Northern Ireland Water has been fined £15,000 for polluting a tributary with poisonous and noxious substances.
A water quality inspector who checked the waterway at Cidercourt Road, Crumlin, Co Antrim, in October 2008 found it was heavily discoloured.
The source was traced to Laurelvale sewage pumping station, Crumlin, which was discharging to an unnamed tributary of the Crumlin River, Antrim Magistrates' Court was told.
Northern Ireland Water said the pumping station was scheduled for inspection every four weeks, but the high sump analogue alarm which is triggered when levels rise to the point of overflow did not appear to have been set before the incident.
A sample confirmed that the discharge contained poisonous, noxious and polluting matter which would have been potentially harmful to fish life in the receiving waterway.