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 (PH2 = 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.