Results of trial winter operation of UV treatment system at Ringsend wastewater treatment plant published

06 October 2022

Irish Water has today published the results of the trial operation of the ultraviolet (UV) treatment at the Ringsend wastewater treatment plant during the winter period.

Irish Water undertook the trial in response to concerns raised by sea swimmers and public representatives about the quality of bathing water outside of the bathing season in Dublin Bay.

An accompanying study of the data collected sought to establish if the operation of the UV treatment system at the Ringsend wastewater treatment plant (WWTP) would have benefits for bathing water quality during the winter period.

The UV system was trialled over the period from September 2021 – January 2022. The evidence-based assessment included an intensive sampling programme of 3,100 bacterial samples from 15 key locations as well as a water quality modelling to assess the likely impacts of the winter operation of the UV system on water quality at bathing sites in Dublin Bay.

Detailed analysis of the data collected did not demonstrate any material improvement in bathing water quality at bathing locations in Dublin Bay as a result of the operation of the UV system at the Ringsend WWTP during the winter period.

The results were independently peer reviewed and endorsed by the UCD Acclimatize project which found that the dataset that was developed was both comprehensive and appropriate for the assessment.  The UCD Acclimatize project is undertaking a research programme to identify pollution sources at urban and rural bathing waters.

The study findings are consistent with previous analyses carried out by UCD Acclimatize and Dublin City Council which have identified near-shore pressures on bathing waters as the primary reason for occasional failures in bathing water quality at designated bathing waters. Nearshore pressures on bathing water quality can include run-off from agricultural land and roads, urban wastewater, dog and bird fouling, and misconnected houses and businesses.

In the absence of a demonstrable improvement in bathing water quality, the significant financial and carbon cost of operating the UV system outside of the bathing water season cannot be justified.

Irish Water will continue to operate the UV system at the Ringsend plant during the bathing water season from 1 June to 15 September in accordance with the requirements of the Wastewater Discharge License.

Irish Water is a member of the Dublin Bay Bathing Water Task Force and is collaborating with Dublin’s local authorities to improve bathing water quality. The Task Force is committed to ensuring that Dublin Bay’s designated bathing locations can be enjoyed by swimmers as often as possible.

Irish Water undertakes a range of initiatives and measures to help improve bathing water quality including designing and operating the wastewater treatment system to achieve compliance with the Urban Waste Water Treatment Directive. A Drainage Area Plan (DAP) programme is underway to investigate the performance of the drainage networks in the Dublin area. This will allow Irish Water to understand what impact the network is having on receiving waters, to prioritise investment to where it is most needed, and to design the necessary upgrades.

Significant investment of over €1bn is being made to upgrade the wastewater infrastructure in the Greater Dublin Area (GDA). We are developing new critical wastewater treatment infrastructure to support the future sustainable growth of the area, to protect the environment and to safeguard public health.

Major projects to enhance the collection, storage and treatment network capacity in the Dublin region include the Dublin City Centre Sewerage Scheme, the Ringsend Wastewater Treatment Plant Upgrade Project (in construction), the Blanchardstown Regional Drainage Scheme (approaching completion) and the Greater Dublin Drainage project.

As a key stakeholder focussed on safeguarding our water, Irish Water also provides support for educational initiatives including the Think Before You Flush, Think Before You Pour and the Green Schools educational programmes.