Project

The wastewater utility Wolfsburger Entwässerungsbetriebe (WEB) is expanding the Stahlberg wastewater treatment plant by adding a quaternary treatment stage. This expansion is intended to substantially reduce the discharge of anthropogenic micropollutants into surface and groundwater. The site is hydrologically and ecologically sensitive. Biologically treated effluent is discharged into the Aller, a second-order water body classified as priority level 3 in Lower Saxony’s action plan, and it is also used for agricultural irrigation on approximately 1,500 ha. Elevated micropollutant concentrations have been recorded in the Aller; and sections of the river fell dry in the summer of 2022. Low levels of anthropogenic residues are detectable in the groundwater beneath the irrigated fields. Against this backdrop, the project aims to optimize the wastewater treatment ecologically and with regard to resource efficiency, as well as to improve surface and groundwater protection.

Technically, the existing gravity secondary clarification process will be replaced with membrane bioreactor (MBR) technology to provide stable effluent quality suitable for advanced treatment. Based on this, a combination of granular activated carbon (GAC) and an adsorbent resin will be implemented in partial flow. The process was developed by Fraunhofer UMSICHT, with the resin being regenerable on-site, and is intended to increase the general micropollutant removal, extend the GAC service life, and thus reduce the amount of required material and transport-related emissions. The goal is to achieve a net positive ecological impact through high energy and material efficiency, reduced micropollutant emissions and reduced CO₂ emissions. Source-oriented measures in the catchment area and regulatory developments at EU and federal levels will also be examined.

Fraunhofer ISI contributes to the project with systemic, innovation-oriented research including the analysis of the local pollution conditions and mapping indirect discharging companies, classification and prioritization of micropollutants, site-specific assessment of quaternary treatment technologies, and evaluation of innovation and sustainability. The implementation of measures is accompanied by public relations and stakeholder campaigns (e.g., with specific industries or medical institutions). Desired impacts include reduced surface and groundwater pollution, quality-assured water reuse, and transferable insights for other locations.

In this project, WEB, Fraunhofer UMSICHT, and Fraunhofer ISI collaborate to substantially reduce micropollutant emissions from municipal wastewater. The scope combines two complementary approaches to an integrated concept: the technical retrofitting of the wastewater treatment plant with source-oriented measures in the catchment aera, supported by systemic analyses, process optimization, and assessment of innovation and sustainability.

Source-oriented approach in the use and application of products

• Identification and assessment of relevant indirect dischargers (industry, healthcare institutions) including loads and dynamics of micropollutant emissions.
• Classification of particularly relevant micropollutants and identification of measures targeting product use and application (e.g., dosing and application practices, collection and disposal pathways, etc.).
• Targeted public relations and stakeholder campaigns to inform and engage relevant stakeholders and reducing emissions upstream of the wastewater treatment plant.
• Coordination of the interaction between upstream/source-oriented measures and downstream processes to maximize overall efficiency and environmental benefits.

End-of-pipe approach in wastewater treatment plant

• Replacement of gravity secondary clarification with membrane filtration (MBR) as a basis for advanced wastewater treatment.
• Implementing a combination of granular activated carbon (GAC) and an adsorbent resin stage in partial flow. The on-site regenerable resin process developed by Fraunhofer UMSICHT is intended to enhance general micropollutant removal effectiveness and extend the GAC service life.
• Planning and construction of a pilot plant (approx. 25 m³/h) with scientific supervision during commissioning; optimization of the interaction of MBR, GAC, and resin regarding removal performance, energy and resource efficiency.
• Classification of relevant micropollutants and ongoing assessment of innovation and sustainability, taking regulatory developments into account.

September 2025 until September 2027

• Wolfsburger Entwässerungsbetriebe (WEB)

• Fraunhofer Institute for Environmental, Safety and Energy Technology UMSICHT
  
• Wolfsburger Entwässerungsbetriebe (WEB)