• Fauzia Haque

Seawater = Freshwater?

With the world’s source of potable water depleting, many have debated over how the human population would survive without readily available freshwater.


Within Earth, approximately 71% of its surface is covered in water, which converts to roughly 326 million trillion gallons of water. Saltwater stays heavily prominent amongst the world’s many bodies of water as the surface contains 97 percent saltwater and three percent freshwater. Of the amount of fresh water, at least two thirds (68.7%) of it remains frozen in ice caps and glaciers whilst 97% of liquid freshwater is underground. The remaining liquid fresh water available to humans on the surface is mainly in lakes, swamps, rivers, and wetlands. However, researchers conclude that the world’s fresh water will run out and create even more shortages by the year 2050.


Why is there a freshwater depletion?

Although water is a renewable resource, many populations throughout the globe suffer from a shortage of potable water as contamination and a general increase in human populations are becoming more and more prevalent amongst poorer communities. About 780 million people worldwide lack or have no access to drinking water supplies within a sanitary and enhanced water source. While some communities have never had a readily accessible freshwater supply, sources for freshwater have been exhausted and are expected to become scarce if used at the unsustainable rate potable water is being consumed at already. With increased demand and needs for food due to a large growing population, the agricultural industry has needed a higher supply of water for their crops to grow; power plants around the globe are also utilizing water at a higher rate due to the increased needs for energy production aided by water. The rising occurrence of climate change and global warming has called for an escalated frequency of droughts that are connected to causing a great reduction of freshwater for the region affected. Additionally, groundwater is consistently being drained for consumption at a rate that is greater than it can be replenished, diminishing the possibilities for its sustainability, while incomplete infrastructure that connects homes to fountains of water creates leaks and more contamination.


What is desalination?

With freshwater availability consistently decreasing, seawater has prompted a question for drinkability; on its own, seawater contains too much salt that it can cause severe dehydration within humans as it is a hypertonic solution. Desalination was thought to be an answer that would help this global issue. Desalination, also called desalinization, is the process of removing salt from water mainly in the procedure to purify salt water into fresh water. The process takes out many mineral properties from saline water to make it safe to drink. It is an option that has been taken under consideration towards seawater to create more potable water for humans and all populations alike. However, with the increased consideration towards using desalination plants to increase the Earth’s potable water supply, desalinated water has brought about questions of practicality and overall controversy. Arguments have spurred over the actual safety of desalinated water and over the efficacy of desalinated water potentially replacing freshwater in daily lifestyles throughout the world.

How does it work?

Desalination has been deemed to be majorly practical only near the coast. However, desalination plants are currently on the rise across 120 different countries with 20,000 already built and in use. In the United States alone, San Diego houses the largest desalination effort in all of North America with the Claude “Bud” Lewis Carlsbad Desalination Plant. Desalination plants work by two methods: thermal and reverse osmosis. Thermal desalination plants require solar or heat energy to boil and evaporate water to the point that it condensates in the form of steam, which is then collected as all the salt is left behind. Multi-stage flashing (MSF) and multi-effect desalination (MED) are the two types of thermal distillation utilized for seawater. MSF is the process where seawater gets heated and condensed at a slightly lower vapor pressure point, and portions of the water get flashed into steam where it is then collected by the tubing machinery. MED is also a low temperature and pressurized desalination process that creates freshwater out of boiled seawater in a series of stages (effects) as the temperature in each stage begins to markedly decrease. Reverse osmosis plants follow the procedure of forcing seawater through a semipermeable membrane that selectively stops salt molecules, ions, and larger, unwanted particles from passing, but allows the much smaller water molecules to come through.



Advantages

Desalination plants bring about many advantageous opportunities for those who need them. With saltwater being extremely plentiful and abundant, communities suffering from water scarcity will have an increase in availability and accessibility of freshwater for household use, drinking, and agriculture. Regions that are severely subjected to droughts, desertlike or arid climates, and absolutely no access to clean freshwater significantly benefit from the water produced by desalination plants. California and Saudi Arabia, both impacted by very little rain each year and critically dry climates, both contain many desalination plants throughout their regions to make up for the lack of water. As desalination plants have gained more and more popularity, the increased prevalence has allowed for a cheaper price on desalinated water. On an international scale, at least 300 million people receive potable water from desalination plants. It also allows groundwater aquifers more time to replenish to the point that may bring about more sustainable freshwater practices. On an ecological standpoint, it may even help with habitat restoration and prevent further damage as freshwater habitats are left alone. Economically, there is a potentiality that the salt derived out of the seawater could be placed in the market for sale; more job opportunities would be created with the construction and maintenance of desalination plants as well. Agricultural industries would also have more water for growing their crops and maintaining livestock.


Disadvantages

However, even with all its beneficial properties, controversy still arises around desalination plants with its much more intense economic and environmental drawbacks. Desalination plants are significant energy-intensive as both desalinating processes require extreme amounts of energy and specialized technology to produce freshwater. These plants can cost almost a hundred million dollars incorporating all of the locational and environmental aspects, which makes it an unrealistic project for those in developing countries. While the creation of more jobs is beneficial, the world’s rapidly aging population may not be able to uphold this kind of work in the future. Desalination plants require fossil fuels to power their machinery; the increased usage not only depletes fossil fuel resources but also causes an escalation in the amount of air and water pollution in the environment. Marine wildlife can also get brutally injured or harmed by these plants if they get sucked in by the motors of the plants during the intake process of seawater; an intensification of salt and chemical concentrations can also occur in the area occupied by the power plant, causing unsafe living conditions for any sea life nearby as they cannot adapt to the briny, toxic water.


How Much Water is There on Earth? (n.d.). U.S. Geological Survey. Retrieved from https://www.usgs.gov/special-topic/water-science-school/science/how-much-water-there-earth?qt-science_center_objects=0


Shaikh, A. (2017, June 16). The Bad News? The World Will Begin Running Out of Water By 2050. The Good News? It's Not 2050 Yet. UN Dispatch. Retrieved from https://www.undispatch.com/bad-news-world-will-begin-running-water-2050-good-news-not-2050-yet/


Global WASH Fast Facts. (2016, April 11). Centers for Disease Control and Prevention. Retrieved from https://www.cdc.gov/healthywater/global/wash_statistics.html#:~:text=Access%20to%20WASH,world's%20population)%201%2C%203.


5 Reasons The World is Running Out of Freshwater. (n.d.). Seametrics. Retrieved from https://www.seametrics.com/blog/running-out-of-freshwater/



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