Fluidized bed membrane bioreactor achieves high sulfate reduction and filtration performances at moderate temperatures

Abstract

The study explored the potential of an up-flow sulfate reducing fluidized-bed membrane bioreactor (SR-FMBR) for biogenic sulfide generation at room temperature together with evaluation of filtration and fouling characteristics developed under various operational conditions. The SR-FMBR was tested at different COD/sulfate (mg/mg) ratios for a total of 127 days, initially at 35 degrees C and then at 23 degrees C. SR-FMBR was able to achieve COD oxidation and sulfate reduction efficiencies up to 98%, and allowed for biogenic sulfide generation up to 600 mg/L (97% of theoretical value) at room temperature. Alkalinity was generated as a result of sulfate reduction and averaged around 1900 mgCaCO(3)/L in the permeate. Hence, starting the bioreactor operation at 35 degrees C and then decreasing it to 23 degrees C did not adversely affect the process performance. High filtration fluxes up to 9.3 L/m(2)/h (LMH) could be maintained at employed hydraulic retention times between 24 h and 6 h. Observing relatively high filtration performance was due to keeping a high fraction of biomass attached to the carrier material, which decreased the cake formation potential on the membrane surface compared to conventional MBR operation. The SR-FMBR performance may further be tested for heavy metal removal under sulfidogenic conditions for acid mine drainage treatment. (C) 2020 Elsevier Ltd. All rights reserved.