Modeling Of Biological Nitrogen Removal Process In Biological Aerated Filter

With the economic development,environmental issues such as water contamination and greenhouse effects has become the major concern of people.Excessive nutrients made of different forms of nitrogen and phosphorus in water may result in eutrophication and threaten the ecological balance.Thus,the nitrogen and phosphorus removal has been defined as the one of the most important role of the wastewater treatment plants.Thanks to its high efficacy,biological nitrogen and phosphorus removal are widely used in wastewater treatment industry.Thus,investigation of the nitrogen removal process in Biological Aeration Filter?BAF?by modelling its mechanism,in order to predicte the evolution of the nitrogen concentration distribution with distance and the nitrogen concentration in effluent,which is relevant to the academic research.This research investigated the nitrogen removal process in a BAF reactor by setting up the model of a multiple-step nitrification and denitrification process applying to biological membrane reactor.Simulation,calibration and validation of the model have been conducted by a numerical analysis software——AQUASIM.A conventional two-step nitrification-denitrification model was extended to a multiple-stelp model by intergrating the Nitrous Oxide?N₂O?production process.Based on the reaction mechanism the stoichiometric relationship and the reaction kinetics of each reaction were discussed for determination of the appropriate parameter intervals and the matrix reaction equation.The nitrogen concentration distribution with the distance under the operating condition A?DO:4 mg/L,HRT:6 h,COD/TN:5:1?was simulated and calibrated in AQUASIM.The result shows that simulation of NH₄⁺,COD,NO₃^-,NO₂^-is highly consistent with the trend of the measured values.In addition,the N₂O concentration simulation almost equals the measured values.Two different operating conditions were conducted for the validation of the model with condition B?DO:4 mg/L,HRT:6 h,COD/TN:2:1?and condition C?DO:4 mg/L,HRT:6 h,COD/TN:8:1?.Simulation results under condition B have a good compliance with the trend of measured value,except for the results of NO₂^-,which deviate from the measured value,while simulation results under condition C are all comply to the trend of the measured values.The model developed in this research can have effective simulation of concentration evalution of the substances and the mechanism of the removal of nitrogen in BAF reactor.This major success would contribute to the more environmentally friendly operation of the biological membrane wastewater treatment facilities.