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Abstract
In this report I will discuss the advantages of underwater desalination over conventional
desalination as well as the potential applications of these advantages. Desalination, the process
of removing salt and other contaminants from seawater, has been seriously considered in
California due to prolonged drought. For first world countries like Israel and Australia the
reverse osmosis process has been successful due to the large quantities of water that can be
desalinated, using high pressure to push seawater through a salt removing membrane. However,
cost and environmental issues have held back this type of desalination and will continue to do so.
Under water desalination, on the other hand, uses natural ocean pressure to filter seawater at a
reduced energy cost and has the potential to be used for much more than fresh water production.
I propose that California expands many of its resources to an underwater environment. From
scientific experimentation to a complete freshwater ecosystem, clean water at no recurring
energy costs could allow for many freshwater functions to occur deep under the ocean.
The Potential Within Our Oceans
As fish supplies are being depleted and underwater ecosystems are dying out, the ocean is
beginning to become more of an international responsibility than a resource. As stated in “The
Struggle to Govern the Commons” it is quite possible that “the ‘tragedy of the commons’ [is]
inevitable anywhere not owned privately” due to the tight restrictions on still decreasing
resources that are required for effective governance (Dietz, 2003). In order to stop the
impending destruction of the commons we must begin generating a new resource from our
oceans that will make commons preservation worthwhile. Using underwater desalination to

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expand food and water sources, we can restore the ocean to its former grandiose as well as
benefit California economically.
Faults in Conventional Desalination
Many drought ridden countries have implemented desalination to fill their water needs,
but for California, which has the simple options of reducing usage and importing water from
nearby more humid climates, desalination remains too expensive. According to the San Diego
County Water Authority, controlling the distribution of water within its boundaries, desalinated
water from the recently built Carlsbad desalination plant costs from ​$2,131 to $2,367 per
acre­foot, over twice as much as imported water (​Seawater desalination, ​2016). Even the newest
and most advanced methods for desalination remain much more expensive than importing water.
A major reason for this high cost is the energy required to for the reverse osmosis process.
Pressurizing water to extreme levels, the cost of energy accounts for forty­one percent of a
typical desalination plant’s expenses says Lenntech, a water treatment company with experience
in desalination (Desalination cost analysis, 2016). With high recurring costs desalination can
remain impractical even once initial costs have been covered, a main reason that the 1992 Santa
Barbara plant shut down after less than a year of water production, according to the City of Santa
Barbara (Desalination, 2016). The conventional reverse osmosis method requires too much
energy to ever become an economically sound alternative to imported water. Head of UCLA
Water Technology Research Center Yoram Cohen explains that while small improvements will
be made to the reverse osmosis process the idea that there will be “a magic membrane that will
reduce the cost of desalination to next to none is misleading” (Talbot 2016). The cost of
conventional desalination will continue to be much higher than other methods of acquiring water

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and unless neighbouring states also reach California’s drought condition importation of water
will remain the cheaper alternative.
On top of the economic reasons that rebut the argument for conventional desalination the
reverse osmosis process results in various environmental deficits. In a 2013 report on the
environmental disadvantages of desalination the Pacific Institute, a nonprofit intended to
preserve natural waters through independent research, explains that reverse osmosis desalination,
usually designed to produce about half as much fresh water as seawater pumped, is left with
large amounts of byproduct (Cooley et. al., 2013). This byproduct, called brine, can be up to
twice the salinity of seawater and contains low levels of corroded metals and chemical additives
used for membrane cleaning (Cooley et. al., 2013). Distinctly different than seawater, brine is
not suited for sea life until sufficiently dispersed. Consequent of increased salinity and therefore
a higher density brine does not disperse easily, creating plumage that “sea grasses [and other
plant communities] are the most sensitive” to, says a California proposal for the management of
brine discharges (Jenkins et. al., 2012). Increased salinity and toxicity in brine is not diluted
until doing notable damage to nearby plant communities. Another environmental deficit of
reverse osmosis desalination is the direct entrainment and impingement of marine organisms.
Information gathered by the California Water Boards concludes that all microorganisms within
seawater sent through the desalination process are killed and suction from seawater intakes can
kill or injure organisms as large as sea turtles that are trapped against intake screens (Marcus et.
al., 2015). Conventional desalination damages marine life on both ends and is more costly than
importation of water, showing that the process of conventional reverse osmosis is not effective.
In order to apply desalination to California’s drought and use the ocean to its maximum potential

