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An underground water treatment system will help Helsinki Airport clean water more effectively

Article published
5.8.2019 at 09:00
Lentokone laskeutuu niityn ympäröimälle kiitotielle.
Water management is an important part of Finavia’s environmental responsibility. The new underground wetland treatment facility will mean cleaner waters for the watercourses surrounding Helsinki Airport.

Good environmental work is part of Finavia’s corporate responsibility. The Sum of Good Things article series highlights details of Finavia’s responsibility work. This article focuses on water management at Helsinki Airport.

Finavia is building a Subsurface Flow Wetland at Helsinki Airport. The wetland improves the condition of the streams in the area by enhancing the quality of the flowing water and boosting oxygen balance.

The underground wetland works so that the airport’s urban runoff is fed to it and filtered through the sediment and the biofilm that grows in it. First the water is led to the surface of the wetland, from which it flows through the gravel into the drainage piping, which is situated above the aeration pipes. Aeration prevents the wetland from freezing in the winter. On top of the treatment layer, a bed of plants becomes a cover that acts as insulation during cold months.

The construction plans for the wetland are almost completed and construction will start in September, says Finavia’s environmental specialist Tuija Hänninen.

“This is an exceptional construction, and there is no equivalent in other parts of Finland. A lot of product development has gone into designing the equipment required by the wetland aeration, and they are made in a specialised machine shop,” says Hänninen.

Underground wetlands are safe and efficient

The underground water treatment system to be carried out in the autumn will be constructed in the western part of the Veromiehenkyläpuro stream basin. The first wetland pool will work as a test structure: based on the information received from testing it, the design of future wetlands can be refined.

New wetlands are needed to control the airport’s urban runoff and to enhance the water quality of the streams. Helsinki Airport is located in an upland area where the waters flow in several different directions to streams in the area. The runoff network has developed for decades as the airport has expanded, and for example the water release areas can’t be changed within the restricted area. We have to adapt planning the water treatment system within the existing situation. To balance the streams, Finavia has already built flood tanks in Veromiehenkylänpuro and Kirkonkylänoja streams.

“We need to temporarily hold the water so that when it rains or as the ice melts in the spring, it does not run into the watercourses all at once, which could cause erosion. We also treat the water to decrease the impacts of aircraft and runway anti- and de-icing fluids on the local waters,” explains Hänninen.

Underground wetlands are a solution tested at world airports. As other wetlands, they do not attract birds, which is important for aviation safety.

First one in the Nordics

The right structure for Helsinki Airport’s new underground water treatment system has been developed through a thesis study at Aalto University, as part of the New Smart & Clean solutions for urban runoff management project. According to Hänninen, this will be the first time that such a solution will be tested for airport urban runoff management in the Nordics. A similar solution is in use at London Heathrow Airport, for example.

A regular passenger won’t notice the underground wetlands, but the inhabitants and recreational users of the Veromiehenkyläpuro stream will benefit from better water quality.

“Water management is a crucial part of Finavia’s environmental responsibility, and we do our best to make sure the local waters are in the best possible condition. New solutions can help us improve our water management from its already good level,” concludes Hänninen.

Read more about Finavia’s water management

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