Water provider United Utilities has been ordered to pay £450,000 after contaminating the water supply of 750,000 homes and businesses

The incident in August 2015 was the largest case of water contamination in 30 years, and caused large scale disruption to homes, businesses, and hospitals across the county after they were forced to boil their water to kill parasites.

In August 2015, tests at the Franklaw Water Treatment works in Garstang, revealed cryptosporidium in the supply from the Barnacre Reservoir, to the north of the city.

The bacteria, found in animal faeces, can cause vomiting, fever and abdominal pain when consumed by humans.

Richard Banwell, prosecuting for the Drinking Water Inspectorate, told the court structural defects at the reservoir, combined with a heavy downpour of rain had led to the water becoming contaminated.

Residents in Mellor, Mellor Brook, Samlesbury, Chorley, Abbey Village as well as those further afield in Preston, Blackpool and the Fylde coast were affected.

United Utilities pleaded guilty to supplying water unfit for human consumption between July 30, 2015 and August 8, 2015.

However, the boil water advice remained in place until early September, Preston Crown Court heard.

Since the incident, the company has invested £100m in infrastructure, including fitting ultraviolet treatment systems which kill the parasite at source.

A further £25m was spent supplying water coolers to schools and bottled water to vulnerable customers.

The firm has made more than £750,000 in voluntary compensation payments with the average household receiving £50-60 as a result of the disruption.

The cost is to be borne by the company and shareholders and not trickle down to the customers.

Judge Brown said: “The normal arrangement was that clean water was supplied to the Franklaw site from the coastal aqueduct.

“However for a short period of time around the end of July works were being undertaken and instead water was being taken from the Barnacre Reservoir.”

The court heard no risk assessment was undertaken for the change of source and damage to the reservoir, coupled with a heavy storm, led to the water becoming contaminated.

Judge Brown added: “For a period of a few weeks the public suffered a great deal of anxiety, inconvenience and disruption, but there was not a widespread outbreak of illness as a result of the contamination.”

GP visits for cases of gastroenteritis increased during the boil water period, however it is believed this was as a result of the widespread concerns and did not reflect an unusual rise in cases of cryptosporidiosis.

Jude Brown ordered United Utilities to pay a £300,000 fine and £150,000 prosecution costs to the Drinking Water Inspectorate.

Speaking after the sentence, Steve Mogford, chief executive of United Utilities, said: “We are very sorry for the impact this has had on our customers. I know first hand the impact this incident caused, having lived in Lancashire for 40 years.

“We have learned valuable lessons from what happened and have put technology ad processes in place to guard against a repeat of this kind of incident.

“United Utilities is now a leading company in terms of resilience to cryptosporidium.

"Customer safety is always our primary concern and customers can be reassured that the North west’s drinking water is of extremely high quality.

“Incidents of the like that affected Lancashire in summer 2015 are extremely rare.

“The fact that we spotted the bug quickly through our routine sampling, and immediately issued precautionary advice, minimised the risk of any customer falling ill.”

Robert Light, Northern Region Chair for the Consumer Council for Water, said: "We are disappointed that serious failings by United Utilities led to such significant disruption to their customers. The company must now rebuild trust with its customers by explaining what it is doing to prevent any similar incident happening again. We will be closely monitoring them to ensure all recommendations from this incident are already or will swiftly be implemented.

Mr Light said the case had lessons for all water companies, not just United Utilities.

He added: "We expect every water company to consider the findings of the Drinking Water Inspectorate's report and address any relevant recommendations swiftly to ensure any potential risk to customers is reduced. As the water customer watchdog we will ensure that this is the case.

“We welcome United Utilities’ offer to share all the issues from this incident with other companies and will work with them to ensure this happens”.