Österåker and Vaxholm's Future Wastewater Treatment

The new wastewater treatment plant in Margretelund, Roslagsvatten’s largest project, is set to become one of Sweden’s most sustainable wastewater treatment facilities. 

The project, led by Roslagsvatten in collaboration with NCC, has been in full construction phase since 2024. The first phase of the wastewater treatment plant is scheduled to be operational by 2027/2028. 

The aim of the wastewater plant is to become an integral and natural part of the archipelago, high-tech and resilient to extreme weather. Built with respect for people and the environment, with technology designed to meet the future and rooted in the nature, culture, and history of Roslagen. 

Project Background

Sweden’s water and wastewater infrastructure faces necessary and extensive upgrades. Roslagsvatten has proactively chosen to lead the way by implementing new technology to support the transition to a more sustainable future. The ambition is to showcase the treatment plant and share experiences that may benefit other municipalities in their development efforts.

To prepare for future needs for increased treatment capacity and to ensure sustainable wastewater treatment in Österåker Municipality and Vaxholm City, Roslagsvatten has decided to build a new, modern wastewater treatment plant. 

The new treatment plant

Roslagsvatten aims for the new wastewater treatment plant to be climate-smart. In addition to contributing to environmental, economic, and social sustainability, the facility will also enhance redundancy in wastewater treatment. 

The new treatment plant in Margretelund is being built with a process solution called MBR, Membrane BioReactor. By using this technology, an almost particle-free water is achieved, which contributes to a high level of wastewater purification.

In addition to MBR, the new facility will use pyrolysis technology. This process allows for the transformation of sludge into biochar - a climate-smart product.

Project status

During 2024, special focus has been on preparing for biochar production, which, according to the requirements of the Klimatklivet initiative, must be operational by 2026.  

Klimatklivet is an investment support, from Naturvårdsverket*, that makes it possible to invest in fossil-free future technology and the green transition. Klimatklivet is co-financed by the EU's recovery fund, NextGenerationEU.

* The agency's mission is to promote sustainable development by protecting nature and the environment, reducing climate impact, and preserving biodiversity.

The work has progressed according to plan, including foundation work, pipeline installations, and the construction of the first part of the facility. Just a slight adjustment to the timeline has been made due to the discovery of more rock in the groundwork than it was anticipated in the preliminary investigation.

– "It feels great to report that construction is progressing as planned. The new plant will not only meet the increasing needs of our growing municipalities, but will also set a new standard for sustainability and technology in wastewater treatment," says Ida Mattfolk, project manager for the new treatment plant.

The focus in 2025 will be on ensuring that the project stays on schedule while maintaining the highest possible environmental standards. 

The construction of the new climate-smart wastewater treatment plant in Margretelund, Åkersberga, has made significant progress during 2024. Serving both Österåker and Vaxholm, this project represents one of the largest environmental investments in the region’s history. Once the new treatment plant is completed, it will increase wastewater capacity, improve water quality, and enable the way for a more sustainable future for Österåker and Vaxholm.

Short information

• Construction start: November 2023
• Trial operation: December 2027
• Capacity: 57,000 PE (population equivalent*) of treated wastewater in the first phase. There is potential for two additional expansion phases, increasing capacity to 93,000 PE and 125,000 PE, respectively. The latter capacity would accommodate demand expected around the year 2050. Capacity expansions require new environmental permits.
• Construction contractor: NCC

*The amount of pollution corresponding to the average emissions per person per day, measured in biochemical oxygen demand.