Twenty per cent of public water supplies and more than 30 per cent of private group water schemes have been found to be contaminated by faecal coliforms, according to the Environmental Protection Agency.
In its latest annual report on drinking-water quality in Ireland, the EPA said the presence of faecal coliforms was unacceptable and called on both public and private suppliers to eradicate the problem as soon as possible.
The report presents the results of drinking-water sampling and analysis carried out by sanitary authorities in 2001, when a record 146,000 tests on 904 public water supplies and 1,536 group water schemes were carried out.
Overall, the quality of drinking water supplied by sanitary authorities was found to be satisfactory, with 96 per cent of all tests carried out rated as "acceptable". This represents a marginal increase of 0.3 per cent on the figure for 2000.
The most important indicator of drinking-water quality is the presence or absence of faecal coliforms, and the EPA welcomed a "noticeable" decrease in the number of contaminated samples taken from both public water supplies and group water schemes.
Compliance with the faecal coliform standard in public water supplies improved from 96.7 per cent in 2000 to 97.2 per cent in 2001. There was also a higher level of compliance in group water schemes, up from 70.8 per cent to 74.1 per cent.
"Although this improvement is to be welcomed, compliance with the faecal coliforms standard is still poor in group water schemes, lagging far behind that of public water supplies and remains unacceptable," said the EPA.
It found that 79.6 per cent of public water supplies and 68.4 per cent of the group water schemes monitored were free of faecal contamination in 2001. However, 184 public supplies and 485 group schemes had some degree of contamination.
The majority recorded were "moderate in nature", the report said, adding that most of the schemes showing contamination were small in size, and many did not have their water disinfected before distribution.
Despite the overall satisfactory quality rating given to public water supplies, the EPA said it was concerned that some public water supplies were consistently in breach of the standards for aluminium and in some cases nitrates.
It advocated priority action to ensure that the supplies were brought to full compliance with the standards laid down in the more stringent EU Drinking Water Regulations, which are due to come into force on January 1st next.
Yet again the EPA found that the quality of water supplied by group schemes to some 145,000 rural households continues to be unsatisfactory, with only 89.5 per cent of all tests being acceptable (down from 91.2 per cent in 2000).
"Successive EPA reports on the quality of drinking water in Ireland provide clear evidence that water supplied by sanitary authorities is safer to drink than water supplied by privately operated group schemes," said the latest report.
It suggested that serious consideration should be given to bringing group schemes with persistent problems under the control of sanitary authorities.
The large number of such schemes in Ireland is seen as a significant barrier to improving water quality.
"Large numbers of small supplies result in operational and management difficulties," it said. "Consideration should therefore be given to rationalising water supply in parts of Ireland . . . with a view to reducing the overall number of supplies."
The EPA also recommended that sanitary authorities make monthly monitoring results available to the public, through both its websites and offices. There was also a need for improved drinking water management and more monitoring, it said.
Copies of the report are available from the EPA Publications Office, telephone 01-268 0100.
