Research initiative on wastewater

According to the revised Urban Wastewater Treatment Directive, Sweden must demonstrate that nitrogen discharges from wastewater treatment plants to water bodies sensitive to nitrogen pollution, are not harmful to the environment, including biodiversity, or to human health and do not alter ecosystems. Furthermore, it must be shown that nutrient concentrations within the catchment meet the condition set out in point 1.2.1 of Annex V to the Water Framework Directive (EU, 2000) defining good ecological status in these areas (EU, 2024, Annex I, Table 2, Note 3).

More knowledge is needed to assess whether inland waters require further reductions in nitrogen loads. In later years, both Lake Hjälmaren and Lake Mälaren have been considered for classification as nitrogen-sensitive areas. To date, however, the conclusion has been that reduced nitrogen loads would not affect eutrophication levels in the manner referred to in Annex II of the revised Urban Wastewater Treatment Directive (EU, 2024). According to Article 7.2 of the same directive, Sweden must update the list of areas that are sensitive to eutrophication no later than 31st December 2027, specifying whether phosphorus, nitrogen, or both need to be reduced. This list must be reviewed every six years.

We invite proposals that address one or more of the following needs:

• Produce data to support, or update, the assessment criteria for nitrogen in lakes and water courses (Fölster, J. & Djodjic, F., 2016), to assess the need for reducing nitrogen loads to inland waters and to further develop the sensitivity assessment of inland waters to nitrogen loading.
• Further develop and apply models describing biogeochemical processes influencing nitrogen dynamics, including retention processes in rivers and lakes—preferably incorporating multiple phytoplankton types, macrophytes, and sediment and water column processes. This is intended to improve assessments of the effects of nitrogen loading in relation to loading and natural concentrations of phosphorus, silicon, and organic carbon in large or polluted lakes, specifically Lakes Vänern, Vättern, Mälaren, Hjälmaren, and Roxen.
• Analyse the effects of enhanced nitrogen removal at municipal wastewater treatment plants or other point sources discharging to inland waters, either in general or for one or more of the large lakes mentioned above.

Project teams are required to inform the Swedish Environmental Protection Agency and the Swedish Agency for Marine and Water Management of results and conclusions at least once every six months, with a first progress report, in September 2027, in preparation for the revision of the list of sensitive areas under Article 7.2 of the Urban Wastewater Treatment Directive in December 2027.

We invite either one larger or several smaller research projects with a maximum duration of three years. The total budget allocated to this research area is SEK 3 million.

To support  integrated urban wastewater management planning under the revised Urban Waste Water Treatment Directive (EU, 2024, Article 5), and in view of the forthcoming requirements for monitoring (Article 21.2) and reporting under the same directive (Article 22.1(a)), as well as for environmental objectives and source apportionment calculations, new knowledge bases and methodologies are needed to estimate pollutant discharges caused by combined sewer overflows (CSOs).

Once the revised Urban Wastewater Treatment Directive has been transposed into Swedish legislation, wastewater utilities will be required to carry out representative monitoring of combined sewer overflows to water bodies at relevant points in the sewer network and of stormwater discharges from urban areas. This is to estimate concentrations and loads of discharged organic matter (such as TOC, COD or BOD) and, where relevant, phosphorus and nitrogen, as well as the ”content of microplastics and relevant pollutants” (EU, 2024, Article 21.2; Swedish Environmental Protection Agency, 2026). Where technically feasible and appropriate, digital tools should be used to support monitoring (EU, 2024, Recital 43). Recital 44 of the directive further states that microplastics and relevant micropollutants should, where applicable, be monitored in discharges via combined sewer overflows and in stormwater discharges from urban areas from separate systems, using representative sampling programmes that enable the estimation of concentrations for the purpose of water quality modelling.

