Negative Aspects of Desalination Need to Be Considered

Article excerpt

BYLINE: TONY CARNIE

THE tantalising notion of converting the most abundant storehouse of salt water into a virtually limitless supply of fresh water has been on the drawing boards for decades.

Forty years ago, United States President John F Kennedy declared that large-scale desalination projects "can do more to raise men and women from lives of poverty than any other scientific advance".

As far back as 1872, residents of Las Salinas in Chile developed a small-scale desalination plant which used the the sun's heat to evaporate and then condense fresh water from sea water.

In Israel and several desert nations in the Persian Gulf, desalination plants now provide much more significant quantities of drinking and irrigation water.

In Europe, more than 20% of Spain's farm irrigation water comes from desalination, while India, China, Australia and the United States are also gearing up to expand this technology considerably.

A desalination plant at Kenton-on-Sea in the Eastern Cape has been generating fresh water for nearly 30 000 people since 1997.

Last year, Umgeni Water confirmed it was planning to build a pilot desalination plant at Zinkwazi, while the developers of a new coastal resort announced plans to build a R50 million desalting plant.

As the number of city dwellers swells around the world, desalination is emerging as an increasingly popular option to address the growing fresh water crisis.

But is desalination the best panacea to water supply problems?

Last year, the Swiss-based conservation group WWF International published research which warns against the large-scale adoption of this technology. The report questions the wisdom of desalination for social, economic and environmental reasons.

Most topically for South Africa, WWF notes that desalination plants require large volumes of energy - from electricity, fossil fuels, nuclear power or more environmentally benign sources.

Traditionally, desalination has relied on heating salt water to condense and then distil fresh water - a technology which can consume up to 60% of the total project costs.

The report notes that the development of more sophisticated technologies has done away with the need to boil sea water to get rid of the salts. Nevertheless, a study by the US Bureau of Reclamation estimated that, even if the reverse osmosis technology is used, energy costs still made up about 44% of the costs of such plants. …