EXECUTIVES at a water company have apologised after admitting breaches which led to the residents of four households becoming seriously ill.

Sembcorp Bournemouth Water have been fined £85,000 - plus an additional £50,000 in costs - after it supplied cryptosporidium-infected water to homes in March and April 2013.

One of the affected victims, Colin Butler, told of how he thought he would die after becoming infected by the poisonous parasite, while a baby aged just nine months old also became ill.

At Bournemouth Magistrates' Court this afternoon, Jacqueline Duff, prosecuting for the Drinking Water Inspectorate (DWI), said victims had recovered from their symptoms before the company was even aware that the water had been contaminated.

Cryptosporidiosis is a gastro-intestinal disease which can show symptoms for up to three weeks.

The first outbreak of the disease in Bournemouth was detected by Public Health England, and on May 15 2013 the organisation contacted companies in Dorset and Hampshire to ask if any operational difficulties had been experienced.

A multi-agency approach was launched, and further investigations later revealed the Alderney water treatment works was the cause of the outbreak.

An inspection by the DWI found that the plant was falling below expected standards, and questions were asked about a sewage spill seven kilometres upstream of the Longham water intake point on March 29 2013.

Ms Duff alleged the company had done "nothing" to investigate this themselves and took no further action.

It was also found that filters should have been allowed to 'ripen' for seven days before being returned to supply after cleaning - however, on more than 30 occasions, filters had been put into supply too quickly, once within just 24 hours.

Mitigating, John Mitchell said that cause was likely have been "an unfortunate combination of circumstances" which had arisen from the "complex operation and running of a water treatment plant".

The firm admitted four counts of supplying water unfit for human consumption to properties in East Howe, Southbourne, Muscliff and Merley, between April 2 and May 3, 2013, and was fined £80,000.

A fifth count, of contravening water quality regulations at Alderney Water Treatment Works between March 13 and May 22 that year, was also admitted, and a fine of £5,000 was given.

Prosecution costs of £48,771.83 and a victim surcharge of £150 was also levied by magistrates, who said that the company were "probably negligent bordering on reckless".

Sembcorp's managing director Roger Harrington has reassured customers that the water is safe to drink.

"We are very sorry that the water we supplied was linked to cases to cryptosporidiosis in our community in the spring on 2013," he said.

"We are particularly sorry for the distress this caused to our customers who suffered gastrointestinal illness. We took responsibility, and within seven months, build and put into operation an ultraviolet plant at our Alderney treatment works as part of a £7 million disinfection improvement project. This gives a near guarantee that this won't happen again."

The company's turnover in the year ending March 2014 was £46.1m, and its net profits, after tax, were £10.9m.