Is water desalination the main solution to Israel's water problems? Processes and methods, advantages and disadvantages
Idan Yisrael Faivish Galileo
Today, the surface of the Sea of Galilee is at a height of about 5.3 m below the upper red line, and 76 cm above the black line. According to the law, from this point onwards the pumping of water from the Kinneret will be stopped
In an era where the demand for benign water exceeds the existing natural reserves, the necessity of water desalination is not in doubt. However, along with the many benefits, desalination may harm the environment. Wise use of knowledge accumulated over the years, outlining appropriate courses of action and long-term thinking may reduce and even prevent damage to the environment.
What is water desalination?
Desalination is a process in which the concentration of the dissolved salts in the solution is reduced, resulting in a solution suitable for agriculture, drinking and domestic and industrial uses. A variety of sources are used for water desalination, and here are some of them: sea water, brackish water, river water, sewage water and effluents.
Today there are two main methods for water desalination: one is based on evaporation processes, and the other is based on membrane processes and is called reverse osmosis (RO for short). In the evaporation method, the older of the two, the water is circulated between several cells where the temperature and pressure gradually decrease. In this process, about half of the raw water gradually evaporates, while the other half contains + salts and returns to the sea as brine. The evaporated water undergoes condensation, and this is how desalinated water is obtained.
The reverse osmosis method is newer. This is a natural process, in which a solvent (usually water) passes through a selective membrane from a solution with a low solute concentration to a solution with a high solute concentration. In the reverse osmosis method, external pressure is applied to a solution with a high solute concentration (for example, sea water) and because of the pressure, water molecules from the sea water pass through a selective membrane, which does not allow the passage of salts, and become desalinated water. The water that did not pass through the membrane contains salts and is returned to the sea as brine.
The evaporation processes are suitable for countries where the price of electricity is very low, since this method consumes a lot of energy. In contrast, the use of membranes saves energy and costs, and therefore the reverse osmosis method has become more accepted in the world and in Israel.
The benefits of desalination
The lack of fresh water in Israel stems from several factors: Israel's geographical location, population growth and an increase in the standard of living that raises the demand for fresh water. There is a restriction on extracting water from the existing water sources of the State of Israel in order not to damage these reservoirs.
The surface of the Sea of Galilee, as of this writing, is at a height of 214.1 meters below sea level - about 5.3 meters below the upper red line, and only 76 centimeters above the black line, from which onwards the pumping of water from the Sea of Galilee will stop according to law! According to the water authority, this is a serious water crisis.
If radical actions are not taken to increase the supply of water and reduce the demand, then we will face a broken trough in the near future, something that will force the decision makers to make a sharp cut in water allocations for agriculture and even initiate the drying of gardens. Increasing the desalination output in Israel will help a little to fill the water shortage.
Advanced desalination technologies that are becoming more and more common around the world enable the supply of water at discounted prices. The low cost is achieved, among other things, by a commitment on the part of the state to buy the desalinated water of a private entrepreneur for a period of about 25 years.
The consequences of desalination on the environment
On the side of the many benefits of desalination, it may be a threat to the environment. The environmental hazards that may be caused by the project are evident in five areas: land use, aquatic environment, noise hazards, increased use of energy and damage to groundwater.
Damage to land uses Possibly because of the zoning of sea beaches for the purpose of establishing desalination facilities and seawater pumping stations. The designation of coastal complexes for industry harms this natural treasure, its flora and fauna, and its ability to serve as a recreation center for residents and tourists. One of the solutions to deal with the expropriation of coastal areas for industrial purposes is to move the desalination facilities away from the sea area to more inland areas.
Damage to the marine environment. The discharge of concentrate water into the sea may increase the turbidity of the water in the area near the outlet pipe and create a dark plume of water in the seawater, which may reduce the permeability of the seawater to sunlight and thereby disrupt the photosynthesis process carried out by plankton algae. In the processes of desalination and washing the filters, water whose composition is different from the composition of natural seawater is returned to the sea. All of these are harmful to the marine biological environment.
noise hazards They are the share of desalination plants that operate with the reverse osmosis method. Smart planning of desalination facilities will require the establishment of the facilities at some distance from population centers. However, it is possible to build the facilities near population centers as long as preliminary actions such as acoustic planning are taken.
Increased energy use Causes environmental damage indirectly due to the energy consumption needed to operate the abortion facility. This energy is reflected in the high consumption of electricity, the burning of fuels and the increase in global warming due to the emission of greenhouse gases such as carbon dioxide.
Damage to the groundwater Possible due to a leak from the pipeline and seepage of salty seawater into the groundwater in the coastal aquifer.
It is worth noting that as of today there is no known actual damage to the environment due to the construction of the large desalination facilities in Israel, however comprehensive and in-depth studies have not yet been conducted to examine the issue.
The future of desalination in Israel
The construction of a large desalination plant in Hadera, which began in July 2007, was recently completed. The facility, which operates using the reverse osmosis method, will provide about 100 mlms which will be about 7% of Israel's total water consumption. According to a government decision, the scope of desalination in Israel in 2013 will be 600 million cubic meters. Two more large reverse osmosis desalination plants are expected to start operating this year: one in Ashdod and the other in Sorek. The facility in Ashdod will discharge about 100 mlm/s, and the facility in Shork about 150 mlm/s that will be discharged into the national water system.
