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desalination
by Bruce McKellar
Physical Geology
Fall 2013
                  

 

Our inevitable thirst for salty water
 

Photo Credit: www.pimagazine-asia.com/wp-content/uploads/2013/04/desalination.jpg

 

When the well runs dry, we know the worth of water.” – Benjamin Franklin

 

            Water is and has been an important part of human life and is perhaps humanity’s most vital natural resource.  Water is necessary to the physiological function of our bodies, as our bodies are made up of approximately 53% water.  Water is the basis of economy, trade, industrial manufacturing, and an important natural  element in everyday life.


 

Photo Credit: www.environment.ucla.edu/media/images/water-fig1.jpg

 

Furthermore, geologically, water has served as an important natural force that has shaped and formed our planet - and continues to do so today.  Water erosion and glacial movement has led to the formation of rivers, streams, and lakes that has produced an above ground and below ground supply of water for the needs of humans for millennia.  Yet, as we grow as a population, so does our dependence on fresh water.  Because we have become increasingly dependent on fresh water for needs beyond ourselves (industrial manufacturing of goods and agricultural needs), the availability and supply of fresh water has been diminishing in quantity, quality, and availability.
 

Photo Credit: http://ga.water.usgs.gov/edu/graphics/watercyclesummary.jpg

 

  One viable solution to fresh water supply is desalination, or the purification and removal of salt from ocean and seawater.
 

            The concept of desalination has been around for many centuries; it has been found in ancient Egyptian Sanskrit, and has a history here in the United States.  The first desalination units were developed for and used in steam ship vessels.  The idea of desalination originated as a way to free up space in the cargo holds of ships carrying freshwater to use in the ship’s steam engine boiler.  Because of the abundant supply of salt water surrounding the ship, desalination made sense on a small scale, as it could supply an infinite amount of freshwater needed for propulsion and on vessel consumption and hygiene needs by stewards.
 

Anatomically, fresh water is important because our body needs it to function properly.  Freshwater is vital to the human race and necessary for the longevity of our population. 

 

On the planet, we have an abundance of water; about 70% (326 million, trillion gallons) of the world is composed of water, but most of it is in the form of salty seawater.  Less than 3% of the world’s water is actually freshwater and about two thirds of that 3% is contained in glaciers and ice; what remains is about one percent water for the seven billion plus inhabitants on the planet. 

 

 

Moreover, with the population increasing at such a rate, the need for life sustaining freshwater is crucial.  Furthermore, the concern is not just an increasing population, but rather, the current populations that have access to sanitary freshwater.  The World Health Organization (WHO) estimates that one in five people on the planet do not have access to clean, sanitary water.
 

  

Photo Credit: water.org

 

However, many of these individuals are fortunate to live within close proximity to a body of water such as an ocean or salt bearing lake: thus, desalination is a feasible option for them.
 

In 1961, President John F. Kennedy proposed a hope for a way to get fresh water from salt water (by utilizing desalination) that would “dwarf any other scientific accomplishment.”  We have moved closer to that goal, and today, there are more than 15,000 desalination plants in operation around the world producing more than 16 billion gallons a day: but, this provides for less than 1% of the total world consumption of fresh water.  
 

Photo Credit: http://ngm.nationalgeographic.com/img/big-idea/desalination-main.jpg

 

In desalination, there are five ways to remove salt from water to create freshwater.  However, there are two methods that are used the most and provide nearly 90% of freshwater from saltwater.  These two methods are reverse osmosis and multistage flash.  Multistage flash is similar to what was used in the steamships and resembles the distillation process of spirits and liquor.  Multistage flash desalination requires an immense amount of heat as well as an elaborate, large, space consuming, set up.  Therefore, reverse osmosis (RO) is the prevalent method used today.  Its benefits are the availability of materials in the manufacturing of RO components and RO’s cost effectiveness over other methods of desalination.
 

 

Reverse Osmosis Plant – Photo Credit: Wikipedia
 

            There are a few drawbacks to desalination.  One is is the accumulation of the salt left over from the processing and purification processes and the other is cost.  Currently, when a desalinization plant is near a body of water, the leftover salt is mixed into a briny mix of water and pumped back into the original body of water with the hope it will become diluted to a similar concentration close to the original solution.  However, if the brine is not mixed thoroughly enough with the original supply, it can potentially increase the total dissolved solids of the water.  This “wastewater” is denser than the surrounding water, which in-turn settles atop organic matter on the ocean floor and depletes the oxygen levels – thus creating a potential of an imbalance in the ecosystem.  
 

