Simulation of anaerobic degradation processes using the Anaerobic Digestion Model No. 1 (ADM1)

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Anaerobic methods are state of the art in many areas of industrial wastewater treatment. However, the four-stage anaerobic process reacts very sensitively to variations of the boundary conditions and to load changes. Therefore, the plants can often not operate at their optimal levels. Dynamic models can contribute to a better understanding of the process and can be used for the examination of various influencing factors. During the first two years of the project, the results of different laboratory investigations with starch wastewater and several synthetic substrates were used to determine substrate and biomass specific parameters and to calibrate the Anaerobic Digestion Model No. 1 (ADM1). In addition, the lactic acid fermentation was incorporated in the ADM1 for accurate simulation of the glucose degradation. The extended model was validated using the data of a second laboratory plant; it could be successfully used to predict main relevant process parameters (like gas quality, gas quantity, COD and VFA in the effluent, pH in reactor). However, the methane production for some of the load tests shows a high methane peak in the simulations results which could not have been observed in the experimental results. This indicates that inhibitions may occur during load tests which are not yet implement in the model. Furthermore, inhibition due to product accumulation is not considered in most of the processes in the ADM1. Therefore, even endergonic reactions are simulated with positive rates. Therefore, these points will be investigated during the intended second part of the project as follows: - Investigation of pH and VFA inhibition of the anaerobic process in order to optimize the inhibition function implemented in ADM1 - Implementation of Gibbs energy calculation depending on actual conditions into ADM1 in order to predict the reaction direction.