Simultaneous removal of H2S and NH3 from raw biogas in hollow fibre membrane bioreactors

H2S and NH(3 )are toxic, corrosive and odorous gases that often co-exist in gas streams emitted from industrial processes, including biogas produced in anaerobic digestion plants. A hollow fibre membrane bioreactor (HFMB) was tested for simultaneous biolog-ical removal of H2S and NH3 from raw biogas. The HFMB achieved a removal efficiency (RE) > 99% for treating up to 1850, 915 and 1200 ppmv of H2S at an empty bed residence time (EBRT) of 187, 92 and 46 s, respectively. The RE of NH3 was > 99% when the inlet NH3 concentrations were up to 460, 355 and 750 ppmv at an EBRT of 187, 92 and 46 s, respectively. At an EBRT of 46 s, the RE of H2S and NH3 was in the range of 85-97 and 73-95%, respectively, for inlet biogas laden with 1200- 1700 ppmv of H2S and 750-1050 ppmv of NH3. The critical loading rates of H2S and NH(3 )were about 150 and 40 g m(-3) h(-1), respectively. S0 (52%), SO2- 4 (48%) and N2 (92%) were the end products of the H2S and NH3 bioconversion. Different sulfide oxidizers including aerobic (e.g. Smithella sp., Sulfuricurvum sp. and Thiomonas sp.) and anoxic (e.g. Rhodanobacter sp., Sulfuritalea sp. and Thiobacillus sp.) chemolithotrophs contributed to the H2S bioconversion. Aerobic (e.g. Pseudomonas sp., Stenotrophomonas sp. and Nitrosospira sp.) and Fe(III) dependent anaerobic (e.g. Clostridium_sensu_stricto_12 sp., Rhodoferax sp. and Dechloromonas sp.) ammonium oxidizers contributed to the NH3 bioconversion. Denitrifiers including denitrifying phosphorus accumulating organisms (e.g Candidatus_Contendobacter sp.) contributed to the denitrification process. (C) 2022 The Author(s). Published by Elsevier B.V.