OperationofBiofilterwithMixedAgriculturalResidueasFilterMaterial: EffectsofHumidificationandInletHydrogenSulfideVolumefraction onthePerformance

Mixed agricultural residue, inoculated with aerobic sulfide oxidizing microbial consortium, was used as biofilter media to study the removal efficiency (,R) of hydrogen sulfide (H2S). The effect of humidification and inlet H2S volume fraction on the performance of biofilter was also investigated. A 3.9 l bench scale biofilter was continuously operated to treat air containing H2S gas in the range of = 275 to 2833 · 10 –6 for 150 days. ,R of 99 % was obtained at = 2020 · 10 –6 of inlet H2S volume fraction during continuous operation with humidification. However, ,R dropped to 51 % when the inlet H2S fraction increased beyond = 2020 · 10 –6. A maximum elimination productivity of 91 g m–3 H2S of filter bed h -1 and inlet mass loading rate of 91 g m-3 H2S of filter bed h -1 was achieved when the tEBRT was in the range of 15 – 155 s. The filter was operated without the humidifier at the inlet H2S fraction of = 2020 · 10 –6 and observed that ,R dropped to 51 % due to the drop in moisture of the filter material. However, ,R could be recovered up to 83 % upon reintroduction of humidifier into the circuit of biofiltration process indicating, that humidification of the waste gas was essential to achieve the highest possible ,R at particular inlet H2S fraction. The filter recorded ,R above 99 % even in the acidic phase at = 2020 ·10–6 of inlet H2S fraction without intermittent washing. The gas dispersion characteristics were comparable to the previously tested bed materials, offering low-pressure drop across the biofilter in the range of 21 – 74 mm of H2O per meter height of packing material.