DISSOLVED-OXYGEN CONTROL AND SIMULTANEOUS ESTIMATION OF OXYGEN-UPTAKERATE IN ACTIVATED-SLUDGE PLANTS

The theoretical basis, practical implementation, and experimental vali dation of an on-off control strategy for dissolved oxygen (DO) in aero bic reactors of pilot-scale activated-sludge plants with simultaneous estimation of oxygen uptake rate are presented. The effect of dead tim e and a long response time for robust DO probes has been carefully ana lyzed and corrected through modeling of the dynamic response of the se nsor. Study results indicate that the amplitude of the control band de pends on the dead time of the probe. Simultaneous estimation of the vo lumetric mass-transfer coefficient for DO (K(L)a) permits a continuous check of the aeration equipment. Experimental validation has been ach ieved in a continuous pilot-scale plant.