Study On Biological Effects Of Additives On Biodegradation Of Toluene By Microorganism

In recent years,the environmental problems occur frequently,and the air pollution is especially serious,which need to be solved urgently.Volatile organic compounds?VOCs?have a serious impact on the environment.The benzene compounds in VOCs have carcinogenicity,teratogenicity and mutagenicity,and cannot be ignored.There are many technical methods of VOCs treatment,including absorption,sorption,combustion,biological,plasma and so on.The biological method has become a highly potential technical means,because of its advantages of high efficiency,good economy and no secondary pollution.In this study,toluene was used as a representative of benzene series.Through the domestication of activated sludge from the leachate of Tianjin Shuangkou landfill,a strain of degrading toluene as a single carbon source was screened out.The degradation pathway of toluene was established,which was toluene plasmid catabolic pathway.The optimum culture conditions were obtained by orthogonal experiment,that is,the incubation temperature was 30?,pH was 7,inoculation amount was 5%,and toluene addition was 60?L.The biological effect of experimental strain of toluene degradation was studied when different surfactants?bromogeramine,stearic acid,Triton X-100 and soybean lecithin?were added into the experimental system.Under the experimental conditions,the solubility increased by 78.8%,35.6%,59.4%and 3.6%,respectively.The removal of toluene degrading was 72.2%,85.7%,90.9%and 84.4%in 120 h with different concentration.The removal of blank sample was 81.7%.Compared with it,when adding the surfactants except for bromogeramine,the removal of toluene was rised in different degree.In the detection of oxygen explosion effect,the activities of kinase?CAT,POD and SOD?and the activities of key enzymes?TDO and C23O?indicated the following conclusions.With environmental stimuli,microorganisms produced kinases in order to better resist environmental changed,thereby removing toluene further through key enzymes.The biological effect of experimental strain of toluene degradation was studied,when different metal ions(Mg²⁺and Mn²⁺),were added into the experimental system.When the concentrations of Mg²⁺and Mn²⁺were 1 mg/L and 0.1 mg/L,the toluene degrading bacteria had the best growth amount.And when the concentrations of Mg²⁺and Mn²⁺were 0.5 mg/L and 5mg/L,the removal efficiency was the highest,which is,81.1%and 84.5%.Meanwhile,the change rule of the removal and key enzymes were studied.When the metal ions were added,the maximum removal was 84.5%in 120 h.When the surfactant?Triton X-100?was added,the removal was 90.9%in 120 h.The results indicated that only adding metal ions can increase microbial activity but cannot reach the best removal efficiency.The reason was that the hydrophobicity of toluene limits the utilization of toluene by microorganisms,so it is necessary to remove toluene by enhancing the solubility.