Total Nitrogen Removal in a Completely Mixed Membrane Biofilm Reactor for Nitrification and Denitrification
نویسنده
چکیده
A Hollow-fiber Membrane Biofilm Reactor (MBfR) was used to nitrify and denitrify synthetic wastewater to remove nitrogenous pollutants such as ammonium, nitrate, and nitrite. Aerobic and anoxic MBfRs were combined to oxidize and reduce these nitrogenous pollutions using biofilms as the catalyst for these chemical reactions. The MBfR is capable of converting ammonium (NH4) to nitrogen gas (N2), through a series of nitrification and denitrification reactions in a completely mixed environment. For these reactions to occur, oxygen gas must be supplied into the nitrifying reactor (NR) to oxidize the pollutants into nitrate (NO3). Hydrogen gas must be supplied to the denitrifying reactor (DR) to reduce the pollutants into N2 gas. Hydrogen is an excellent electron donor because it is inexpensive, nontoxic to humans and leaves no residual in the water. Hydrogen gas is normally a substantial safety hazard, but the hollow fiber membrane’s design eliminates the possibility of an explosion and thereby the danger. The aerobic/anoxic MBfR was tested to determine the nitrogen removal at several different O2 pressures while H2 pressure was held constant. The reactor was also tested at different H2 pressures while constant O2 pressure was maintained. The aerobic/anoxic MBfR was successful for nearly total nitrogen removal (97.1%) from the 50 mg NH4-N/l medium, which represents the typical nitrogen content of municipal wastewater. Total nitrogen removal was strongly influenced by the O2 pressure, in that low O2 pressure (1.25 psi) caused poor nitrification and high O2 pressure (6.0 psi) caused poor denitrification. Total nitrogen removal was slightly influenced by H2 pressure, although increasing the H2 pressures to 5.0 psi provided better denitrification. The optimal gas pressures for O2 and H2 gas were determined to be 2.1 psi and 2.0 psi respectively.
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