Sinn Féin has complained to the European Parliament about the pollution in Dublin Bay.
Recent wastewater discharges into the sea from the Wastewater Treatment Plant in Ringsend have led to swimming bans on several beaches.
Sinn Féin says Irish Water and the government are in breach of EU environmental laws.
Councillor Chris Andrews is confident the EU will find in his favour.
He said "There is now way any right thinking person would believe that ongoing disposal of wastewater is acceptable."
Odours
Earlier this week, Irish Water warned about potential smells in Ringsend due to maintenance work at the plant.
The company says the works are essential to reduce the risk of unpleasant aromas from the facility.
Councillor Andrews said "Cleaning of odour filters is ongoing, for weeks at a time, over the warms summer we had.
He added "There was period where it was unbearable for families and businesses."
