Thirty-eight of the Republic’s largest sewage treatment plants are defective – including those serving Dublin and Cork – according to the Environmental Protection Agency.
The EPA Urban Waste Water Report 2013 also found that a further 44 urban areas are discharging raw sewage into lakes, rivers and coastal areas.
The report’s authors concluded that the defects were a risk to human health as well as the environment.
Irish Water has described the report as “stark” and calculated the cost of addressing the main issues in it at more than €2 billion between now and the 2020s. It plans investment of about €750 million in the State’s sewage treatment plants over the next three years.
The Environmental Protection Agency said that 20 years after Ireland signed up to the EU Directive on Urban Waste Water treatment, there were “quality failures” in many of the State’s largest sewage plants. These include inadequate infrastructure, poor management and mistakes in operation of infrastructure.
In addition to problems in Dublin and Cork, it said “sewage is receiving no effective treatment” in a number of large towns and locations, such as Killybegs, Youghal and Lower Cork Harbour.
The report found there was a “failure to achieve standards” at Ireland’s largest waste water treatment plant at Ringsend in Dublin, largely due to it operating beyond capacity. In all some 44 urban areas effectively provided no sewage treatment in 2013, according to the report.
Nine large urban areas did not meet the directive requirement to provide secondary treatment, including plants in Co Donegal serving Convoy, Bundoran and Killybegs.
There was no treatment of sewage in Co Cork at Passage West/Monkstown, Youghal and Cobh and only preliminary treatment serving Ringaskiddy, Crosshaven and Carrigaline. There was preliminary treatment at Clifden in Galway, and no treatment at Arklow in Co Wicklow.
Eight large urban areas did not meet the requirement to provide infrastructure to reduce nutrients, or did not meet nutrient quality standards. These were Cork city; Carrigtwohill; Killybegs; Ringsend in Dublin; Dundalk; Cavan; Navan and Roscrea.
The report found 29 per cent of the 441 plants with secondary treatment failed minimum standards, while 45 audits found a maintenance programme for plant and equipment was not in place.
Waste water discharges contributed to poor bathing water quality status at four designated bathing waters in 2013 including Clifden and Galway City, Lough Ennel in Co Westmeath and Doogort on Achill Island, Co Mayo. Four additional designated bathing waters are at risk from discharges.
Elizabeth Arnett of Irish Water said the report illustrated the need to leverage money to pay for work, as "the taxation model" would not have raised the sums needed. The full report is available on the EPA website.