Nearly 30 per cent of the sewage load from urban areas throughout the State still receives no treatment before being discharged into lakes, rivers and estuaries, according to the Environmental Protection Agency.
But Ms Anne Butler, a director of the EPA, said she anticipated the picture would change dramatically over the next 18 months as a result of the £1 billion sewage treatment investment programme.
She was speaking at a press briefing on the publication of an EPA "Report on Urban Waste Water Discharges in Ireland", covering the years 1998 and 1999.
This is the third such report the agency has produced on this issue in recent years.
One of the major findings is a significant increase in the quantity of urban waste water, particularly in the Dublin area. According to Ms Butler, the growth of Dublin has added a population equivalent of 800,000 to the sewage load being discharged.
"The figures are skewed at present because the vast majority of urban waste water - 60 per cent - is generated from five urban areas . . . which receive little or no treatment," the EPA said. But the figures would have been "much worse" but for ongoing investment.
Sewage treatment results for a total of 390 urban areas, with populations as low as 500, are analysed in the report.
These include seaside resorts such as Courtown, where there has been a large spread of holiday home development over the past four or five years.
The EPA has calculated that the Co Wexford resort, where some 1,500 holiday homes have been built, now has a sewage load equivalent to a population of 10,000.
At present, this is barely treated, although a £12 million treatment plant is under construction.
Sewage receives no treatment, or only preliminary treatment, prior to discharge in 53 of the 390 urban areas studied, or 36 per cent of the load. A further 38 per cent receives primary treatment, 21 per cent secondary treatment and only 5 percent have nutrient reduction facilities.
Ms Butler noted that both Dundalk and Drogheda had just completed new sewage treatment plants. In the case of Dublin and Galway, new plants were under construction, while Cork and Waterford were about to start building similar facilities to treat their sewage.
A further £1 billion has been provided under the National Development Plan 2000-2006 for waste-water treatment.
The EPA is anxious that this significant capital expenditure should be matched by improved management and monitoring systems.
The report shows, apart from three local authorities, sampling programmes for soil testing are either non-existent or in need of improvement, while none of the 10 local authorities audited by the EPA had implemented new management systems.
About three-quarters of the sewage sludge produced in treatment plants is not put to any beneficial use, according to the report.
