Monitoring metabolic activity of denitrification processes using gas production measurements

The aim of this study was to determine the impact of biological parameters on the overall performance of a biological denitrification process. A method for evaluating the metabolic activity of the microorganisms was developed based on measuring nitrogen production rate. The method was found to be particularly valuable in monitoring batch and continuous-flow processes and confirmed the existence of several phases in denitrification. Nitrate and organic overload imposed upon the denitrification process were found to be well reflected by the gas production rate, but did not have a significant long-term impact on the denitrification performance of the process. The influence of pH on the denitrification performance was studied. The results showed that the specific activity of adapted denitrifying microorganisms was not affected by a modification of the pH control set-point. However, it was also found that small (± 0.5 unit), short-term variations in the pH control set-point affect the performance of non-adapted denitrifying micro-organisms.