INVENT technology has been powering the Schwalbachtal wastewater treatment plant since 1997
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.
