Waste Water Directive (UWWTD): Clean water through new standards for wastewater treatment systems and micropollutant removal
Water quality, the environment, and public health - they all need significantly better protection: micropollutants such as pharmaceutical residues or industrial chemicals, increasing nutrient inputs, and more frequent extreme weather events are putting existing systems under noticeable strain. The revised EU Urban Waste Water Treatment Directive (UWWTD) therefore significantly tightens the requirements for wastewater treatment and turns these developments into binding standards.
he Directive pursues several key objectives at the same time: the introduction of a fourth treatment stage for the removal of micropollutants, stricter requirements for the removal of nitrogen and phosphorus, and phased requirements for energy neutrality. For wastewater treatment plants with a load of 10,000 population equivalents (p.e.) or more, a balance between annual energy consumption and eligible energy from renewable sources, as defined by the Directive, is to be achieved at national level by 2045.
Together, these requirements provide the basis for more resilient water infrastructure that reduces environmental impacts while preparing for future challenges. In this way, the Directive is becoming a key driver of the transformation of the water sector.
he timeline is ambitious: The directive has applied since 1 January 2025, with obligations phased in on different timelines through 2045. For wastewater treatment, this means a clear mandate to transform existing infrastructure. A particular challenge is the increasing energy demand resulting from additional treatment processes. What is needed is a comprehensive optimisation of the entire plant because only by coordinating all process steps can a lasting balance between treatment performance and energy use be achieved.
Phased introduction of micropollutant removal requirements: The grey line shows wastewater treatment plants serving 150,000 people and more. The yellow line shows the discharge of wastewater from communities of 10,000 to 150,000 people in sensitive areas. Larger treatment plants are subject to stricter requirements earlier, and by 2045, covered discharges must meet the directive’s quaternary-treatment requirements.
From directive to practical solution
Implementing the UWWTD presents wastewater treatment plants with a range of technical challenges – from additional treatment stages and stricter treatment requirements to energy use. This is where Wilo comes in: with pump and system technology, digital solutions and services for different areas of wastewater collection and treatment.
From sewer networks to wastewater treatment plants, from wastewater transport to the fourth treatment stage: Wilo brings together solutions for the different tasks involved in implementing the UWWTD. These include the modernisation of pumping stations and networks, pumps and mixers for treatment processes, digital solutions for monitoring and plant operation, as well as services and energy analyses. In this way, we support operators in the targeted development of existing infrastructure and the integration of new technical requirements into plant operation.
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The requirements of the UWWTD are complex – the right solutions do not have to be. Talk to us about how to prepare your treatment plants for foreseeable technical and regulatory requirements.
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New requirements for smaller municipalities
The UWWTD extends the requirements for wastewater collection to smaller municipalities. For municipalities with 1,000 population equivalents (p.e.) or more, collecting systems or, under certain conditions, suitable individual systems will generally be required. This brings the expansion and adaptation of existing infrastructure into greater focus.
This changes not only the structure of the systems, but also their complexity. Wastewater treatment plants are frequently merged – the number of treatment plants decreases while their size and catchment areas increase significantly. Greater distances, varying elevations and fluctuating inflows require precise hydraulic sizing and stable operation, even under changing conditions.
Wilo provides support with high‑performance systems for sewage pumping stations, sewage pumping stations solids separation (Wilo-EMUport CORE), as well as intelligent concepts for the control and management of sewer networks from Wilo FSM. Together with engineers and planners, we develop solutions tailored to the hydraulic requirements of the respective network and varying operating conditions.
Reduced nitrogen and phosphorus limits for wastewater treatment plants
Nutrient inputs are among the primary sources of pollution in water bodies. Nitrogen and phosphorus drive eutrophication - leading to excessive algae growth, oxygen depletion, and significant impacts on ecosystems. The directive responds with stricter requirements for nutrient removal.
