Press Release

Following the insolvency of Kabel Premium Pulp & Paper GmbH, the Ruhrverband took over the paper mill’s wastewater treatment plant at Hagen-Boele, Germany. The plant was originally designed for wastewater from the paper industry and municipal wastewater and had to be converted at short notice to operate exclusively with municipal wastewater. This created the need to set up unventilated zones for denitrification in existing aeration tanks without interrupting plant operation for long periods or carrying out extensive structural modifications.

The plant has two large donut-shaped tanks, the outer ring of which is divided into several segments. For the new process control, some of these segments were to be operated as denitrification zones. The boundary conditions were challenging. Due to existing scraper bridges, only very limited installation space was available above the water level. There was considerable time pressure for implementation. Complete emptying of the tanks was out of the question for operational and economic reasons.

INVENT developed a suitable solution concept, which centered on the use of HYPERCLASSIC^®-Mixers in combination with steel bridges adapted to the specific plant. The vertical design of the mixers and the compact drive design allowed them to be installed under the existing scraper bridges without impairing their function. At the same time, the mixers could be aligned in such a way that accessibility and operational safety were guaranteed under the cramped space conditions.

The steel bridges were the second central element of the concept. They were designed to rest on existing structural elements and could be installed without extensive modifications to the con , concrete, or basin walls. This eliminated the need for costly preparatory work and significantly reduced installation time at the plant. In addition, open side brackets were provided to accommodate the mixers. In combination with the HYPERCLASSIC^®-Mixers, this bridge concept enabled complete installation in the filled basin. The load was transferred and assembly carried out via existing structures, incorporating the existing scraper bridge. For the operator, this meant rapid implementation with manageable project costs.

With their characteristic geometry, the HYPERCLASSIC^®-Mixers ensure uniform flow distribution and reliable suspension of the activated sludge at a comparatively low power density. Especially in denitrification zones, stable mixing without air ingress is crucial for process reliability.

The INVENT solution at a glance:

• Fast and cost-efficient retrofit, without new construction and without downtime of the basins
• Installation in filled basins, made possible by steel bridges and vertical hyperboloid mixers
• High energy efficiency with reliable denitrification, low power density with high circulation capacity
• Optimized for donut tanks and confined installation situations, even under existing scraper bridges
• Operator-friendly and future-proof, suitable for municipal requirements and stricter discharge values from 2026

The Hagen-Boele project exemplifies that stable denitrification will remain a central element of municipal wastewater treatment in 2026, especially when taking over and converting existing plants. At the same time, it illustrates how intelligent concepts can be used to continue using existing tanks in the short term and adapt them to new operational requirements without new construction or lengthy downtimes.

The municipal wastewater treatment plant in Schwalbachtal, Bavaria, was upgraded in the mid-1990s to improve the efficiency and reliability of the biological treatment stage. As part of this modernization, the Utility selected INVENT technologies in 1997: a first-generation HYPERCLASSIC^®-Mixer for continuous, homogeneous basin mixing and an E-FLEX^®-Aeration System for fine-bubble oxygen transfer.

The treatment facility consists two aeration basins, each 14.5 m in diameter with a total volume of approximately 1,350 m³. Both tanks operate as Sequencing Batch Reactors (SBR) and treat roughly 2,000 m³ of wastewater per day across three shifts.

The original FRP components of the mixers installed in 1997 remain in service today. Only the gear motors have been replaced during normal lifecycle maintenance. The shaft and mixer body made of fiber-reinforced high-performance polymer (FRP) provide long-term corrosion resistance and eliminates material fatigue even under continues intermittent SBR operation.

Each basin is equipped with five E-FLEX^®-aeration modules for efficient fine-bubble oxygenation. Their stainless steel frames have operated unchanged since commissioning. The flexible membrane hoses move during aeration, preventing fouling and deposit formation. This maintains low headloss, stable oxygen transfer and reduced blower energy demand over time.

