BritishFlora

Contaminated Water

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Courtesy of BritishFlora

Treatment of Contaminated Mine Water Discharge

Recent estimates have suggested that in the UK 2,500 km of streams and an area of 9,000 km2 of groundwater bodies are at risk of failure of Water Framework Directive Objectives due to mine water pollution (Jarvis & Rees 2004).

For over two decades the Loughor Estuary in South Wales, which carries SSSI status, had been polluted by high iron loadings in minewater discharged from the defunct Morlais and Brynlliw Collieries. Since their closures in 1983 an estimated 400 tonnes of ochre (ferric hydroxide) had polluted the estuary each year.

In 2002, with flow rates as high as 289 l/sec and iron concentrations up to 53mg/l being recorded, the Coal Authority approved a major remedial scheme designed by Parsons Brinkerhoff. The solution required the contaminated water to be cascaded into two settlement lagoons and thereafter into three large surface flow wetlands where a full 24 hours of water-retention was needed to reduce the iron concentration to environmentally acceptable levels of below 1mg/l. It was to be the largest and most ambitious phytoremediation scheme the Authority had ever undertaken.

After their appointment to the scheme by Civil Engineering Contractors Edmund Nuttall Ltd, BritishFlora faced a number of horticultural challenges: the 3.1ha site was large and hostile; the planting substrate was extremely variable and had a very low organic content resulting in over compaction and virtually no permeability. All in all a potentially expensive and project delaying scenario.

As microbially mediated geochemical transformations generally occur at the interface of substrate and root biomass, serious consideration had to be given to the suitability of the planting medium. However, after exhaustive testing, BritishFlora provided the appropriate solutions, on time and on budget, resulting in the MMTS being not only the largest but also amongst the most successfully established engineered wetlands commissioned by the Coal Authority.

BritishFlora was thus able to introduce a sustainable horticultural solution that not only neutralised the discharge, but also ensured that the landscaping of the site merged naturally into the unique setting of the Loughor Estuary.

Morlais Mine Water Treatment

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