Is there a nice salty solution to the global clean water crisis? | News from the world

IWe believe this is the main environmental challenge of the century – and the competition is fierce for this honor. Water. The planet has a lot of it, but most of it is unusable, trapped in salty oceans. But demand is skyrocketing and tensions are beginning to show, from China to Latin America, from India to California.

Nearly one billion people do not have access to safe water, and this number is expected to increase sharply over the next few decades. Last year, Cape Town nearly ran out of water. Even rainy England has been warned: keep it up and you will not have anything to do in 25 years.

There are no easy solutions – but a controversial technology in the past might well be at the dawn of a new dawn. Call it desalination 2.0. Freshwater supply is under increasing pressure around the world, the 4 billion people currently living in areas where water is scarce, are expected to reach 5 billion by the middle of the century. Climate change, population growth and our consumption habits are all key factors, while the technology we use relies on the extraction of the water table faster than it can be restored naturally; which only stores problems for the future.

The process of converting seawater into a less salty solution that could be used on the farm and at home has long been considered a last resort to meet our water needs. The technology is expensive, consumes a lot of energy and is only suitable in certain regions. It also generates a powerful by-product: a very salty brine, which is generally released into the sea, and this process unfortunately has the effect of disrupting local fish populations by sucking them into the incoming stream. But could desalination be sufficiently reformed to make it a viable solution to our water needs?

David Binns of the Development Innovation Company Epicuro believes that advances in renewable energy technology could make small scale desalination plants a breakthrough for poor communities in developing countries, especially in hot countries. "It's a lifesaver," he says. "It could make a huge difference in a terrible problem."

In a prototype that he co-invented with start-up funding from the tycoon of beverages and goods, Howard Raymond, Binns uses solar collectors that heat water to a boil and then condense it separately from salt or water. dirt that made it unviable. A small photovoltaic system is connected to power the processors necessary for the regulation of the machine. This method can be used not only for desalination, which requires users to be near the coast or other source of salt water, but also in areas where water is available but severely contaminated, implying a much larger portion of the world's population under water stress. .

Binns is now looking for government and charity partners to make the technology widely available, and estimates that £ 2 million to £ 3 million would allow the company to start manufacturing. He plans to use the devices at a small local scale, each unit being sufficient to meet the drinking water needs of an average family.

Other innovators are also exploring the possibilities of renewable energy, one of the biggest handicaps of traditional desalination being its huge consumption of fossil fuels. For example, the US engineering and technology company Honeywell has provided 480,000 people with water stations (which purify water contaminated with fluorides, nitrates, and salinity) in India, where 70% of the water supply is contaminated and 200,000 people die each year from lack of access to safe water. Honeywell has installed 150 solar-only stations, in addition to the Safe Water Network India network.

More recent technology is also helping desalination advocates. The miracle substance, graphene, is inevitably a way to explore. A graphene "sieve" was created two years ago at the University of Manchester. It removes salts from brine and, if it can be increased, can be used for desalination at lower cost. Professor Rahul Raveendran Nair, who published an article in the Nature Nanotechnology peer-reviewed journal, said: "Achieving scalable membranes with uniform pore size, at the atomic scale, is a significant step forward and will open new opportunities for improving membrane efficiency. desalination technology. "

Separately, the UK company G20 is working on another way to use graphene oxide filters for desalination, with a process to apply a graphene oxide coating to polymer-based water filtration membranes. existing.

More traditionally, XPrize's $ 1.75 million water supply was attributed last year to a technology that uses distillation to extract moisture content from moist air. Skywater machines use a distillation process to turn the water vapor into liquid, then treat the water with ozone to prevent contamination by microorganisms. The more humid the air, the more water can be extracted. However, technology remains expensive, with prices ranging from $ 18,000 to $ 28,000 for units that can process up to 300 gallons per day.

For some large urban areas, desalination is an urgent solution to an increasingly pressing problem. Cate Lamb, director of water safety at CDP, who measures the environmental performance of companies, talks about the success of Cape Town, which last year managed to overcome the worst of its crisis. 39 water by investing in desalination and by limiting the use of water. .

