POLLUTION - 27.11.2020

Caustic effluent killed off sewage plant

Unfortunate events

On 18 December 2019 an automated cleaning process went awry at the Belhaven Brewery Company Ltd in East Lothian. As a result of the overnight mechanical failure, approximately 8,000 litres of concentrated sodium hydroxide was discharged into the public sewer. When managers at the brewery realised what was happening they halted the discharge and informed Scottish Water. But the damage had already begun.

Response

Water company technicians found that the filtration tanks at the sewage works were being damaged by the caustic solution. The biological organisms in the tanks had been killed and the tanks were foaming and overflowing onto the ground. The company closed the treatment plant which then created a further problem in that it had to reduce the effluent flow coming in to the plant. It also had to deal with the spillage and clean and replace the filtration equipment. The Scottish Environment Protection Agency (SEPA) was alerted and an environmental pollution incident raised.

On investigation an outlet pipe appeared to have sustained damage and there was a concern that untreated sewage might reach the watercourse which receives the discharge from the sewage works. As a result East Lothian Council erected signs at Belhaven Bay beach warning of the risk of possible water contamination and advising against bathing until further water quality investigations were completed.

In court

Belhaven Brewery Company Limited pleaded guilty to a contravention of the Sewerage (Scotland) Act 1968 . In doing so it admitted that it had breached the conditions of its consent with Scottish Water which required it to adequately treat the effluent and meet SEPA consent limits. The company was fined £10,000. Following the hearing, a spokesperson for Belhaven apologised for the incident and said it had worked with Scottish Water to ensure an effective incident response. It also gave an assurance that it had invested in changes which would prevent a recurrence.

Prevention

As this case shows, once things go wrong with discharges from industrial premises there is a cascade effect. A simple breakdown or mistake on site can require a multi-agency response and cause significant public concern. It also illustrates how even those sites which discharge to sewage works rather than directly to watercourses need to be cautious. Sewage works are fragile environments and when they fail, there can be catastrophic effects.

Tip. If you have an industrial discharge from your site for which special consent has been required from the water company, or for which you have an environmental permit, carry out a periodic review examining the potential failures which could occur, and their consequences.

Tip. If your review identifies critical points of failure, work out how you can protect your system, either with additional or improved equipment to prevent failure, or using overflow devices and alarm systems in order to trigger human intervention. Consider what will be needed to monitor and routinely test any safety systems you install.