Calculation of the periodic steady state of sequencing batch reactors from oxygen uptake rate (OUR) measurements in batch tests

Abstract

This paper investigates whether it is possible to calculate the periodic steady state of sequencing batch reactors (SBRs) using kinetic parameters obtained from batch tests. Two industrial wastewaters were treated in SBRs with measurement of the substrate removal and biomass production. Three batch tests at different initial substrate to biomass ratios (S0/X0) were carried out on each wastewater, with measurement of the oxygen uptake rate (OUR). The OUR profiles were used for the estimation of the kinetic parameters using a mathematical model consisting of substrate hydrolysis, biomass growth and endogenous metabolism. The estimated kinetic parameters were then used to calculate the substrate and biomass concentration at the periodic steady state of the SBRs and the obtained values were compared with the experimental data from the SBR runs. It was not possible for one set of kinetic parameters to describe different tests, even for the same wastewater. However, when each test was fitted individually, the model gave good description of the OUR profiles. When used to calculate the periodic steady state of the SBR, the estimated parameter values gave in all cases a complete or almost complete COD removal, in agreement with what observed in the SBR, but satisfactory predictions of biomass concentration for both wastewaters were only obtained with the parameters estimated in the low S0/X0 tests (highest discrepancy 37%).