Part of a pilot study here, it reduces the evaporation of water from reservoirs
Grace Chua Straits Times 2 Jul 10;
SINGAPORE could save about 20 million cubic metres of water each year, or 8,000 Olympic-sized swimming pools' worth, by using a thin film of organic molecules to cut evaporation from reservoirs.
That is what a PUB pilot study found when the national water agency tested the technology, called WaterSavr, at Bedok Reservoir for three months last year. Blocking or cutting evaporation from Singapore's 17 reservoirs is a key research and development concern here.
About 60 million cubic metres of water escape into the air each year from 3,000ha of reservoir surface area because of the island's sunny climate, the study found.
That amount of lost water is enough on its own to meet Singapore's water demand for more than two months.
Other evaporation barriers, such as big plastic covers, are only about 10ha in size at most and they are also costly. For example, plastic barrier VapourGuard would cost about $180,000 per hectare by some estimates.
And they are not suitable for reservoirs here, such as Bedok, where people kayak, wakeboard and fish.
WaterSavr has a solution. The technology, invented by Canadian company Flexible Solutions, uses a fine powder containing non-toxic fatty alcohols and calcium hydroxide.
When placed on the surface of water, it spreads evenly to form a clear, colourless liquid 'blanket', a single layer, molecules thick, which blocks evaporation.
Tests here and in other parts of the world, such as in Australia and California's arid Owens Valley, have shown that WaterSavr can cut water loss by an average of 30 per cent.
The idea of putting fatty alcohols on water to curb evaporation - just as lanolin in moisturisers keeps skin moist - stretches as far back as the 1920s. But when such fatty alcohols are put on water, they clump together and do not spread. Adding calcium, however, makes the molecules repel each other and spread across water.
To allay fears that the powder is toxic, the PUB tested water quality before, during and after the pilot survey.
PUB researcher P. Suresh Babu, presenting the study findings at the Singapore International Water Week on Wednesday, said the WaterSavr application had had no impact on dissolved oxygen, water pH, or other quality measures.
It biodegrades within two to three days and measures up to international standards, like the Water Quality Association's gold seal and the NSF ANSI 60 safety standard, for chemical additives.
Though the chemicals used are not harmful, National University of Singapore biologist Peter Ng said the long-term impact on ecosystems of cutting evaporation was not known.
'I'm not too worried about Bedok reservoir as it's a totally artificial system, but I would advise caution with the natural catchments in central Singapore,' Professor Ng said.
The PUB's presentation estimated it would cost about $4 million a year to continually minimise water loss at Singapore's reservoirs. That works out to 20 cents or so per cubic metre of water, a fraction of the cost of desalinated water.
PUB does not have any plans to roll out the WaterSavr technology across reservoirs at the moment, as it says the study was only a pilot test.
However, WaterSavr's Singapore office is already manufacturing automatic-spreader machines together with the Singapore branch of New Zealand engineering firm Nu-Con, and plans to market these in the region and worldwide, said WaterSavr Singapore director Anthony Price.
