A new procedure has been defined for the respirometric assessment of bacterial storage yield as defined in the Activated Sludge Model No.3. The procedure was used to determine the storage yield, Y(STO), associated with acetate, glucose and domestic sewage, together with mixtures of acetate/glucose and acetate/domestic sewage at different initial F/M ratios. Y(STO) was calculated as 0.78 gCOD(gCOD)(-1) for acetate, 0.87 gCOD(gCOD)(-1) for glucose and 0.96 gCOD(gCOD)(-1) for domestic sewage. The Y(STO) of substrate mixtures was found to reflect the characteristics of the dominant fraction in the mixture.

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Activated Sludge Model No. 1 (ASM 1) has been used extensively for the design and simulation of biological treatment systems. Batch respirometric experiments have been described in the model for the determination of model coefficients and respirometric studies have been proved to be useful in kinetic parameter estimation and wastewater characterisation for ASM 1. Activated Sludge Model No. 3 (ASM3) has also introduced a number of kinetic and stoichiometric coefficients with the new processes defined in the model, also suggesting some default values. Recent studies on the application of ASM3 are limited to special cases in terms of parameter determination. Proper calibration of ASM3 parameters can be a difficult task without involving respirometric procedures as experimental tools. Respirometric batch tests were conveniently used in this study in order to estimate ASM3 parameters and the main kinetic and stoichiometric model coefficients were successfully and uniquely determined for aerobic and anoxic conditions for acetate.

The study presents an evaluation of the oxygen requirement and sludge production, modeled in terms of fundamental processes reflecting different biochemical transformations in activated sludge systems. Modern modeling concepts define substrate utilization and endogenous decay as major processes requiring final electron acceptors. Substrate and sludge components may be defined in terms of different parameters. Chemical oxygen demand (COD) and biochemical oxygen demand (BOD5) are the traditional substrate parameters. COD also serves to define biomass along with volatile suspended solids (VSS) parameter. Estimation of oxygen requirement and sludge production for aerobic activated sludge systems covering basic biochemical processes are defined for different substrate and sludge parameters, considering that each calculation is associated with a different stoichiometry on the basis of a selected parameter set. The German regulations are examined and the biochemical bases of the coefficients in the regulatory expressions are set in terms of fundamental model constants.