Global water crisis sparks surge in desalination
The world’s unquenchable thirst for clean water drove a record increase in the desalination of seawater and reuse of sewage last year, new figures reveal, as water-stressed countries around the world try to build their way out of trouble.
Making fresh water from the sea was once the preserve of cruise ships and oil-rich Gulf states that could afford the huge cost of energy required to remove the salt. But as rivers, lakes and aquifers dry up, rains become less reliable, and the cost of desalination has fallen, communities in all parts of the world have begun to build and plan plants to turn oceans, river estuaries, salty ground water and even sewage into clean water for factories, farms and homes.
The rise in fresh water production was the biggest ever recorded at 9,5-million cubic meters a day, the annual report by analysts Global Water Intelligence will say on Wednesday. That is equivalent to about 10% of global capacity.
Those desalinating and reusing water now include some of the world’s poorest countries, including Algeria, Chenai in India and Ghana; wet but over-populated cities like London and Dublin; and those far from the sea, most notably a plan by the United States state of Nevada to build a desalination plant in Mexico in return for keeping a greater share of the Colorado River.
Rivers flowing backwards
With water “manufacturing” technology allowing people to change fundamentally the geography of freshwater on such a large scale, Christopher Gasson, GWI’s publisher, talks of “rivers flowing backwards”.
“People do desalination when they run out of opportunities, and the problem is the world overall is running out of opportunities: groundwater is over-exploited to the extent it’s becoming saline and unusable; rivers are being drained; new dams are becoming less and less viable [and] long-distance transfer is expensive and controversial,” said Gasson.
“People are being forced to look to non-traditional alternatives for water supply. For coastal people desalination is the obvious one; if you’re inland then there may be some brackish water underground you could desalinate, or you might need to look at reuse.”
The fundamental reason for the rise of water manufacturing is a simple gap between demand and supply: in 2006 a report from the International Water Management Institute found one-in-three people in the world were “enduring one form or another of water scarcity”—such as “when women work hard to get water, [or] you want to allocate more but can’t”.
Growing numbers of people; richer lifestyles; demand for more water-intensive food such as meat, and dwindling supplies are expected to increase that number—to up to half the projected global population or more in the middle of this century.
And that is despite an expected doubling of total water manufacturing capacity between now and 2016, according to UK-based GWI.
The falling cost of desalination, thanks to technology improvements is key, and the reuse of water can be cheaper still.
Developments in membranes
Contacts have been signed to deliver desalinated water in Algeria and Israel for 55-56 cents per cubic metre, and reuse plants can now turn sewage into drinking water for between 40 and 45c per cubic metre, said Gasson.
Comparisons between the energy needs of different desalination methods—heating up water for distillation or pushing it through membranes to filter the salt—have also become much closer. Continuing developments in membranes—which one day are likely to be modelled on the “technology” nature uses in kidneys and mangroves—will continue to bring down costs and energy needs, said Gasson.
Systems using carbon-free energy are also being trialled: nuclear desalination in the United Arab Emirates, solar power in Australia, and biodiesel from plants—with cooking fats also slated as a future possibility—at a desalination plant built by Thames Water in London.
Despite the advances, there are still serious objections to manufacturing water. The WWF remains concerned about building new facilities in often environmentally-sensitive coastal and wetland areas; about the intake of seawater which is home to millions of tiny species, and discharge of the remaining brine, which can be contaminated with chemicals from cleaning the membranes and particles from corroding pipes.
Concerns about the energy use of plants also still remain, especially where they are still dependent on fossil fuels, or if they could divert renewable resources which could otherwise replace existing carbon-intensive energy supplies. Residents in upmarket Monterey, California have long objected to a desalination plant being built there because they fear it would encourage more development.
Barrier of cost
The Namibian capital Windhoek is unusual in that it pumps recycled sewage directly back into the public drinking supply, whereas every other water reuse project in the world—from Salt Lake City to Singapore—adds unnecessary cost by using the recycled water only for irrigation or industry, or pumping it into reservoirs, aquifers or rivers, and then pumping it back out and cleaning it again, in order to avoid a public outcry.
Instead, critics prefer a combination of dozens of small improvements to existing pipes and irrigation channels, switching to less thirsty crops and other measures to save water. This approach was recently backed by a major report from the 2030 Water Resources Group, an alliance of mostly private companies with huge water needs, including Coca-Cola and brewers SAB Miller, and the World Bank group.
And there remains the barrier of cost. Desalination and reuse might be getting cheaper, but prices are still unaffordable for millions of farmers worldwide who have long relied on “free’“water, said Gasson: “There’s no solution to the over-exploitation of natural water resources in agriculture. Full-stop.”
Namibia: toilet to tap
The capital Windhoek, surrounded by desert, has the world’s only system that treats wastewater and putts it straight back into the public water supply system, mixed with water from the city’s main reservoir. The success of the scheme is credited to a long-standing public acceptance campaign, including advertising, education in schools and an “excellent” water-quality record.
Arizona and Nevada, US: Desert desalination
US states and Mexico share the Colorado river under a treaty signed in 1922. Now it is suggested Nevada funds a desalination plant in Mexico or California in return for more of their river water. In Arizona they have discussed reopening a mothballed desalination plant to process farmland runoff and pump it back into the river.
UK: Desperate measures in the capital
Despite its rainy reputation London receives less rainfall than Rome, Dallas or Istanbul. To cope with an expected 800 000 more residents by 2016, and more water-hungry appliances like power showers, Thames Water, the capital’s water company, has built a desalination plant next to its Becton sewage works, which it says will help cope with peak demands.
Jordan: Simple, cheaper solutions
Jordan is one of the most water-stressed nations on Earth, and one of the poorest. There is talk of a desalination plant and mega water transfer across the country. For now, though, the focus is on improving irrigation, collecting rainwater in cisterns and small dams, replacing water-hungry crops with food suited to an arid climate, and researching wastewater reuse for irrigation. - guardian.co.uk