Castletroy Wastewater Treatment Plant

Wastewater Project

Uisce Éireann, working in partnership with Limerick City and County Council, is proposing an upgrade to the Castletroy Wastewater Treatment Plant to support existing and future population and economic growth.

Castletroy Wastewater Treatment Plant (WWTP) has been providing wastewater treatment to the area since the early 1990’s. It serves the East Limerick suburbs of Castletroy, Annacotty, Mountshannon and Castleconnell, as well as the University of Limerick and other local industry. The plant is currently operating at the upper limits of its capacity and Uisce Éireann has identified that an upgrade is required.

The continuation of appropriate wastewater treatment is vital to safeguard human health and the environment especially as population grows and industry expands in East Limerick.


Project Need

The plant is currently operating at capacity of 45,000 population equivalent (PE), which is appropriate to cater for existing wastewater loads. However, the demands of population growth and industrial development will cause Castletroy WWTP to become overloaded in the coming years. The proposed upgrade project will increase its capacity to treat wastewater for the calculated 10-year growth projections of 77,500 population equivalent (PE).

Moreover, there is currently no provision for stormwater storage at Castletroy WWTP which means that occasionally during heavy rainfall events excess stormwater is discharged untreated into the Lower River Shannon. This proposed project upgrade will include the construction of a stormwater storage tank in order to store excess stormwater until the main plant can accept and treat the excess flow.

The Lower River Shannon is an area of environmental conservation under the Habitats Directive 92/43/EEC (Commission of the European Communities, 2007) and must be protected from any potentially harmful wastewater emissions.


The proposed upgrade at Castletroy WWTP will bring many benefits including:

  • Modernise and improve the performance of the existing wastewater treatment plant
  • Improve the health and integrity of the environment
  • Protect the water quality in Lower River Shannon and conservation habitats
  • Provide sufficient capacity to facilitate future population and industrial growth
  • Protect recreational waters for fishing and boating activities
  • Ensure compliance with Irish and EU legislation now and into the future

What’s involved?

​The proposed upgrade at Castletroy WWTP will involve:

  • Construction of a new stormwater storage tank
  • Installation of new primary treatment filters and lifting pump
  • Upgrade of the existing secondary treatment tanks to provide additional capacity
  • Construction of a new primary sludge holding tank
  • Upgrade of the plant’s sludge treatment facilities

Stakeholder Engagement

Members of the public are welcome to contact the Project Team if they have any questions on the Castletroy Wastewater Treatment Plant Project via

These dedicated webpages will be updated as the project progresses.

Public Consultation

Public consultation was held between the 1 June and 15 July 2022 on the Castletroy Wastewater Treatment Plant Upgrade Project. The purpose of the consultation was to gather feedback from statutory bodies, interested parties and the general public on the project.
A recording of the presentation held on 13 June 2022 can be seen here.