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Now the streets of Sweden are being vacuumed from gravel and sediments. Photo: Richard Renberg View original picture , opens in new tab/window

Swedish streets are being vacuumed

Published: 22 April 2015

PhD student Matthias Borris, Urban Water Engineering at Luleå University of Technology, examines the way in which large particles that accumulate on roads in dry weather and are not conveyed further by runoff during rainfall, can affect storm water quality. After winter, large amounts of sediments can be found along the roads.

–  All the sources that cause heavy metals or other harmful substances to infiltrate our groundwater present a hazard for our health. Though, the Urban Water Engineering Research Group works continuously on this issue to minimize the risks, says Matthias Borris.

Large particles from roads are collected at several different locations in Sweden (eg, Luleå, Malmö and Stockholm) using a cyclone vacuum cleaner. The advantage of this type of vacuum cleaner is its absence of filters that otherwise would be clogged relatively fast.

The contents of the cyclone vacuum cleaner used on the streets of Luleå is analyzed right now at Luleå University of Technology in order to examine the amount of heavy metals. After having sampled by means of the vacuum cleaner, a first sighting of the desired size of particles is carried out in the lab followed by leaching tests with synthetic rainwater. In these experiments, the sediments are mixed with synthetic rainwater and then shaken to simulate the turbulence in the runoff during a rain. The shake time is determined based on the time corresponding to the average residence time of storm water on the surfaces generating runoff. When the separation is completed the total content of heavy metals is analyzed.

The first partial results of the study indicate that the most likely scenario is that large particles act as traps for smaller particles formed during dry weather and then are conveyed further by the water stream when it rains. This has implications for stormwater management and confirms the benefits of sweeping the streets regularly, especially after winter.

The results of this research conducted at Luleå University of Technology will be presented at a conference in Oslo later this spring.