The Study On Bioaugmentation Efficiency Based On Construction Of Bacterial Agent For Simultaneous Btex Degradation And Ammonia Removal

Benzene,toluene,ethylbenzene and xylene?BTEX?are the representatives of benzene pollutants.They are widespread,harmful and from a wide range of sources.They exist in air,surface water,groundwater and soil environment.And the actual industrial wastewater is often BTEX and nitrogen coexist.The traditional method of degradation of BTEX can achieve good results,but it can't coupling the function of nitrogen removal,As a result,the wastewater treatment process is long and the operation cost is high.With the emergence of heterotrophic nitrification-aerobic denitrification?HN-AD?technology,it is possible to remove the refractory organic matter at the same time.In this study,we screened the HN-AD strains which are also capable of degrading benzene,toluene and ethylbenzene?BTE?,constructed HN-AD complex bacteria with simultaneous removal of BTE and nitrogen.The degradation mechanism was studied by microbiological analysis.The biodegradation of BTE and denitrification were also conducted in sequencing batch reactor?SBR?and the process parameters were optimized.High-throughput sequencing was used to study the microbial flora structure of the bacteria after the pre-and post-treatment of activated sludge in SBR reaction.It provides a basis for the development of HN-AD complex bacteria and the practical application of HN-AD technology,and lays a foundation for the engineering application of biological strengthening technology.With the activated sludge in the treatment of simulated coking wastewater in the reactor in the laboratory as the raw material,we successfully screened 9 strains of BTE degrading bacteria?B1-1,B1-2,B1-3,J2-1,J2-2,J2-3,Y3-1,Y3-2,Y3-3.Among them,B1-1,B1-2,J2-1,J2-3,Y3-3 are HN-ADbacteria?,plus 2 aromatic degradation strains already preserved in the laboratory?Diaphorobacter sp.PD-7 and Candida maltose BF-2?.By comparing the degradation effect of single substrate with two concentration gradient analysis as well as the degradation of BTE and nitrogen,with the principle of separation of strains from each other,B1-1,B1-2,J2-1,PD7,Y3-1 and Y3-2 were preliminarily screened for their strong ability to degrade single substrates,good tolerance and good degradation spectrum as the candidate strains.To investigate the effect of co-substrate on the degradation activity of a single strain.The optimal strain was determined to be PD7,and then the multistrain mixture test was conducted through the permutation and combination of PD7 and other strains.The results showed that M4,composed of b1-2,PD7 and y3-1,had the best degradation effect on BTE.Haldane model was used in the analysis of single substrate aerobic degradation kinetics of BTE by Origin software with the test data of the nonlinear least squares fitting,the maximum specific growth rate of cell growth were:0.228 d^-1,0.192 d^-1,0.168 d^-1.Double substrate degradation kinetics equationby Abuhamed was used,the benzene/toluene as the fitting resultsofI_1,2=2.02,I_2,1=8.05,correlationcoefficientR²=0.89;benzene/ethylbenzene as I_1,2=3.25,I_2,1=4.08,the correlation coefficient R²=0.91;toluene/ethylbenzene as I_2,1=5.27 I_1,2=4.56,the correlation coefficient R²=0.91.It was concluded that the inhibition of the three substrates is in agreement with the experiment.On the basis of enzyme activity test,the degradation pathway of BTE was discussed.The specific activity of 2,3-(C₂₃O)was greater than that of catechol 1,2-(C₁₂O),and it was concluded that the degradation of BTE was mainly in the open loop cleavage pathway.The simultaneous removal of BTE and nitrogen by NH⁴⁺-N,NO^-3-N and NO^-2-N as the sole nitrogen source was investigated by using BTE as the sole carbon source.Under the condition of the same initial concentration,the change of cell concentration and the degradation rate of BTE were from large to small:NH₄⁺-N>N0₃^--N>NO₂^--N.BTE and NH⁴⁺-N were the sole carbon and nitrogen source,and the nitrogen removal was achieved by heterotrophic nitrification and aerobic denitrification,The total nitrogen removal rate was 51.13%.At the same NO₃^--N concentration and the same concentration of BTE,The C/N ratio was adjusted to investigate the effect of C/N ratio on the degradation and denitrification performance of the microbial community.The results showed,When C/N ratio was 15,the bacteria could use BTE and nitrate nitrogen simultaneously to achieve high efficiency removal.the high C/N ratio was beneficial to the removal rate of nitrate nitrogen and nitrite nitrogen accumulation.Too high or too low C/N ratio was not conducive to the simultaneous removal of BTE and nitrate nitrogen.By measuring the enzyme activity of heterotrophic nitrification aerobic denitrification process,combined with nitrogen balance analysis,it was concluded that the metabolic pathway of ammonia nitrogen was through the coupled heterotrophic nitrifying-aerobic denitrifying pathway.Based on the start-up and operation of SBR reactor with adding compound inoculants,comparing enhancement of SBR in the removal of pollutants COD,benzene,toluene,ethylbenzene and nitrogen efficiency by before adding and after adding.The removal rates of COD,benzene,toluene and ethyl benzene were increased by 17.5%,16.5%,15.1%and19%respectively.and the removal of ammonia nitrogen was not significant.The removal rate of total nitrogen increased from 51.2%to 64.1%.The results showed that the compound bacteria agent had a significant effect on improving the operation efficiency of the reactor.During continuous operation,the removal efficiency of COD was increased by 0.8%,and the average removal rate of benzene,toluene and ethylbenzene decreased by4.7%,2.6%and 1.8%,respectively.The removal rate of ammonia nitrogen was about 85%,and the average removal rate of total nitrogen decreased by about 1.4%.The results showed that the specific degradation bacteria screened in this study had good stability,and had a strong sustainability in the removal effect.The effect of the enhanced sludge in different operating conditions was analyzed and the optimal operating conditions were obtained.Comparative analysis of removal efficiency under different aeration and pH conditions,the results show that the removal efficiency of COD,benzene,toluene and ethylbenzene were optimized under the condition of 1.0 mL/?mL·min?,and the removal efficiency of ammonia nitrogen and total nitrogen was the best under 1.5 mL/?mL·min?conditions,and both of them had the best effect when the pH value was 7.5.High throughput sequencing technology was used to analyze the activated sludge samples before and after bioaugmentation in SBR treatment system.The bacteria distribution and relative content were compared at the phylum,class,order and genus levels respectively.The results showed that,on the phylum level,Proteobacteria and Firmicutes were the two groups with the highest relative content.At the class level are Betaproteobacteria and Gammaproteobacteria.At the order level,the deriales were Burkholderiales and Pseudomonadales.At the genus level are the genera Comamonas and Thiobacillus.At the four levels,the relative contents of colonies all changed,and the genus level was the most obvious,but the difference was not significant.