Stricter limit values will apply in future and must be achieved gradually by 2045. Existing facilities will come under greater pressure. Processes must be controlled more precisely and material flows managed more effectively. Operating conditions must also remain stable, even when inflow volumes vary greatly.
For implementation, the biological processes need to be specifically adapted to the new requirements. Wilo supports this with coordinated pump, mixer, aeration and dosing technology. The aim is to support the process conditions required for nitrification and denitrification while keeping energy use and operational requirements in view.
Speed-controlled recirculation, for example with Wilo-Flumen EXCEL-RZPE recirculation pumps, allows the recirculation rate to be adapted to different operating conditions. Mixers and aeration systems support the required conditions in the tanks, while dosing systems enable operating materials to be added according to demand. This allows key process parameters to be specifically influenced and helps create the conditions required to achieve the specified effluent values.
Energy targets of the UWWTD
Wastewater treatment plants are among the largest energy consumers within municipal infrastructure. At the same time, new requirements such as micropollutant removal can increase energy demand. By 2045, the UWWTD sets a national-level target for wastewater treatment plants with a load of 10,000 population equivalents (p.e.) or more to balance their annual energy consumption with eligible energy from renewable sources.
Alongside renewable energy generation, reducing energy consumption is therefore a key focus. Energy audits will gradually become mandatory for certain plants and can be used to identify measures for improving energy performance.
Wilo considers the plant as an integrated system and identifies relevant opportunities for reducing energy use. In biological treatment in particular, depending on the plant, potential savings can be achieved through optimised recirculation, precise mixing and demand-based aeration. Recirculation pumps, mixers and coordinated aeration systems with compressors can be used for these processes.
Combined with wastewater pumps for internal transport, the different processes can be coordinated with one another. Targeted modernisation can help reduce energy use in selected process steps and thereby contribute to the energy targets of the UWWTD.
Micropollutant removal: Integrating additional treatment stages
175 pharmaceutical substances, 229 pesticides and biocides, as well as numerous other chemicals – a Europe-wide study by the Helmholtz Centre for Environmental Research (UFZ) shows the wide range of organic micropollutants that can be found in European waters. Many of these are not sufficiently removed in conventional wastewater treatment plants. The revised Directive is therefore driving the introduction of an additional treatment stage for micropollutant removal at wastewater treatment plants of different sizes.
Quaternary treatment aims to remove selected micropollutants in accordance with the requirements of the Directive. At the same time, it places additional demands on plants: further process steps, increased energy demand associated with these processes, and additional effort for operation and maintenance.
Depending on the specific conditions, different combined treatment processes using membrane bioreactor technology, activated carbon or ozonation can be applied. The key is to plan the respective processes according to the specific plant requirements and integrate them into existing treatment processes.
Wilo supports this with solutions for feeding, mixing and further treatment within the fourth treatment stage for micropollutant removal. In the PAC process (powdered activated carbon) in particular, precise dosing and precipitation processes, uniform mixing in the contact tanks and controlled solids removal are important. Combined with systems for pumping and recirculation, the individual process steps can be coordinated and integrated into existing plant operation.
The result is a coordinated overall system that supports the required treatment performance and can be designed to meet the specific operating conditions of the plant.
Monitoring combined sewer overflows
During intense heavy-rainfall events, sewer networks can face higher hydraulic loads. Combined sewer systems have to absorb large volumes of water in a short time, yet the available storage volume in sewers and tanks is often not sufficient. The result: overflows from stormwater structures are occurring significantly more often and with higher volumes.
This increasingly leads to untreated wastewater entering water bodies. The UWWTD therefore calls for systematic monitoring of these overflows – including recording volumes flows and pollutant loads. At the same time, the pressure is increasing to reduce these discharges through targeted technical measures and permanently lower the burden on water.
