Effect of Dissolved Oxygen on Hydrogenotrophic Denitrification in Membrane Biofilm Reactors

摘要

Hydrogenotrophic denitrification requires inorganic carbon as a carbon source, and hydrogen as electron donor. Hydrogenotrophic denitrification within a membrane biofilm reactor has operational advantages such as low biomass production and efficient use of hydrogen gas. Dissolved oxygen (DO) is known to hamper heterotrophic denitrification, while the effect of dissolved oxygen on hydrogenotrophic denitrification is controversial according to previous studies. The effect of oxygen on hydrogenotrophic denitrification in MBfRs with hydrogen supplied through diffusion from the membrane fibers was investigated. Two separate membrane biofilm reactor systems for consecutive nitrification-denitrification and one for separate denitrification were operated under various DO conditions. Consecutive nitrification and denitrification membrane biofilm reactors were operated for 55 d without dissolved oxygen control followed by 30 days with dissolved oxygen control. Average dissolved oxygen concentrations inside the denitrification reactor before and after DO control were 1.0 mg O_2/L and 0.2 mg O_2/L, respectively. Specific denitrification rates (SDNR) before and after DO control was 1.46 g N/m~2d and 1.47 g N/m~2d, respectively. This suggested that the effect of DO on hydrogenotrophic denitrification was negligible in consecutive nitrification and denitrification systems. A wider range of DO (reactor levels from 0 to 4.9 mg O_2/L) was tested in the stand-alone denitrification reactor. No noticeable difference of SDNR between various DO levels could be found. It was concluded that hydrogenotrophic denitrification within an MBfR was not affected by the presence of dissolved oxygen in the bulk liquid.