Abstract

The paper presents aspects related to the performance of an anoxic biotrickling filter designed for hydrogen sulphide (H2S) removal from biogas. In this process, nitrate was supplied through a nutrient solution as an electron acceptor for anoxic growth of H2S-oxydizing microorganisms. The biotrickling filter's packing media consisted of a layer of plastic fibres over volcanic rocks in a ratio 0.78:1 by volume. The total volume of packing media was 0.014 m3. Several H2S loading rates (IL) were tested under continuous dynamic conditions, ranging between 20 and 550 g of H2S feed/(m3bed·day). Maximum process performance (>95%) was observed for IL ranging up to approximately 300 g of H2S feed/(m3bed·day). The degradation of hydrogen sulphide occurred with the formation of both sulphate and elemental sulphur, their formation ratio being dependent on H2S loading rate. Elemental sulphur was found to be the dominant degradation product, particularly at IL > 96.18 g of H2S feed/(m3bed·day). The use of two biotrickling filters in series was also tested, and a significant improvement in process performance was observed. This technology allows simple operation with low maintenance and has the potential for sulphur recovery.

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