Cryptosporidium and Giardia detections

Cryptosporidium and Giardia are parasites that are found in human or animal waste and, if they are present in drinking water, can cause persistent diarrhoea.

The Drinking Water Regulations do not explicitly require Cryptosporidium or Giardia monitoring to be carried out; but because of the risk to health from these parasites, the EPA has requested Irish Water to test for them.

Irish Water is required to assess all water supply sources across the country and determine if there is a risk that the raw water could have Cryptosporidium or Giardia present. If either parasite might be present in a supply, then appropriate treatment processes (referred to as a ‘barrier’) must be put in place.

Cryptosporidium and Giardia may be detected in treated water where:

• There is no treatment barrier in place at the water treatment plant;

• The treatment barrier is not being properly operated, controlled or maintained.

When Cryptosporidium or Giardia detections are reported, the EPA ensures that Irish Water carries out investigations into the cause; takes corrective action; and consults with the Health Service Executive regarding the risk to public health. If the Health Service Executive is concerned that using the water might endanger people’s health, Irish Water will issue a boil water notice for the supply.

The EPA may also carry out audits of treatment plants to see if further action is necessary. If the EPA is concerned about a supply not having a treatment barrier or a treatment barrier not performing adequately, it will add that supply to the EPA Remedial Action List. Once a supply is added to the Remedial Action List, Irish Water must provide the EPA with an action plan and prioritise that supply for improvement.

Note: Clonmel Poulavanogue supply has been on the Remedial Action List since 2008

Note: There are supplies where treatment barriers are not being operated, controlled or maintained adequately. For example, operational issues at Leixlip Water Treatment plant meant that the treatment barrier for Cryptosporidium was compromised and this led to two boil notices on the supply in 2019.

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