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Dealing with pollution in urban water systems - a research film

Our Technical Director Peter Worrall has been advising on urban and rural sustainable drainage (SuDS) design since the early 1980s. This work is now the subject of a short research film commissioned by Middlesex University which focuses on the science and research that underpin sustainable drainage design.

The film can be seen here

Lian Lundy who heads the Urban Pollution Research Centre at Middlesex University describes the work she is doing around the treatment of pollutants in the urban environment and the importance of research that can be applied by practitioners.

At PAA this research gives us the confidence that our sustainable drainage schemes are founded in science.

In one example at Catesby Business Park near Doncaster we designed and installed a scheme in 2005 where under normal flow conditions the reed dominated wetland SuDS provides pollution buffering of the runoff which eventually flows through nearby Poterric Carr SSSI.

Inlet of Catesby Business Park SuDS in December 2013.

The challenge was whether higher than normal flows could be effectively treated other than by the dilution effect of high flows. In this case the inflow end of the wetland has a deep-water sediment trap and, downstream, a floating wetland system. As higher flows lift the water level in the system the rafted wetland rises and the curtain of roots and rhizomes beneath the rafts assists in the filtration of sediment in the throughflow. The steep sides of the SuDS (based on sub-soils) were planted with a flower rich grassland mix that would tolerant recurrent short period inundation.

During a recent review of the site (December 2013) it was apparent that no maintenance had been undertaken since completion of the system in 2004. The floating wetland component was still operational and the reed stem density was not causing any problems in terms of water short-circuiting the system. It was also apparent that whilst the development site was not yet fully occupied the drainage system of inter-connected ditches and SuDS wetlands were supporting a broad range of invertebrate and bird life. However, as can be seen in the illustration the overgrown inlet and overflow structures are unlikely to operate efficiently without some management intervention.

You can read more about PAA’s approach to sustainable drainage design in the Routledge Handbook of Urban Ecology (2001) edited by Ian Douglas, David Goode, Mike Houck and Rusong Wang.