We invite proposals that develop methods to quantify or estimate loads of at least nutrients, TOC (or COD), and BOD from combined sewer overflows on water bodies. The methods must be applicable to wastewater systems of different sizes. The following elements shall be included:

• Compile and describe current practices for monitoring and follow-up of combined sewer overflows, including which methods are used for which purposes. The description should cover a range of methods; from simple estimates, measured overflow volumes, calculation methods, and hydraulic models to different approaches for measuring pollutants, use of default assumptions, or modelling to estimate pollutant loads, preferably including a Nordic perspective.
• Verify identified calculation methods and model assumptions, through existing or new measurements or literature reviews, for the methods or models inventoried as described above.
• Assess data input requirements in relation to the quality of results for different applications and pollutants, including consideration of factors such as land use in the catchment area of the sewer network, the age and materials of the system, proximity to or density of rain gauges, the significance of different technical solutions for overflow control or overflow outlet design, the chosen resolution of input data and modelling, and other relevant factors.
• Propose a minimum methodological standard capable of providing sufficiently useful data both for the purposes of the Urban Wastewater Treatment Directive and for assessing the environmental impacts of combined sewer overflows on receiving waters, based on the findings above.
• Contribute input to, or assist with qualified review of, the Joint Research Centre’s (JRC) proposal for the forthcoming implementing act under the Urban Wastewater Treatment Directive establishing alternative indicators for monitoring pollution from combined sewer overflows (Article 5.6(b)). These contributions will need to be carried out during the first half of 2027.
• Provide results that can form a basis for further technical development of monitoring and discharge modelling of wastewater overflows.

Projects may also:

• Develop criteria to assess which pollutants are relevant to monitor, and use them to propose additional pollutants to be monitored (Article 21.2).
• Develop methodologies to quantify or estimate loads from unintended or unplanned discharges from separate domestic wastewater sewers. The methodology should describe the considerations and data required where discharges are caused by operational disturbances at pumping stations, blockages, hydraulic overloading (proportion of extraneous water), or incorrect connections.
• Examine how the temporal distribution of precipitation under current conditions and according to climate scenarios affects the pollutant content of overflowed wastewater in terms of nutrients, TOC (or COD), and BOD.

We invite either one larger or several smaller research projects with a maximum duration of three years. The total budget allocated to this research area is SEK 4 million.

Today’s urban wastewater systems are predominantly linear, with different wastewater streams mixed. Source-separating systems are technically relatively mature but need to be introduced gradually and often in parallel with existing systems. When implemented in appropriate contexts, they can contribute to increased water efficiency and resource recovery; however, their application may also face legal, economic, and institutional barriers.

The risk of water scarcity is driving interest in technical solutions at the municipal level, such as wastewater reuse and desalination. These solutions require costly investments but often entail limited changes to existing linear pipeline infrastructure. The technologies involve increased costs and provide weak incentives for reducing water consumption. Source-separating systems, by contrast, enable more far-reaching improvements in water and resource efficiency but often require adaptations in both the built environment and public water and wastewater infrastructure. Water savings can, however, already be achieved through application at the building level, without simultaneous changes to municipal sewer networks.

To date, the expansion of source-separating systems has mainly taken place through innovation projects rather than as a response to concrete supply challenges. Development often occurs in conjunction with the planning and construction of new urban districts. It remains unclear to what extent municipalities can promote such solutions in other contexts through spatial planning, building permits, or other policy instruments, as well as what legal barriers may exist.

Transition can take place at different levels—through detailed development plans and new public water and wastewater infrastructure in new urban areas, or in existing built environments through building permits, renovations, and building-level solutions. Local diversification of water supply, for example through the reuse of greywater for toilet flushing, local irrigation, shower-to-shower reuse, or other water qualities, also raises questions about the distribution of responsibilities between municipal water and wastewater managers and private property owners, as well as the need for new organizational models. The introduction of water-efficient and source-separating technologies also touches upon issues related to water and wastewater tariffs, individual metering of water consumption, and social and institutional acceptance.

