Membrane bioreactor for TCE cometabolism with toluene
Biofilters have been of limited use for cometabolism of chlorinated organic compounds such as trichloroethylene (TCE). In cometabolism, cosubstrates must be available as primary carbon and energy sources and to induce synthesis of necessary enzymes to cometabolize the target compound. The cosubstrates often inhibit cometabolism of the target compound, however. A hollow fiber membrane bioreactor was investigated that allowed for addition of cosubstrates to the microbial population while maintaining low enough concentrations to prevent inhibition. The system involves a bundle of polypropylene fibers through which VOC contaminated air passes. The fibers are immersed in a recirculating nutrient/cosubstrate solution. This system is suited to cometabolism as the cosubstrate is diluted into the nutrient solution. A mixed culture of toluene degraders was developed from a municipal wastewater mixed liquor sample. Batch experiments were performed to determine whether the culture could cometabolize TCE, the toluene degradation rate kinetics and the extent of toluene and TCE inhibition. In batch experiments, TCE was cometabolized only after toluene was degraded. No inhibition or injury to the toluene degrading ability was observed at up to 15 mg/L toluene or up to 1.5 mg/L TCE. The culture was inoculated into the hollow-fiber membrane bioreactor. Initially toluene was supplied to the reactor at a concentration of 200 ppm to build a sufficient biomass density on the fibers. After steady-state toluene removal was achieved, a toluene-TCE mixture was added to the reactor. This paper investigates if addition of toluene to the reactor in gas or liquid phase is more favorable for cometabolism, the use of a pulsing strategy, and the benefits of including a simple biomass removal method.
- Research Organization:
- Univ. of Massachusetts, Amherst, MA (US)
- OSTI ID:
- 20002190
- Report Number(s):
- CONF-990608--
- Country of Publication:
- United States
- Language:
- English
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