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Microbial Fuel Cells for Sulfide Removal

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journal contribution
posted on 01.09.2006 by Korneel Rabaey, Kirsten Van de Sompel, Lois Maignien, Nico Boon, Peter Aelterman, Peter Clauwaert, Liesje De Schamphelaire, Hai The Pham, Jan Vermeulen, Marc Verhaege, Piet Lens, Willy Verstraete
Thus far, microbial fuel cells (MFCs) have been used to convert carbon-based substrates to electricity. However, sulfur compounds are ubiquitously present in organic waste and wastewater. In this study, a MFC with a hexacyanoferrate cathodic electrolyte was used to convert dissolved sulfide to elemental sulfur. Two types of MFCs were used, a square type closed to the air and a tubular type in which the cathode compartment was open to the air. The square-type MFCs demonstrated a potential-dependent conversion of sulfide to sulfur. In the tubular system, up to 514 mg sulfide L-1 net anodic compartment (NAC) day-1 (241 mg L-1 day-1 total anodic compartment, TAC) was removed. The sulfide oxidation in the anodic compartment resulted in electricity generation with power outputs up to 101 mW L-1 NAC (47 W m-3 TAC). Microbial fuel cells were coupled to an anaerobic upflow anaerobic sludge blanket reactor, providing total removals of up to 98% and 46% of the sulfide and acetate, respectively. The MFCs were capable of simultaneously removing sulfate via sulfide. This demonstrates that digester effluents can be polished by a MFC for both residual carbon and sulfur compounds. The recovery of electrons from sulfides implies a recovery of energy otherwise lost in the methane digester.