title: Sulfide oxidation at halo-alkaline conditions in a fed-batch bioreactor.
abstract: A biotechnological process is described to remove hydrogen sulfide (H(2)S) from high-pressure natural gas and sour gases produced in the petrochemical industry. The process operates at halo-alkaline conditions and combines an aerobic sulfide-oxidizing reactor with an anaerobic sulfate (SO(4) (2-)) and thiosulfate (S(2)O(3) (2-)) reducing reactor. The feasibility of biological H(2)S oxidation at pH around 10 and total sodium concentration of 2 mol L(-1) was studied in gas-lift bioreactors, using halo-alkaliphilic sulfur-oxidizing bacteria (HA-SOB). Reactor operation at different oxygen to sulfide (O(2):H(2)S) supply ratios resulted in a stable low redox potential that was directly related with the polysulfide (S(x) (2-)) and total sulfide concentration in the bioreactor. Selectivity for SO(4) (2-) formation decreased with increasing S(x) (2-) and total sulfide concentrations. At total sulfide concentrations above 0.25 mmol L(-1), selectivity for SO(4) (2-) formation approached zero and the end products of H(2)S oxidation were elemental sulfur (S(0)) and S(2)O(3) (2-). Maximum selectivity for S(0) formation (83.3+/-0.7%) during stable reactor operation was obtained at a molar O(2):H(2)S supply ratio of 0.65. Under these conditions, intermediary S(x) (2-) plays a major role in the process. Instead of dissolved sulfide (HS(-)), S(x) (2-) seemed to be the most important electron donor for HA-SOB under S(0) producing conditions. In addition, abiotic oxidation of S(x) (2-) was the main cause of undesirable formation of S(2)O(3) (2-). The observed biomass growth yield under SO(4) (2-) producing conditions was 0.86 g N mol(-1) H(2)S. When selectivity for SO(4) (2-) formation was below 5%, almost no biomass growth was observed.
authors.affiliation: Sub-Department of Environmental Technology, Wageningen University, Bomenweg 2, 6700 EV Wageningen, The Netherlands.
authors.forename: Pim L F
authors.initials: PL
authors.lastname: van den Bosch
authors.forename: Otto C
authors.initials: OC
authors.lastname: van Beusekom
authors.forename: Cees J N
authors.initials: CJ
authors.lastname: Buisman
authors.forename: Albert J H
authors.initials: AJ
authors.lastname: Janssen
mesh_terms: D000393:Air Pollutants / Q000378:metabolism*; D001673:Biodegradation, Environmental; D019149:Bioreactors / Q000382:microbiology*; D003198:Computer Simulation; D005740:Gases / Q000378:metabolism; D006862:Hydrogen Sulfide / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008954:Models, Biological; D010084:Oxidation-Reduction; D020560:Proteobacteria / Q000378:metabolism*
chemical_list: D000393:Air Pollutants; D005740:Gases; D006862:Hydrogen Sulfide