The present paper evaluates the technical and economical feasibility of converting wet chemical scrubbers to biotrickling filters for H2S control at the Orange County Sanitation District (OCSD), California. Results of 8 months of continuous operation of a biotrickling filter treating 16,000 m3 h-1 of foul air are analyzed. The reactor was operated at a gas contact time of 1.6 to 2.2 seconds reaching H2S elimination capacities up to 105-110 g H2S m-3 h-1, consistently maintaining outlet concentrations well below the regulatory limits (24 h average of 1 ppmv) and demonstrating to be very robust against temporary changes. Also, a cost-benefit analysis of the conversion was performed. Savings from chemicals, energy and water usage compared to a chemical scrubber operated in parallel to the biotrickling filter throughout the project indicated that the payback time of the conversion was about 1.3 years. Cost savings ranged between US$ 40,000 per year, per scrubber. While the above number may be specific to OCSD conditions, the cost analysis suggests that there is a significant benefit of converting chemical scrubbers to biotrickling filters over a wide range of operating conditions.

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