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Last month,a boil water notice impacted 600,000 customers in the greater Dublin area. Shutterstock/fizkes
Drinking Water

Water treatment 'not sufficient' to manage Cryptosporidium risks at Leixlip plant, says EPA

The EPA says the level of treatment at Leixlip is not sufficient to manage the risk posed by the River Liffey source water.

THERE IS A “deficit” of treatment for Cryptosporidium and Giardia at the Leixlip Water Treatment Plant, according to the Environmental Protection Agency (EPA).

The EPA will tell an Oireachtas committee today that the level of treatment at the plant “is not sufficient to manage the risk posed by the River Liffey source water”.

Officials from Irish Water, the Department of Housing, Planning and Local Government, and Fingal County Council will also appear before the committee today.

Their appearance comes as a boil water notice was reissued last night. The renewed notice impacts some 600,000 customers in the greater Dublin are, including Meath and Kildare. 

Irish Water said said that cloudy water in the source water for the old Leixlip Plant has exceeded acceptable levels, yet again.

A similar boil notice was issued at the end of last month, which resulted in the officials being called before today’s Oireachtas committee.

Dr Tom Ryan, Director Office of Environmental Enforcement (OEE) and the EPA will tell TDs today that in particular, there is currently a deficit for treatment of parasites such as Cryptosporidium and Giardia at the Leixlip plant.

While filter upgrade works are underway to reduce this deficit, it “will not be sufficient to confirm adequate treatment”, Ryan states in his opening statement. 


Cryptosporidium is a parasite that is found in human or animal waste.

If it is present in drinking water, it can cause diarrhea. Illness is often more severe in
small children and elderly people.

Giardiais is a microscopic parasite that also causes the diarrhea. 

The EPA has recommended that ultraviolet disinfection be considered by Irish Water as an additional treatment barrier to deactivate Cryptosporidium and Giardia at the Leixlip water treatment plant.

“As an ultimate fail safe, ultraviolet disinfection will inactivate any Cryptosporidium/Giardia parasites in the water supply, to ensure the protection of public health,” he states. 

Outlining the series of events that led to October’s boil notice, Ryan states the incident began at 3pm on Monday 21 October and ended at 5am on Tuesday 22 October when remedial works restored the affected production line.

The committee will be told that a blockage resulted in operational difficulties with the water treatment processes and gave rise to elevated cloudiness levels in treated water, also known as turbidity levels.

This is the same reason cited last night for the boil notice being reissued.

The cloudy water from the source water indicated last month that there was a significant risk to the safety of the water supply because the treatment barrier for removal of Cryptosporidium and Giardia was compromised, states Ryan.

He adds that there was a risk of breakthrough of microscopic parasites into the water supply.

The committee will also be told that there was a failure to respond to multiple alarms that were activated in response to the elevated turbidity.

Members will also be told today that the EPA highlighted the risk of this type of incident occurring during an audit of Leixlip water treatment plant in March 2019, following a mechanical failure of chemical dosing pumps at the plant.

It recommended that plant operators respond immediately to any alarms generated and that if an operator fails to respond to an alarm, that Irish Water should ensure that the plant automatically shuts down, to prevent inadequately treated water being supplied to consumers.

The EPA’s 2018 report highlighted that Cryptosporidium detection has increased in the past three years. It was detected in 25 public water supplies in 2018, up from 17 in 2017 and 12 in 2016.

During 2018, 44 boil notices were in place in 14 counties affecting 97,204 people. This is
an increase compared to 2017, during which 42 boil notices were in place affecting 21,657

Over 13,500 people were also affected by 12 precautionary boil notices issued due to Storm Emma in March 2018.

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