South West Water Ltd has been ordered to pay more than £57,000 in fines and costs after discharging too much ammonia from its sewage treatment plant at Praze-an-Beeble near Camborne.

The prosecution was brought by the Environment Agency after South West Water breached permit conditions by allowing inadequately treated effluent to enter nearby watercourses.

Strict limits are set on effluent discharged from sewage treatment works to ensure they don’t adversely affect receiving watercourses. It is the responsibility of the site operator to ensure a treatment works operates in accordance with its permit. They must carry out regular maintenance and repairs.

The sewage treatment works at Praze an Beeble requires a lot of maintenance and is permitted to discharge only a very limited amount of ammonia. Every month South West Water must take a sample of the discharge and notify the Environment Agency of the result.

In May and August 2016 the amount of ammonia discharged exceeded the amount allowed by the permit. When further inquiries were made by the Environment Agency, it transpired that the site’s online ammonia monitor had recorded that too much ammonia had been discharged from the treatment works for some 15 days in April 2016 as well.

In May, part of the site was not being cleaned often enough and equipment needed repairing. In August, part of the site had been blocked by moss, blanket weed and sludge. South West Water said the monitoring equipment had not always worked accurately in April.

"Water companies must ensure effluent is treated to a sufficiently high standard to protect the environment," said Mark Pilcher for the Environment Agency. "Regular maintenance of sewage treatment works helps with the early detection of faults and allows repairs to be made in good time before treatment deteriorates to the point where a site breaches its permit."

Appearing before a district judge at Bodmin magistrates court, South West Water Ltd was ordered to pay a £53,334 fine along with £3,957 costs and £120 victim surcharge for the Praze-an-Beeble breach. The company had earlier earlier pleaded guilty to a charge of breaching Regulation 38(2) of the Environmental Permitting (England and Wales) Regulations 2010.

In a statement, South West Water said it accepts and apologises for the temporary drop in final effluent quality on two occasions in 2016 at Praze-an-Beeble Sewage Treatment Works. 

It added: "Surveys confirmed these temporary drops in final effluent quality had no environmental impact on the Praze River.

"We have fully investigated the causes of the individual sample failures and improved the monitoring and performance of the works, which has remained fully compliant with its permit since August 2016."