The Swiss village of Rheinfelden has been using Dynamic Sewer Control to automatically optimise its rainwater storage tanks during thunderstorms. Thereby, it has minimised combined sewer overflows, which has been better for the community and better for the environment.
The situation
In Rheinfelden, Switzerland, Stephan Bürgi used to be concerned if it had rained during the night. Bürgi is Plant Manager for the Rheinfelden-Magden Wastewater Treatment Plant. The plant has six rainwater storage tanks dispersed throughout the city to prevent overflows. But the tanks did not always fill up when needed. This caused combined sewage overflows (CSOs), meaning untreated wastewater was flowing out of the sewage system.
“Previously the rainwater basins actually ran on their own. When it rained, they might have filled up, but maybe not,” he says.
The untreated flood water from the CSO could sometimes run into a creek that flows through the old part of the village, where the pollution and smell caused was a major issue. Or it ran uncontrolled into the Rhine. As is typical of many municipal treatment plants, the tanks were controlled in a static manner.
“Static control is designed by engineers to only have a certain amount of water ever arriving at the treatment plant,” explains Alex Cornelissen of RTC4Water, a Grundfos Service Partner. “But that means that if it doesn't rain in some parts of the city and it rains into another part, you're not using all the city’s infrastructure to the full of its ability. In Rheinfelden, not all the storage was used as best that it could be used.”
Some municipalities solve this by building new infrastructure, he says. But that is expensive and takes a long time. He offered Stephan Bürgi another solution, based on real-time system monitoring, flow forecasts and automatic adjustments of pumps, valves and storage tanks: Dynamic Sewer Control.
Stephan Bürgi, Plant Manager for the Rheinfelden-Magden Wastewater Treatment Plant, opens one of the city’s combined sewer storage tanks outside the central train station.
The solution
In autumn 2021, the Rheinfelden-Magden plant began a collaboration to design and test Dynamic Sewer Control for the town of Rheinfelden.
“Dynamic Sewer Control looks at all the tanks in a network from an overall, ‘global’ perspective and determines where there is still available space to store wastewater,” says Alex Cornelissen of the dynamic, data-driven software. “It looks at the levels in the tanks. It looks at the outflows that are coming out of the tank. It looks at the available space at the treatment plant and in the tanks, and it computes the best solution to achieve the best possible result with the available infrastructure that is there. In that way, it produces much fewer overflows than in a static control situation.”
Implementation partner Rittmeyer Group delivered and maintains the RITUNE data automation systems. Chief Product Officer David Dürrenmatt says the main goal of wastewater treatment is to protect the environment. “We see wastewater treatment plants that are very advanced, and we see that their sewer systems – and very often the storage basins in the sewer systems – aren't controlled properly,” he says. “And we see it as a good way forward to let these different structures communicate with each other, and in a very clever way, reduce the direct discharges into the receiving waters and help the operators, help the municipalities to reduce their environmental impact.”
The RITUNE visualisation of the system data shows monitoring, flow forecasts and automatic adjustments of pumps, valves and storage tanks.
The system is always one step ahead of me before I've even seen it myself.
The outcome
The outcome for Rheinfelden has so far been positive, says Stephan Bürgi. “The system anticipates my thoughts: ‘Ah yes, now the rainwater tank, if I were to fill that now, then it would be ready in time.’ So the system is always one step ahead of me before I've even seen it myself.”
The advanced, load-based control has reduced overflow volume by 33% and overflow load by 47% in simulation.
“Before we got the system, we didn't actually see much on our PLCs,” says Stephan. “And now with the software, we can see everything. It [Dynamic Sewer Control] functions autonomously. I can rely on the system always working perfectly, and I don't always have to check it myself at night when there is heavy rain. In the past, I used to wake up and then go and check with remote access and control it myself. And now it runs by itself.”
He adds: “The most important advantage is, of course, that the system is monitored 24 hours a day, seven days a week, and the entire volume of the rainwater basins is utilised.”
Alex Cornelissen says that sometimes it rains so much that it is impossible to avoid an overflow – and when that has happens now, the system can steer it away from certain areas like the the creek running through town. “Dynamic Sewer Control is able to say, ‘Okay, when I have to have an overflow, it goes into the Rhine, and I prevent it from going into the creek. And that way, it's a better solution for the residents of Rheinfelden.”
The creek running through Rheinfelden.
Expansion
In 2026, the municipality of Magden will join the dynamic control system, meaning the system will be controlling 100% of the catchment area, says Stephan Bürgi. “Magden is a side valley. It may be raining in Magden, but not yet or not at all in Rheinfelden. So the system can hold back dilluted sewage in Magden and later, when there is capacity, send it to the Reinfelden sewage treatment plant.”
Now, for Stephan, rain events at night do not worry him anymore. “When there's a thunderstorm in the evening and there's nothing exciting on television, I turn on the screen, watch the rainwater basins fill up and be pumped out, and then I wonder how it does that,” he says. “But the bottom line is, it works really well. We use the entire capacity of the entire catchment area, of the rainwater basins. That's a huge advantage and exciting to watch. You don't have to do anything.”
Stephan Bürgi, Plant Manager, Rheinfelden-Magden WWTP
The product
The Rheinfelden-Magden wastewater treatment plant uses Dynamic Sewer Control to diminish or avoid combined sewer overflows.
One of six rainwater tanks in Rheinfelden.
Sources
The facts and quotes in this story come from interviews onsite at the Rheinfelden-Magden Wastewater Treatment Plant in September 2025.
Acknowledgement
Thank you to Rittmeyer AG, our channel partner, for the additional PLCs programming needed and collaborating on the visualisations using their RITOP and RITUNE software and the city of Rheinfelden for making available the needed infrastructure maps and network data as well as cooperation on defining their needs in this project.