Cr(Ⅵ) Reduction from Groundwater by Hydrogenbased Membrane Biofilm Reactor

Abstract:

The hydrogenbased membrane biofilm reactor (MBfR) was used for biodegradation of Cr(Ⅵ) in groundwater.The autohydrogentrophic bacteria on the surface of membrane used hydrogen as electron donor to reduce Cr(Ⅵ) to Cr(Ⅲ).Then Cr(Ⅲ) was removed by sedimentation and filtration.The acclimatization was achieved by culturing the biofilm,altering the Cr(Ⅵ)concentration in influent and the supplied hydrogen pressure.After 120 days ,the Cr(Ⅵ) and NO-3N removal rate was 83% and 99%,respectively.Series experiments of 3 influence factors,such as H2 pressure,NO-3N loading and pH value were conducted.The results show that lowering the NO-3N loading and increasing the H2 pressure can increase the extent of Cr(Ⅵ) reduction.The Cr(Ⅵ) reduction is also sensitive to pH value,with the optimum pH value of 7.0(removal rate near 78.2%).If the pH value is above 8.0 or below 7.0,the removal rate will significantly decline.The research reveals that the MBfR can be effective for removing Cr(Ⅵ) or coexisting of NO-3N and Cr(Ⅵ) in groundwater,and critical operational parameters including the H2 pressure,NO-3N loading and pH value.