Water & Wastewater Treatment

WWT September 2017

Water & Wastewater Treatment Magazine

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Page 26 of 43

Getting to Grips with… highway pollution Pollution from urban highways, trunk roads and motorways poses significant risks to the environment from toxic metals and hydrocarbons that are carried in surface water runoff. The risks are well-documented and the regulatory tools are in place, yet outfalls are inconsistently monitored and controlled. Here, we look at tools and techniques available to tackle the problem. The Knowledge Q: How does road runoff affect water quality? A: Rainwater washes pollutants from the road surface into the drainage network and, during peak and prolonged rainfall, into the receiving rivers and streams. Although highway runoff is frequently considered as diffuse pollution, it's more o en point-source outfalls that lead to cumulative, chronic pollution and build- up at the bottom of rivers and streams. Q: What causes the pollution? A: The pollution is caused by tyre erosion, dust from brake and clutch pads, engine wear, exhaust emissions, and oil and fuel leakages. Suspended solids settle out in rivers and streams, blocking up gravel where fish spawn and limiting light penetration. Hazardous HIGHWAY RUNOFF Q&A www.wwtonline.co.uk | WWT | SepTember 2017 | 27 Jo Bradley mArkeT DevelopmenT mAnAger SDS lTD pollutants are bound to the sediment and dissolved in the surface water. The pollutants of most concern for the aquatic environment and also for human health are metals, particularly copper and zinc, and a spectrum of chemicals known as polyaromatic hydrocarbons (pAHs), including benzo[a]pyrene. A Wrc monitoring study, conducted between 1997 and 2002 on behalf of the Highways Agency (now Highways england) together with the environment Agency (eA), established a list of 'significant pollutants' in highway runoff and, in europe, the Water Framework Directive sets out environmental Water Quality Standards (eQSs) for some of these significant pollutants. The data from the Wrc monitoring study revealed that the eQSs are o en exceeded in runoff from busy trunk roads and motorways. Among the pollutants that wash away from roads are polyaromatic hydrocarbons

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