Technical and economical analysis of the conversion of a full-scale scrubber to a biotrickling filter for odour control

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 m(3) 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 ppm(v)) 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.