Standards for waste water are set out in the individual licences for each sewage treatment plant.
These licences are issued by the Department of Environment and Climate Change (formerly the Environmental Protection Agency).
The number of tests, frequency of reporting and acceptable levels for each test vary, depending in where the plant discharges its treated effluent.
Licence conditions are related to the volume of of the receiving waters and the sensitivity of the environment.
Testing of the water in the receiving environments like rivers, creeks or boreholes is done to ensure the effluent is returned safely into the natural water cycle.