By dividing waste water streams into separate systems in residential properties, resources such as water, energy, and plant nutrients can be managed more efficiently. One of the world’s largest areas with a source-separated waste water system is now planned for the last phases of Stockholm Royal Seaport.
Two waste water sewers rather than one are planned in Värtahamnen (excluding Valparaiso), Loudden and Frihamnen. The system will connect 7,000 apartments and 400,000 m² of commercial space once the area is built.
Heat, biogas, and sewage sludge rich in phosdphorus are already recovered at the Henriksdal wastewater treatment plant (WWTP). But by channelling and managing flows separately, resources in waste water can be recycled to a greater degree. Apart from phosphorous, valuable nutrients such as nitrogen and potassium can also be recovered. In addition, more biogas can be produced.
“This project is extremely interesting and may lead to a paradigm shift in Stockholm’s development of waste water systems,” says Erik Karlsson, Director of Strategic Planning, Stockholm Vatten och Avfall.
Waste-water from baths, showers, and washing from households is currently treated at the Henriksdal (WWTP). However, large amounts of heat is lost on the way there. If heat can be captured earlier in the system, heat recycling can be dramatically increased. By collecting household waste water without mixing it with toilet water, it can be treated and used for a variety of purposes, for example irrigation. In this way, resources in waste water can be reused more effectively.
Source-separated waste-water systems have been built and tested in a number of cities, including Hamburg and Amsterdam and such a system has been commissioned in Helsingborg in March 2020. The system planed for Värtahamnen and Loudden will be one of the world’s largest. The collection system for Värtahamnen will be planned in 2020 and 2021 and is scheduled to enter service in 2025.
Since 2011, the issue of extending source-separated waste water system has been reviewed in different projects. The MACRO project has been running since 2015 with financial backing from Vinnova. The first phase focused on establishing a cross-silo collaborative projects. The other had the goal of reviewing the legal, technical, and organisational conditions needed to implement a source-separated waste water system in urban- and peri-urban areas. Based on experiences from other projects such as in Helsingborg, the aim of the third phase is to conduct further studies into how a source-separated waste water system could be designed as well as produce the basis for planning the system in Stockholm Royal Seaport. This will then be documented in more general planning and design guidelines for cities.
The City of Stockholm is one of 10 partner organisations along with three municipalities, business, and academia. The budget for the third phase of MACRO is SEK 18.4 million and the project is expected to have considerable significance for the future of waste water management in Stockholm.