The facility in Shork will be the largest facility in the world that operates with reverse osmosis technology. These two new facilities are expected to be joined by 2015 by a medium-sized facility that will be built in the Western Galilee with a desalination capacity of about 50 million cubic meters.
Currently, the Water Authority is working on a master plan that intends to increase the volume of desalinated water to two billion cubic meters per year by 2050. The working assumption is that the demand for water will continue to rise, the desalination technology will remain as it is, and no peace agreements or settlements will be signed with neighboring countries - which may change the situation.
* The author thanks Mr. Avraham Tana, Director of the Desalination Division at the Government Authority for Water and Sewerage, Dr. Racheli Einav, CEO of Blue-ecosystems, and Mr. Rani Amir, Head of the Seas and Coasts Division at the Ministry of Environmental Protection, for their help in preparing the article.
11 תגובות
Is it possible to produce water by mixing hydrogen with oxygen?
Eran M, there is a difference between a meal in a restaurant which is a luxury, and water which is something basic...
Laren M you are right and wrong at the same time. The price does include the cost of setting up and maintaining the plant. This is a price including per square meter. But on the other hand, the price is until it leaves the factory and does not include the transmission of the water throughout the country and the maintenance of the filter pump system and the national and municipal plumbing. Is the price for the end consumer in relation to the factory cost price of $5 justified? I don't know this anymore, but as large systems and not competitions work, it's probably not a minimum price for the consumer... On the other hand, I'm not sure I'm interested in competition in the water sector
I'm satisfied with the price, only that they don't raise it and impose fines on it...
When the price of desalination of 1 cubic meter of water is about 2 NIS, and the price to the consumer is 5-8 NIS, it is clear that the problem is not the water crisis in Israel, but the level of corruption.
I understand that this is a scientific and non-political site, but you can certainly check my assumption with accurate tools.
Laurie Q - Just a thought, when you eat at a restaurant and you pay more than the price of the basic ingredients, do you resent it?
The answer is that there are also associated expenses here, such as the maintenance of the facilities and of course their construction. It costs Intel a few dollars to produce a chip, on the other hand, it costs around 5-6 billion dollars to set up the factory. The price per cubic meter of water does not include, of course, the factory price, etc.
: )
Michael Rothschild - The idea that you brought up was already realized in the television series "SpongeBob" where Sandy, which is a land formation, is hosted by sea creatures, but she resides and conducts research in a space enclosed by a sealed dome. Although there is no explanation there about the process of desalination of water for consumption inside the dome, the things in this dome are less illusory than the processes taking place in the marine environment outside the dome.
I accept that I exaggerated about the full offset of the cost of electricity. The point is that I was very surprised by the prices of desalination of a cubic meter of water (around 2.5 NIS or less per cubic meter), which is the direct cost. The cost of water for all consumers in the State of Israel (urban and farmers) should be as low as possible. I just took a look at the water bill I received this month and saw that I pay starting at 2.2 NIS per cubic meter for the first quota and then over 2.5 NIS per cubic meter. Without a doubt, a payment almost double the price that should be set. A nice profit for the public sector at the expense of the consumer public.
Uri Vetal:
Not really (or not really - as you like).
The pressure that must be exerted on the water to pass it through the reverse osmosis process is similar to the water pressure at a depth of about 800 meters.
In other words - beyond all the cost of the technology and the consumable components - this is an investment of energy equivalent to raising the water from a point that is twice as low.
At the time, I looked into the issue when I came up with the idea to carry out the desalination in the depths of the sea and enjoy the hydrostatic pressure to carry out the desalination without investing energy to create the pressure (in retrospect it turned out to me that the idea was thought of before me and even implemented and there are desalination plants that work this way).
I knew that the whole thing was a replacement of one type of work for another, because you have to invest exactly the energy you earn to raise the water back to sea level, but I thought that it was still something that might be too easy to do.
During the test, I asked my friend at Mekorot (Zvika Gleichman, who is in charge of the computer) if there are wells more than 800 meters deep because I knew that this is what we are talking about - it is a well (which is dug in the sea and not in the ground, but that is its depth) and he told me that there are. I understood from this that the issue is feasible and competitive with the most expensive water that we pump from deep wells, but this is still not something that is as cheap as the Kinneret water (if these were available in abundance).
By the way, what remains of that idea is the understanding that if we lived in the depths of the sea we could get desalinated water without investing any energy at all!
I am toying a bit here and there with the idea of establishing cities (or at least agricultural facilities for crops with high water consumption) at such a depth.
Of course there are many problems to solve such as structures that will withstand pressure and efficient transport of light and air but this does not seem completely unreasonable to me.
Uri is right, the energy consumption remains the same and if the desalination plant is close to the coast and the pipeline does not pass over the coastal aquifer there is no danger of damage to the groundwater.
Transferring the Kinneret water to the national carrier consumes a huge amount of energy. Therefore, the cost of energy for desalination of sea water is offset against the cost of raising the water of the Sea of Galilee to sea level.