The Advantages and Disadvantages to Desalination

Desalination

Pros and Cons of Desalination

By Jeffrey Haynes Biology 338

Desalination California has experienced seven major droughts in the past century, while we are currently in the midst of our 8th with little relief in sight (CDWR, 2015). As California’s population increases, so does the demand for clean potable water for use in residential, commercial, and increasingly in agricultural. The large demand is currently being met by a majority of imported water, especially in the central and

southern California region, from sources such as the Hetch Hetchy reservoir in Yosemite National Forest, and the Colorado River. The thirst in California is growing, new methods are being tested and developed to meet the needs of the millions demanding clean water each day. We look to the Pacific Ocean, and its seemingly endless expanse of water, and until recently, we were unable to drink any of it. Desalination looks to be a small part of a sustainable water source, as it remains drought proof, and has proven to be effective in northern San Diego by providing nearly 400,000 residents with their daily water needs. The benefits seem to be completely harmless, at least that’s how it seems on the surface.

The process of converting ocean water into potable water has many great benefits for a growing demand of clean water in an arid region, such as Southern California. The potential for supplying

millions of residents with the limitless amounts of water from the ocean is highly appealing to a state that is importing a majority of its water. The Bay Area imports water from the Hetch Hetchy Dam 167 miles away (BAWSCA. 2018), while the Los Angeles County receives water from the Owens Valley nearly 233 miles away (Water Education Foundation,

2016). The benefits are reduced need on imported water, uses reliable technology, replenishes local fresh water supplies, lessens burden of local rivers and streams, and is gaining popularity among residents and

government agencies. The potential impact from these processes come in the form of environmental damage, high energy costs, expensive infrastructure, complex equipment configuration, membrane

filtration fouling, and continuous water quality monitoring. To better understand the potential benefits and harms of the process, we look at evidence of existing desalination plants around the world.

Advantages The process of desalination takes ocean water from an intake that is located several hundred yards out to

sea, in the cases of some plants, they can be located several miles offshore. The intake is designed to allow water to freely enter without suction, however there is a mild current as the water around the intake is being drawn inward, it only allows small debris to enter over a specially designed cage, as not to allow marine life such as fish and crustaceans to enter,

with minimal impact on local habitats (Gille, 2003). Once the water has entered the pipes, it is moved into holding tanks via gravity, as the tanks are located underneath sea level to allow for minimal pumping costs. Once the water has entered the facility, it is run through a preliminary

separator, separating algae, debris, twigs, and any other significant particulate that is larger than a pinhead. After this process, water is forcibly pressurized up to 1,000 PSI, and ran through a series of membranes in a process known as Reverse Osmosis.

Osmosis is the process of a solute trying to balance out a solution through a semipermeable membrane, like water moving from one concentration to balance out a high concentration of solution such as salt water, this is the rudimentary definition for this process (Kirshner, 2008). The process of reverse osmosis is exactly that, the reverse, using the process of highly pressurized water to separate minerals through a membrane into a low-pressure system, which in this case, is pure potable water (Wang, 2018). This process

is done on the scale of millions of gallons per day, which provides water to the surrounding residents, businesses, and agriculture. In 2015, the International Desalination Association

(IDA) derived

that more than 300 million people depend on water from 18,426 desalination plants in 150 countries, accounting for more than 86.8 million cubic meters daily (Ahmed Alkaisi et al., 2017).

These types of plants relieve areas like the arid region of Southern California, through a resource as vast as the Pacific Ocean. The Bud Lewis Carlsbad Desalination Plant produces nearly 50 million gallons daily through the process of reverse osmosis (Wisckol, 2018), with outstanding water quality records that support an overall low risk to residential consumers. This amount makes up roughly 10% of the water need in its service areas on a daily basis.

As the largest of its kind in the western hemisphere, The Poseidon plant in Carlsbad, has led to the momentum of other municipalities in the state of California to move forward with their proposals.

The cities looked at the benefit of how tax payers and governments were not fiscally responsible for the construction and operation of the North County plant. The funds were raised through investment and private markets (Williams, 2017).

The Orange County Water District has taken steps for the future, using a system of aquifer replenishment through recycling of wastewater. In 2008, the OCWD implemented a purified wastewater program that pumps water underground into aquifers, replenishing the groundwater and becoming re-purified by the earth’s natural processes. This accounts for 103,000-acre feet of

potable water annually, expected to expand to 134,000 acre feet by 2023 (Wisckol, 2018). Steps

Disadvantages The need for renewable clean water sources heightens, there are some clear opponents to thebuilding and implementation of desalination plants along California’s coasts. The greatest concern to the environment comes at the expense of the marine life closest to the intake screens located at the bottom of the ocean.

