Environmental Science Water Research & Technology PAPER Cite this: Environ. Sci.: Water Res. Technol., 2018, 4, 1190 Received 13th April 2018, Accepted 26th June 2018 DOI: 10.1039/c8ew00232k rsc.li/es-water Microaeration through a biomembrane for biogas desulfurization: lab-scale and pilot-scale experiences Lucie Pokorna-Krayzelova, * ab Jan Bartacek, a Shelmith Nyawira Theuri, a Camilo Andres Segura Gonzalez, a Jindrich Prochazka, d Eveline I. P. Volcke bc and Pavel Jenicek a Microaeration, a biological method to remove H 2 S from biogas by oxidizing it to elemental sulfur, has been shown to be highly efficient, simple and reliable. However, dosing air directly into an anaerobic fermenter results in the dilution of biogas with nitrogen and oxygen and can cause clogging of biogas pipes by ele- mental sulfur. These disadvantages can be overcome by the use of a biomembrane, i.e. a membrane cov- ered with a biofilm that separates air and biogas. Experiments with bare, wet and biofilm membranes were conducted with a commercially available PVDF LM-P2 membrane to evaluate the chemical and biological oxidation rates of H 2 S. Different amounts of air were dosed through the biomembrane to determine the optimum air-to-biogas ratio, to evaluate methane losses and to evaluate biogas contamination with nitro- gen and oxygen. The H 2 S content decreased from 3000 ppm to less than 100 ppm within two days. The loss of methane was 3.7% of the total methane production and the specific H 2 S removal rate was 32 mg m -2 d -1 . 1. Introduction During the anaerobic treatment of wastewater with high sulfate concentrations, sulfate-reducing bacteria produce a high amount of hydrogen sulfide, 1,2 which causes major technologi- cal problems such as inhibition of anaerobic processes, corro- sion of tanks, piping, engines and boilers, and emission of sul- fur dioxide from biogas combustion. 3 Because of these negative effects, hydrogen sulfide has to be removed from biogas. The available methods for desulfurization are physico- chemical (e.g. absorption, precipitation) or biological (e.g. biochemical oxidation of sulfide) methods. 4,5 Biological pro- cesses are often simpler and more cost-effective compared to physico-chemical methods. 3 One of the options for biological H 2 S removal from biogas, which has been used on a full- scale, 6 is microaeration, i.e. the controlled dosing of a small amount of air into an anaerobic reactor. 7–9 In microaeration, sulfide is oxidized to elemental sulfur by sulfide-oxidizing bacteria, at low oxygen concentrations. The elemental sulfur produced is insoluble and could be possibly removed from the system. Both the total concentration of sulfide in the ef- fluent and the concentration of hydrogen sulfide in biogas can be significantly decreased with this process. 10 The possible drawbacks of microaeration are the dilution of biogas with nitrogen and little or no control over the exact location where elemental sulfur is deposited. Elemental sul- fur usually accumulates on the walls in the reactor head- space 11 or in the liquid effluent. 12 However, sulfur could also accumulate in the three-phase separators of anaerobic high- rate bioreactors or in gas pipes, which may cause serious clogging problems. These problems could be overcome by using a biomembrane, where air needed for microaeration is 1190 | Environ. Sci.: Water Res. Technol., 2018, 4, 1190–1200 This journal is © The Royal Society of Chemistry 2018 a Department of Water Technology and Environmental Engineering, University of Chemistry and Technology Prague, Technicka 5, 166 28 Prague 6, Czech Republic. E-mail: lucie.krayzelova@vscht.cz; Tel: +420 220 443 143 b Department of Biosystems Engineering, Ghent University, Coupure Links 653, 9000 Gent, Belgium c Department of Green Chemistry and Technology, Ghent University, Coupure Links 653, 9000 Gent, Belgium d FARMTEC a.s, Tisová 326, 391 33 Jistebnice, Czech Republic Water impact A pilot-scale biomembrane unit for the microaerobic removal of H 2 S from biogas has been successfully tested. Over 99% of H 2 S was chemically and bio- chemically removed from biogas thus significantly improving its quality. Better biogas quality leads to important money savings for the wastewater treat- ment process. Published on 02 July 2018. Downloaded by Ghent University Library on 10/12/2018 8:45:48 AM. View Article Online View Journal | View Issue