimal operating process conditions of the reaction device should be HRT 16 h,DO concentration 2～3 mg/L,sludge reflux ratio 100%and filler addition ratio 30%.In addition,the extreme and variance analysis of the orthogonal experiment shows that the factors affecting the removal rate of COD and TN in descending order are HRT,filler addition ratio,DO concentration and sludge reflux ratio;the factors affecting the removal effect of NH₃-N in descending order are filler addition ratio,DO concentration,HRT and sludge reflux ratio;the factors affecting TP removal effect in descending order are filler addition ratio,HRT,DO concentration and sludge reflux ratio.In addition,the four factors all have an impact on the removal of these pollutants,but the sludge reflux ratio is the smallest,and the addition of fillers has a significant impact on the removal of ammonia nitrogen.The reaction device is operated under the best process conditions,and the operating data indicate that the COD of the content is kept below 35 mg/L after the wastewater treatment.The average removal rate of COD is 75.62%,the average removal rate of NH₃-N is 94.08%,and the NH₃-N effluent concentration is lower than 0.76 mg/L.The removal rate of TN,TP and SS of the whole system is 75.46%,84.41%and 89.8%respectively,and the chromaticity is also reduced from 32 to 4.In addition,the composition of the wastewater entering the reaction device exists fluctuating,but the effluent quality is relatively stable,which demonstrates the excellent impact load resistance of this process.The system is generally operating stably,and its effluent quality is better than the Class A standard in the Pollutant Discharge Standard for Urban Wastewater Treatment Plants（GB 18918-2002）.The sludge in the pool A and the pool O was studied by high-throughput sequencing,and has 43 phyla,89 classes and 572 genera in total.Among them,the sludge in the pool A has 23 phyla,51 classes and 257 genera;the sludge in the pool O has 35 phyla,64 classes and 424 genera.The sludge in the pool A,the dominant phylum are mainly Chloroflexi,Euryarchaeota and Bacteroidetes,the dominant class are mainly Anaerolineae,Methanomicrobia and Bacteroidia,the dominant genus are mainly Methanothrix,Levilinea and Syntrop Hobacter;the sludge in the pool O,the dominant phylum are mainly Proteobacteria,Chloroflexi and Planomyomytytes,the dominant class are mainly Anaerolineae,Betaproteobacteria and Planctomycetia,the dominant genus are mainly Ignavibacterium,Aridibacter and Bellellia.Heterotrophic bacteria are mainly present in the sludge in the pool A and the pool O.These microorganisms have a degrading effect on the pollutants in petrochemical wastewater and the degrading effect of dominant bacteria is significant.During the actual operation of the MBBR suspended filler+A/O process,sufficient contaminated organic matter and appropriate DO concentration should be supplied to ensure the role of the dominant bacteria.Use CFD（computational fluid dynamics）software to simulate the tubular aerator,by simulating the air flow conditions in the tubular aerator with circular,square and elliptical holes under the same intake conditions,and according to the velocity distribution cloud diagram,the turbulent kinetic energy distribution cloud diagram at the orifice,the orifice velocity diagram and the volume flow rate at the orifice,the aeration efficiency of different hole shapes is analyzed.Numerical simulation results show that the air flow rate is 5 m/s,the tubular aerator aeration holes are circular holes,aeration stability and uniformity reach the best state,and the aeration efficiency is the highest.This research has reference significance for upgrading and reforming wastewater treatment processes of similar petrochemical enterprises.The analysis of the sludge microbial community structure provides theoretical and technical support for the stable operation of the system;at the same time,it provides an optimized design for the tubular aerator certain reference effect.