30 years ago, for the only time, the rotational arch technology by engineer Günter Kupczik was integrated into the Dresden sewer system. Aiming to achieve better volume management during heavy rainfall and to solve the issue of sediment removal without requiring personnel, Kupczik began working on the innovative rotational arch solution as early as the 1980s. Comparative analyses conducted by TU Dresden revealed that, at the time, the rotational arch was the only technical solution in which mechanical components did not come into contact with wastewater, the full flow cross-section remained available at all times, and precise control was possible even under backed-up operational conditions.
All other available solutions were either limited in their volume management, achieved only a fraction of the cleaning performance, or had to be installed directly into the sewer cross-section. To this day, the rotational arch, in combination with the so-called ASA weir, remains one of the few viable methods for implementing an intelligent sewer management system without restricting the flow cross-section. Moreover, it continues to be the only technology that maximizes storage potential within a sewer.
In collaboration with HST Systemtechnik GmbH & Co. KG, the Water Infrastructure and Digitalization research group, led by Prof. Günter Müller-Czygan, is analyzing the existing rotational arch concept as part of the “Rotational Arch 4.0” project. This initiative, funded by the German Federal Environmental Foundation, explores how this unique solution can be effectively enhanced using intelligent digital elements to enable climate-resilient and future-proof sewer network management.
The rotational arch technology was developed through an indirect path. Its origins date back to the early 1980s, when Günter Kupczik was heavily involved in solving sedimentation issues in the Hamburg sewer system. During this time, he developed and operated the so-called “Sielwolf” system for many years. This specialized system for removing sediments from large-diameter sewers could operate without interrupting the flow, utilizing a semi-automated cleaning mechanism that extracted deposits from the sewer floor. The Sielwolf (where “Siel” is the Hamburg term for a sewer) was pulled through the sewer pipe using a winch, while core jet nozzles—producing an air-encased water jet—dislodged the sediment. This process created a suspension, which was then pumped into settling containers.
After approximately five years, the goal of sediment removal had been achieved. However, a significant drawback emerged: the extracted sediment reached annual volumes of around 8,000 m³, requiring extensive disposal and treatment efforts. Kupczik developed an appropriate solution for this as well. While the results were effective, the effort involved, as well as the environmental and health impacts on workers, were considerable. Seeking a solution that required no personnel intervention and allowed sediments to remain within the sewer, Kupczik leveraged his experience with the Sielwolf to develop the rotational arch. This innovation was first implemented in Dresden in 1994.
For nearly three decades, the potential of the rotational arch remained untapped, with its only installation in the Dresden sewer system (see technical photos). However, the increasing capabilities of digitalization now allow the rotational arch to be utilized far more effectively than 30 years ago. Additionally, with the introduction of the new EU Urban Wastewater Treatment Directive, the demand for intelligent sewer management solutions is rising sharply. Cities and municipalities are now required to minimize the discharge of untreated wastewater into water bodies during rainfall events. To meet these requirements, either costly storage basins must be constructed, or existing sewer systems must be retrofitted with technologies such as the rotational arch to achieve improved volume management in a cost-effective manner.
The system is based on two key functions. First, the arch structure itself, which gives the system its name. Second, the specialized rotational connection (the so-called torsion compensator), which links the arch structure to the sewer infrastructure and enables rotation. This allows (waste)water to be deliberately retained within the sewer and then released in a controlled wave, using wave energy to remove sediment over long sewer stretches and direct it efficiently to the wastewater treatment plant.
In addition to examining potential applications and user requirements, the “Rotational Arch 4.0” project is investigating how to scale the technology efficiently, based on its previously unique diameter of approximately 1,200 mm. As part of his doctoral research, Imam Burhani, a member of Prof. Günter Müller-Czygan’s team, is conducting various simulations and calculations in collaboration with Prof. André Niemann of the University of Duisburg-Essen.
During a working meeting on January 27, 2025, Prof. Günter Müller-Czygan presented the current project status to the inventor of the rotational arch (see photos of both men). In turn, Günter Kupczik shared further valuable technical insights, actively supporting the ongoing development process by contributing his decades of expertise in mechanical engineering and sewer systems. “I am delighted that we are now working together to bring the rotational arch technology to success,” said Günter Kupczik in conversation with Prof. Müller-Czygan, emphasizing his personal commitment to the project.
The “Rotational Arch 4.0” initiative is part of the broader research focus on “Climate-Resilient Water Infrastructure” within the Water Infrastructure and Digitalization research group. Here, researchers explore various developments and approaches to better adapt urban and municipal water infrastructure to extreme weather conditions, such as heavy rainfall and drought periods. This work includes projects like the German Federal Ministry of Education and Research (BMBF) initiative “InSchuKa4.0” and efforts within the Competence and Transfer Center for Sustainable Sponge Cities/Regions at the Institute for Sustainable Water Systems (inwa).
“In the ‘Rotational Arch 4.0’ project, we have the opportunity to further develop an extraordinary technology that was ahead of its time back then, and make it a key component of future climate-resilient sewer system management,” concludes Prof. Müller-Czygan.
Prof. Günter Müller-Czygan
+49 9281 409 - 4683
guenter.mueller-czygan(at)hof-university.de
Rotational arch technology by Hamburg engineer Günter Kupczik in the Dresden sewer system.
Hochschule Hof
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