Balbriggan Beach in north Co Dublin was declared safe for swimming today after a serious pollution incident earlier this week.
The beach had been closed after raw sewage pumped into the sea had caused E.coli contamination to reach five times the upper limit for safe bathing waters.
Fingal County Council said today water quality at the popular bathing spot had returned to within European bathing water quality limits.
The council said results from a water sample taken at the beach on Wednesday confirmed the bathing water quality had returned to within Blue Flag limits.
Raw sewage was discharged into the sea for up to 26 hours because a malfunction went unnoticed at a pumping station. A member of the public raised the alarm on Tuesday afternoon when the waste water was washed back on to the beach with the tide.
Water quality tests revealed the E.coli contamination was five times the upper limit for safe bathing waters and 100 times the Blue Flag standard for beaches. Significant faecal matter was found in the water.
Campaigners against the construction of a Dublin regional sewage treatment plant in Fingal said this pollution showed engineers and technology could not stop an environmental disaster.