A major €300m sewerage treatment plant is already overloaded and must be upgraded, just seven years after it was opened.
The Republic's Environmental Protection Agency (EPA) has admitted that the Ringsend plant was treating more sewerage than it was designed for, and that it "sometimes" failed to treat waste to EU water quality standards.
The agency has told Dublin City Council it must upgrade the plant and increase capacity by 2015, or risk losing its licence to operate. Consultants have been appointed to extend the plant, and planning permission is expected to be sought before the end of the year, the council said.
The Ringsend plant was built in 2003, and designed to treat waste from 1.79 million people, which includes waste from industry and businesses. But the EPA says a capacity to cater for 2.2 million people is needed, and that the works must be carried out as soon as possible.
The council has also been told to stop discharging treated water from Doldrum Bay and the Nose of Howth as part of its licence to operate, which was issued yesterday.
The new licence has more than 66 conditions relating to the environmental management, control and monitoring of discharges to water from the greater Dublin area.
Despite problems with the facility, it has produced a dramatic improvement in water quality in Dublin Bay. Dollymount beach has Blue Flag status this year, which means the bathing water quality complies with the highest EU standards.