Development and Implementation of a RealTime Control System for Nitrogen Removal Using OUR and ORP as End Points

This paper presents the development and implementation of a real-time control strategy based on end-point detection of biological reactions responsible for carbon and nitrogen removal in order to optimize the sequencing batch reactor (SBR) process. The control system is an algorithm that automatically adjusts the cycle length to the influent wastewater characteristics according to the end points. The algorithm acts in the reaction phases of the SBR cycle using the oxygen uptake rate (OUR) and oxidation-reduction potential (ORP) values as the aerobic and anoxic phase end points, respectively. Real-time control was employed in the 1-m^3 pilotplant SBR treating urban wastewater with some industrial components. Despite the influent variability, the effluent levels, 57 mg of COD·L^-1 and 4.7 mg of N·L^-1, were lower than those of the European Directive 91/217/CEE. These results demonstrate that the real-time control, using a conventional online ORP probe and the respirometer measurement, OUR, can be applied in the SBR to wastewater treatment.