Microbially Catalysed Selenate Removal in an Inverse Fluidised Bed Reactor
Selenate removal from mine waters is required to mitigate human and environmental health impacts. In this study, the performance of an inverse fluidised bed reactor (IFBR) for the biological removal of selenate from synthetic mine water (pH 6.0-7.0) was evaluated. A laboratory-scale IFBR was set up with floating biomass carriers. Selenate reducers were enriched from environmental samples and anaerobic sludge. The synthetic medium contained ~10 mM (~1.4 g L-1) selenate, nutrients and 10 mM ethanol as electron donor. During stable performance the bioreactor achieved 94 % removal of selenate representing a removal rate of 251 mg L-1 d-1 at a hydraulic retention time of 5 d. Selenite concentration remained < 1 mg L-1 during stable performance, and the formation of a red precipitate indicated that selenate was reduced to elemental selenium. The biological selenate reduction generated alkalinity, increasing the wastewater pH from 6.0 to 8.6. The redox potential gradually approached a value ranging from -300 mV to -400 mV against standard hydrogen electrode. Overall, the results showed that the IFBR can be used for removing selenate and acidity from mine waters. Moreover, it has potential to facilitate recovery of elemental selenium. Therefore, the bioprocess provides an opportunity to reduce the costs and liabilities associated with selenium containing mine drainage and the associated environmental impacts.
Sabrina Hedrich, Kathrin Rübberdt, Franz Glombitza, Wolfgang Sand, Axel Schippers, Mario Vera Véliz and Sabine Willscher
K. Y. Cheng et al., "Microbially Catalysed Selenate Removal in an Inverse Fluidised Bed Reactor", Solid State Phenomena, Vol. 262, pp. 677-681, 2017