Present methods for determination of kinetic and stoichiometric parameters are mostly based on simple and rapid batch cultivation. An alternative technique of mathematical simulation and a batch cultivation was proposed for estimation of maximum specific growth rates of heterotrophic and autotrophic microorganisms in activated sludge. Estimation of heterotrophic and autotrophic fractions in the biomass is based on mathematical model calibration of continuously operated system. Maximum growth rates are then calculated from the maximum OUR measured in batch tests. The proposed method was compared with a batch test cultivation based on an exponential growth of microorganisms when a proportion of filtered wastewater is mixed together with a small proportion of biomass and aerated in time. Comparing both methods, a disproportion between obtained results was found (μH,max = 4 d−1 from the proposed, and μH,max = 10 d−1 from the batch test method). An explanation of this observation was based on a hypothesis that under batch test conditions (higher S0/X0 ratio) faster-growing microorganisms can be favoured in their growth. This phenomenon was mathematically simulated with a simplified model and confirmed. Therefore, it is recommended that some constants for mathematical modelling obtained from batch tests should be applied on continuously operated systems only with care.

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