Britain's mainland desalination plant

Desalination: is it the saviour of drought-ridden countries?

A reported drop in water quality is causing serious health problems among some of the world's fastest-growing populations. Could new developments in desalination provide an answer?

The Gaza Strip has endured more than its share of problems, but the quality of its water doesn't often make headlines. Perhaps it should, described as it was by Palestinian George Rishmawi as "not a liquid suitable for animal, plant, or human consumption".

In a little-viewed interview on YouTube, Rishmawi, the advocacy officer for water issues of the Near East Council of Churches in Gaza, said the water was "unbearable", "as if you were touching oil", and now has "raw sewage" seeping into it.

For decades the Gaza Strip has grappled with shockingly poor water quality. The region's sole source of fresh water is its underlying coastal aquifer, which Palestinians in Gaza have long resorted to over-pumping in a bid to quench the thirst of a rapidly growing population, currently 1.6 million and set to reach over two million by 2020.

Water extraction rates currently come in at 190 million cubic metres a year, more than three times the aquifer's sustainable yield. And so, groundwater levels are down, sea water is infiltrating from the nearby Mediterranean Sea, and Gaza's tap water is getting saltier, far beyond World Health Organisation safe-drinking water guidelines.

Factor in the tens of thousands of cubic metres of sewage, pumped into the sea every single day, along with the steady stream of nitrate fertilisers from farmland irrigation, and you have what the United Nations and World Bank call a "critical" situation. Cases of 'blue baby' syndrome, due to nitrate poisoning from the tap water, are rising; 26'per cent of disease along the Gaza Strip is water-related and the UN predicts the aquifer could become unusable in just four years.

However, desalination may transform Gaza's water supplies. As Dr Rebhi al-Sheikh, deputy chairman of the Palestinian Water Authority explains, the region is already home to numerous small, reverse osmosis desalination plants that treat brackish water - water that has less salinity than sea water, but more than fresh water - which is then distributed across the region in tankers.

While this goes some way to supplement Gaza's salty drinking water, the ad hoc operations are riddled with problems. "Many poor people can't afford this and are forced to use the water with high salinity from the taps," Dr al-Sheikh says. "And it's not easy for us to control the water quality across this large number of disparate desalination plants and distribution tankers."

These systems need regular, and often costly, maintenance, but numerous reports cite instances of salt water pre-treatment filters not being washed frequently enough, or membranes only being descaled intermittently, leaving the water a breeding-ground for bacteria and viruses. Alarmingly, reports of system effluent, containing anti-scaling chemicals, surfactants and acids being discharged to nearby fields, rather than collected and sent to a post-treatment plant, have emerged.

Long-term view

To tackle the problem, the Palestinian Water Authority now intends to introduce large-scale desalination to the region. In a first step, three small sea-water desalination plants will be constructed on Gaza's coast that will process 13'million cubic metres of water a year.

Not enough to serve Gaza's growing population, but enough to quench its thirst for a couple of years, says Dr al-Sheikh. "These small plants will be operational within two years and will give the aquifer a chance to recover," he adds.

The next step is to build a central desalination plant with a 55 million cubic metres per year capacity by 2017. "This will cover more than 60 per cent of the domestic needs in Gaza," explains Dr al-Sheikh. "The plan is to mix this water with other potable water sources in Gaza, for example from the desalination plants and some areas of the aquifer, and distribute this."

Development of this facility will continue until 2020 when the plant will turnaround some 100 million cubic metres of water every year, and, if all goes to plan, reach a capacity of 130 million cubic metres a year by 2030.

The technology of choice for Gaza's central plant is, like the existing ad hoc operations, reverse osmosis. According to Dr'al-Sheikh, studies dating back to 1995 point to this well established membrane-based method as being more feasible for the region than one of the widely used but energy-hungry thermal distillation-based processes.

"Gaza is not an oil country. We have to purchase oil from outside the country, and thermal processes are generally applicable in countries where oil is cheap; this is not so in Gaza," he says.

Still, reverse osmosis desalination demands significant inputs of energy, primarily to pressurise the water under treatment, a factor of which Dr al-Sheikh is well aware. "Of course, we know electricity is the major component of the operational cost of the plant," he says. "We are in negotiations with Egyptian authorities to provide a gas pipeline to Gaza. We want to build [a gas-fired power plant] to provide electricity for desalination with gas from the Egyptians."

Clearly much has to take place before the Palestinian Water Authority's bold plans are realised, but despite painfully sensitive Israel-Palestinian politics, progress has been made. Arab Gulf States have expressed a wish to finance half of the costs alongside an Arab-European finance partnership, while France has pledged '10m in support.

Total required investment is a hefty US$455m, but Dr al-Sheikh is confident monies, and water, will flow. "Procurement starts this month and a tender for contractors to start building the plant will be issued by the middle of next year," he says.

Reverse osmosis

The Gaza Strip is hardly alone in its ambitious plans for water desalination. Around the world more than 15,000 desalination plants are either being built or already operating, churning out some 70 million cubic metres of water a day. And this number is set to grow. But why now?

As Christopher Gasson, publisher at UK-based analyst business Global Water Intelligence, explains, an increase in desalination projects was inevitable. "People are eating more protein, which means more water is needed to grow animal feeds. They also want to grow more crops for biofuel. Water is the ultimate limiting factor," he says. "And with urban [and industrial] demand for water growing apace, the only solution is to make more of what we've got."

