Scottish Water has been fined for supplying water contaminated with hydrocarbons, iron and manganese to more than 6,000 households.
The incident, in June 2015, left residents without water for drinking, cooking or washing, meaning that businesses and schools had to close for more than 24 hours.
An investigation by the Drinking Water Quality Regulator for Scotland (DWQRS) found that the inadvertent shutdown of the water main supplying the area during maintenance resulted in contaminated water being drawn back into the water supply system.
Although some of the contamination arose from a third party industrial source, some was residual contamination left in a length of redundant water main that remained connected to the network, the regulator said.
However, the water was deemed unlikely to cause illness to anyone drinking it, according to health professionals who analysed samples of the water.
Sue Petch at the DWQRS, which bought the case for prosecution, said: ‘This incident caused considerable inconvenience and worry to a large number of consumers in North Lanarkshire.
‘People’s confidence in the safety of the water supply was compromised, and our investigation found deficiencies with Scottish Water’s operational processes. It was for this reason that we took the highly unusual step of reporting the case for prosecution.’
Peter Farrer, chief operating officer of Scottish Water said the company apologised unreservedly for the disruption caused by the incident.
The firm distributed 600,000l of water to households whose supply was contaminated, he said. High quality tap water supply was restored within 24 hours, with drinking water supplies reinstated within a further 12 hours, he added.
‘Our staff worked closely with a wide range of partners in the community, including public health specialists, who assessed the health risk was minimal.
‘We have systematically reviewed operational and management processes and conducted a Scotland-wide assessment of our underground infrastructure. This is to minimise the risk of a repeat of this incident,’ he said.
The firm was prosecuted for supplying water unfit for human consumption under Section 76C of the Water (Scotland) Act 1980 and fined £3,250.
