SPREADING an ultra-thin layer of organic molecules on the surface of reservoirs could prevent millions of cubic metres of precious water evaporating each year, according to a Canadian company that is the first to commercialise the technique.
The molecules form an invisible, biodegradable blanket that blocks the escape of water molecules into the air. Field tests of the technology in several countries show an average of 30 per cent reduction in the rate of evaporation. And saving the water costs less than half the price of replacing it, says Dan O鈥橞rien, chief executive of Flexible Solutions in Victoria, British Columbia, the company that developed the process.
鈥淚t鈥檚 pioneering work,鈥� adds Moshe Alamaro, an atmospheric scientist and an expert on monolayer applications at the Massachusetts Institute of Technology. 鈥淭hey are the first commercial enterprise using monolayers [to retard evaporation],鈥� he says.
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The idea of using monolayers of molecules in water is not new, and scientists have been experimenting with the notion for more than 50 years. The biodegradeable 鈥渇atty alcohols鈥� hexadecanol and octadecanol are ideal for making the monolayers. Each molecule consists of a water-repelling hydrocarbon chain connected to a water-attracting chemical group. This structure makes the molecules organise themselves into a self-sealing uniform layer one to two molecules thick when spread on the surface of water.
But fatty alcohols tend to cake when prepared in bulk as a fine powder, and so are difficult to distribute evenly onto water. 鈥淵ou put fatty alcohols in water and they sit there like candle wax,鈥� says O鈥橞rien. That鈥檚 where Flexible Solutions comes in. The company鈥檚 founder, Robert Neville O鈥橞rien (Dan O鈥橞rien鈥檚 father), is a pioneer in this field. He patented a technique to add calcium hydroxide to the organic chemical, which makes it easy to produce in powder form. The compound also makes the alcohols acquire a positive electrical charge when they hit the water, which causes them to repel each other and rapidly spread across the surface.
This week Flexible Solutions announced results from trials in India and Morocco that showed between 30 and 45 per cent reduction in evaporation. In one 650-hectare reservoir the total amount of water saved in two weeks was 199,000 cubic metres, the company reports.
If the technology becomes widespread, some questions will need to be addressed. While the fatty alcohols are considered non-toxic and safe in drinking water at the concentrations used, little research has been done to examine longer-term ecological effects of retarding evaporation in lakes or reservoirs, says Alamaro. Preventing evaporation for long periods might increase the water temperature and affect the exchange rates of gases such as oxygen, nitrogen and carbon dioxide. This could have unforeseen effects on the local ecosystem.