Some companies are also investing in smaller scale technology to power their operations in areas where water is scarce. Lamb explains, "Desalination already has a role to play in helping cities and businesses meet the challenges of water. The deployment of technology in Cape Town is one of the main ways the city is building resilience. "

A positive report recently released by financial badysts at Moody's Investor Service revealed that the success of Cape Town's desalination, as well as demand management and increased investment in water, have also paid dividends for economic growth and growth. stability. "A resilient water sector is critical to the health of the Cape economy and the city's fiscal situation," said Zoe Jankel, Senior Analyst. "A new investment will strengthen this resilience."

While Cape Town is the most recent and most used example of desalination to bridge an urgent gap, Israel holds the crown for long-term investments in technology as a strategic public service. The country is home to the world's largest reverse osmosis desalination plant and can now produce more water than is needed for water desalination and recycling. This could potentially allow the export of fresh water to the surrounding area, and more importantly, the export of "virtual water", that is, products. agricultural products ranging from vegetables and cereals to textile fibers, including manufactured goods, to stimulate its economy.

About 80% of Israel's drinking water comes from coastal desalination plants, depending on the time of year and weather conditions. This is so energy-consuming that the largest power plants operate mainly at night so as not to overload the electricity grid. Crucially, however, the country has also invested heavily over decades in wastewater treatment, recycling nearly 90% of its wastewater through wastewater treatment plants, which then redirect treated water to l & # 39; irrigation.

The sludge byproduct is also used as a fertilizer and to generate biogas. This strategy underscores the need to integrate desalination, as in Cape Town, into a comprehensive water management plan. There is no point in relying on such an expensive way of generating water while wasting the resource in another way.

But when desalination is used on a large scale without renewable energy, there are still related problems. "It has a cost – a carbon cost," says Lamb. "In addition, there are risks badociated with rejecting the large amounts of salt generated. Finally, it is important to realize that this is a technology that really only applies near the sea. For those who do not have this luxury, other interventions will be necessary. "

A recent report from the United Nations University revealed that the use of large desalination plants posed a growing threat to the health of the seas. Every liter of fresh water created from a conventional desalination plant generates an average of 1.5 liters of brine. Globally, desalination plants release 142 million cubic meters of high-salt brine daily, about 50% more than previous estimates. In one year, this amount would be enough to cover 30 cm of brine on an area the size of Florida.

The report warned that runoff of brine depletes dissolved oxygen in the surrounding seas, with adverse effects on marine life. They called for investing in promising new technologies that can reduce the amount of wasted effluent by converting metal byproducts – such as sodium, magnesium, lithium, calcium, and potbadium – into a useful form. , which is currently not profitable. They also suggested that saline byproducts could be used in fish farms, where saltier water can yield larger fish and for irrigation of salt-tolerant crops.

Even with advances in desalination technology, its widespread use will always have drawbacks, particularly in terms of adapting technology to the size of the problem of water scarcity. Virginia Newton-Lewis, Senior Water Security Policy Analyst at the WaterAid charity, said governments needed to focus on a myriad of ways to provide the most basic service – a clean water – to their people, before getting bogged down in what could be expensive and at the forefront of technology. desalination equipment. "What we need to see is that household drinking water supply becomes a major political priority," she said. "The lack of access to safe water is often due to insufficient funding or political will to support basic services, rather than a physical lack of available water."

Even in areas where water is physically scarce, there are alternatives that should be explored as a matter of urgency. "Improved water management that gives priority to household water supply could have a huge impact on economic costs, at a very low cost," she says. "It's about prioritizing communities' water supply before industry and agriculture. Desalination is expensive, causes pollution and has a number of limitations. Therefore, although it certainly has a role to play in some areas, much more appropriate solutions are often available. "

• Fiona Harvey is an environmental correspondent for the Guardian

• This article is part of a series on possible solutions to some of the world's most difficult problems. What should we cover? Write to us at [email protected]