Salt Heat Insulation Tile

Photo Credit: www.alibaba.com

 

One possible use for the remaining salt is to use it to make building materials such as insulation tiles or wallboard.  In addition, new research is being developed on a saltwater fuel for automobiles.  As with all things in the natural world, moderation is necessary.  Water should only be taken and processed at a rate at which it can be recharged or replenished.
 

There are other options that we do have.  Drilling for water; however this can be costly, and we can never know, with certainty, about the quality, longevity or the quantity of water that the well will produce.

            Manufacturing water out of hydrogen and oxygen atoms is a costly and dangerous process.  Furthermore, it cannot be created from these elements alone, but rather resourced from the water that is available on the planet.
 

Another option is the possibility of harvesting, or mining water from outer space.  However, at this time, this is also cost prohibitive and logistically difficult. 
This leaves desalination as the most likely source of future water collection.

  

Asteroid Mining

Photo Credit: http://www.philipmetzger.com/blog/wp-content/uploads/2013/05/neo_eva.jpg

 

            There are other methods to produce freshwater such as cloud seeding.  This process is inconsistent and sometimes produces undesirable results.  It is worth mentioning a historical event of cloud seeding by the British in the 1950s.  As a response to curb invasion during World War II, the British flew planes into the clouds and seeded the clouds with dry ice, salt, and silver oxide to induce rain.  The result was more than anticipated; the mission worked too well and resulted in a disastrous flood in the town of Lynmouth, England, uprooting trees and producing 250 times the normal amount of rainfall.  This is proof that humankind cannot duplicate the natural geologic process with the same certainty and replication.

 

Cloud Seeding

Photo Credit: http://savethewater.org/wp-content/uploads/2012/08/Rain-Cloud-Seed.jpg

 

Other possible foreseeable benefits of desalinization would be its usefulness with agriculture production and genetically modified foods or GMOs.  Having an ample supply of water for irrigation and agriculture processing would lessen the need to create GMOs to utilize less water while growing.  Also, as population does increase, other issues will arise such as an increase in pollution, increased dam construction for fresh water reservoirs, and the threat of drought to wetland wildlife areas due to underground water pumping.
 

Currently, technology and research on desalinization and plant production is on the threshold of an expansive growth period.  This means that as groundwater drilling becomes increasingly more expensive due to dwindling groundwater supplies, environmental restrictions and legislation, the construction of desalinization plants will become more prevalent.  

 

Photo Credit: http://www.abc.net.au/reslib/200907/r408688_1929336.jpg.

 

In addition to the construction of freshwater production plants, pipeline capacity and infrastructure to get fresh water to the population of people will also occur.  As population increases, the cost of desalinization will decrease.  Desalinization costs today are less than half of what they were just ten years ago.  Adding to the conundrum is the fact that wastewater production will increase as population increases; thus, the reclamation and purification costs of wastewater will invariably decrease.  Therefore, initially, wastewater purification will prevail as a choice of fresh water - until this resource becomes diminished and energy costs decrease.
 

Photo Credit: www.studentreporter.org/wp-content/uploads/2012/04/

 

Ultimately, the deciding factor in the prevalence of desalination is a reliable and dependable source of energy.  Considering the abundance of saltwater available on the planet; if we, as a population, are able to find an inexpensive source of energy, and can combine saltwater with new, cheaper water purification technologies, then we can all enjoy a long-term solution to the current freshwater shortage crisis.


 

 

Works Cited

 

 

http://ga.water.usgs.gov/edu/drinkseawater.html

http://www.worldpumps.com/view/924/focus-on-sea-water-desalination/

http://science.howstuffworks.com/environmental/earth/oceanography/desalination1.htm

http://www.planetaryresources.com

http://www.npr.org/2013/09/13/222101254/us-cities-quench-growing-thirst-with-saltwater

http://www.idadesal.org

http://carlsbaddesal.com/project-overview

http://hbfreshwater.com/desalination-101/desalination-worldwide

http://news.bbc.co.uk/2/hi/uk_news/1516880.stm