Dundalk’s water woes solved? Uisce Éireann's new filter trial significantly reduces discolouration

Uisce Éireann yesterday met with Louth County Councillors to provide an update on the recently completed pilot study at Cavan Hill Water Treatment Plant, which trialled new filters to remove manganese from raw water.

Discolouration issues affecting the Cavan Hill supply, which supplies Dundalk and surrounding areas, has been particularly prevalent in the summer with rising temperatures increasing levels of manganese in raw water which result in instances of discoloration.

Uisce Éireann says it continues to prioritise works to address the intermittent water discolouration and has undertaken works both at the water treatment plant and in the network to manage the issue. 

Along with network flushing, a pilot study began in September 2024 which involved commissioning a new purpose-built containerised unit at the treatment plant to trial new filters which remove manganese from treated water. 

The results of the trial showed that the filters were effective in significantly reducing manganese levels in the water, and the design of a project to upgrade the water treatment plant with these new filters is underway.

James O’Hagan, Uisce Éireann’s Water Network Operations Manager, said: “The increase in water temperatures during the summer months leads to intermittent instances of discolouration on the Cavan Hill water network. Last year our team rolled out a 16-week targeted flushing programme, completed in June 2024, which proved effective in reducing instances of discolouration. The pilot project commenced in September 2024 to find an enduring solution.”

Following the pilot, an upgrade project is now being designed. Commissioning of the new filters will require upgrades to residual processes in the water treatment plant. To progress with this project, statutory consents such as environmental assessments and planning permission may be required.

Mr O’Hagan continued: “While the design and planning of the Cavan Hill Water Treatment Plant upgrade project is ongoing, we will take a proactive approach to minimising incidences of seasonal discolouration by scheduling flushing programmes when ambient temperatures are forecast to rise.”

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Upgrade works to Cavan Hill Water Treatment Plant in 2021 were successful in removing organic material and have led to improvements in the colour of the water. Since then, in a bid to eliminate the intermittent colour which can occur in the summer months, two further trials on the treatment process have taken place. These results have led to the recently completed pilot study which aimed to find a permanent solution.

A spokesperson for Uisce Eireann said: “Protecting public health is the top priority for Uisce Éireann. Regular sampling is carried out on the network, along with operational sampling at the water treatment plant. This provides reassurance that the water is compliant once running clear and assists with investigations into discolouration reports.

“Uisce Éireann reiterates its advice to customers not to drink discoloured water. When water is discoloured, we recommend people to run the cold water tap in the kitchen for several minutes, as this will usually restore water to a clear colour. The water is safe to drink once it is running clear.  Should discolouration persist after twenty minutes customers are encouraged to contact our customer team on 1800 278 278.

“As part of Uisce Éireann's continuing commitment to keep the community informed, we will continue to engage with all local elected representatives and issue updates as the design of the upgrade progresses.”