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Water desalination, an option to end droughts

Eliminating salt from saltwater to turn in into freshwater is one of the alternatives which could definitely end the drought in regions such as La Guajira (north of Colombia) or Buenaventura (southeast Colombia). In these regions, water supply is not 100% covered despite living on the coast of the Atlantic and Pacific oceans.

Experiences of this type of treatment –technically known as water desalination– have demonstrated to be successful in countries such as Israel, where in 2008, this technique ended one of the toughest droughts its inhabitants had ever suffered in 900 years.

Today, Israel does not only obtain 55% of its water used in homes for its 8,544,000 inhabitants but now, thanks to desalination, the offer exceeds the demand.

Óscar Rodríguez Bejarano, Universidad Nacional de Colombia (UNal) Chemist and Sciences Ph.D. has followed the progress of this water treatment and says it could be a permanent answer to solve the structural lack of water, exploiting the closeness of both Colombian regions to the sea.

The desalination process is carried out using a method known as reverse osmosis, which was described back in 1953, but not applied much in Latin America.

Only Chile has desalination plants for supplying freshwater to the city of Antofagasta, near the Atacama Desert, in the north of the country.

Obtaining a drop of water: a daily challenge

The Guajira peninsula is a desert-like territory of 20.848 sq. km.  (8,049 sq. miles), where according to the Colombian National Administrative Department of Statistics (DANE, for its Spanish acronym) close to a million inhabitants live and of which 39% belong to the Wayúu Indian community. It is the driest area of Colombia, with temperatures ranging between 35º and 40º C (95º - 104º F).

Although most part of its territory is surrounded by the Caribbean Sea, 50% of its inhabitants live without water. They need to obtain the precious liquid from water wells or jagüeyes, in a trip which can last up to two-hours by donkey. A task usually assigned to the children of these communities.

Buenaventura is the main Colombian port on the Pacific Ocean and located in the Province of Valle del Cauca. The lack of access to quality water was one of the demands to the authorities of the 21-day strike of May of this year. The leaders of the strike demanded better water because up to now, only 71% of the population had access to water between four to eight hours a day, every other day.

Both regions endure the rigors of the weather and have deficient freshwater supply and both also have the advantage of being next to the sea.

Alternative: Reverse osmosis

Professor Rodríguez says the World Health Organization (WHO) establishes that “freshwater should have at least less than 500 parts per million (ppm) of dissolved solids (500 milligrams per liter). However saltwater has, on average 35,000, therefore they need to lower it from 35,000 to 500 ppm. This process is called desalination.

One of the most common techniques used in the world to “clean” water is reverse osmosis, which consists of separating the salt from the water using a small membrane or plastic mesh with tiny holes which only allow water to pass, filtering the salt, therefore it is semipermeable.

It is like passing flour through a sieve or making coffee in an artisanal fashion, just that in this case, it is much more sophisticated because it is carried out in treatment plants which have giant water collector pipes.

In the process, saltwater is pushed through a pipeline after which pressure is exerted for it to pass through a semipermeable membrane and exit the other end as freshwater; the salt concentration of the resulting water is known as brine.

“Usually yields of 35, 50 and up to 70% are obtained,” claims Rodríguez. Meaning that for every 100 liters of water the process can obtain up to 70 liters of freshwater.

Another benefit of reverse osmosis is that given the tiny pores of the membrane, it usually also filters out solid microorganisms, therefore the water is almost considered potable.

“The saltwater treatment plant in Sorek (Israel) uses natural sand filters first and lastly the reverse osmosis procedure. It is not a unique process, just like in any water treatment plant, there are several stages in the process, but the main process is reverse osmosis,” said Rodriguez.

World experience

According to figures of the International Desalination Association (IDA), there are 18,000 desalination plants around the world. The largest is the Sorek water treatment plant, located 15 km (9.3 miles) from Tel Aviv (Israel). “It costs around US $400 million and produces 624,000 cubic meters (165,000 gallons) of water a day.

There are also saltwater treatment plants in Saudi Arabia, United Arab Emirates, Libya Kuwait, Qatar, United States, Japan and Spain which supply a good part of the water for its inhabitants.

“If WHO suggestions are taken into account, the optimal level of water per inhabitant is 100 liters (26.4 g) of water in their place of residence, therefore the Israel water treatment plant could supply a city of approximately 6,000,000 inhabitants,” claims Rodriguez.

For the Province of La Guajira, Rodriguez thinks they need to produce at least 100 cubic meters (26,400 g) of water, taking into consideration that they have a population of close to 1.000.000 people. However, they are dispersed throughout the territory, so the expert says they need several water treatment plants.

Taking into account that the Province has a budget of approximately US $150 million in royalties, Rodríguez says: “Thinking of investing US $100 million in a desalination plant or several US $10 million plants is not a big deal and it can solve the drought issue in a definitive manner.”

This is an alternative which may be considered in government policies which could offset this issue for both strategic areas of the country.

Consejo Editorial