Wilo solutions can contribute to retaining selected solids and reducing associated discharges. Solutions for solids retention, such as lamella clarifiers in flow‑through tanks or Wilo FSM screening systems at overflow structures, tackle the problem directly at source. In addition, sewage pumps and mixers in stormwater tanks help to avoid sedimentation and ensure onward transfer of the collected volumes.
In this way, our solutions make a targeted contribution to better technical control of overflow situations.
Water reuse: Relieving pressure on an increasingly scarce resource
Longer dry periods and rising demand are putting existing water resources under increasing pressure. At the same time, large volumes of already treated wastewater are discharged unused. Water reuse opens up new options here and can be a component of water strategies.
The directive provides clear guidance, with defined requirements for quality, monitoring and risk management. The main focus is on agricultural irrigation – with different quality classes depending on the intended use.
Depending on the intended use and required water quality, additional treatment steps may be necessary: fine filtration to remove remaining substances, advanced treatment processes such as activated carbon or membrane technologies, as well as disinfection. This can be achieved, for example, through UV disinfection or the use of chlorine or chlorine dioxide in distribution networks.
Wilo supports the treatment and distribution chain with pump and system technology. Pump systems handle transport between the individual treatment stages and to the intended application. Pressure-boosting systems provide the required pressure conditions for distribution. This allows the hydraulic infrastructure to be tailored to the respective processes and requirements of water reuse.
Following appropriate treatment, the water can be reused for applications whose quality requirements it meets.
Service and solutions throughout your system’s lifecycle
Wilo supports you from planning and system design through to commissioning and maintenance. We tailor our services to the technical and operational requirements of your system.
Our offering at a glance:
- Support with planning and design (e.g., product selection, simulations, documentation)
- Commissioning and acceptance testing
- Maintenance, repair, and spare parts service
- Energy analyses
- Digital services for condition monitoring and predictive maintenance and repair
- Training for operation and maintenance and repair
With standardised and individually combinable service packages and digital tools, we create transparency around operating conditions. Our solutions can help reduce unplanned downtime as well as support maintenance and operational planning for water-management assets.
Advancing water management to meet regulatory requirements
Implementing the UWWTD is about more than meeting regulatory requirements. It is part of the long-term development of the European water sector – with the aim of protecting water bodies and adapting water infrastructure to changing requirements. After all, well-functioning water management is an essential foundation for cities, municipalities, businesses and society.
As a water technology company, we want to help shape this development. We combine pump and system technology with digital solutions and services, taking an integrated view of water infrastructure. In this way, we help develop existing systems and create the technical foundations for the water management of tomorrow.
FAQ | Frequently asked questions about the Urban Wastewater Treatment Directive (UWWTD)
When do the new UWWTD requirements apply?
What does energy neutrality mean for wastewater treatment plants?
The UWWTD introduces phased energy neutrality requirements for wastewater treatment plants with a load of 10,000 population equivalents (p.e.) or more. At national level, eligible energy from renewable sources is to equal the annual energy consumption of these plants by 2045. Alongside renewable energy generation, reducing energy consumption therefore also plays an important role – for example through adapted processes and plant technology.
What impact does the UWWTD have on existing wastewater treatment plants?
What benefits can implementation offer beyond meeting regulatory requirements?
Modernising wastewater treatment plants can offer operational benefits beyond meeting regulatory requirements. These include more controllable processes, more targeted use of energy and operating materials, and greater transparency for operation and maintenance planning. Coordinated process control can also help achieve the required effluent values reliably.
Is investment in new technologies and modernisation worthwhile?
Whether and when an investment pays off depends on factors such as investment costs, energy prices, operating conditions, funding and service life. Optimised processes can reduce energy and operating costs, improve operational reliability and provide a basis for meeting future requirements. Funding programmes and financing models may also be available.
What funding opportunities are available for implementing the UWWTD?
Solutions along the water cycle
Our solutions cover the entire water cycle – from extraction and storage through responsible use to treatment and return to the natural environment. In this way, we ensure water quality and availability for current and future generations.
