Fresh Water From The Sea
With five desalination plants annually converting 20,000 million cubic feet of seawater into drinking water, Israel is a world leader in desalination, the process of removing salt from water. Forty percent of Israel’s domestic water comes from the sea, the largest percentage anywhere in the world. Desalination and water-saving measures have not only saved the Kinneret from sinking below the red line, the point at which no more water can be extracted without wreak- ing irreversible harm, but are saving Israel’s very existence.
To Boil Or To Filter
Clouds, animals and plants turned seawater into fresh water for thousands of years before men figured out the secret. Turning salt water to fresh water was a novelty for man, not for nature. Seawater rises to the clouds and leaves salt behind in the sea. Seabirds like pelicans, albatrosses and gulls have a “rete mirable” gland near their nostrils which extracts salt from their blood and enables them to subsist on seawater when they are far from land. Mangrove trees secrete salt from their systems by storing it in their leaves or roots. Some mangroves even have a gland similar to that of seabirds which extracts salt from leaves in the form of salt crystals which then fall off.
Surrounded by endless stretches of seawater, man long pondered how to remove its salt but only hit on an efficient method of doing so in the second half of the last century.
Aristotle was one of the first to tackle the issue. In Meterologica (1:3), he wrote that if a person submerged a wax container in the sea it would eventually fill with fresh water by filtering out the sea’s salt. Apparently, as with much of what he wrote, Aristotle never actually tried this experiment because as a matter of fact, wax does not filter seawater.
Around 200 CE, sailors began extracting water from sea- water by boiling it on board ship and gathering the steam in sponges. Which of the two methods is better: the sailors’ boiling or Aristotle’s filtering? In modern times, boiling and distilling water on a mass scale is prohibitively expensive and is only popular in certain water and oil rich Arab coun- tries. Most countries prefer Aristotle’s approach.
Filtering works by forcefully pressuring salt water through a semi-permeable membrane, a membrane that lets water molecules through but keeps the larger salt molecules behind. The difficulty is to find a membrane permeable enough to allow water through, but strong enough not to rip under the enormous pressure involved in the process. The Father of Israel’s desalination program was Professor Sidney Loeb (1917-2008), who developed special membranes for the purpose in the United States and Israel.
Loeb made the process commercially viable for the first time in 1959 as a student of Samuel Yuster (1903-1958) of the University of California, Los Angeles, together with
another student, Srinivasa Sourirajan. The threesome developed the revolutionary Loeb-Sourirajan membrane, which made it possible to filter salt from water at reasonable flow rates and realistic pressures.
The United States was enthusiastic about the process. President John Kennedy acknowledged the importance of providing fresh water to a growing world population, declaring in April 1961 that “In this administration we will put a man on the moon and make the desert bloom.” He added, “If we could ever competitively, at a cheap rate, get fresh water from saltwater, that would be in the long range interests of humanity and would dwarf any other scientific accomplishments.”
Looking back at his achievement at an honor ceremony in 2006, Loeb recalled how he got started.
“In looking for a particular research project, I was attracted to desalination and in particular to a California state- sponsored project and fellow student, Srinivasa Sourirajan, who invited me to partner with him,” he said. “He was working with Professor Samuel Yuster on a project called ‘surface-skimming’ [an attempt to skim off microscopic layers of fresh water that lie on the surface of salt water]. However, after a time it appeared more appropriate to call it Reverse Osmosis…
“Sourirajan and I worked about two years together to make the process practical, i.e. producing fresh water from saline water such as seawater at an adequate permeation rate through the membrane without the use of excessive hydrostatic pressure.”
Loeb described the membrane they used as “a very thin active salt separation layer surmounting a relatively thick support layer. This thin separation layer holds back the salt but allows the permeation and water into and through the support lager [membrane].”
Interest in the process increased dramatically after the installation in 1965 of the first commercial reverse osmosis plant in the small town of Coalinga, California, which began supplying a third of the town’s freshwater. Loeb re- called, “The plant was situated in the firehouse garage and was operated by the fireman when he was not putting out
fires. He also took care of an experimental electro dialysis plant [a procedure of extracting fresh water from salt water using electricity] and the town sewage disposal plant.”
