Removal of Low Concentrations of Carbon Tetrachloride in Compost-Based Biofilters Operated under Methanogenic Conditions

Abstract

Research was performed to demonstrate the removal of carbon tetrachloride (CT) using compost biofilters operated under methanogenic conditions. Biofilters were operated at an empty-bed residence time of 2.8 minutes using nitrogen as the atmosphere. Hydrogen and carbon dioxide were supplied as an electron donor and carbon source, respectively, during acclimation of the bed medium microbes. Once methanogenesis was demonstrated, CT flow to the biofilter was established. Biofilters were operated over a CT concentration range from 20 to 700 ppbv for 6 months. Bed medium microbes were able to remove up to 75% of the inlet CT. At excessively high CT concentrations (>500 ppmv), methane production and hydrogen utilization by the bed medium microbes appeared to be inhibited. CT removal by the biofilter decreased when the hydrogen supply was removed from the biofilter inlet, indicating that hydrogen acted as the IMPLICATIONS Several emission sources, such as soil vapor extraction (SVE) systems, contain chlorinated solvents, such as carbon tetrachloride or perchloroethylene, that are not biodegradable under the aerobic conditions typically utilized for biofiltration. Anaerobic biofilters developed at the Idaho National Engineering and Environmental Laboratory have capitalized on the simplicity of compost biofilters coupled with the large amount of information that has been generated related to anaerobic bioremediation of recalcitrant chlorinated solvents in groundwater. Biofilters operated under anaerobic conditions using hydrogen as an electron donor and carbon dioxide as the carbon source and electron acceptor represent a feasible technology for treatment of off-gas streams containing chlorinated solvents such as CT. Bed medium microbes within the biofilter transformed the contaminant by reduction rather than oxidation. Microbes operated under these conditions could be useful for treating chlorinated-solvent-laden offgas streams from SVE as well as industrial off-gases created during degreasing and cleaning operations.electron donor for reductive dechlorination. The removal efficiency and relatively low empty bed residence times demonstrated by these laboratory-scale biofilters indicate that anaerobic biofiltration of CT may be a feasible full-scale process. INTRODUCTIONThe U.S. chemical industry produces about 20 million tons of chlorinated aliphatic hydrocarbons annually.

Elimination of chlorobenzene vapors from air in a compost‐based biofilter

“…Inoculation of this biofilter was effected with anaerobic sewage sludge, and several weeks of acclimatization were observed. The removal of CT has been reported by Lee et al,15 in anaerobic biofilters operated either in the presence of methanol (primary substrate and electron donor), or in methanogenic conditions with hydrogen and carbon dioxide as the carbon and electron donors. The degrading populations were enriched from species indigenous to the compost beds, and several weeks were needed to acclimatize the microflora.…”

Estudio sobre la operación y modelado de un biofiltro para la eliminación de vapores de tolueno

“…De esta manera, si se dispone de una planta de tratamiento de aguas, es posible instalar únicamente un contactador gas-líquido y pasar la corriente líquida contaminada a la planta de tratamiento de aguas a fin de que los compuestos contaminantes sean degradados. Se han presentado estudios que muestran y comparan la operación de los biofiltros y los filtros de escurrimiento (Torres y Basrai 1998;Lee et al, 1998). En ambos casos, se obtuvo una mejor operación en los biofiltros, sin embargo son casos específicos.…”