environmental sciences

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The Pros And Cons Of Desalination Environmental Sciences Essay

Desalination is a technological solution that some believe would provide ample supplies of additional water resources.  Discuss the pros and cons to this technological solution and whether or not you support it. Less than 3% of the earth’s natural water is viable for human use and consumption. This brings light to the need for a solution to the quickly depleting resource in the rapid growth of population, industry, and increased overall use of water. What is desalination? Put simply, desalination is the conversion of seawater and or brackish water into consumable quality water. To elaborate, this process can be done through a few different methods depending on the location and need for quality, the main process being distillation and reverse osmosis (preferred method). Of the more than 7,500 desalination plants in operation worldwide, 60% are located in the Middle East. The world’s largest plant is in Saudi Arabia. In contrast, 12% of the world’s desalination capacity is in the Americas, with most of the plants located in the Caribbean and Florida. To date, there are currently 23 proposed desalination plants on the coast of California. With these facts in mind it is the responsibility of human kind to weigh the benefits and the consequences of this somewhat deceivingly simple solution.

Pros: There is no doubt that an answer to the ongoing discussion of the potential exhaustion of water is indeed overdue. With that in mind, facts supporting the use of desalination as a good alternative remains to be seen. One factor supporting the use of desalination is that desalination can provide a backup water source and a partial solution to a growing problem. While some believe that the use of desalination plants can provide an infinite supply of water and make it possible to put an end to the depleting resource, in reality, as idealistic as this illusion may be, it is far from true. Another favorable point includes the idea that desalination can remove drug contaminated water and other substances such as arsenic and fluoride which is an ongoing issue in places such as Asia and sub-Saharan Africa. It should be noted however, that the use of desalination is not currently present in either place, and the likelihood of implementing a plant, anytime in the near future, is most likely unattainable due to topographical and economic limitations. Another supporting idea proposes that desalination may reduce the need to take additional water from the environment and, in some cases, offers the opportunity to return water to the environment. In some areas it is proposed that desalination facilities may help reduce the dependence of local water agencies on climate sensitive sources of supply. Furthermore, desalination is currently an efficient and reliable water source in use among military operations world wide including naval ships. It is also used on some cruise ships as a reliable source of potable water.

Cons: Desalination is costly not only ecologically but economically. Desalination costs are subjective due to many factors, which include location and methodology, making comparisons complex and estimates vague. For example, Tampa Bay Florida’s desalination plant ended up $48 million dollars over its original estimate and is still not in full working capacity due primarily to poor planning. Previous desalination plants have cost in upwards of an estimated $100-$150 million dollar range, just to start the facility, this does not include what it costs to run after it is already built. Although Costs have come down over the past decade, as technology has become more efficient, desalination still perpetuates a cost of approximately $500-$2,000 per acre foot of water (325,000 gallons), compared with approximately $250 per acre foot for water in urban Los Angeles, and $10 per acre foot paid to the federal government by farmers in the Sierra foothills, according to Haddad, the author of Rivers of Gold: Designing Markets to Allocate Water in California (Washington, D.C.: Island Press, 2000). Furthermore, the assumption that desalination costs will continue to fall may be false, in fact future costs may actually increase. Another negative factor is that more energy is required to produce water from desalination than from any other water-supply or demand-management option in California, this in turn brings to light the concern of further dependence on fossil fuels. Conversely, it should be noted that the use of fossil fuels can and has been reduced in many facilities by using solar, wind and wave energy to power the facility.

According to an executive summary by the pacific institute “desalination can produce high-quality water however it may also introduce biological or chemical contaminants into our water supply” this will weigh heavily on the design and location of the plant and should be monitored heavily by local government agencies to ensure consumer safety. Desalination produces highly concentrated salt brines that may also contain other chemical pollutants. More specifically, seawater contains approximately 35,000 parts per million of salt. During the reverse osmosis, water molecules are strained through membranes while the salt particles are retained by the membrane and result in a "reject stream" nearly twice as salty (70,000 ppm) as seawater. Safe disposal of this effluent presents a significant challenge. Additionally and perhaps of the most devastating of the negative aspects to this process is the Impingement and entrainment of marine organisms. This is among the most significant of the environmental threats associated with seawater desalination. “Impingement occurs when marine organisms are trapped against intake screens by the velocity and force of water flowing through them.” The inevitable outcome of impinged organisms varies between intake designs as well as marine life species, age, and water conditions. Some resilient species may survive impingement and be returned to sea; however the 24-hour survival rate of less healthy and/or juvenile fish is potentially less than 15%. Entrainment happens when smaller organisms pass through an intake screen to the processing equipment. Organisms entrained into processing equipment are projected to have a mortality rate of 100%. The number of affected organisms will, of course, vary with the volume and velocity of feed-water as well as the mitigation measures developed to minimize impact. Lastly, the use of desalination is a concern because with its implementation and commercialization, the general public could potentially begin a more relaxed view of water use than they already do. Meaning, if people think that we have manufactured a solution to the need for conservation there will not be a need to be water use conscious e.g. the more we have the more we spend. This can lead to higher costs to the environment, more unnecessary development and less environmental consciousness.

While desalination is what some have considered the “holy grail” of water scarcity issues, the reality seems quite the contrary. One of the most difficult factors being faced in light of desalination seems to be the idea that desalination has not been in use long enough to perpetuate actual evidence of overall environmental impacts. With that in mind, an environmental analysis conducted under CEQA (California Environmental Quality Act) and NEPA (National Environmental Policy Act) should consider the assessment of cumulative impacts not only of the proposed project but future projects (and existing facilities) in the area. These impacts would include the cumulative entrainment/impingement impacts, cumulative energy consumption, cumulative growth-related impacts, and cumulative wastewater & urban runoff impacts. These factors are especially important in areas where pre-existing air quality, water quality and ecosystem health are already compromised. More specifically, developed areas where water use is higher and environmental impacts are considered / monitored, have the potential of being the proverbial guinea pig when it comes to testing the idea at max capacity. This information should also be part of heavy public education to ensure a full public understanding of its costs and benefits as part of most growing problems in the world come with the lack of education and understanding. Furthermore, there is little evidence that desal plants are any more or any less of an impact than other alternatives, not because they are incapable of causing issues but more because the potential issues have not been fully investigated. Primarily the concern is that the pressing issue and urgency may prematurely cause major environmental impacts (especially long term) to be overlooked or dismissed as something we can conquer at the time it becomes an issue. This vary idea is precisely the reason why most, if not all, environmental catastrophes currently exist. Question is, when is the “woops” factor going to cause all parties involved to finally get a clue?

In closing, the benefits and consequences of desalination are vast and seem to be vaguely understood. While on some levels desalination should be considered as a supplemental potable water source, many other alternatives which are far less costly economically and environmentally do exist. These alternatives include treating low-quality local water sources, encouraging regional water transfers, improving conservation and efficiency, accelerating wastewater recycling and reuse, implementing smart land-use planning and fixing leaks in already existing distribution pipes and plants. Furthermore a tax deductible option to home owners encouraging water wise appliances and repair allowances should be considered as an encouragement to fix what we already have. For example it is estimated that US Homes Leak 1 Trillion Gallons of Water Annually, which is said to be enough water to supply the entire state of Colorado for three years! Is desalination the answer? To me, it seems a desperate attempt to “band-aid” a far larger and blaringly obvious issue. If we continue to use and waste, as a human species, regardless of the “solutions” we find, our existence will inevitably be self limiting.


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