New pavement material helps clean metals from stormwater

A new kind of pavement material is showing promise in retaining some heavy metals from stormwater runoff to prevent pollution.

Dec. 8, 2003 -- Heavy metals such as lead, cadmium, copper and nickel are causing serious and growing environmental concern in towns, cities and other built-up areas where there is risk of them being washed into rivers, streams and other water courses.

However, a new kind of pavement material is showing promise in retaining some heavy metals from stormwater to prevent pollution.

During the past eight years Formpave Ltd. has pioneered new approaches to paving systems at over 500 sites with an emphasis on stormwater detention, cleansing and even recycling. Formpave's system retains silts and other fine material on a geotextile beneath a stone laying course.

It had been found that heavy metals have an affinity to this fine material and adhere to it. However, Formpave wanted to test in controlled scientific conditions precisely how effective its unique paving system is in removing these different types of heavy metals from normal surface run-off.

During the past couple of years, the Urban Water Technology Centre at the University of Abertay, Dundee, has been testing the performance of pavements designed by Formpave at removing metals from surface run-off.

Pavements were dosed with run-off deliberately designed to simulate that seen in typical urban conditions. Samples of exit water were then collected after drainage through the Aquaflow permeable paving blocks and the special sub-base below.

These samples were analysed and the results showed that for lead, cadmium, copper and nickel more than 95% of the metals had been removed. The University's research established quite clearly the ability of the paving system to remove very high levels of metals from run-off.

The trials are now being re-run with more exotic heavy metals, for example those of the platinum group, which are of increasing environmental concern. These metals are used in the catalytic converters of motor vehicles and therefore affect urban run-off.

Bearing in mind the implementation of the Water Framework Directive, Formpave looks forward to assessing further the performance of its paving in controlling this source of water pollution.

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