However, the company said there may still be traces of the parasite remaining in the water distribution network, so the boiled water notice will remain in place until at least Tuesday evening.
Speaking to Utility Week, UU customer services director Gary Dixon said: “The plant is running fine and we has a clear sample at 5 o’clock this morning, so we now know the plant is producing high quality water and the cryptosporidium is not coming out the plant.”
He added that the “vast network” which serves 300,000 people across Lancashire “is going to take some time to flush out” but added that the more people that use water, despite the boiled water notice, will help to clean the system.
“The more water we pass through the system, the sooner we can make sure we have negative tests, out there on the network, and the sooner we can lift the boiled water notice.”
The Franklaw treatment work in Preston is not believed to have been faulty as Dixon said UU has spent a lot of money at this plant over the last five years and has been producing 140 million litres of water every day “to a high quality for many years”.
Dixon added: “For me this is about something that’s gone on somewhere else that has caused this issue.”
The source of the parasitic contamination is currently under investigation by UU and the Drinking Water Inspectorate (DWI).
So far only “a handful” of customers have complained about feeling unwell during the course of the boiled water notice, although Dixon said: “It is difficult for us to link that to this incident at this stage.”