AbstractA literature study was conducted to compare the feasibility of biofilters and biotrickling filters for the treatment of complex odorous waste air containing hydrogen sulfide (H2S), organic reduced sulfur compounds, and chlorinated and nonchlorinated volatile organic compounds (VOCs). About 40 pilot‐plant studies and full‐scale applications at wastewater treatment plants and other facilities were reviewed. Reactor design and pollutant removal efficiencies were summarized in tables for easy reference and for a perspective on the current state of the art, and to allow comparison between different projects. The survey indicated that both biofilters and biotrickling filters are capable of combining a high H2S and odor removal efficiency with VOC removal. Apart from odor abatement, biological treatment therefore holds promise for reducing the overall toxicity and potential carcinogenicity of VOC‐containing odorous waste air from wastewater treatment plants and other facilities. VOC removal efficiencies were in general lower than those of H2S and odor, although concentrations of individual VOC species were relatively low. This indicates that for effective treatment of VOC‐containing odorous waste air, the design and operation should emphasize VOC removal as the rate‐limiting parameter. © 2005 American Institute of Chemical Engineers Environ Prog, 2005