Sediment microbial fuel cells reduce sulfide production in marine sediments

Sulfate-reducing bacteria proliferating in anoxic marine sediments can lead to release of toxic hydrogen sulfide (H2S) due to absence of dissolved oxygen in the bottom water. Sudden H₂S fluxes from the sediment can be devastating to marine life. H₂S is oxidized both biotically and abiotically, and here we show that emplacement of sediment microbial fuel cells (SMFCs) can reduce H₂S formation in anoxic sediments. In this study, part of the project “Remediating marine dead zones by enhancing microbial sulfide oxidation using electrodes”, we investigated two different SMFC configurations’ ability to reduce the formation of H₂S in anoxic marine sediment in laboratory two-cell reactors:

i. stainless steel anode emplaced in the sediment
ii. carbon brush anode positioned on the sediment surface
Cathodes were placed in the oxic catholyte. Sediment and water from Roskilde Fjord were used. Data showed that both electrode configurations strongly reduced sulfide in the water phase. Additionally, disconnecting the closed-circuit reactors (CC→OC) rapidly lead to accumulation of H₂S, and similarly, connecting the open-circuit reactors (OC→CC) resulted in reduction of H₂S. SEM imaging and EDX analyses furthermore revealed deposition of S on the carbon brushes. Next step will be in situ emplacement in Roskilde Fjord.