Nitrification process control in activated sludge using oxygen uptake rate measurements

A method, based on oxygen uptake rate measurements combined with the application of selective nitrification inhibitors, is presented which allows monitoring nitrifying activities of activated sludge samples. Nitrification activity measurements, only requiring a dissolved oxygen probe, can yield information on NH4+ and N0₂' concentrations in mixed liquor samples. In this way, oxygen uptake rate measurements are a helpful tool to monitor the completion of the oxidation of NH₄⁺ and NO2' in activated sludge processes. Some examples, demonstrating the value of alternate oxic and anoxic periods for nitrogen removal during sequencing batch reactor processes, also indicate the value of activity measurements for nitrification control purposes. The presented method offers a possibility to optimise the length of oxic-anoxic sequences in sequencing batch reactors which results in a better effluent quality of the treatment plant.