Odor and Voc Removal from Wastewater Treatment Plant Headworks Ventilation Air Using a Biofilter

Laboratory scale experiments and field studies were performed to evaluate the feasibility of biofilters for sequential removal of H2S and VOCs from wastewater treatment plant waste air. The biofilter was designed for spatially separated removal of pollutants in order to mitigate effects of acid production resulting from H2S oxidation. The inlet section of the upflow units was designated for H2S removal and the second section was designated for VOC removal. Complete removal of H2S and methyl tert-butylether (MTBE) was accomplished at loading rates of 8.3 g H2S/m⋅h (15 second EBRT) and 33 g MTBE/m⋅h (60 second EBRT) respectively. In field studies performed at the City of Los Angeles' Hyperion Treatment Plant, excellent removal of H2S, moderate removal of non-chlorinated VOCs such as toluene and benzene, and poor removal of chlorinated VOCs were observed in treating the headworks waste air. During spiking experiments on the headworks waste air, the percentage removals were similar to the unspiked removals when non-chlorinated VOCs were spiked, but feeding high concentrations of chlorinated VOCS reduced the removal percentages for all VOCs. Thus, biofilters offer a distinctive advantage over chemical scrubbers currently employed at publicly owned treatment works in that they not only remove odor and H2S efficiently at low cost, but also reduce overall toxicity by partially removing VOCs and avoid the use of hazardous chemicals.