Optimizing nitrification on biological filters

A recently developed nitrification model for biological filters has been applied to the design of three sites to increase nitrification. The first site was upgraded by the installation of a dedicated recirculation facility, the second by reconfiguration to double filtration, and the third by the installation of a chemical pre-precipitation plant. All three sites responded well to the modifications and achieved compliance with ammoniacal nitrogen consents of 3–5 mg/l on a 95%oile basis. The key influence of hydraulic load on nitrification capacity and reliability was demonstrated on all three plants. The ability to upgrade existing biological filter installations to meet stringent ammoniacal nitrogen consents allows a significant reduction in environmental impact and revenue costs when compared with energy-intensive options such as the activated-sludge process.