Event-based cascade controller for nitrogen removal in wastewater treatment plant

This paper addresses the problem of nitrogen removal in wastewater treatment plants. The plant operation is stated in terms of a cascade control configuration where the ammonia concentration at the output of the last reactor determines the set-points of the three aerated tanks. In addition, the usual nitrate control loop for the second anoxic tank is also in place. The problem is addressed here within the framework provided by the Benchmark Simulation Model Number 1 (BSM1) and by the use of an event-based solution. As far as to the knowledge of the authors, no solution based on this kind of controllers has been proposed already in the literature. The controllers are taken as of similar complexity as the ones provided as default control strategy in the BSM1, therefor being the main difference, the possibilities provided by the event-based implementation. It will be verified that the solution can improve the performance of the already existing controllers both at loop level as well as at plant operation level.