A second desalination plant was installed in Firebaugh, California, in 1971.
At the honor ceremony mentioned earlier, Loeb discussed his pioneering reverse osmosis work in Israel, where he set up a pilot plant to desalinate brackish water pumped from beneath the Negev desert.
“In 1966 I went to Israel under UNESCO auspices to teach RO [reverse osmosis] at Ben-Gurion University in Be’er Sheva,” he recalled. “A pilot plant was setup in the south of Israel at a kibbutz called Yotvata situated in the
desert. Probably because this was the first publicly available RO plant in Israel, the inhabitants refused to drink the water. However, the women did bring buckets to the plant for the allegedly soft water to wash their hair. Then an outspoken doctor came down to the plant (from Be’er Sheva) and informed the Yotvata residents that they were all going to get rigid spines if they continued to drink the saline ground water. Then they began to drink our RO water. Later a full- scale plant was installed in Yotvata.”
After he was offered a University Professorship in Israel and after meeting his future wife, Miriam, Loeb decided to stay in Israel for good.
Energy From Sea Salt
In the early ‘70s Israel was planning to build the Red-Med channel to bring water from the Red Sea to replenish the dying Dead Sea. In anticipation of the plan, Loeb invented an energy producing process called Pressure-Retarded Osmosis (PRO). This was the exact opposite of desalination in which pressure is exerted to draw water from salt. Instead, by absorbing fresh water through a membrane, salt-water in a closed container would swell, push against a piston, and produce energy. The salt water would absorb fresh water through a membrane due to the principle of osmosis, the tendency
of liquid to move from an area of lower salt concentration to a region of higher salt concentration until the two concentrations become equal. Loeb’s idea was to have Dead Sea water separated in a container by a semi-permeable membrane. As the Red Sea Water seeped into the closed Dead Sea container and raised its volume, the excess water would push against a piston and produce energy.
Nothing much resulted from Loeb’s scheme at the time, but years later, the world’s first osmotic plant was opened in November 2009 at Tofte, Norway.
The Situation Today
Israel is supplying water to a population which is growing 1.8 percent yearly even as it struggles through years of drought. Israel has contaminated ten percent of its natural water sources through pollution, particularly the coastal aquifer where winter runoff gathers beneath Israel’s most densely populated region. Desalination is one of the answers. Desalination is conducted in a number of steps. Water is drawn from a system of pipes, filtered from sea creatures and dirt, and then purified through reverse osmosis. Afterwards, some minerals removed by the process are replaced to make the water healthy and tasty.
45 percent of every cubic foot of water removed from the sea is returned to the sea as a saline solution which contains 7.5 percent salt instead of seawater’s 4 percent, as well as a high concentrate of iron, both of which can potentially harm marine life. With over 20,000 desalination plants across the globe this is becoming an international ecological concern.
Despite ecological risks, Israel has no choice but to forge ahead with every means available to produce more water. The situation would be disastrous otherwise. Last winter, which came after two years of drought, was one of the driest winters on record, with the Kinneret rising less than one foot instead of an average five feet. This was after a seven-year drought
that paused for only one year in 2013.
A 1998-2012 drought that affected the whole eastern Mediterranean was ranked by NASA as the region’s worst drought in nine hundred years. Global warming is expected to make things even worse.
To help provide enough water, Israel has five desalination plants including one of the world’s largest, the Sorek plant near Tel Aviv which became operational in 2013.
In addition to five seawater desalination plants, Israel has smaller desalination facilities to desalinate brackish water (water with high salt content) from groundwater wells in Eilat, the Tel Aviv area, and near Haifa. The latest of Israel’s desalination plants is being built in Ashdod at the cost of 1.6 billion shekels and is expected to eventually supply 4,500 million cubic feet of water a year.
A new way has been found to make the desert bloom.
(Sources: A Tribute to Sidney Loeb the Pioneer of Reverse Osmosis Desalination Research, Yoram Cohen and Julius Glater Water Technology Research Center Chemical and Biomolecular Engineering Research University of Cali- fornia, Los Angeles Los Angeles, California; Wikipedia)