Since start-up in 1997, only two membrane replacements (2008 and 2024) and two motor replacements were required. The original FRP mixer shaft and hyperboloid mixer body remain fully intact and in service, without any signs of corrosion or material fatigue. Because the plant operates two biological tanks, all maintenance work could be carried out on one basin while the other remained fully operational, so overall plant operation was never interrupted.

The combination of hyperboloid mixing and fine-bubble aeration ensures rapid and uniform oxygen distribution. This supports stable biological performance, promotes compact activated sludge flocs and enables efficient nitrification and denitrification. During anaerobic phases, the characteristic hyperboloid flow pattern ensures efficient redistribution, contributing to robust SBR process stability.

The plant’s three decades of continuous operation without corrosion or material fatigue highlight the long-term reliability of the INVENT equipment installed. This durability minimized downtime and maintenance interventions, providing stable process performance for the operator. Today’s INVENT HYPERCLASSIC^®-Mixer Evolution7 and the iGSR^®-System for intermittently operated and granular sludge reactors build directly on this legacy. They follow the same high-quality production standards and retain the flow characteristics, material durability and energy efficiency of the technology that has been operating successfully in Schwalbachtal since 1997.

Innovative strength and the certainty to do the right thing – this is the foundation on which one of the world’s leading water and wastewater treatment companies was able to emerge from a university research project in just three decades. A success that the 150 employees of INVENT Umwelt- und Verfahrenstechnik AG are celebrating together in 2025. However, it will not stop at looking back. INVENT sees its 30-year success story above all as an incentive to courageously push ahead with new projects, even in challenging times – in a commitment to the responsible use of one of the most valuable resources of our time: Water.

When an innovative scientific project was formed at the Chair of Fluid Mechanics at the Friedrich-Alexander University Erlangen-Nuremberg, Germany, in 1995, it not only marked the birth of INVENT, but also the start of ambitious new developments for modern water and wastewater treatment. In 2025 INVENT looks back on the successes achieved with joy and honors them with a summer anniversary celebration to which around 300 employees, companions and partners from three decades of the company are invited.

“With a highly specialized, energy-saving product range and innovative process technology, we have set new standards for the biological wastewater treatment of the future. As a result, we are now one of the top 5 in the industry worldwide – a great success and at the same time a driving force for future innovations,” says Dr. Marcus Höfken, founder and current CEO of INVENT, summarizing the company’s success story.

2024: Solid annual financial statements in challenging times

In the economic turbulence of the recent past, success cannot be taken for granted. INVENT is therefore all the more satisfied at the end of a year in which the German mechanical engineering industry registered a drop in turnover of over 7%. In contrast to the industry trend, INVENT was able to match the previous year’s record pre-tax profit. Incoming orders also remained at a stable high level in 2024 after the record year 2023 (over EUR 40 million).

Commitment to Germany as a business location

In times when there sometimes is too much talk about challenges and too little about opportunities, INVENT remains committed to Germany as a business location. The expansion of the production facility in Erlangen-Dechsendorf continued in 2024. The modern plant now offers optimal conditions for the production of the iFILT^®-Diamond Filter, an innovative product in tertiary wastewater treatment that sets new standards with its performance, sophisticated energy and resource efficiency – especially in the fight against microplastics and trace substances.

In addition, construction work began on a new production hall at the headquarters in Erlangen-Eltersdorf in 2025, which will expand production capacity and secure the location in the heart of Central Franconia in the long run.

International location decisions bring resilience in challenging times

INVENT is rooted in Germany and at home in the world. International expansion therefore remains a central component of the corporate strategy.

• INVENT subsidiaries were founded in Argentina and Uruguay in 2024 to strengthen access to the growth markets in South America.
• The USA remains a key market for INVENT, which is why the company plans to open its own production site in South Carolina in 2025. It will mark a new chapter in the North American strategy and guarantee optimal options for action locally, even in times of customs disputes.

Dr. Marcus Höfken: “North and South America are becoming increasingly important for us. The current developments confirm our decisions to expand our local sites. They allow us to act faster, more flexibly and with a greater focus on our customers.

