Research Projects

Project at a Glance

Title: Biodegradation technology for volatile organic compound removal from airstreams. Phase I: Performance verification

Principal Investigator / Author(s): Ergas, Sarina J

Contractor: Center for Environmental Water Resources Engineering, UC Davis

Contract Number: A032-127


Research Program Area: Emissions Monitoring & Control

Topic Areas: Stationary Sources


Abstract:

This report presents the results of laboratory and field studies designed to verify the potential application of microbial packed bed systems generally known as "biofilters," for the removal of volatile organic compounds (VOCs) from off-gases resulting from wastewater treatment. Volatile organic compounds are known to be emitted in significant quantities from many wastewater treatment plants and landfills, as well as various industrial operations. Wastewater treatment plant off-gases are characterized by the diversity and the relatively low concentrations of the compounds present. Six target compounds, benzene, toluene, chloroform, dichloromethane, trichloroethene, and tetrachloroethene were selected for particular emphasis in this study. However, other compounds were monitored during the field segment of the study , including hydrogen sulfide, oxylene and total VOCs. The target compounds were generally present at levels less than 1 ppmv and many are present at concentrations below 100 ppbv. Biofilters are packed beds that utilize microbial cultures growing on the packing medium to oxidize VOCs and other degradable compounds in an air stream. The packing medium used in these studies was a mixture of sewage sludge derived compost, wood products, and perlite. Oyster shell was added as a buffering material to control pH. Moisture content of the medium was maintained at greater than 507c by weight throughout the experiments. Gas fluxes used are typically in the range of 1 to 7 ft/min. which was the range used in these studies. The objectives of the project were (1) to determine the potential of aerobic biofiltration as a method of removing VOC's from gas streams at POTWs and (21 to determine the extent of degradation and potential by-products of six selected compounds (benzene,chloroform, dichloromethane toluene, tetrachloroethene, and trichloroethene) in a microbial gas cleaning process. In the laboratory experiments, the removal of toluene and benzene was above 80.8 and the removals of the chlorinated VOCs were generally less than 50%. However, there seemed to be an improvement with time in the laboratory work. In the field excellent removals of benzene, toluene, and hydrogen sulfide were observed, with values generally over 90%. Removals of the chlorinated compounds were varied and generally below 40% of the inlet concentrations. The reasons for the limited removals of chlorinated VOCs are not clear. Possible factors include mass transfer limitations and problems in generating cometabolism.


 

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