SCOTTISH Water has been fined for a pollution incident in which more than 2000 gallons of sulphuric acid leaked into a top Scottish fishing river.

Alloa Sheriff Court was told that the incident, in July 2011, was caused when a corroded bolt on a tank of sulphuric acid, used as part of the process for purifying drinking water, failed, and allowed up to 2640 gallons (12,000 litres) of the chemical to leak out. The bolt had not been maintained in accordance with the manufacturer's recommendations.

The tank, at Scottish Water's Glendevon Water Treatment Plant near Dollar, Clackmannanshire, is surrounded by a holding "bund" that should have caught the spill.

However, the strength of the acid - 96 per cent concentrated - was so high that it burned through the bitumen coating of the bund and the road surface outside and drained into the nearby Castlehill Reservoir.

There, it reacted with sludge and caused a "slug" of pollution to make its way down the River Devon.

The combination of the river being turned acidic, and poisonous aluminium being released from the sludge, caused a massive kill of fish, molluscs and shrimps.

Investigators from SEPA, the Scottish Environmental Protection Agency, noted dead trout, perch and sticklebacks littering the river margins. An estimated 30,000 fish, including 2000 brown trout, were killed in the incident.

The firm pleaded guilty and was fined £10,000.

It also admitted a second charge relating to a discharge of sewage from St Serfs Sewage Pumping Station, Clackmannan, into the Goudnie Burn on August 1, 2011. Scottish Water said it had spent "in excess of £4 million" throughout Scotland on work to ensure the sulphuric acid leak could not be repeated.