Within this call, we seek analyses that are based on a limited number of case studies and that highlight the socio-economic, legal, as well as social, cultural, and institutional conditions for the introduction of technologies that increase source separation of wastewater and improve water efficiency. The analyses should also include acceptance of the promotion of these new technologies among professionals working within relevant authorities and institutions, as well as among residents.

The studies should concern technologies that regional and municipal authorities and/or private actors have implemented or considered implementing, for example:

• Technologies for modern source-separating wastewater systems,
• Technologies for water efficiency in buildings, such as water-saving fixtures, individual water meters, and local water reuse,
• Technologies for municipal wastewater reuse and reuse systems, as well as municipal desalination of seawater.

The analyses should focus on a limited number of concrete projects, including both those that have resulted in successful implementation and those that have encountered barriers or setbacks during planning, implementation, or operation. The call should be viewed in light of, inter alia, EU (2025/1179), EEA (2025), and SOU 2023:72.

The following questions may, but do not have to, be addressed in the analyses:

• Is regional or local community development in Sweden constrained by limited water availability? Are there examples of establishments or developments that have not been realized because access to drinking water could not be ensured?
• To what extent do municipalities assess that they can, in the long term, fulfil their responsibilities for housing provision and water services within the current regulatory framework and with predominantly linear systems?
• Is there a need for or interest in applying complementary technical solutions (such as individual water meters, low-flow fixtures, urine separation, vacuum toilets, or source-separating sewer pipes) to address actual problems in the provision of water services? What economic drivers exist, for example cost savings?
• Are there legal barriers to requiring or promoting the use of source-separating or other technical solutions in specific locations? Can such barriers be overcome through voluntary regional or local cooperation? Do stakeholders perceive a need for clarification in the regulatory framework?
• How are increased construction costs resulting from choices of water supply and wastewater solutions managed?
• How are issues of water conservation and source separation integrated into the planning process, the construction process, and later into the operational phase? What is feasible in existing versus planned developments?
• Can requirements be set sufficiently early in processes to make them predictable?
• Are there examples where these issues are actively driven in planning, construction, or operation and lead to success, and conversely where initiatives encounter resistance or obstacles?
• How is the use of the connection point (förbindelsepunkt) under the Swedish Act on Public Water Services applied as a basis for distribution of responsibilities between public and private actors when introducing building-level technologies for water efficiency and reuse?
• How is environmental supervision related to water conservation and water efficiency conducted, and how is the resource-efficiency principle of the Environmental Code applied in municipal spatial planning? Do issues of efficient water use have a given place in the design/planning of the built environment?
• How do local and regional actors perceive that the national level (legislators and central authorities) addresses regional and local problems related to water scarcity?
• How is the municipal water and wastewater tariff used to promote water savings and the introduction of new technologies? Is there scope for greater use, and what barriers exist?
• Are source-separating systems and other water-efficient technologies compatible with the principles of full cost recovery and equal treatment under the Swedish Act on Public Water Services and the Local Government Act?

We invite proposals for a research project with a duration of approximately 1.5 years and a maximum budget of SEK 1.5 million.

Swedish wastewater treatment plants apply so-called upstream measures to reduce the amounts of pollutants in influent wastewater and in sludge or other resources that can be recovered from wastewater. By identifying pollutants and tracing them upstream in the sewer network to connected activities, households, stormwater sources, or infiltration into the sewer system, many primary pollution sources have been identified. Through targeted mitigation efforts, there are several good examples where wastewater treatment plants, sometimes with support from supervisory authorities, have achieved measurable success in reducing incoming pollutant loads from both diffuse and point sources.

Despite many years of upstream work, even those wastewater treatment plants that have progressed furthest in such efforts still detect significant amounts of known pollutants in influent wastewater that lack source attribution. The chosen focus for this area is PFAS, for which there are currently deficiencies in data on both the quantities and types of PFAS contributed by households.

Improved knowledge of the primary sources contributing to PFAS loads in household wastewater will enhance the ability of different actors to take action within their respective mandates to reduce the spread of pollutants via wastewater treatment plants in the most socio-economically cost-effective manner.

