What is it that’s so unusual about Dublin’s water?

Dublin City Council has been at pains to stress this week that there is no problem with the quality of the water processed by the Ballymore Eustace treatment plant.

In fact city engineer Michael Phillips has said the raw water coming into the plant is "cleaner" than what it usually processes.

That is in essence the problem. The plant is designed to deal with the type of water that has been collecting in the Poulaphouca reservoir for at least 20 years.

Different nature

The current problem has been caused by water of a different nature arriving in the reservoir.

This water has smaller particles of sediment in it and these are not being fully caught by the filters used in the first stage of treatment. They then pass to the next stage of treatment and the water has to be filtered again.

The solution the council began using to ensure the particles are removed is to change the filters more frequently than it usually would have to. This slows down the treatment process, which means not as much water can be treated in a 24-hour period as is required by the consumers of Dublin and surrounding counties.

Right size

The council has also been trying a number of methods to change the character of the water to make the particles the right size for the filter. New polyelectrolytes – chemicals that help gather impurities into larger particles – were introduced last Thursday night and were proving effective, Mr Phillips said.

Production at the plant is now improving, but levels are still 20 per cent below that required to meet daily demand for the Dublin region and the council said it needs to keep the restrictions in place until at least Thursday to try to get production back to normal.