Removal Of Low Concentration Styrene Waste Gas In Biotrickling Filter

Volatile organic compounds (VOCs) are major organic pollutants which are only fewer than the particle pollutant. VOCs are difficult to be removed at low concentration specially, and which has been become the hot subjects at all over the world. Biological method is very promising due to many advantages, such as simple devices, less investments, lower operation cost and no second pollutions. Biotrickling filter has been focused on more interesting because of the simple operation parameters.Styrene is one of the typical aromatic organic compounds, which has seriously harmful to the human body and the nature environment. On the other hand, styrene is hydrophobic, and it is suitable to be removed by the biological methods. Therefore, styrene is chosen as the target object in this experiment. The modified PE is selected as padding and the method of rapid sludge discharging is employed to inoculate and domesticate the biomass. The influences of empty bed residence time (EBRT) of filter, styrene concentration, the nutrition and the pH value of the circulation solution on the removal of styrene in biotrickling filter have been investigated. Furthermore, the pressure drop and the the mineral ratio of the filter are also considered. The results are shown as following:1. In the biofilters, the biomass could be domesticated using the method of rapid sludge discharging in a short period, and the biofiiters exhibited the high ability of VOCs removal. Concentration of styrene and EBRT had important influences on the performance of the reactor. The elimination capacities were 82 g.m^-3.h^-1, 31.2 g.m^-3.h^-1, 35.6 g.m^-3.h^-1 and 40.8 g.m^-3.h^-1 at EBRT of 60 s, 45 s, 30 s and 15 s with the inlet concentrations of 1400 mg·m^-3, 430 mg·m^-3, 350 mg·m^-3 and 200 mg·m^-3, respectively. The effluence of the reactor could achieve the national discharge standard. At the same time, the elimination capacity of the three stages filter is the order: the upper bed > the second bed > the lower bed. When the empty tower gas velocity was shorten, the pressure drop increased largely with shortening the empty tower gas velocity in line.2. The effect of the nitrite and nitrate in the sprayer circulation solution on the ability of the biotrickling filter was very clearly. At the starting times, nitrite would exhaust quickly and the nitrate would exhaust much slowly. When the TN concentration of circulation solution dropped from 532.7 mg·L^-1 to 102.63 mg·L^-1 and the styrene inlet concentration kept 500 mg.m^-3, the removal efficiencies were fluctuating between 92%-99%, and the total elimination capacities were fluctuating between 46.0 g.m^-3.h^-1 more or less. When the TN concentration of the circulation solution dropped from 102.63 mg·L^-1 to 24.24 mg·L^-1, the removal efficiencies dropped from 94% to 43%, the styrene inlet concentration dropped from 500 mg.m^-3to 220 mg.m^-3 else, the total elimination capacities of the biotrickling filter decreased from 45.1 mg·L^-1to 22.3 mg·L^-1. The reason could be that the capacity to use carbon resource decrease due to the lack of NO_x^-, which could be supported by the fact of the increase of pH in the solution treated. In this process, the mineral ratio of the biotrickling filter at large inlet styrene capacity was much lower than that of the low inlet styrene capacity.