Irish Water is lodging an application with An Bord Pleanála to upgrade the Ringsend waste water treatment plant in Dublin.

It has been described as among the worst industrial sources of water pollution in Europe.

The company said the existing plant, which is the largest in Ireland, is overloaded and the €400 million project was critical for the future of water services.

Speaking on RTÉ’s Morning Ireland Jean Hobbs, project manager at Irish Water, said permission granted to Dublin City Council for a previous application in 2012 included plans to construct a 9km long sea outfall tunnel to discharge into Dublin Bay.

New technology available to Irish Water, following its establishment in 2014, led to a reassessment and upgrade of the project.

The 'Aerobic Granular Sludge technology,' described as cutting edge, has been trialed by Irish Water at Ringsend since April 2015.

Use of the technology enables the company to omit the need for an outfall tunnel in the new application.

It is proposed the sludge, which generates 'biosolids' as a result of treatment, would be stored at a regional storage facility at Newtown, near St Margaret's in Fingal in north Dublin.

Ms Hobbs said these biosolids contained nutrients that were suitable for use in agriculture.