Water passing through Southwest Finland’s water circulation system begins its journey at the Kokemäenjoki River. It is pretreated before being absorbed as artificial ground-water in Virttaankankaa. From there, the water travels to Saramäki rock storage in Turku. The water is then used within the municipalities of Turku, Naantali, Paimio, Kaarina, Lieto, Nousiainen, Parainen, Masku and Raisio. Following use, it makes its way to the Kakolanmäki Waste Water Treatment Plant in Turku where it is used to produce district heating and cooling. Finally, the sludge from the waste water is dried and transported to Biovakka Finland where it is turned into biogas, which can be used to produce electricity and district heating.
%20.jpg "© Turku Region Water Ltd.")
.jpg "© Turku Region Water Ltd.")
.jpg "© Turku Region Water Ltd.")
.jpg "© Turku Region Water Ltd.")
Planning the water circulation system
In the past, Southwest Finland used water from the Aurajoki River. This was far from ideal, with the following problems evident:
- Water varied in both quality and availability.
- Lack of integration between the waterworks of the different municipalities made it difficult to deal with disruptions in supply.
- Separate waste water treatment plants induced great stress on the drainage basins of the area.
- Waste waters were not utilised efficiently.
Developing a system on the scale necessary to address this wide range of problems took time. The initial investment required was high and there were strict regulations and legislation that needed to be adhered to. In the end, however, policymakers were motivated to pursue the project due to environmental and public health concerns. In addition, it was suspected that, in the long term, the renewal of existing plants would be more expensive than building the new system.
Implementation of the system
As a complete package, the Southwest Finland water circulation system is a pioneer in its field, engaging regional municipal companies to carry out the many different phases of this multi-scale concept. The system creates a good reference point in terms of selling the concept of integrated water resource management and showing that it is more than just a good idea on paper. The Kakolanmäki Waste Water Treatment Plant’s ability to efficiently cater for the 200,000–250,000 inhabitants of the region is a clear example of the success of the system as a whole. Ideas for potential start-up companies have come from the project; for example, purifying medical residues from waste waters. Two doctoral dissertations on the water production part of the system have also been written.
Artificial ground-water production
A special feature of the water circulation system is the manufacturing of artificial ground-water for household water use that was introduced in 2012. The raw water is taken from Kokemäenjoki River in Huittinen and pretreated by sieving, sedimentation and filtration. The sludge derived from pretreatment is dried and utilised elsewhere. After pretreatment, the water is transported to Virttaankankaa (by 30-km-long pipeline) where it is absorbed into an esker (a long, narrow, winding ridge composed of stratified sand and gravel deposited by a subglacial or englacial meltwater stream). The water flows inside the esker for three months and is then transferred to Turku and Lieto (by 60-km-long pipeline). At the end of the pipeline in the Saramäki rock storage in Turku there is a turbine that produces electricity used for water production. The water is stored in the rock storage until it is passed for usage through the Halinen waterworks. The total length of the pipeline is approximately 120 km and the cost of the whole water system was approximately €150m.
Regional dimension
The greatly improved water quality and protected water supply are good examples of the regional added value brought about by the water circulation system. Today, the water is very close to ground-water quality even though artificial ground-water is used. The better water quality is also good for the regional economy (especially for the food and beverage industries), increasing the regional sustainability and competitiveness. On a broader scale, centralising all municipal waste water treatment plants in one location at Kakolanmäki has resulted in fewer load point centres, which has had a positive effect on water quality in the Baltic Sea.
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