Simulation of tertiary denitrification with methanol in an upflow biofilter

A biofilm model for the simulation of denitrification with methanol in a 3 m high upflow biofilter is presented. This model considers mass transfer at the bulk/biofilm interface, mass transport in the liquid phase of the biofilter and mass transport and substrate utilization in the biofilm. The biofilter was run with different filtration rates between 11 and 29 m/h. The methanol dosage ranged between 2.6 and 3.8 g CH₃OH/g NO₃−N. The denitrification rate ranged between 1 and 4.8 kg/m³d and depended mainly on the filtration rate and the methanol dosage. To carry out a simulation, the biofilter was divided into five segments. Each segment was simulated as a totally mixed reactor tank. The experimental results were used to fit the maximum growth rate of the denitrifying bacteria and the yield coefficient for the process growth in the simulation. The simulation of nitrate and COD concentration in the effluent matches very well the experimental results even when the filtration rate changed. It was also possible to simulate the measured concentration profiles in the biofilter with the presented model.