Control of Wastewater Collector Tunnels: Implementation of real-time control for the central collector tunnel in the city of Graz

Nowadays the protection of our ecosystem and the responsible use of our natural resources are of high importance to us. Therefore, the conservation or the re-establishment of a good chemical and ecological state for all surface water bodies is a high priority for every local sewer operator. In a city like Graz that mainly uses a combined sewer system where rainwater and municipal sewage come together in one pipe, an untreated overflow of that polluted water into a receiving water body should be prevented by all means.
This thesis deals with the management of the newly constructed collector tunnel in Graz and the possible control actions that can be taken to raise the efficiency of the system using an integrated model that combines a rainfall model, a conceptual model for the sewer system of the city and a detailed model of the collector tunnel.
The work focuses on two main points concerning the central storage tunnel. The first one is to maximize the cleaning efficiency by flushing the sewers to reduce sediments in the tunnel. The newly developed flushing schemes show clear advantages over the currently used strategy. The second point is developing a global real-time control strategy to minimize combined sewer overflows during storm events. Two control schemes were developed and compared with each other, a rule based real-time control system and a model predictive control system. Both proved to be significantly better in handling storm events than the currently used local control system.