We invite proposals for a project that begins with a synthesis of existing knowledge on which PFAS compounds enter wastewater from households and what their primary sources are. This synthesis shall be followed by a project phase focusing on analyses to trace remaining sources. Any subsequent verification measurement campaigns, source-tracing activities, and further analyses shall be informed by the findings of the initial synthesis. The project shall address the following questions:

• Which actors have which tools to reduce which types of PFAS loads originating from households?
• Under what circumstances is treatment at wastewater treatment plants justified compared to measures taken at the source? How do such conclusions differ depending on which PFAS compounds are considered?
• Who currently bears PFAS-related costs, where do mitigation costs ultimately fall, and does this have implications for the selection of possible policy instruments?

A combined expertise and prior experience in chemical analysis, targeted sampling and source tracing, and socio-economic analysis is considered highly meritorious. Joint applications from several research groups with complementary expertise are therefore encouraged.

The results will be used in national PFAS coordination efforts, as input for the Swedish implementation of the EU Urban Wastewater Treatment Directive, the Sewage Sludge Directive, and the EU Water Reuse Regulation, as well as for the water authorities´ preparations for the next river basin management plans for 2033 and for risk assessments of decentralized wastewater solutions.

We invite proposals for a research project with a maximum duration of three years and a maximum budget of SEK 4 million.

In Sweden, there are approximately one million properties that are not connected to the municipal wastewater network, and around 700,000 of these properties have a flush toilet connected to an on-site wastewater system. On-site wastewater systems designed for up to and including 200 population equivalents (p.e.) serve both households and smaller businesses. In addition, there are shared facilities designed for more than 200 p.e. that are also classified as on-site systems. Many holiday homes are likewise served by on-site wastewater systems.

A large proportion of on-site wastewater systems require electricity to function. This includes more advanced treatment technologies such as package wastewater treatment plants, but also many simpler soil-based systems depend on electricity for pumps to operate. Access to water is further a prerequisite for, for example, flushing a toilet. In most cases, water supply is also dependent on electricity.

Electricity supply is therefore a key factor for both effective treatment in on-site wastewater systems and access to drinking water outside the municipal water and wastewater network. At present, there is a lack of knowledge on how electricity supply and access to functioning wastewater systems and drinking water in rural areas can best be secured in the event of a crisis.

We invite proposals for a synthesis on what is required to maintain functioning wastewater systems during a crisis for properties not connected to the municipal wastewater network. The synthesis shall compile existing research findings and practical experiences. In addition to peer-reviewed scientific articles, the compilation should include government reports and other ”grey” literature. The methodology used for the literature search and the criteria applied for selecting the literature to be included must be clearly described.

Based on the synthesis, an analysis shall then be conducted of the validity and reliability of the conclusions, and the generated knowledge shall be assessed from a holistic perspective. Both national and international perspectives should be considered. International knowledge may need to be adapted to Swedish conditions.

The following aspects should be included in the synthesis:

• Mapping of approaches used in Sweden and other countries. Can experiences from other countries be applied in Sweden? What barriers and opportunities exist?
• Can, for example, municipal resilience hubs, energy communities, island operation (stand-alone grid operation), energy storage, or backup power increase preparedness, and what is required for such measures to function? Are there other ways to secure access to electricity in order to ensure access to on-site water and wastewater services in an emergency preparedness context?
• Which actors can influence the level of preparedness for on-site water and wastewater systems in rural areas, and what can or should these actors do?
• Are there key factors other than electricity supply that need to be considered in order to ensure adequate preparedness for on-site wastewater systems?

The results should be usable by an actor wishing to proceed, for example, with an application to the Swedish Civil Contingencies Agency for project funding under Appropriation 2:4 Civil Emergency Preparedness to strengthen societal crisis preparedness and defence capacity, or Appropriation 2:6 Grant Compensation to Non-Governmental Organisations.

We invite proposals for a synthesis study with a maximum duration of one year and a maximum budget of SEK 1.5 million.