The eels were found on top of the filters at the Carlow plant.
Small eels were discovered in a treatment plant that supplies drinking water to residents in Carlow, Kildare, and Wicklow.
The State environmental watchdog was concerned by the discovery, which was made earlier this summer.
According to The Irish Independent, inspectors found “silvery creatures approximately 20 centimetres long” during a visit to Carlow North Regional Public Drinking Water Supply on June 23.
They believe the small creatures were eels.
It is believed the eels were located on top of the filters at the Carlow plant.
The discovery of cryptosporidium in a water sample lead to the investigation.
Cryptosporidium can cause nausea and diarrhoea.
They believe numerous faults at the plant and a deterioration in the raw water quality resulted in the presence of the eels.
“The presence of eels in the filters indicates that the intake screens are not effective enough in protecting the drinking water treatment process,” the EPA stated.
It is understood that some filters at the plant had not been replaced since the 1980s.
Other issues highlighted during the investigation included a large build-up of supernatant that needed to be cleaned up urgently, a weak online alarm system and a faulty monitor that was supposed to measure the discolouration of the water.
The EPA is considering adding the Carlow based plant to its remedial action list.
They stressed that actions must be taken immediately to resolve any issues at the plant.