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a different process with reduced recurring energy costs and less environmental deficits must be
used.
Underwater Desalination
Moving the reverse osmosis process deep into the ocean, proposed underwater
desalination meets the criteria, having significantly reduced recurring costs when compared to
conventional desalination, as well as all but eliminating impingement, entrainment, and brine
production. In a 2010 Econopure white paper, written by vice president of engineering Kurt
Roth, the company, which focuses on finding energy efficient new methods for water filtration,
introduces three key concepts that work in unison in order to reach these goals from natural
functions within the ocean. Proposing that “lower energy consumption is possible by using the
natural hydrostatic pressure in the sea,” underwater desalination uses the ocean to its advantage
(Roth, 2010). Although fresh water must still be pumped to the surface, the primary concept
behind underwater desalination cuts energy costs in half, conventional desalination requiring the
pressurization of all feedwater, fifty percent of which will become brine.
Using the unending water source supplied by natural water movement, underwater
desalination is able to significantly reduce pressure requirements. While conventional reverse
osmosis attempts to produce as much water as possible from limited amounts of feedwater,
underwater desalination can ignore higher pressure requirements and shorter membrane life
required for higher yield percentages. As gravity and ocean currents disperse brine before
salinity is increased by more than a few percent, new water is brought in and the process can
occur near the 22.4 atmosphere pressure requirement rather than the over double pressures used
in conventional desalination (Roth, 2010). Placing the underwater desalination system far

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shallower and with less pressure, pumping up fresh water produced can cost approximately one
half as much as pressurizing the same amount of feedwater for desalination. By using the ocean
as a direct salt water source underwater desalination can cut recurring energy costs and eliminate
brine as a byproduct of desalination.
The third principle of underwater desalination, low fresh water production rate,
coincides with the reduced pressure requirements previously stated. Although reverse osmosis
of salt water can occur a decreased pressures, the rate at which it does so decreases alongside it.
Reduced flow rates and therefore reduced pressures, result in less fresh water produced, a
seemingly even trade. When reduced environmental impacts are considered reduced pressure
requirements are the obvious choice over faster production. Only removing product from the
waterstream, and at a reduced rate, suction drawing in water and potential organisms is
significantly reduced. Larger organisms being capable of escaping the draw of underwater
desalination and only microorganisms within product water being killed, all practically
removable environmental deficits has been eliminated. With recurring energy costs reduced by
up to seventy five percent and environmental impacts all but erased, underwater desalination
seems to be the perfect option for a long­term desalination investment.
Limiting Factors
Recognizing that all stated principles of underwater desalination came from the same,
potentially biased source the facts presented in the Econopure report cannot be considered
credible. The reasoning behind underwater desalination, however, is unrelated to the credibility
of the facts, and in the untested and new technology the three key principles, backed by well
known facts, are as good as anything.

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Installation costs are a major concern for underwater desalination. With no predicted
costs we can only assume that production and installation of an underwater desalination system
would be extremely expensive. Extended membrane lives, reduced energy costs for seawater,
and potential environmental grants could hope to pay off initial investment, however, without
any numbers, there is no way to be sure.
Underwater maintenance, at an extreme depth could be just as costly as installation.
Although theoretically ocean currents could clean out membranes with no maintenance costs,
having no need for a self maintaining system for conventional desalination no studies have been
conducted to determine whether such a feat is possible. There are clearly many uncertainties
within underwater desalination, but if applied correctly there are infinite possibilities brought
about by natural occurrences within the ocean.
More Than Just Water
As the only recurring cost of underwater desalination is from pumping water to the
surface, a system using desalinated water at the source could reduce the cost of underwater
desalination to practically nothing. While most light does not penetrate to the required depth for
reverse osmosis to occur, there are a variety of ways that this technology could be used in this
manner. From an energy efficient way to provide fresh water for submarines, to a gateway
towards theoretical underwater civilizations, I believe that the commons hold infinite
possibilities in our visible future. (1630).

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References
Cooley, H., Ajami, N., & Heberger, M. (2013, December). Key issues in seawater desalination in
California: Marine impacts. Retrieved April 17, 2016.
Desalination. (n.d.). Retrieved April 18, 2016, from http://www.santabarbaraca.gov.
Dietz, T., Ostrom, E., & Stern, P. C. (2003, December 12). The struggle to govern the commons.
Science​, ​Vol. 302​(No 5652), 1907­1912.
Jenkins, S., Paduan, J., Roberts, P., Schlenk, D., & Weis, J. (2012, March). Management of brine
discharges to coastal waters recommendations of a science advisory panel. Retrieved
April 17, 2016.
Marcus, F., Spivy­Weber, F., Doduc, T. M., Moore, S., & D'Adamo, D. (2015, May 6).
Amendment to the water quality control plan for ocean waters of California. Retrieved
April 17, 2016.
Reverse osmosis desalination costs analysis. (n.d.). Retrieved April 17, 2016, from
http://www.lenntech.com.
Roth, K. (2010, May 14). Depth exposed membrane for water extraction for seawater
desalination. Retrieved April 18, 2016.
Seawater desalination. (n.d.). Retrieved April 17, 2016, from www.sdcwa.com.
Talbot, D. (2014, December 16). Desalination out of desperation. Retrieved April 17, 2016.