Purification of low concentration toluene waste gas by an enlarged cross-flow bio-trickling filter

For make full rational use of the packed media surface, the fluent software was used to the section area of the bio-trickling filter's inlet is enlarged and the outlet gradually converged. The enlarged cross-flow bio-trickling filter is characterized with low pressure drop and uniform distribution of gas and spray liquid. The filter inoculated with efficient Pseudomonas putida on the ceramic pellets was developed to degrade toluene. With inlet concentration ranging from 342 mg/m³ to 690 mg/m³, at the residence time of 140 s and the temperature ranging from 13.5 °C to 29.6°C, 8 days were needed to start the filter and the removal efficiency of toluene was up to 85 %. The effects of nutrient N, P content was studied, which showed that the improved type of MS culture medium (N: P = 5:1) of the microbial biofilm play an important role in promoting biofilm forming. In the stable operation stage, the temperature ranging from 16.5 °C to 35.7 °C, when the residence time is 47 s, the removal efficiency fluctuates with the inlet concentration increases during 40 days. When the inlet concentration is lower than 650 mg/m³, removal efficiency is higher than 95 %, and with the inlet concentration increases to 1000 mg/m³, the removal efficiency decreases to 84 %. But the efficiency increases in a short time and residences in a high level. When the residence time is for 140 s, 93 s, 70 s, 56 s, 47 s, 40 s, 35 s and 32s respectively, and the inlet toluene concentration is about 500 mg/m ³, the average removal efficiency is 100 %, 99.5 %, 99.2 %, 96.2 %, 94.1 %, 91.8 %, 91.6 % and 88.8 % respectively. Contamination and circulation fluid bed filter in the cross-flow operation, circulating fluid pH value of 7.0 ∼ 8.0, the biofilm system can better adapt to the changes of inlet toluene concentration.