Donegal remains one of the counties which has the highest number of public water supplies in need of improvement.
Of 33 supplies in the county originally on a list for remedial work, 12 were still on the list at the end of last year.
The latest update on drinking water from public supplies comes in the Environmental Protection Agency’s 2016 report.
The twelve water treatment plants in County Donegal that remain on the remedial action list include Cashelard, Creeslough, Fintown, Glenties/Ardara, Owenteskna/Kilcar, Pettigo and Portnoon/Narin.
Work on five of these is to be completed this year and on six next year.
In January 2015, the EPA issued directions in relation to excess trihalomethane in the Owenteskna/Kilcar scheme.
At the end of last year, an action programme on that scheme was being implemented by Irish Water.
Trihalomethanes are chemical compounds that are believed to be a potential cause of cancer..
Meanwhile, compliance with regulations on trihalomethane has yet to be determined on a number of Donegal schemes, including Cashelard and Portnoo/Narin.
Two Sligo schemes — from an original 12 — are on the list for remedial action: the Lough Gill and Lough Talt regional water supply schemes.
On the Lough Gill (Cairns Hill) supply, the EPA says enforcement action is under consideration in relation to excess trihalomethane and an inadequate cryptosporidium barrier.
It’s a similar situation in respect of excess trihalomethane on the Lough Talt supply.