Drinking water quality

The EPA report, The Provision and Quality of Drinking Water in Ireland: A Report for the Year 2010, assesses the safety and security of drinking water supplies covered by the European Communities (Drinking Water) (No. 2) Regulations, 2007.  These Regulations assign the role of supervisory authority over public drinking water supplies to the EPA and give powers of enforcement to ensure action is taken where the quality of public drinking water is deficient. This report provides an assessment of the quality of drinking water based on the results of monitoring carried out in 2010 and highlights EPA enforcement in the same period.  

The Provision and Quality of Drinking Water in Ireland - A Report for the Year 2010

The Safety of Drinking Water in Ireland

The safety of water supplies in Ireland is determined by comparing the results of monitoring tests carried out on 945 public water supplies, 671 public group water schemes, 497 private group water schemes and 1,284 small private supplies with the drinking water standards. 

On water supply safety, the EPA found that in 2010:

• Escherichia coli (E. coli - a bacteria that is an indicator of whether human or animal waste has entered a water supply) was detected during compliance monitoring on at least one occasion in 2.2% of public water supplies (20), continuing the downward trend of recent years.  The incidence of E.coli in the larger public water supplies (i.e. serving > 5,000 persons) was 0.01% of samples.  This figure is now in line with countries such as England and Wales (0.02%), Netherlands (0.02%) (2009 data) and Scotland (0.01%).
• The number of private group water schemes where E.coli was detected dropped from 87 (17.0%) in 2009 to 56 (11.6%) in 2010.  In general, the microbiological quality of private group water schemes remains inferior to public water supplies.
• Chemical standards compliance in public water supplies was 99.2% in both 2009 and 2010.

The Security of Drinking Water in Ireland

To improve the performance of a supply and to enable a supply to be removed from the Remedial Action List, the necessary remedial works should be completed to the satisfaction of the EPA.  For a supply to be ultimately secure, a Water Services Authority need to put in place a safety plan.

In relation to the security of water supplies, the EPA found that:

• A remedial action list (RAL) of public water supplies was prepared by the EPA in 2008. Since then, 49% (166) of supplies on the original RAL have been removed from the RAL because the necessary remedial actions have been completed. Remedial works have been completed in a further 39 supplies and the Water Services Authorities are currently in the process of verifying the effectiveness of the remedial works. Remedial works in a further 97 supplies are scheduled for completion by the end of 2011.
• At the end of September 2011, 240 public water supplies remained on the RAL (67 new supplies have been added to the RAL since 2008). The remaining supplies on the RAL collectively supply water to a population of 1,078,739 persons.
• There has been an 18% increase in the provision of chlorine monitors and alarms at treatment plants. At the end of 2010, 99% of public water supply treatment plants had such equipment in place. The remaining work was completed in 2011 and all public water supplies now have a chlorine monitor and alarm in place.
• 43 new boil water notices and 7 new water restrictions notices (serving approximately 65,000 persons) were put in place by 16 Water Services Authorities in 2010. Adverse weather conditions (freezing) in December 2010 alone led to the imposition of boil water notices on 6 public water supplies (serving approximately 21,000 persons). 

The Enforcement of Drinking Water Quality in Ireland

The EPA was notified of the detection of E. coli in public water supplies on 46 occasions in 2010, down from 63 occasions in 2009.  Analysis of the cause of these failures indicates that there has been a dramatic drop in the number of failures attributed to inadequate treatment at the plant (down from 24 failures to 13) and chlorination process breakdown (down from 35 to 13) compared to 2005 when this analysis was previously carried out.  This is undoubtedly due to the improvements to the security of disinfection systems such as the installation of chlorine monitors and alarms, duty/standby dosing arrangements and flow proportional/residual based dosing. 

There has been a drop in the number of public water supplies where the detection of trihalomethanes was notified to the EPA from 96 in 2009 to 79 in 2010. THM exceedances can be eliminated by reducing organic matter in the raw water, optimising treatment to remove organic matter and optimising chlorination.  However, care must be taken not to reduce chlorination in such a way as to compromise the microbial safety of drinking-water. 

The EPA carried out 83 audits of water treatment plants in 2010.  Improvements were found across all key indicators examined with the exception of source protection and reservoir security which were identified as areas for further improvement. The EPA issued 9 legally binding Directions to 7 local authorities in 2010.

The EPA continues to adopt a risk based and outcome-driven approach to the enforcement of the Drinking Water Regulations – focusing on issues that present the greatest risk to health, such as contamination with E. coli and Cryptosporidium. 

Provision of Drinking Water Information to the Public

The posting of up-to-date monitoring results by Water Services Authorities on their websites is important as it allows consumers to gain timely access to information on the quality of their drinking water. To this end, the Minister for Environment issued a circular on 20^th July 2009, requesting Water Services Authorities to provide up to date information on the quality of drinking water on their respective websites. The EPA found that just over half of the Water Services Authorities (19) are currently publishing some or all of their drinking water quality data as required by the Ministerial direction.