Purification performance of regnant strains Trametes versicolorto toluene in biofilter

Abstract: Aimed to study the purification performance of the regnant strain Trametes versicolor in biofilter on toluene, the biological filter system packed with pine bark and lava rock was utilized to remove the toluene which was taken as a target pollutant by Trametes versicolor. The pine bark had a higher organic matter content and the lava rock had a bigger mechanical strength. The higher organic matter content could offer more nutrition to microorganism and the bigger mechanical strength could slow down blocking of the biofilter. Toluene is one of the typical contaminants in volatile organic compounds (VOCs) and has a great harm to human health. Biological methods treating low inlet concentration of VOCs have many advantages, such as less investment, low energy consumption, and no secondary pollution. The Trametes versicolor is regnant strain to remove toluene and belongs to the white rot fungi. Relying on a variety of enzymes secreted, white rot fungi follow different degradation mechanisms to remove polycyclic aromatic hydrocarbons, alkyl benzene, chlorinated aromatic and other compounds. Experiments on the growth situation of Trametes versicolor in the biological filter were carried out. Meanwhile the effects of different GRT (Gas rentention time) and ILR (inlet loading rate) on removal efficiency, elimination capacity and pressure drop were also studied. It was found that biofilm was formed on the surface of the packing material within 20 days by the compulsive circulation method. And the biological filter showed a high performance to remove toluene without lignin oxidase involved. The Trametes versicolor did not secrete lignin peroxidase (Lip), manganese peroxidase (Mnp) and laccase (Lac) at the same time in the biofilter system to purify toluene, and only secreted a small amount of Mnp and Lac enzymes. The full functioning enzymes and the degradable mechanism of Trametes versicolor purifying toluene needed be further studied. Under the optimal conditions, i.e. the GRT of 148.3 s and the ILR of 7.28 g/(m3·h), the maximum removal efficiency and the maximum elimination capacity of the system were found to be 92.4% and 6.73 g/(m3·h), respectively. For the EBRT of 37.1 s, the best performance was observed at the ILR of 58.25 g/(m3·h), while the maximum elimination capacity was 47.07 g/(m3·h) and the removal efficiency was above 80%. The desired result attributes to the fungal structure and the growth of mycelium. The fungal structure and aerial mycelium have huge specific surface area which there by can adsorb a mass of gaseous toluene to increase the mass transfer of hydrophobic VOCs from gaseous phase to bio-phase and improve the removal rate. In comparison, fungi have obvious advantages over bacteria in terms of removing hydrophobic volatile organic pollutants. Under test conditions, the biological filter system did not have obvious jam phenomenon and the pressure drop of biological filter system was less than 500 Pa, which indicated it also has a good economy. The results provide the basic data and the theoretical support for industrial application of biological filter method in VOCs treatment.