An audit of the drinking water supply to Cork city was initiated this summer after a consumer complained of worms coming out of a tap.
A report by the Environmental Protection Agency (EPA) revealed worms were also subsequently found in a filter at the Inniscarra water treatment plant which provides drinking water to over 131,000 homes in the Cork Harbour area including the city.
Irish Water informed the EPA that a customer based in Carrigaline had reported white worms coming from a kitchen tap on July 2.
An official checked and flushed the pipe network in the vicinity of the house and the report said no further worms had been observed by the complainant.
The audit said Irish Water had promptly initiated an investigation following receipt of a complaints of worms coming from a customer’s tap.
The EPA said the species of worms was identified as Nais elinguis – otherwise known as sludge worms – which it said were “not parasitic and are harmless to human health”.
Cork County Council took samples of water from the property in Carrigaline on both July 4 and July 8 and found they were compliant for all tests for various parameters including E coli.
Follow-up tests on the Inniscarra plant, which extracts drinking water supplies from the River Lee, revealed the presence of worms in a filter.
The audit said daily samples were taken from the treated water reservoir as well as the raw water tanks and lake at Inniscarra over the following week which revealed no further evidence of any worms.
It noted that Irish Water and the council had been in contact with the HSE on the issue to consult over any potential risk to public health.
Irish Water said it intended increasing backwashing flow rates to provide more effective cleaning of filters where there had been a build-up of material.
The affected filter was chlorinated to a higher concentration to ensure any remaining worms were killed.
Irish Water also carried out flushing in the distribution system starting with the pipe network close to the complainant’s house.
The EPA recommended Irish Water to undertake sampling of all filters at the Inniscarra plant as part of its regular maintenance operations.
An Irish Water spokesperson said it was continuing to update the EPA “with a view to closing out all recommendations”.
Meanwhile, former justice minister and attorney general Michael McDowell said the story of Irish Water demonstrates a failure of political will.
Launching In Deep Water, a book that charts the sorry story, Mr McDowell said the tale needs to be written about and understood because it is replete in lessons for the political establishment.