Erik Hanson, director of product management from US-based GE Water and Process Technologies, is involved with many of GE's desalination projects that are based on the well-established reverse osmosis membrane technology. He too is now seeing a fast-growing demand for desalination projects, especially for industrial use.

"We're starting to see Middle Eastern economies growing and diversifying from oil-based economies," he says. "There's a surprising amount of industry development going on, and as this grows, water demand grows."

He also points to south east Asia, noting a tremendous increase in desalination demand across Indonesia following industrial growth. "This country has high GDP growth and you don't think of it as water scarce as it consists of islands," explains Hanson. "But the water they have is largely used by agriculture, so as new industry comes in it needs its own water sources. A lot of our desalination units are feeding its power plants, we've seen a significant number of these in Indonesia in the last five years."

At the same time, Hansen notes more and more projects coming from oil companies clamouring to extract oil from remote regions of the world. "Oil extraction uses a lot of water that ends up with a lot of hydrocarbons and suspended oils in it," he says. "It's hard to treat but we've won a lot of projects in the oil sands of northern Alberta, Canada, using complex water treatment systems that include reverse osmosis desalination. We're certainly going to see growth in harder to treat markets."

With this in mind, GE and competitors such as OPUS and Veolia have has been chipping away at operating costs in a bid to capture a share of these growing markets. Earlier this year, GE introduced its so-called Integrated Pump and Energy Recovery (IPER) system, a positive displacement pump system based on a hydraulic drive. Crucially, the system promises to cut the energy demands associated with pumping water by 10 per cent in large plants.

Global Water Intelligence's Gasson believes incremental improvements that increase energy efficiency are crucial to the success of desalination, and given progress, providers of reverse osmosis systems will dominate the market. "For example, the waste-water from oil extraction in tar sands is becoming a bigger deal, and is difficult to deal with," he says. "Reverse osmosis with improvements will dominate here."

Alternative methods

As the demand for cleaner water has grown, myriad innovative desalination technologies have emerged, including improvements in reverse osmosis using novel membranes, membrane distillation units and ion exchange systems.

Some wackier examples include US entrepreneur Dean Kamen's Slingshot purifier, and Gasson is only half joking when he quips "this industry attracts all sorts of charlatans", but still, several novel systems are making significant in-roads into the well-established desalination industry.

One key technology, forward osmosis, has been understood for many years, but has only been put into practice relatively recently. Osmosis describes the process in which a solvent flows from a region of lower osmotic pressure across a permeable membrane to a region of higher osmotic pressure. This natural phenomenon can be exploited by using a solution with higher osmotic pressure to draw 'pure' water out of seawater. The solution becomes diluted and is later treated to remove the fresh water.

Peter Nicoll, technical director of UK-based water monitoring company, and developer of forward-osmosis systems, Modern Water, says this desalination technology is cheaper to operate and consumes less energy than conventional reverse-osmosis systems, particularly with difficult feed-waters. This is due to the fact that forward osmosis does not require the high pressures of a reverse-osmosis system to remove salt from solution, and is less prone to fouling. Consequently, the process is 'easier' on the membrane, as foulants will not be forced against, and stick, to it.

As Nicoll says, during trials that lasted nearly three years at one of the company's two desalination plants in Oman, the membranes in its forward-osmosis plant didn't need chemically cleaning. "The membranes in the reverse-osmosis plant [operating alongside this system] needed cleaning every two to four weeks and had to be changed three times," he says.

With its pilot plant in Gibraltar and the two plants in Oman - with a combined capacity of 300 cubic metres a day - the company is looking to take forward-osmosis to China. "We're still working on membranes and new draw solutions, which will make a difference, and have a number of people in China, looking at the market there," says Nicoll. "This is just the beginning."

Brian Reed, lecturer in water and sanitation for low-income countries at Loughborough University, points out that population growth is fuelling rising water shortages, and this isn't going to stop.

"Your big problems are going to be in China, a lot of mega-cities are built on the coast and a lot of people are moving here," he says. "People are moving onto marginal land and being forced to use water sources that 10 or 20 years ago they wouldn't have done."

He also points to Bangladesh, the Pacific Island States and Philippines as either having or about to encounter significant problems. So can desalination save the day? Well, that depends.

"We've known since the 1980s that technology is not the answer, just part of it," says Reed. "To operate a system you need other elements in place."

First, money for maintenance must be secured, backed up by a solid supply chain to ensure a community can actually get hold of, say, the replacement filters and membranes it needs. As Reed points out"The supply chain is a key barrier for longer-term development."

Crucially, cultural and gender issues must be considered, especially in developing countries. According to Reed, community involvement is great, but install your all-singing and all-dancing desalination unit and suddenly men become more interested. "Most water has traditionally been collected by women, so putting in something that is too technologically advanced excludes them, yet its women that keep things going," he says.

So where does this leave today's water-short nations? Having visited many such regions, worldwide, Reed is optimistic about only some.

"Nations, such as Gaza, that have relative wealth and educated people, can always sort out problems; so even in these low-income countries you can have a sophisticated desalination system," he says. "Other communities can't even keep a standard water pump operating. What hope is there for desalination here?"

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