Optimierte Bewirtschaftung von Kläranlagen basierend auf der Modellierung mit Modelica (English shop)

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Abstract

This thesis deals with the simulation-based application of a model predictive control method using a nonlinear system model for the optimal operation of municipal biological wastewater treatment plants, illustrated by the example of the wastewater treatment plant of the city of Jena. Two tasks are at the forefront here: a suitable mathematical modelling of the system and the application of an appropriate numerical optimisation tool. The components of wastewater treatment plants are modelled using the object-oriented modelling language Modelica, on the basis of which the system models are generated with the simulation environment Dymola. For this purpose, an extensive Modelica application library WasteWater is developed, containing established models for, e.g., the aeration tank and the secondary clarifier. For the formulation and solution of the optimal control problem within the model predictive control algorithm, the optimisation solver Omuses/HQP is employed, which was developed specifically for high-dimensional nonlinear problems involving dynamic systems. The automatically generated overall model of the treatment plant is linked to the optimisation via the S-function interface contained in the optimisation solver. The formulation of the problem comprises the nonlinear system model, the cost functional with the objectives of the optimisation, the necessary control and state constraints as well as the specific cost functions for the reference treatment plant. Both the energy-optimal and the cost-optimal model predictive control of the reference plant show that, in sustainable wastewater treatment, the minimisation of the variable operating costs is possible while simultaneously maintaining low effluent values of the monitored parameters.