Optimization of the intermittent aeration in a full-scale wastewater treatment plant biological reactor for nitrogen removal.

The optimization of the intermittent aeration in a full-scale biological reactor treating municipal and industrial wastewater has been studied by means of an experimental design, where the main factors considered have been the on-off period of aeration and the dissolved-oxygen set point. The objective of the work has been to determine the optimal configuration of the aeration control to achieve a simultaneous removal of carbon (expressed as chemical oxygen demand [COD]) and nitrogen. The results were obtained in a full-scale bioreactor located at the wastewater treatment plant of Sant Celoni (Barcelona, Spain), where a nitrogen removal based on a nitrification-denitrification process is being tested. It has been shown that the crucial parameter to ensure a complete removal of COD and nitrogen is to give the system a long time of on-off aeration to complete both the nitrification and the denitrification processes, whereas the dissolved-oxygen set point has a minor influence on the overall performance. The results presented can be applied to a great number of similar systems, in which a nitrogen removal, based on a nitrification-denitrification scheme, is currently being tested or implemented.