Studies On The Treatment Of Off-gases Containing Benzene Homologue Compounds By Biofiltration

Traditional VOCs control technologies such as incineration, absorption, adsorption, and condensation have been commonly used to remove VOCs vapors in air streams. The use of biofiltration technology for controlling air contaminated with various VOCs vapors is a new application and has been researched by a number of investigators. These studies have proven that the biofiltration technology is a more cost-effective process for treating medium-strength and low-strength VOCs vapors in air streams than are traditional technologies.Three kinds of ceramic pellets were filled into the biofilters and inoculated withethylbenzene biodegraded bacteria-Staphylococcus Rosenback, which screeningby incubator shaker experiment. The purifying ethylbenzene performances of biofilters were investigated. Moreover, the effects of inlet volume loadings, three different ceramic pellets, the temperature of nutrient liquid, the pH of nutrient liquid, the water content of ceramic pellets, surfactant, and empty bed retention time on biofilters' performance were thoroughly examined. Biodegradation kinetic model of ethylbenzene were obtained by both ethylbenzene diffusion from the gas phase to the biolayer and biodegradation rate inside the biolayer. The effects of biomass accumulation and distribution on air pressure losses in biofilters were experimentally studied. The paper presented a comparative study of the biodegradation of four benzene homologue compounds: benzene, toluene, ethylbenzene and xylene.Biodegradation performance of ethylbenzene in biofilters that were filled into three different ceramic pellets were experimentally studied. The results show that volume removal loadings of biofilters increase along with the inlet volume loadings, but the relationships between them are non-linear. The biofilter packed with 2# ceramic pellets gain a better performance compared with the other two ceramic pellets. So, 2 ceramic pellets should be selected as filtering media.The biofilter appears to be a most effective treatment process in the temperature of nutrient liquid of 25. A theoretical evaluation on the temperature coefficient (0) indicates that the temperature effects on the performance of biofilter are more significant under first order reaction than zero order reaction, and no significant for 1# ceramicit pellets and 2 ceramic pellets. Furthermore, the mean 9 value for 1 ceramic pellets, zero order reaction was equal to 1.013, first order reaction 1.037, for 2# ceramic pellets, zero order reaction was equal to 1.010, first order reaction 1.045. The efficient of biofilter appears to be a highest in the pH of nutrient liquid of 7 for 1# ceramic pellets and 2n ceramic pellets, in the water content of 34.61% and 46.51% for 1# ceramic pellets and 2# ceramic pellets individually. The purifying efficiency of biofilter would be affected if the ceramic pellets could be kept dry for a long time. So, in order to keep the biofilter run normally, the water content of ceramic pellets should be made in normal range.The results indicate that the performance of the C15H31COOK-added biofilter is better than the other, but that inclusion of silicone oil in biofilter only slightly increases removal efficiency for ethylbenzene. For example, in the condition of empty bed retention time of 28.3s, if the concentration of C15H31COOK 0.03mol/L is added, the removal efficiency of biofilter of 25.86% can be increased. The lower empty bed retention time is, the worse the removal efficiency of biofilter is.The biofiltration model is derived from a mass balance on diffusion and biodegradation reaction of ethylbenzene. The results show that the zero orderbiodegradation kinetic model in the case of diffusion limitation within the biofilmcoincides with experimental results well. And, the constant changed along with the inlet concentration ceramic pellets, Cg,in 6000mg m-3for 2# ceramic pellets, Cg,in <6500mgm-3for 3# ceramic pellets, Cg,in <6500mgm-3for three kinds of ceramic pellets, Cg,in <6500mgm-3The value of...