Study Of Purifying Wastegas Containing Low Concentrated Volatile Organic Compounds By Biological Method

Biotricking filter is a relatively recent air pollution control(APC) technology in which off-gases containing biodegradable volatile organic compounds(VOC) or inorganic air toxics are vented through a active biofilm packing-material. This technology has been successfully applied in Germany and The Netherlands in many full- scale applications from a wide range of industrial and public sector sources, control efficiencies of more than 90 percent have been achieved for many common air pollutants, due to lower operating costs. Biotricking filter can provide significant economic advantages over other APC technologies if applied to off-gases the contain readily biodegradable pollutants in low concentrations. Environmental benefits include low energy requirements and the avoidance of cross media transfer of pollutants.Firstly,This paper reviews the history and current status of biofiltration ,outlines its underlying scientific and engineering principles, and discusses the applicability of biofilters for a wide range of specific emission sources.secondly,this paper reports experiments on the purification of exhaust air containing organic pollutants by a new process using abiotrickling filter.The experimental results shows that the maximum elimination capacity(EC) of the biotrickiing filter for toluene could reach l88.5mg/h.l.For the problems in describing the mechanism of purifying the waste gas containing volatile organic compounds by using the "Absorption-Biofilm theory" which is often used in the world. A kinetic model for the process of purifying waste gas containing toluene in low concentration by using the biotrickiing filter with biofilm packing-material was established. By contrast, a good suitability of the kinetic model for practical process was verified. The interrelation coefficient between calculated data and experimental data was very inosculated.The results indicated that the process of purifying waste gas containing toluene in low concentration by using the biotrickiing filter is a mass transfer process and controlled mainly by gas-film. The biodegradation of toluene in the biotrickiing filter is an instantaneous high-speed biochemical reaction. The biodegradation of toluene is obvious bigger than the deffusion rate of its passing through liquid-film, so that the bioreaction can be accomplished at the gas-liquid interface.the macroscopical expression of this procession of this process is that toluene-gas is directly adsorbed on the surface ofwetted biofilm and then is rapidly biodegraded by microorganism, for this reason, the kinetic process of biopurifying the waste gases containing low concentration .VOC could be described,from a new point of view, by using the gas-adsorption theory. For the design and operation of facilities in the biological method, the every measure of improving the mass transfer condition or decreasing the gas-film resistance can strengthen this biopurification process.