Study On Toluene-Polluted Air Purfication By The Combination Of Microorganism And Plants

The purification of gaseous organic pollutants by microorganisms associated with plants is an environmental-friendly technique. Toluene is one of the pollutants which is commonly found in indoor air and industrial production practice, and its presence seriously affect the air quality and human health. In this study, biofiltration assisted by ryegrass planted in the bioreactor was used to investigate the effect of planted ryegrass on soil microbial community and soil enzyme activity. The results showed that in the same height of bioreactor packing, and different rhizosphere distribution, the number of bacteria, fungi, actinomycetes horizontal distribution surrounding ryegrass appeared as:rhizosphere> transitional zone> non-rhizosphere. Microbial populations were negatively correlated with the toluene concentration in the same position, indicating that ryegrass roots increase the degradation of toluene by promoting the activity of microbe. At the same time, ryegrass roots had inhibition effects on soil catalase activity in packing height of50-100mm,and smaller impact on catalase activity in the100-200mm packing height. However, soil dehydrogenase activity, which were nearly at the same level, had little effect on toluene purification.The experiment also identified the enhancement of ryegrass rhizosphere to toluene, and investigated the influences of environment factors, i.e, inlet toluene concentration, packing height, temperature and light intensity on the purification efficiency. The results showed that the purification efficiency of toluene in a bioreactor with ryegrass was more than that without ryegrass under the same conditions. At the same inlet concentration of toluene, the purification capacity increased with the increase of the packing height. When in the same packing height, and toluene inlet concentration is less than500mg·m-3, the purification capacity improved with the increase of toluene concentration. In the range of5-35℃, increasing temperature improved the activity of microorganism to promote the microbial degradation of toluene. When the light intensity was240μmol·m-2·s-1, the purification efficiency of toluene is the highest, followed by light intensity of80μmol·m-2·s-1, and the light intensity inhibite purification product with light intensity of160μmol·m·2s-1, thus resulting in a loss of toluene purification efficiency. Contrast planted with unplanted processing, at the same temperature or light intensity conditions, toluene purification efficiency was more than unplanted treatment.Kinetic model was used to simulate the biological purification process of toluene, the results showed that the toluene purification efficiency calculated by kinetic equation coincided with the experiment measured values, indicating that the kinetic equation can be used to guide biological purification of toluene waste gas process design.