Tens of thousands of cubic metres of sludge contaminated with aluminium and other pollutants are being stored at sites near Wigtown, Barrhead, Coatbridge, Falkirk, Cupar and Inverness, as well as across Argyll, Aberdeenshire, Sutherland, Orkney and elsewhere (see table below).
An investigation into the safety of the sludge lagoons has been launched by the government company, Scottish Water, while environmentalists are demanding that the sites be cleaned up.
According to the Scottish Environment Protection Agency (Sepa), 18 of the sites are left over from when drinking water was treated with an aluminium compound to remove impurities. The resultant sludges have been contaminated with aluminium, which has been linked to breast cancer, Alzheimer's disease and other health problems.
“There is a possible risk of such aluminium leaching,” Sepa said, though its “binding nature” meant that it was likely to stay in the sludge. Other lagoons contained old sludges from sewage treatment that were “relatively benign”.
"Many people will be shocked to learn of these potentially toxic lagoons dotted around Scotland,” said the Green MSP, Alison Johnstone. “They are an unfortunate legacy and it's vital Scottish Water and Sepa properly assess them and figure out what to do with them.”
She called for assurances that the sites posing the greatest risk would be safely cleaned up as soon as possible. “These lagoons are proof that we need sustainable infrastructure systems to minimise our impact on the environment and prevent future generations being left to clear up the mess we leave behind.”
She was backed by Dr Richard Dixon, the director of WWF Scotland. “Aluminium is certainly not something we want leaching out of these lagoons because it represents a danger to human health and to wildlife,” he said. “This is a large and potentially nasty legacy that Scotland needs to deal with.”
He added: “The public needs to be assured first of all that all these sites are currently in good condition, and that, at the least, there is a detailed plan in place to make sure they stay that way. But we need to go further and look for permanent ways to remove this threat to the environment.”
It is uncertain exactly how much sludge is in the lagoons, but Sepa said that the “middle-sized” one at Cupar in Fife could contain up to 2,000 cubic metres. “Almost all of these sites are still within the curtilage of existing Scottish Water works and are being maintained and managed to some extent,” said Sepa manager, Colin Anderson.
“To develop greater understanding, Scottish Water is commissioning an extensive study to assess these sites and any potential risks they pose, including leaching. Sepa will continue to work closely with Scottish Water to ensure suitable remediation is undertaken where required.”
Scottish Water pointed out that the sludge lagoons dated back to when local authorities provided water and waste treatment. It had inherited them when it was formed in 2002.
“Our focus is always to ensure we manage the material in a sustainable way,” stressed a Scottish Water spokesman. For the sewage sludge, this meant recycling it to land to use its nutrients.
The aluminium-contaminated sludge was “predominantly inert” and was mostly disposed of as landfill. “It is not believed these sites present a particular risk,” he said.
“We are delivering a project to undertake environmental surveys to understand the extent and nature of them, and to confirm any environmental issues. This will help us determine the most appropriate means to manage them, in agreement with Sepa.”
26 toxic sludge sites
Bareagle, Wigtown, Dumfries and Galloway
Coatbridge, North Lanarkshire
Orbiston, North Lanarkshire
Barrhead, East Renfrewshire
Giffnock, East Renfrewshire
Kinneil Kerse, Falkirk
Loch Eck, Argyll
Torra, Isle of Islay
Craignure, Isle of Mull
Assynt, 15 miles north of Inverness
Old Calder Works, Caithness
Big Breck Quarry, Orkney