Abstract
Organosulfur compounds, present in e.g. the pulp and paper industry, biogas and natural gas, need to be removed as they potentially affect human health and harm the environment. The treatment of organosulfur compounds is a challenge, as an economically feasible technology is lacking. In this study, we demonstrate that organosulfur compounds can be degraded to sulfide in bioelectrochemical systems (BESs). Methanethiol, ethanethiol, propanethiol and dimethyl disulfide were supplied separately to the biocathodes of BESs, which were controlled at a constant current density of 2 A/m2 and 4 A/m2. The decrease of methanethiol in the gas phase was correlated to the increase of dissolved sulfide in the liquid phase. A sulfur recovery, as sulfide, of 64% was found over 5 days with an addition of 0.1 mM methanethiol. Sulfur recoveries over 22 days with a total organosulfur compound addition of 1.85 mM were 18% for methanethiol and ethanethiol, 17% for propanethiol and 22% for dimethyl disulfide. No sulfide was formed in electrochemical nor biological control experiments, demonstrating that both current and microorganisms are required for the conversion of organosulfur compounds. This new application of BES for degradation of organosulfur components may unlock alternative strategies for the abatement of anthropogenic organosulfur emissions.
Highlights
Organosulfur compounds (OSCs) are naturally present in various environments, including oceans, marine estuaries, volcanos and salt marshes
We demonstrate that methanethiol, ethanethiol, propanethiol and dimethyl disulfide can be converted at biocathodes, and that degradation requires both microorganisms and electricity
The inocula were obtained from (1) a chain elongation reactor fed with high methanol concentrations (250 mM)(total nitrogen (TN) 1.47 g/L) [17],(2) a granular anaerobic reactor operating at a high salt concentration (20 g Na/L) [18] (TN 4.3 g/L), (3) a digester for municipal wastewater treatment sludge (Ede, The Netherlands) combined with anaerobic sludge treating wastewater from paper industry (Eerbeek, The Netherlands)(4.4 g/L TCOD), and (4) sulfide oxidizing biomass adapted to the presence of 0.5–2.5 mM dimethyl disulfide (TN 0.6 g/L) [19]
Summary
Organosulfur compounds (OSCs) are naturally present in various environments, including oceans, marine estuaries, volcanos and salt marshes. The state-of-the-art treatment strategy for conversion and removal of organosulfur compounds is the oxidation to insoluble disulfides. This process, known as the Merox process, is in many cases economically unfavorable due to complex processing schemes, high OPEX and CAPEX and low efficiencies [3]. Several studies report successful biological reduction of methanethiol and dimethyl disulfide to methane and hydrogen sulfide by methylotrophic methanogens [5,6,7]. We demonstrate that methanethiol, ethanethiol, propanethiol and dimethyl disulfide can be converted at biocathodes, and that degradation requires both microorganisms and electricity
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