Sorption and biodegradation of vapor-phase organic compounds with wastewater sludge and food waste compost

To test the possible use of composted food waste and wastewater sludge as b iofilters to treat gas-phase volatile organic compounds (VOCs), batch exper iments were conducted with an isolated strain that could degrade aromatic c ompounds under aerobic conditions. A benzene and trichloroethylene (TCE) mi xture was used as the gas-phase pollutant in experiments with composted foo d waste, sludge, and soil. Under aerobic conditions, benzene was degraded a s a primary substrate and TCE was degraded cometabolically, with water cont ents varying from 6 to 60% (volume of water added/volume of solid). Optimal water content for VOC removal was 12% for the soil, 36% for the composted food waste, and 48% for the sludge. The extent of VOC sorption and biodegradation at the optimal water content was different for each material. With the same initial VOC concentration, m ore VOCs were removed by sorption onto the composted food waste and the slu dge, while less VOCs were biodegraded in comparison with the results using soil. The reason the biodegradation in the soil was greater may be partly a ttributed to the fact that, due to less sorption, the aqueous-phase concent ration of VOCs, which microorganisms could utilize as a carbon source or co metabolize, was higher. We also speculate that the distribution of microorg anisms in each medium affects the rate of biodegradation. A large number of microorganisms were attached to the composted food waste and sludge. Mass transfer of VOCs and oxygen to these microorganisms, which appear to have b een heterogeneously distributed in clusters, may have been limited, resulti ng in hindered biodegradation.