A small municipal wastewater treatment plant in Hesse, Germany, treats the wastewater generated by a local community using an existing lagoon treatment system. The plant has operated for many years based on a largely conventional treatment concept. Wastewater first enters the inlet area through a coarse screen before passing through a grit and solids removal stage.
From there, the wastewater flows by gravity through the existing treatment lagoons. After biological treatment, it enters a polishing pond before being discharged into the receiving watercourse. Over the years, the operator had already upgraded parts of the existing system with additional aeration equipment. However, the fundamental treatment layout remained unchanged.
The wastewater treatment plant receives influent from a combined sewer system. As a result, hydraulic loading varies significantly depending on weather conditions. During dry-weather periods, relatively small wastewater volumes reach the plant. At the same time, pollutant concentrations increase considerably.
Rainfall produces the opposite situation. Large volumes of water enter the treatment plant within a short period, placing substantial hydraulic stress on the process. These fluctuations create particular challenges for ageing lagoon treatment systems.
At the same time, discharge requirements continue to become more stringent. The municipality therefore required a long-term solution that could be integrated quickly into the existing infrastructure. A complete new-build treatment plant would have required substantially higher investment and extensive civil engineering works.
The existing lagoon treatment plant was increasingly reaching the limits of its treatment capacity. In particular, the pronounced differences between dry-weather and wet-weather conditions placed significant stress on the biological treatment process.
Under the original plant configuration, wastewater flowed largely uncontrolled through the individual treatment stages. There was no targeted regulation of the hydraulic load entering the biological process. During periods of heavy rainfall, high flow rates therefore reached the biological treatment stage directly.
Dry-weather conditions presented a different challenge. Lower wastewater volumes resulted in significantly higher pollutant concentrations. Reliable removal of ammonium nitrogen was particularly important under these conditions. The municipality needed to ensure continuous compliance with the required discharge limits.
Simply increasing the existing aeration capacity would not have addressed the underlying hydraulic and biological limitations. The operator therefore looked for a compact and economically viable alternative.
The new solution also needed to make practical use of the existing infrastructure. At the same time, it had to provide additional biological treatment capacity and remain stable under changing load conditions. A short implementation period was another key requirement.
After comparing several treatment concepts, the municipality selected a containerised ClearFox® solution from PPU Umwelttechnik.
PPU integrated a new biological treatment line into the existing wastewater treatment plant. Two compact containerised treatment stages form the core of the upgrade.
The first step involved installing a new dual-pump station. Two submersible pumps now feed the wastewater into the new treatment system under controlled conditions. The pumps operate alternately and respond automatically to the water level.
At lower water levels, only one pump operates. When influent volumes increase during rainfall events, the second pump starts automatically. This allows the plant to regulate the hydraulic loading of the new treatment process far more precisely than under the previous gravity-flow configuration.
From the pump station, the wastewater enters the ClearFox® FBR.
The fixed-bed reactor provides the biological treatment stage. Inside the container, the wastewater passes through several reactor chambers arranged in series. These chambers contain specially designed fixed-bed media that provide large surface areas for microbial growth.
A stable biofilm develops on the carrier material. The microorganisms remove organic pollutants and oxidise ammonium nitrogen. Fine-bubble diffusers installed beneath the media continuously supply the biofilm with oxygen.
The cascade design supports stable and efficient biological treatment. Different microbial communities develop throughout the individual reactor stages and adapt to the pollutant load present in each section.
This process offers particularly high stability under fluctuating influent conditions. The biofilm responds robustly to both hydraulic and organic load variations. The ClearFox® FBR is therefore especially well suited to smaller municipal wastewater treatment plants in rural areas.
After biological treatment, the wastewater flows into a ClearFox® lamella clarifier. This stage separates the biological solids from the treated water.
The water flows upwards through inclined lamella modules. The lamella plates significantly increase the effective settling area within a very compact footprint. Solids settle onto the inclined surfaces and slide down into the sludge hopper.
Clarified water collects above the lamella modules and leaves the system through the outlet. The lamella clarifier requires very little space and operates without moving parts within the actual clarification section.
The overall solution uses compact 20-foot and 40-foot container modules. This kept the required civil works on site to a minimum. At the same time, the modular design allows the treatment capacity to be expanded in the future.
Only around six months passed between order placement, delivery and installation. Following a short biological start-up phase, the system reached stable operation.
Today, the new ClearFox® solution reliably treats the municipality’s wastewater and significantly relieves the existing lagoon treatment plant. The municipality now has a compact, economical and long-term treatment solution without the need to construct an entirely new wastewater treatment plant.
This solution is particularly suitable for existing small and medium-sized municipal wastewater treatment plants that no longer provide sufficient treatment performance. Typical applications include lagoon systems, ageing biological treatment plants and sites exposed to significant fluctuations in hydraulic or organic loads. PPU designs the treatment process individually based on the existing infrastructure, wastewater volume, pollutant load and required discharge limits.
The ClearFox® FBBR combines a compact footprint with highly stable biological treatment performance. Microorganisms grow as a biofilm on specially designed fixed-bed media, where they degrade organic pollutants and oxidise ammonium nitrogen. The biofilm adapts to changing influent conditions, making the process particularly suitable for smaller municipalities with fluctuating wastewater volumes and pollutant loads.
The ClearFox® lamella clarifier separates suspended solids from the treated water after the biological treatment stage. Inclined lamella plates significantly increase the effective settling area within a very compact footprint. Settled sludge moves into the lower section of the system, while clarified water flows above the lamella modules towards the outlet. The clarification process operates without moving parts in the settling section and requires very little energy.
The required footprint is small compared with conventional treatment plant extensions or new-build solutions. PPU integrates the treatment technology into compact 20-foot or 40-foot shipping containers. The lamella clarifier also achieves a very small footprint due to its large effective settling area. This makes the solution particularly suitable for existing wastewater treatment plants where space for expansion is limited.
The containerised design significantly shortens project implementation. PPU manufactures and pre-assembles large parts of the treatment technology at its production facility in Germany and delivers the containers largely ready for connection. This considerably reduces installation work on site. In the project in Hesse, only around six months passed between order placement, delivery and installation.
Yes. ClearFox® containerised treatment plants feature a modular design. If population numbers increase, wastewater volumes rise or treatment requirements change, PPU adds further treatment modules to the existing system. Depending on the project, additional containers are installed either in parallel or in series. This gives operators a flexible solution that adapts to the long-term development of the site.
