United Utilities has just be slapped with a £300,000 fine for providing water unfit for human consumption. United Utilities is the UK’s largest listed water company, and will also have to pay £150,000 costs for the prosecution.

The problem came about in Lancashire in the summer of 2015 when animal waste seeped into underground tank, contaminating drinking water supplies with cryptosporidium parasite, which can cause diarrhoea and abdominal cramps.

This led to a “boil water” notice being sent out to around 700,000 locals, some of whom could not drink tap water in their homes for a month after the bug was found at the Franklaw water treatment works in Preston. Panic buying led to supermarkets in the area setting a limit on the amount of bottled water per customer.

The parasite was noticed after it was picked up by a filter system at the Franklaw site on 5 August. Inherent hazards were found at the reservoir, as well as on a neighbouring farm, and structural defects at the site led to cryptosporidium getting into the water after a heavy downpour of rain.

The warning for customers to boil their water was issued the next day and stayed in place until early September. United Utilities pleaded guilty to the charge in July.

The incident had a massive impact on the public as well as on businesses in the area, including a dentist who had to cancel 100 procedures and could only perform emergency services that did not require water.

The water company apologised for the incident, and said that it had learned “valuable lessons” and had implemented new procedures to prevent similar contaminations happening in future. The court heard ultraviolet irradiation, a treatment which inactivates the parasite, had since been installed after a £100m investment by the company.

Speaking after the sentencing on Tuesday, the firm’s chief executive Steve Mogford said: “We are very sorry for the impact this had on our customers.

“I know from first-hand the inconvenience this incident caused, having lived in Lancashire for 40 years.”

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