Effect of gas pressure and ammonium loading on nitrication in O2 - based membrane biofilm reactor

Effect of Gas Pressure And Ammonium Loading on Nitrication in O2 ? Based Membrane Biofilm ReactorDischarge of high nitrogen loading to rivers and lakes causes a severe reduction in water quality due to the excess algae growth. Biological nitrogen removal processes(BNR) has advantages due to its lower cost. BNR take places basically at two steps. First step is nitrification including oxidation of ammonium to nitrite and nitrate. Second step is also denitrification process including reduction of oxidized nitrogen to nitrogen gas. In the BOD oxidation/Nitrification process, the competition between heterotrophic and autotrophic bacteria affects adverse nitrifies because the specific growth rate for autotrophic bacteria is lower than that for heterotrophic bacteria. For beter nitrogen removal, nitrification process prior to denitrification is required to be performed successfully.Providing that hydrophobic gas transfer membranes were used as a biofilm supporting material, the gas (oxygen) as electron acceptor is utilized completely by microorganisms because it reached to biofilm with bubble-less gas diffusion in the membran biofilm reactor (MBfR). In this study, nitrification process was investigated on detailed under different oxygen pressures and ammonium loadings. For this purpose, the oxygen pressure was gradually decreased from 6 to 0.5 psi after biofilm formed in the system. The hidrolic retention time was also varied in the range of 1.0-7.5 h. at the O2 pressure of 0.5 psi, the hydrolic retentaion time was found to be 2.5 h. A complete nitrification occured in the case of 4.4 g N/m2-d. In this case, nitrification rate and oxygen flux were 3.98 g N/m2-d and 9.2 g O2/m2-d, respectively. In addition, the microbial ecology was defined using PCR-DGGE technique.Key words: Membrane Biofilm Reactor, Nitrification, Microbial Ecology