Retrofitted biotrickling filters for odor, VOC, H 2 S and reduced sulfur compound emission control
This paper evaluates treatment of odorous compounds (hydrogen sulfide, reduced sulfur compounds, VOCs, ammonia, and total odor) in wet chemical scrubbers that were converted to biotrickling filters at the Orange County Sanitation District (OCSD), California. Results of over two years of continuous operation in five biotrickling filters are discussed. The biotrickling filters were usually operated at a gas contact time of 1.6 to 2.2 seconds (nominal gas contact time) or up to 10 seconds during specific experiments with various effects on odor removal. In all cases outlet concentrations of sulfur compounds (calculated as H 2S) were well below the emissions permit limits (24 h average of 1 ppm) while total odor exhaust concentrations depended on the particular biotrickling filter. The biotrickling filters were resilient to temporary changes in inlet gas composition, including a highly-fluctuated hydrogen sulfide concentration. Overall, the study results indicate that there is a significant benefit in converting chemical scrubbers to biotrickling filters for odor control. Improvement of the odor removal performance should focus on the treatment of residual total odor which, in many but not all cases, is believed to originate from trace reduced sulfur and organic compounds.
