Sewage did not cause a surge in bacterial pollution at Portobello Beach which made it unsafe for swimming, according to tests.
Bathers were advised to avoid the water at the Edinburgh seaside resort on July 10 because of an unusually high bacteria count, with signs erected by Scottish Water to deter people from swimming.
Sewage has been discounted as causing the surge in bacteria, because of microbial source tracking (MST) which uses DNA-based techniques to determine the sources of bacteria in water.
Long-term sampling and MST analysis has shown the main sources of pollution at Portobello tend to be human, dog and gull waste.
Officers from the Scottish Environmental Protection Agency (Sepa) checked Scottish Water assets in the area, as well as other potential sources, but no signs of pollution were detected, the agency said.
On July 11, further sampling was taken which showed water quality was “back to normal”, according to Sepa.
The agency said that “results of further analysis of a water sample taken at Portobello Central have been unable to identify the source of the high bacteria count”.
Advice against bathing was removed on July 12 when analysis showed water quality was back to normal.
Vicki White, Sepa senior manager in environmental performance, said: “The fact that a follow-up sample taken on July 11 showed water quality was already back to normal indicates this was a short-lived event that had no lasting impact.
“Microbial source tracking can be very helpful in identifying a source, but in this case our analysis of this one sample has not been able to identify one.
“However, these results, combined with the fact our officers found no issues when we checked Scottish Water assets in the area, do indicate that this was not a sewage-related incident.
“While this single result cannot give us a definite answer, it is a good reminder to clear up litter, as food sources can cause gulls to gather in large numbers.
“Picking up after your dog is another simple thing people can do to help protect water quality and make a beach visit more pleasant for other visitors.
“Water sampling will be ongoing throughout the bathing season as part of routine testing, and we will continue to investigate any high bacterial results and take actions to tackle any pollution sources identified.”
