Performance and Kinectics Aspects of Nitrogen Removal in a Biofilm Sequencing Batch Reactor

A biofilm sequencing batch reactor with a volume of 1.42 m3, nylon nets providing a 4,140 m2/ m3 support area for biofilms and an automated operation with 8 hour cycles was studied. The duration of the experiment was 135 days. Removal efficiencies e≥ 80% were obtained for carbonaceous matter, producing an effluent with 31±26.8 mg/L of filtered COD, 7±3.6 mg/L of BOD5 and 12±3.2 mg/L of TOC. The average removal efficiency of ammonium was 77 ± 16.6%, with a mean concentration in the effluent of 14 ± 10.2 mg NH4-N/L. The denitrification efficiency was 80±14.7%. The effluent characteristics met the requirements of Brazilian environmental standard for discharge to receiving water bodies. A kinetic study of nitrification and denitrification showed that during the aerobic phase the specific rate of ammonium consumption was 0.057 g NH4-N/g VSS.d and the production of NOx-N was 0.074 g NOx-N/g VSS.d, while the specific rate of NOx-N consumption was 0.05 g NOx-N/g VSS.d during the anoxic phase. The suspended and fixed biomass was composed of 50% ammonium-oxidizing bacteria (AOB).