Elimination of toluene vapors in biotrickling filters: Performance and carbon balances
- Univ. of California, Riverside, CA (United States). Dept. of Chemical and Environmental Engineering
Performance of two toluene-degrading biotrickling filters was systematically investigated under different conditions of supply of toluene (0, 1 or 2 g/m3) and nutrients (feed of phosphate buffer or mineral medium). The focus of the investigation was on quantification of biomass growth and determination of the influence of biomass growth on filter performance. Treatment of 1 g/m3 toluene at a volumetric load of 64 m3/(m3.h) while feeding a mineral medium to support growth resulted in an increase of wet biomass at a rate of 3.2--9.8 kg/(m3 reactor.day). Biomass accumulation in the reactor resulted in decreasing toluene elimination capacities, i.e., from about 40 g/(m3.h) at 0.3 kg wet biomass/(L reactor) to 20 g/(m3.h) at 0.7 kg/L. When using 2.5 cm Pall rings as packing, a sharp increase of the pressure drop may be expected at 0.5 kg wet biomass/(L reactor). Carbon mass balances show that on average 69% of C-toluene degraded was oxidized to C-CO{sub 2}, whereas 21% was incorporated into biomass and 6% washed out via the liquid purge. It is estimated that decreasing performance due to clogging of these reactors may be expected after 3 months of operation with continuous feed of mineral medium. Changing to a nutrient-limited environment resulted in a loss of toluene elimination capacity of 25--50% within two weeks. Although nutrient limitation may delay biomass accumulation, larger reactor volumes are required to compensate for the loss of microbial activity. Endogenous respiration resulted in an average CO{sub 2} production of 2 g C-CO{sub 2}/(m3.h). Under starvation conditions, an average loss of wet biomass of 2.2 kg/(m3 reactor.day) was observed. Periods of starvation to maintain a constant amount of biomass is not a realistic option for these reactors as this would require shut-down of the biotrickling filter for two to five days per week depending on the biomass accumulation rate at nutrient-rich conditions.
- OSTI ID:
- 682225
- Report Number(s):
- CONF-980632--
- Country of Publication:
- United States
- Language:
- English
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