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In this study, biofiltration using a natural wood chip medium and a commercial biofiltration medium was evaluated for the removal of moderate concentrations of hydrogen sulfide (H[sub2]S) (up to 100 parts per million by volume [ppmv]) in the presence of significant concentrations of ammonia (NH[sub3]). These levels were chosen as representative of wastewater lift station emissions in the Brownsville, TX, area. NH[sub3]-removing portions of the biofilms may compete with H[sub2]S-removing portions and inhibit H[sub2]S removal. H[sub2]S process removal efficiencies for the commercial and natural media ranged from 90 to 96% depending on inlet loading and media type and bed height. Kinetic analysis of the H[sub2]S removal process followed apparent first-order reaction behavior. The average first-order reaction rates were 0.03 sec[sup-1] for the commercial medium and 0.09 sec[sup-1] for the natural medium. Pressure drops across the columns ranged from 0.41 in. H[sub2]O/ft for the commercial medium to 1.41 in. H[sub2]O/ft for the natural medium. NH[sub3] gas levels of up to 80 ppmv did not affect the H[sub2]S removal process efficiency, and calculated kinetic rate constants for H[sub2]S removal remained almost the same. The NH[sub3] gas also was removed simultaneously with the H[sub2]S up to 98% removal efficiency by the commercial medium. [ABSTRACT FROM AUTHOR]