Wessex Water has been fined £280,000 plus a £190 victim surcharge at Swindon Magistrates court after pleading guilty to an offence under section 70 of the Water Industry Act 1991 for the supply of water unfit for human consumption.

The case was brought by the Drinking Water Inspectorate (DWI)- costs of £21,656.60 were agreed out of court.

During a three-week period from the end of March 2021 consumers in the Amesbury area of Wiltshire complained of an unacceptable taste to their tap water which made the water undrinkable. 

The complaints came after a Granular Activated Carbon (GAC) filter was brought back into supply at the Newton Tony water treatment works supplying drinking water to approximately 17,000 consumers in the Amesbury, Wiltshire area. 

The GAC filter had been out of supply as the media had been removed and regenerated. Removal and regeneration of GAC media is a routine maintenance operation.

On return to supply of the GAC filter, according to the DWI the testing and analysis of the GAC filter had been inadequate, the company did not correctly follow their own internal procedure, which required certain tests to be completed which would have identified the presence of the iodinated compounds.

Following consumer complaints about the taste of their tap water and reactive sampling and analysis by the company, iodinated compounds were detected in the supply from the GAC adsorber at the water treatment works, downstream service reservoirs and at properties in the area supplied.

The company then removed the water treatment works and a service reservoir from supply and undertook extensive flushing and sampling of the affected area. Bottled water was supplied to consumers on request.

Iodinated compounds have a low taste threshold and are therefore readily detected. Although there was no direct health risk to consumers, the taste issues caused concern and media and social media interest.

The DWI commented:

“The company has experience of a similar events within their operating region from sites which use carbon treatment yet the lessons learnt from these previous events did not prevent this issue from happening.”

Since the event the company has taken corrective measures including strengthening its own internal procedures which cover returning carbon filters to supply.

Marcus Rink, Chief Inspector of Drinking Water said:

“Consumers experienced water with an unpleasant taste which would not have happened had the required checks been carried out on the carbon filter before it was brought into use.

“This prosecution acts as a reminder to companies that a water quality first approach must be taken when providing a service to the public. I am content that the court has recognised the seriousness of this event.’