Domestic waste water and partly also industrial waste water can be utilised as a source of carbon and nutrients. Nutrients important for the nutrient cycle are phosphorus and nitrogen.
Approximately 3,500 cubic litres of domestic waste water is generated in Finland every year. According to investigations by Sitra, nutrients and carbon worth several millions of euros are lost in waste water processing in Finland. With efficient nutrient recycling, the nutrient load causing the eutrophication of water, and the harmful climate impacts of the manufacture of mineral-based fertilisers, could be reduced.
The municipal waste water processing methods currently in use are based on a technology developed in the 1970s. In the method, nutrients are lost when most of the nitrogen and part of carbon and phosphorus end up in the atmosphere or in a non-useful final repository.
The opportunities for using waste water sludge as a fertiliser have been limited so far. The heavy metals, pathogens and medicine residues in the sludge impair its usefulness in agriculture, and its phosphorus is not in a form easily utilisable by plants. As a result, most of the processed sludge is currently used for green area development.
A waste water processing method has been developed in VTT's Resource Container project for purifying water and recovering the nutrients and carbon compounds found in waste water. The aim is to develop a movable waste water processing unit that can be scaled according to needs.
Finnish equipment manufacturers focusing on developing equipment for each phase of the process are also involved in the project. The best technologies are combined to create a movable waste water purification container that can be used in small-scale waste water purification projects.
"With the container, Finnish companies can demonstrate the technological strengths of their products. In my opinion, this also offers good business opportunities for Finnish companies on the global market", says Hanna Kyllönen, Senior Scientist at VTT.
The concept has already been tested at a waste water purification plant in Parainen. The aim of a further project is to test the system in the archipelago, where challenges include customising waste water purification for a varying number of inhabitants, utilising purified water on site for irrigation, for instance, and commercialising nutrients and solid matter.
The purpose the development work in 2018–2019 is to proceed to the company-based pilot phase. If the concept can be made to work in a sufficiently small, multipliable scale, it will offer new business opportunities for Finnish sub-process suppliers, the owner of the complete solution and possibly also for suppliers offering waste water purification services. The further project is currently being prepared as a parallel project.
hanna.kyllonen (at) vtt.fi
The Resource Container project is one of the Breakthrough in Nutrient Recycling ecosystem (RaKi) projects of Tekes' BioNets programme. The aim of the ecosystem is to allow the breakthrough of nutrient recycling and to create new Finnish business for the global market.
Text: Suvi Salmela
Photo: Hanna Kyllönen