Easing Demand on Water Systems - Irish Examiner

13-Oct-2008

Easing Demand on Water Systems.

It’s hard to credit in this rain-sodden country that we are going to have water shortages in the years ahead.  Despite a year of almost non-stop rainfall, scientists and weather experts are predicting much drier times as the century progresses, particularly for eastern areas, due to climate change. There are proposals to pipe water from the River Shannon to Dublin, for instance.

But, as people seek new water sources, they’re beginning to look upwards with a view to directly capturing that which falls so abundantly from the skies. Long before piped water became widespread in Ireland — it didn’t reach some rural areas until the 1960s — rain barrels were a common sight at the corners of dwelling houses and farm outbuildings. Farmers also used outdoor troughs to store rainwater for their cattle in the fields.

But the ability to drill wells deep into the earth and the advent of water schemes made barrels redundant. It’s unlikely they’ll make a return, but something more sophisticated will take their place to store rainwater. It’s called rainwater harvesting and the idea is to provide an alternative to conventional piped water.

A two-year study, commissioned by the National Rural Water Monitoring Committee, has found that in terms of quality and quantity, rainwater provides such an alternative.

A project team led by Dr Seán Ó hOgáin and Liam McCartan, from Dublin Institute of Technology (DIT), carried out what is said to be most comprehensive study yet into rainwater harvesting in Ireland.

They are responding to a situation where an increase in demand for water is putting pressure on sources — mainly lakes and rivers — and on treatment plants.

A key question is: should we continue treating water to bring it up to a safe standard for human consumption when so much of it is, literally, being flushed down toilets? The project team looked at the possibility of using rainwater to augment public supplies.

“Rainwater collected from domestic roofs could be used to replace a considerable portion of urban water consumption, reducing storm water discharges to downstream environments and significantly reducing the need to harvest and store a treated water supply,” they said in their report.

They rebut suggestions that such systems could pose health hazards, arguing that the use of modern technology can deliver high quality water. The harvested water could have a number of uses, including toilet flushing, gardens and washing machines.

Agricultural uses of harvested rainwater potentially include replacement of mains water supplies for cattle, or washing water used to clean yards and sheds, according to the report.

The team had a large body of international research to draw from, especially data in Australia where rainwater harvesting is widespread — unsurprisingly, given the long droughts Down Under — according to Rural Water News.

In Australia, the experience has been that treatment within the harvesting system greatly improves the quality prior to use.

The DIT study was concentrated in areas of counties Carlow and Meath — not exactly the wettest parts of the country — and found rainwater has the potential to replace a substantial amount of treated, piped water.

Rainwater collected from a house in Carlow, for instance, far exceeded the amount needed for toilet use, with potential savings of up to 33% in piped water. There was little rainfall during the months of the study, but water stored in previous months maintained supply.

Tests on domestically-harvested rainwater showed 100% compliance with bathing water regulations, even though there was no first flush device and disinfection in place.

“The report confidently asserts that the addition of a first flush device, regular maintenance and disinfection would ensure that the quality of harvested rainwater was consistently in compliance with microbiological drinking water regulations,” said Rural Water News.

Money, of course, comes into all of this and the study stressed grant aid will be needed for rainwater harvesting to make financial sense to people.

In other EU countries, including Germany, there’s a reduction in water charges based on roof size for houses with rainwater harvesting facilities.

“The utilisation of harvested rainwater for domestic hot water use is a safe alternative to mains water. It is also a sustainable use of harvested rainwater and reduces mains use by up to 80%,” said the DIT team.

It would also be welcomed by farmers. In one Co Meath farm, the system supplied 43% of livestock demand. It was also found to be capable of meeting 40% of demand in houses.

The study team is preparing a final report for presentation to Environment Minister John Gormley.

Irish Examiner



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