Based on on/off aeration strategies, this paper describes all the steps involved in the development and implementation of three identification algorithms aimed at monitoring the oxygen uptake rate (OUR), the oxygen mass-transfer coefficient (KLa), and oxygen transfer efficiency (OTE) in aerated biological reactors. Firstly, a detailed explanation of the theoretical background behind every algorithm is given. In addition, practical issues have also been taken into account in order to guarantee the quality of estimations. Finally, the three algorithms have been implemented and validated in a full-scale industrial wastewater treatment plant with satisfactory results. Although short-term noise has been observed in the estimated data (especially at high OURs), the medium and long-term data trajectories have been correctly reproduced.