Rasender Roland, Buskam, Mönchgut: anyone who doesn’t immediately think of sun, beach and sea when they hear these words has never been on holiday in Göhren on Rügen - and is therefore not one of the more than one million tourists who make Germany’s largest island one of the country’s most popular destinations. The large, continuously increasing demand and the associated strong seasonal fluctuations in inflow volumes of course also have an impact on facilities such as wastewater treatment plants. Flexible concepts and efficient solutions are required. The management of the Göhren wastewater treatment plant has therefore decided to take extensive measures to renew and optimise its machinery and plant technology, expanding its capacity from 30,000 PE (population equivalents) to 45,000 PE. In times of energy transition and CO2 balance, sustainability and environmental protection are among the central requirements. Construction started in 2021. The project was divided into a total of three construction phases. 

Funding measures support financing 

The massive investment required - including optimisation of the two existing aeration tanks, construction of a third aeration line and installation of a photovoltaic system - would not have been possible without public subsidies. “For this reason, subsidies were applied for and approved via the project management organisation ZUG - Zukunft, Umwelt GmbH. The funding organisation is the Federal Ministry for Economic Affairs and Climate Protection. A total of just under 5.3 million euros has been paid out for the Göhren wastewater treatment plant modernisation project by the Federal Ministry alone. The total investment for this construction phase amounts to 8.9 million euros,” summarises Uwe Repenning, General Manager of Zweckverband Wasserversorgung und Abwasserbehandlung Rügen (ZWAR). 

Redesign of the biological purification stage 

The redesign of the biological purification stage with AERZEN technology has already been completed. An optimally coordinated system of AERZEN blowers, RMU Classic plate aerators and dynamic control system in biology including variable pressure control and pulse aeration (no need for agitators) ensures that low discharge limits are safely maintained even during peak loads and high tourist volumes. The treated wastewater is of almost bathing water quality and thus fulfils the highest requirements. The first step was to optimise the energy efficiency of the two existing aeration tanks and equip them with new aeration technology. This was followed by the construction of a third aeration tank (volume per tank = 2,400 m³). 

Rental machines ensure reliable operation during the conversion work

A decisive factor in the successful conversion was the temporary aeration, which was provided via Aerzen Rental. The international rental service offers complete solutions for short and medium-term rentals and holds the entire AERZEN machine portfolio for vacuum and com pressed air applications in pressure ranges from vacuum -650 mbar (g) to +10.5 bar (g). Ventilation elements can also be delivered on prefabricated frames, including pipework equipment. Aerzen Rental delivered three plug-andplay machines to the Baltic coast of Rügen. In this case, it was two Delta Hybrid packages and one Delta Blower package including VFD, intelligent control system and complete piping. The machines were ready for use in just two hours and worked reliably and efficiently for seven months. 

Capacity fluctuations of up to 400%

With an increase in capacity of up to 400% during the peak season, it is essential to ensure the efficiency and performance of the plant at all times. It was therefore necessary to replace the outdated machines and the control and regulation technology in operation,” explains Christoph Kruse, Water and Wastewater Manager Mönchgut at Zweckverband Wasserversorgung und Abwasserbehandlung Rügen (ZWAR), adding: “The quick set-up and uncomplicated commissioning of these temporary solutions guaranteed that the process values could be adhered to at all times during the entire conversion phase.” The ZWAR is an association of the currently 39 towns and municipalities on the islands of Rügen, Ummanz and Hiddensee and operates 35 wastewater treatment plants in the association’s area. The Göhren wastewater treatment plant is the second largest and is located in the south-eastern component of the island of Rügen, on the so-called Mönchgut peninsula. While the small Baltic seaside resort tends to be quieter in the autumn and winter months, workload increases up to fourfold during the holiday season between April and October. 

The AERZEN Baltic Sea Quintet: 

efficiency as a principle Today, 

• two Aerzen Turbo AT 200-0.8 S (volume flow rate range from 2,600 to 7,600 m³/h),
• two Delta Hybrid D 62 S (volume flow range from 850 to 3,650 m³/h) and
• one Delta Blower GM 25 S (volume flow range of 200 to 1,000 m³/h) 

provide optimum oxygen supply in the aeration tanks. The mix of technologies used between positive displacement blowers and turbo-machines enables effective process air generation over a high turndown. The turbo blower, for example, offers above-average energy efficiency at the design point, while the screw blowers are characterised by an adjustable range of 25-100% and almost constant efficiency even in partial load operation. The combination of both technologies results in a highly efficient and flexible system. The selection of suitable blowers is handled by the intelligent AERsmart control system. Depending on the workload, the turbo blowers, screw blowers and positive displacement blowers are switched in combination or as individual solutions to achieve the best energy solution for aeration. This means that the load changes can always be operated precisely and efficiently despite the strong seasonal fluctuations at the wastewater treatment plant in Göhren. 

Sustainable investment into the future 

The Göhren wastewater treatment plant has been relying on process air solutions from AERZEN since 2000. With the recent conversion to the latest machine, aeration and control technology, the municipal company is igniting the efficiency booster and setting sail for the future. The new compressor technology means that employees at the plant benefit from a significant reduction in noise emissions, as do local residents and visitors to the island. In addition, an impressive energy saving of 42% has already been achieved thanks to the optimisation of biology and the installation of a photovoltaic system. At 280,000 kWh, this equates to € 84,000 in savings per year, which exceeds all expectations. These measures are not only an important contribution to sustainability but also strengthen the energy self-sufficiency of the wastewater treatment plant,” emphasises Christoph Kruse, who adds: “Many thanks once again to AERZEN for their expert advice and the excellent and straightforward cooperation.” 

“Many thanks once again to AERZEN for their expert advice and the excellent and straightforward cooperation.”
Christoph Kruse, water and wastewater manager Mönchgut at the Zweckverband Wasserversorgung und Abwasserbehandlung Rügen (ZWAR)