Uisce Éireann has been criticised for not prioritising treatment works in two Kerry areas where discharge continues to be the main source of pollution.
The environmental watchdog has also criticised Uisce Éireann for failing to complete works where water quality is affecting freshwater pearl mussels in South Kerry.
The Environmental Protection Agency has highlighted Tralee and Abbeydorney as priority areas, because discharges from these areas were identified as the main source of pollution affecting local rivers, estuaries, lakes, and coastal waters.
The EPA says water quality in these affected areas should improve when impacts from wastewater discharges are resolved.
The environmental watchdog has said Uisce Éireann has not given sufficient priority to progressing improvements in these areas, despite being aware of the need to improve water treatment there since 2017.
The EPA says Uisce Éireann must accelerate the delivery of works needed to prevent pollution at priority areas.
Currently, Uisce Éireann has no timeline for the delivery of corrective actions for Tralee, while infrastructural upgrades are planned in Abbeydorney in 2029/2030.
Also in its report, the EPA says wastewater treatment must improve in Kilgarvan, to protect freshwater pearl mussels.
These are critically endangered molluscs that need clean, free-flowing, well-oxygenated rivers and a clean riverbed, but have been declining nationally and internationally due to deteriorating water quality.
The EPA says Uisce Éireann has again been aware of the need for action at Kilgarvan for over seven years, and must accelerate the pace of delivery of these works.
Uisce Éireann currently plans to begin infrastructural upgrades at Kilgarvan towards the end of this decade.
