Sulfate-reducing bacteria in a biofilm sediment related to underground hydrogen storage

Deep saline aquifers are considered feasible geological formations for a large-scale underground hydrogen storage (UHS). Sulfate-reducing bacteria (SRB) contained in the formation groundwater of sedimentary rock formations (e.g. limestone and sandstone) may use aqueous H₂ to reduce sulfate to dissolved sulfide. The occurrence of this reaction can change the amount of the stored H₂.

Two batch experiments filled with a biofilm-sediment from the La Muerte endorheic lagoon (Spain) were used to elucidate the capacity of SRB communities to oxidize H₂ and reduce sulfate. Under H₂-free conditions, the SRB contained in La Muerte biofilm-sediment could not reduce sulfate, indicating that the organic matter contained in the sediment could not trigger the reaction. In contrast, as SRB contained in the biofilm-sediment were in contact with aqueous hydrogen (P_H2 = 2 bar and 30 °C), sulfate reduced to sulfide.

Numerical reproduction of the temporal variation in pH and concentrations of sulfate and dissolved sulfide in the H₂-rich solution by means of geochemical modelling enabled us to calculate the bio-kinetic coefficients used in the implemented Monod kinetics rate laws.