With population growing and fresh water resources running dry, desalination seems like the perfect solution to the world’s increasing thirst. Just take some sea water, or brackish water from an underground source, and remove the salt. What could be simpler?
In principle, the process really is that simple. The salt is removed either through evaporation or by forcing the salty water through filters. But it takes a lot of energy and, depending on how it’s produced, the end result could be more greenhouse gas emissions or nuclear waste.
Under pressure from environmentalists, Australian engineers are using wind energy at a new desalination plant in Perth. James Duggie of the World Wildlife Fund (WWF) in Western Australia is equally firm about a second project. “If there is to be a desalination plant, it should be zero emissions in terms of greenhouse gas emissions and it shouldn’t cause environmental impacts when it’s established,” he says.
Worldwide, desalination plants have been built where energy is affordable. It’s no surprise that more than half of all seawater desalination plants are located around the Arabian Gulf, where cheap oil and water shortage come together. Nearly all the remaining plants are in countries rich enough to pay the energy bills—such as Spain and the U.S. The U.S. has the world’s second-largest desalination capacity.
Energy is not the only environmental impact of desalination. In the case of sea water plants, there’s the risk of sucking in marine organisms along with the water, and all desalination plants produce extremely salty water as waste. If this is thrown back in the sea undiluted, the salt concentration is lethal for most sea creatures. Solutions exist to minimize these problems—but at a price.
What are you going to pay for your glass of desalinated water? Costs at the plants range from $700 to $1,160 per acre foot, not including distribution costs. Desalinated water is generally more expensive than natural fresh water, at least while the latter remains available for exploitation. Looking at the costs another way (for membrane-filtered water) energy makes up nearly half of the cost, with around 40 percent going to fixed charges (repaying the original investment) and the rest on daily operations and maintenance.
Cost benefits are in some cases marginal or non-existent, so why is there such an interest in desalination projects at the moment, particularly at a time of rising energy prices? Part of the answer may be that treated water costs have been presented at unrealistically low levels to win contracts. This has been one of the key reasons for the delays to the troubled reverse osmosis plant in Tampa Bay, Florida. Several of the companies involved have gone bankrupt. After a 10-year history in which little water was produced, it is hoped that the plant will be fully operational this year.
The California Department of Water Resources is funding a range of desalination projects, some on a commercial level that would produce drinkable water for a variety of uses, and some as pilot projects or research tools. In the department’s view, a key advantage is the possibility of treating diverse water sources—including from the sea or brackish sources, as well as waste water. Costs of desalination increase with the level of salt concentration in the water, so brackish water treatment is considerably cheaper. The vast majority of U.S. plants built so far treat brackish water.
Despite the current enthusiasm for desalination, not everyone is convinced. Pacific Institute Research Associate Heather Cooley notes, “While reliability is an important benefit of desalination, alternatives can usually provide these same benefits with far fewer social, economic and environmental costs.” The Institute’s report “Desalination: With a Grain of Salt” calls for true-cost water pricing, greater transparency and recourse to desalination only after all cost-effective water conservation and efficiency measures have been exhausted.
The WWF 2007 report “Desalination: Option or Distraction for a Thirsty World?” came to similar conclusions. “Those who look to desalination as the future panacea to the world’s water problems may be glossing over considerable environmental, economic and social difficulties,” it said. The report highlights the benefits of reducing demand and treating wastewater as cheaper options, as well as the politically sensitive diversion of resources from agriculture.
Agricultural water use is a hot issue. Two-thirds of the global fresh water supply is used for irrigation, and the percentage is rising. In Spain, there are even plans approved to devote a large proportion of the country’s desalinated water to agriculture. But there are difficulties in getting farmers to take and pay for desalinated water when there is groundwater left, even though the levels are so low that it is illegal to pump it. The UN Food and Agriculture Organization says that desalted water is not affordable for most crops without subsidies.
London Mayor Ken Livingstone opposes the project to build the country’s first large-scale desalination plant for hiscity. He argues that the water company should first fix leaks, introduce water-saving devices and educate customers on water conservation. A third of London’s water supply is lost through leaks.
The reaction to a resource shortage is usually to increase supply rather than reduce demand. Few people are prepared to lower their standard of living, but water use can be cut fairly painlessly. The problem is that reducing demand is less glamorous than adding supply, and corporate interests can make more money out of selling a new plant than pushing conservation. Desalination has a role to play in future water supplies, but it is clearly not a panacea, despite ambitious claims and proposals to the contrary.