59% of Ireland's urban water treatment plants failed to consistently meet standards set out in in their licences for water discharge, the Environmental Protection Agency (EPA) has said.

The EPA's Urban Wastewater Treatment in 2024 report, which has been released today (Thursday, October 9), said that investment at priority areas is delivering some improvements, with the volume of raw sewage discharged daily decreasing by half since early 2024.

However, wastewater discharges continue to harm water quality in rivers, estuaries, lakes and coastal waters, the agency said.

EPA licences set out the treatment standards necessary to prevent pollution and protect the environment.

The agency said its assessment of wastewater discharges highlights that 59% of licensed treatment plants fail to consistently meet these standards, with failures ranging from occasional, short-term breaches to persistent discharges of poorly treated sewage.

The main causes are inadequate infrastructure and poor operation and maintenance of treatment plants, according to the EPA.

The agency called for operation and maintenance issues to be resolved as a matter of urgency; however, the EPA said that addressing infrastructural deficits is a longer-term challenge that requires investment.

Due to the length of time that will take, the EPA called on Uisce Éireann to give priority to the areas where improvements are most needed and will bring the greatest benefits.

The EPA has identified 78 priority areas for improvements. Uisce Éireann has not yet started the works needed at half of these, the EPA said.

The report also showed that treatment at 14 large towns and cities failed to meet EU-wide standards set in the Urban Wastewater Treatment Directive.

Six of these met the standards in 2023, with the EPA calling for Uisce Éireann to take action to prevent previously compliant treatment plants becoming non-compliant.

The agency said that wastewater treatment in Ireland has not kept pace with the needs of a growing population, and that significant and sustained investment will be required over many years to upgrade all deficient treatment systems.

The EPA has identified the following as priority areas for improvements:

15 towns and villages that discharge raw sewage;
14 large towns and and cities where wastewater treatment failed to meet EU standards;
34 priority areas where wastewater discharges are adversely impacting the quality of rivers, estuaries, lakes, and coastal waters;
2 sewer networks where upgrades are necessary to prevent sewage overflows near beaches with poor bathing water quality in 2024;
10 owns and villages where wastewater treatment needs to improve to protect endangered freshwater pearl mussels;
5 coastal towns and villages where upgrades are needed to protect waters designated to support the life and growth of shellfish;
6 large urban areas where sewer networks must be upgraded to protect the environment and address a 2019 judgement from the Court of Justice of the EU.

Commenting on the urban wastewater report for 2024, EPA director for environmental monitoring Pat Byrne said: "Targeting improvements at priority areas identified by the EPA is delivering environmental benefits.

"However, delays in designing and delivering infrastructural upgrades required at many more areas are prolonging negative impacts on water quality and the wider environment," Byrne added.

Commenting on the operation of maintenance of treatment plants, EPA programme manager Noel Byrne said: "Too many wastewater treatment plants are failing to meet licence standards due to poor management and maintenance practices.

"This is simply not good enough. When treatment plants break down or are not managed properly, our environment pays the price.

"Poor operational performance will not be tolerated by the EPA. Uisce Éireann must take immediate action to improve the operation and management of treatment plants and implement effective maintenance programme to prevent equipment breakdowns," Byrne said.