A lasting mission: working for clean water worldwide with innovative solutions

In its commitment to global trade, INVENT is committed to a strong drive; it is the same mission that laid the foundation for 30 years of successful innovation: “Our goal remains to be a technological leader – and at the same time to be perceived as a powerful partner in the water industry worldwide. We want to contribute to solving water problems all over the world with high-quality future technologies – and we are ready to be present wherever our solutions are needed,” says Dr. Marcus Höfken.

For INVENT Umwelt- und Verfahrenstechnik AG, there is no doubt that the demand for innovative water and wastewater technology will continue to grow worldwide. The company’s course is therefore set, even in challenging times: INVENT remains focused on growth with a spirit of invention, a sense of responsibility and passion – in Europe, in America, worldwide.

The innovative Floating HYPERCLASSIC^®-Mixing and Aeration System gaining popularity in industrial plants across Sweden, particularly in lagoon wastewater treatment facilities operated by pulp and paper manufacturers. These facilities are specifically designed to address the challenges associated with wastewater treatment and require efficient aeration technologies.

In Sweden, lagoon wastewater treatment plants are widely utilized for treating wastewater from the pulp and paper industry. However, traditional aeration technologies such as surface aerators, membrane aerators, and submerged aerators often encounter issues such as underutilization of volume, poor circulation, and high maintenance requirements. The HYPERCLASSIC^®-Mixing and Aeration System is the solution to these challenges by being mounted on a floating platform, enabling aeration close to the bottom and ensuring effective mixing of wastewater through high turbulence.

The adoption of the HYPERCLASSIC^®-Mixing and Aeration System has resulted in significant improvements in treatment performance at wastewater treatment plants within the global process industry. Notable enhancements include increased mixed volume, extended mixing range, and improved sludge quality. Additionally, the system’s flexibility and robustness contribute to reduced maintenance costs.

One example involves the replacement of a membrane aeration system in a Swedish industrial wastewater treatment plant with a lagoon capacity of approximately 50,000 m³. By utilizing the HYPERCLASSIC^®-Mixing and Aeration System, aeration performance increased by approximately 30% without the need for additional blowers. This led to reduced maintenance costs and overall more efficient wastewater treatment.

In another case, a Swedish industrial wastewater treatment plant replaced three surface aerators with just one HYPERCLASSIC^®-Mixing and Aeration System in 2021 This resulted in consistent dissolved oxygen concentrations near the shore. Maintenance requirements decreased significantly, with only an oil change needed every two years. The system’s flexibility allows for adjustments in aeration capacity or switching to agitation mode without aeration to prevent sludge deposits on the lagoon floor.

In the north of Sweden, an industrial wastewater treatment plant retrofitted its lagoon with six mixing and aeration systems and two mixing systems to accommodate higher production volumes. Consequently, some surface and submersible aerators previously in use were decommissioned. The HYPERCLASSIC^®-Mixing and Aeration System is mounted on a floating steel platform, with an optional maintenance platform for easy access during oil changes. Connected to a compressed air supply, the system does not require any other fixed or high-maintenance equipment in the tank. Installation on land and subsequent lifting into the lagoon are straightforward. Once secured in place and connected to the process air, the system can be put into operation.

The meticulously planned design facilitates straightforward installation on land and seamless lifting into the lagoon afterward, as illustrated. Lastly, the Floating HYPERCLASSIC^®-Mixing and Aeration System is securely positioned as intended, connected to the process air, and put into operation.

INVENT‘s extensive expertise in wastewater treatment is evident in the successful deployment of the Floating HYPERCLASSIC^®-Mixing and Aeration System. Engineers in Erlangen consistently develop comprehensive solutions tailored to meet specific needs. The production of these systems primarily utilizes regional materials and services. Since its inception in 2019, the floating mixing and aeration system has proven to be highly effective and is gaining popularity not only in Sweden but also in other regions.