Within urban development areas domestic and trade wastewater as well as extensive quantities of rainwater dependent on the percentage of impermeability accrue. Since the middle of the 1970s real-time control has been applied to manage systematically existing drainage assets and thus to utilise the maximum of the systems capacities. The development of the integrated control of sewer network and wastewater treatment plant has been furthered in the last decade. However, the operational application on large and complex systems is still rare. Due to that reason, the research project EVA is carried out in Berlin aiming at the implementation of a decision support system for the global control of sewage pump stations. SewerNetOpt is a subproject within the joint project EVA.

Goal of the subproject is the derivation of strategies for the control and dynamic distribution of wastewater to different treatment plants during rain. Definition of the control strategies is carried out by mathematical optimisation based upon an algebraic modelling system.

## SewerNetOpt

### Optimal Control of Sewer Networks

Within urban development areas domestic and trade wastewater as well as extensive quantities of rainwater dependent on the percentage of impermeability accrue. Since the middle of the 1970s real-time control has been applied to manage systematically existing drainage assets and thus to utilise the maximum of the systems capacities. The development of the integrated control of sewer network and wastewater treatment plant has been furthered in the last decade. However, the operational application on large and complex systems is still rare. Due to that reason, the research project EVA is carried out in Berlin aiming at the implementation of a decision support system for the global control of sewage pump stations. SewerNetOpt is a subproject within the joint project EVA. Goal of the subproject is the derivation of strategies for the control and dynamic distribution of wastewater to different treatment plants during rain. Definition of the control strategies is carried out by mathematical optimisation based upon an algebraic modelling system.

### Modeling

The mathematical model is based on a system of differential-algebraic equations (DAE) describing several dozen sewage pump stations and the pressurized wastewater network containing distributor valves, coupled with the sewer network on the inflow side and wastewater treatment plants on the outflow side. Altogether one obtains a large-scale discrete-continuous DAE optimal control problem defined over the network graph.

### Optimization

The mathematical optimization aims at the prevention of spill-over during heavy rainfalls or, if this is not possible, at minimizing the wastewater content of the spill-over volume. This helps reducing the pollution of rivers and lakes in the urban environment.