An experimental study on monitoring Oxidation Reduction Potential (ORP), pH, Conductivity and Dissolved Oxygen (DO) in an Enhanced Biological Nutrient Removal process has been carried out. In the anaerobic phase, while ORP and conductivity were not reliable in monitoring simultaneously denitrification and P-release, pH showed the best performances. A significant relationship between P-released and pH variation was found.
During the aerobic phase both ORP and pH were able to monitor successfully the nitrification, even though pH was much more reliable. pH can be also used for monitoring and control enhanced P-uptake. It has been concluded that, for a reliable and effective control of biological N and P removal processes a more sophisticated control system seems to be necessary.