Experimental Study On The Purification Of VOCs By A Biotrickling Filter And Analysis Of Microbial Community

Benzene and formaldehyde are two important organic pollutants in the VOCs,They are widely distributed and pose a serious threat to human health and ecological environment.In recent years,the increasing number of children with leukaemia also causes people to pay more attention to the treatment of benzene and formaldehyde pollution.In the treatment technology of benzene and formaldehyde,the biological droplet filter has become a research hotspot due to its advantages such as high porosity,easy to control,impact load and small resistance.The key factors for the treatment of benzene and formaldehyde by biological trickling filter are microorganism,and the in-depth and detailed study on the degradation bacteria of benzene and formaldehyde can provide the theoretical basis for the development and practical application of the biotrickle-filter purification organic exhaust gas.The subject takes benzene and formaldehyde as target pollutants,and the removal effects of benzene,formaldehyde,and mixed gases of benzene and formaldehyde under different process parameters are studied,The interaction between benzene and formaldehyde was analyzed,and the applicability of the"adsorption-biofilm"and"absorption-biofilm"models was verified.Through metagenomic sequencing,the community structure of microorganisms in the biological trickling filter was studied in the three different stages of treatment of benzene,formaldehyde and mixed gas of benzene and formaldehyde.(1)With the preparation of benzene-containing waste gas as the gas source,the effect of the inlet air concentration,EBRT,and liquid-gas ratio on the treatment of benzene-containing waste gas in the biotrickling filter was studied.The removal rate of benzene increased first and then decreased with the increase of intake air concentration,while the biochemical removal showed first increase and then flattened.The maximum removal efficiency was 82.8%;The removal rate of benzene increased first and then decreased with the increase of EBRT.The removal rate was the highest when EBRT was 60 s,and the maximum removal rate was 80.3%when the concentration was 80 mg/m~3.The biochemical removal decreased with the increase of EBRT.At the concentration of 110 mg/m~3,the biochemical removal was the highest,which was 5.85mg/(m~3·h).With the increase of the ratio of liquid to gas,it first increases and then gradually becomes stable.At the ratio of liquid to gas of 4:1,the removal rate of benzene and the amount of biochemical removal reach the maximum.When the concentration is 50 mg/m~3,the corresponding removal rate and Biochemical removals were 72.3%and 2.69 mg/(m~3·h),respectively.When the concentration was 80mg/m~3,the corresponding removal rate and biochemical removal were 82.4%and 4.01 mg/(m~3·h)respectively.EBRT 60 s,liquid gas ratio:4:1 is the best parameter for purification.(2)With the configuration of formaldehyde-containing waste gas as the gas source,the effect of the inlet air concentration,EBRT,and liquid-gas ratio on the treatment of formaldehyde-containing waste gas in the biotrickling filter was investigated.With the increase of inlet air concentration,the removal rate of formaldehyde in the system has been maintained at about 99.5%,while the biochemical removal volume has increased linearly with a maximum of7.63 mg/(m~3·h).Formaldehyde removal rate and biochemical removal rate increased first and then decreased slowly with the increase of EBRT.When EBRT was 60 s,the removal rate was the highest.When EBRT was gradually increased,the biochemical removal capacity at 110mg/m~3 was 12.93 mg/(m~3·h).drops to 4.11 mg/(m~3·h);With the increase of liquid-gas ratio,there was no significant change in the biochemical removal of formaldehyde.Considering,EBRT and liquid gas ratio are 60 s and 4:1 respectively,which are the best parameters of this experiment.(3)Taking the mixed waste gas containing benzene and formaldehyde as the gas source,the effects of the feed gas concentration,EBRT and liquid-gas ratio on the treatment effect of the mixed waste gas containing benzene and formaldehyde in the biotrickling filter were studied.Simultaneously with a single exhaust gas,in the presence of formaldehyde,changing the inlet concentration,the benzene removal rate decreased by 9.1%,and the biochemical removal volume also decreased by 1.47 mg/(m~3·h).When EBRT was changed,the maximum removal rate of 50mg/m~3 was 67.6%when EBRT was 60 s,which was a decrease of 4.7%.Biochemical removal rate has been reduced.When the ratio of liquid to gas was 4:1,the maximum removal rate and biochemical removal amount of benzene were achieved.At the concentration of 80 mg/m~3,the removal rate and biochemical removal decreased by 6.3%and 0.29 mg/(m~3·h),respectively.For formaldehyde,Two kinds of air intake methods have no obvious effect on the removal effect.The results showed that under the coexistence of benzene and formaldehyde,the removal effect of formaldehyde on benzene was inhibited by competition,while benzene had no effect on formaldehyde.(4)According to the“absorption-biofilm”and“adsorption-biofilm”model theories,the experimental values of benzene(formaldehyde)outlet gas concentration,benzene(formaldehyde)removal rate,and benzene(formaldehyde)biochemical removal were compared with the simulated calculation values.The correlation between formaldehyde and the“absorption-biofilm”model theoretically verified results is good,and the correlation coefficients are:0.995,0.891,and0.994,and the correlation between benzene and the“adsorption-biofilm”model theoretically verified results is good.The correlation coefficients were:0.994,0.929,0.991.The results show that the model theory of"absorbing-biofilm"is applicable to formaldehyde organic waste gas which is soluble in water,and"adsorption-biofilm"is more suitable for hydrophobic benzene organic waste gas.(5)Bamboo charcoal packing on microbial SEM photos showed that biological trickling filter in the middle of microbial quantity significantly greater than the upper microorganism quantity,through high-throughput sequencing results show that when the door of the classification level mixture of benzene,formaldehyde and benzene and formaldehyde degrading bacteria dominant fungi door are Proteobacteria deformation bacteria(door),in the classification of the genus level,the advantage of formaldehyde degrading bacteria species for Methylibium,Gp4,etc.,and the advantage of benzene bacteria genera Pseudomonas,Reyranella,Ohtaekwangia,etc.