Isolation And Identification Of Two BTEX Degrading Fungus And Benzene Biofiltration By Fungus

Volatile organic compounds are a class of very common pollutants which are harmful on human. Biofilter is widely recognized as the most cost-effective waste gas treatment method. The removal efficiency can be higher and no secondary pollution produced when treatment of low concentration waste gas by biofilter on the appropriate operating conditions. So it is of great significance and value to degrade VOCs emission with the microorganisms. In this study, benzene, toluene as the VOCs representative, screening of fungus which effectively degrade BTEX, optimizing of degradation conditions of fungus, researching of the degradation intermediate of benzene and tolunen and investigating benzene removal efficiency by Aspergillus versicolor immobilized on Coal Quality columnar carbon, bio-ceramic and bamboo on condition of different benzene concentration inlet.The results of BTEX degrading fungus screening and identification: A fungi HD-3 that could effectively degrade benzene was isolated form sludge collected from the aeration tank in sewage treatment plant. A fungus strain H1 that could effectively degrade toluene was screened form seven fungus strains preserved in my laboratory. According to its morphological characteristics and sequence analysis of ITS, strain HD-3 was identified as Aspergillus versicolor; Strain H1 was identified as Trametes hirsute. Research showed that Aspergillus versicolor could more easily degrade benzene ; Trametes hirsute could more easily degrade toluene .Optimization of degradation conditions: 78.56% of benzene was degraded by strain HD-3 within 8 days under the conditions of initial benzene concentration 439.3mg/L, but only 33.96% of benzene was degraded within 8 days under the conditions of initial benzene concentration 4393mg/L. The most suitable temperature was 30℃and the most suitable pH was 4.5 when benzene concentration was 439.3mg/L. Results of orthogonal experiment of 4 factors (temperature, pH, initial concent-ration of toluene, Tween concentration) involved in H1strain degrading toluene. temperature was 30℃, pH was 5.0, initial concentration of toluene was 300mg/L, tween 80 concentration was 0.5ml/L. 85.3% of toluene was degraded by strain H1 within 10 days under optimal conditions. Degradation rate on optimum conditions has been significantly improved comparing to that without optimization.Investigating the amount of enzyme activity puduced by Trametes hirsute cultured in three kinds of medium, the amount of laccase produced by Trametes hirsute in potato glucose liquid medium was the most. On the 7th, The quantity of laccase was 16500U/L, at the top of all. The content of P450 in Aspergillus versicolor was 126pmol/mg protein when benzene as inducer. The content of P450 in Aspergillus versicolor was 95.3pmol/mg protein when toluene as inducer. The content of P450 induced was higher compared with the content of P450 uninduced. Detecting intermediate poduced by fungus during degrading toluene and benzene in the way of GC-MS,the intermediates were catechol, protocatechuic acid and benzaldehyde. The mechanism of degrading benzene and toluene by two fungus needs to be further research.To compare the benzene removal efficiency of each biofilter packed with coal quality columnar carbon, bio-ceramic and bamboo, the influence of benzene inlet concentration on the benzene removal efficiency of three biofilters was investigated. The experimental results showed: (1) benzene removal efficiency gradually decreased with the benzene concentration increasing. The REave of CQC biofilter, BCC biofilter, BAM biofilter were 93.63%, 93.16%, 91.75% respectively when benzene concentration was 200mg/m3; the REave of three biofilters were 61.89%, 52.42%, 42.16% respectively when benzene concentration was 3000mg/m3. (2)The benzene removal capacity of packing material decreased in the order of coal quality columnar carbon, bio-ceramic and bamboo. Investigating removal efficiency of benzene by three sets of biofilter under different residence times, retention time had an large impacton the removal efficiency of benzene. The impact trend of the three biofilter was the longer the retention time, the higher the removal efficiency of benzene. But the longer residence time will increase the volume of biofilter. The residence time determined to be 106s under comprehensive consideration. The biofilm of microorganisms on the surface of three kinds of filler were observed by Scanning electron microscopy. The results showed that cylindrical carbon and bamboo coal suitable for packing fungus biofilm.