Long term performance of an AMD treatment bioreactor using chemolithoautotrophic sulfate reduction and ferrous iron precipitation under in situ groundwater conditions

► A bench scale reactor for autotrophic sulfate reduction was operated at 10 °C for 3.5 years without biomass replenishment. ► The process showed long term stability and the rate of sulfate reduction was biomass limited. ► Process conditions are controlled by adjusting gas partial pressures. ► Electron turn over was dominated by sulfate reduction at c(SO4) > 2 mM. ► Technical in situ reactors are applicable to reduce the sulfate and eliminate iron loads from groundwaters.