The intakes are located anywhere from 1 meter to 6 meters in smaller sized facilities, inducting surface water increases the chances for more debris and marine life such as; sand, fish, algae, jellyfish, seaweed and micro-organisms (Gille, 2003). Intakes such as these can be found in Mediterranean regions or smaller islands. In the case of larger plants that induct a high volume of water, much better seawater quality is extracted from depths below 35 meters because the debris load is up to 20 times less and is therefore relatively clean (Gille, 2003). In these cases, the intake is a large cylindrical mesh grate, only 11mm by 20mm on the more commonly used. This is designed to keep creatures larger than goldfish from entering

the intake tubes, however, this leaves a serious concern for microscopic life such as tiny fish eggs, larvae and microscopic organisms that would be inducted and die as a result (Wisckol, 2018). The large volume of water is certainly causing a drift of local currents towards the protection screens, and Wisckol makes a valid argument for the need to protect environments near the intakes, that will see a decline in successful reproduction numbers. In addition to microscopic debris, the concern for larger marine life is that they would be held against the induction screens due to the suction against the screens, leading to their deaths (Wisckol, 2018).

As marine life is the largest impacted in the process of desalination, it does not only occur during the collection of sea water. Secondly, a major concern is the high salinity brine, which is a higher concentration of the excessive salt removed during the process. This is called brine, and it can create dead zones around the area of release due to significantly higher salt levels, potentially shocking marine organisms. A lawsuit filed against the proposed

Orange County location, accused the company of pumping high concentration of brine, leaving dead zones from oversaturation at the point of returning seawater after processing (Wisckol, 2018). By forcibly pressurizing the water out into the ocean, the hope is within only meters of the outlet that the water will reach equilibrium and do minimal damage outside of a few meters. The environmental damage caused from water induction and dispersal is said to be at a minimum, and various studies have proven that effects are localized to only meters of these zones.

The process of reverse osmosis is most common on high volume desalination facilities, making for large amounts of energy consumption. Traditionally facilities consume fossil fuels, during the times of the late 80’s, 90’s, and 2000’s. Producing 1,000 cubic meters of potable water from desalination would consume 5 tins of crude oil,

producing roughly 10 tons of CO2 emissions (Alkaisi, 2016). The costs of fuel are high, but the cost of greenhouse gas emissions on the environment were substantially higher. Many newer renewable energy resources are being used and incorporated, like solar, wind, geothermal, and underwater current turbines. However, in California, space is limited for

many of these proposed locations along the coast. Nuclear power is ideal; however, the Edison San Onofre power plant went offline in 201, with no hope for re-opening. San Diego

currently receives half of its energy from natural gas (KPBS, 2015). The Carlsbad Poseidon plant runs at a cost per foot acre at $2,000, which is roughly double the amount from the

water provided by local California water districts (Fikes, 2015). Solar panels are to be installed on the rooftop of the plant to lessen the need for imported power, while the carbon

emissions currently emitted will be paid off at a premium.

In summary, the use of desalination in California and around the world is ideal for a growing

global population and sustainable water resources in an increasingly desertification of regions around the globe. The technology is efficient and reliable, with low risk to health for

humans and lessening the need for imported water from counties away. The benefits are met with opposition in the form of environmental concerns. The potential to destroy localized

habitats as proven to be true in underwater inflow, and outflow pipes. However, damage has proven to be minimal and localized versus the benefits seen from

desalinating water. The cost has been decreasing annually as more renewable energy sources are becoming available to offset the energy consumption. I believe the desalination is validated in its effective supply and treatment with minimal damage from brine and emissions. The future of California is set to build 15 more within the next 15 years, and the potential for lessening the demand from water at the sources of the Colorado River, Owens Valley, and Hetch Hetchy reservoir are crucial (Pacific Institute, 2016).

Works Cited Page

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Alkaisi, Mossad, & Sharifian-Barforoush. (2017). A Review of the Water Desalination Systems Integrated with Renewable Energy. Energy Procedia, 110(C), 268-274. https://doi.org/10.1016/j.egypro.2017.03.138

Williams, Lauren. (2017, October 19). Poseidon desalination plant clears hurdle, sparks outcry. Orange County Register (Santa Ana, CA), p. Orange County Register (Santa Ana, CA), Oct 19, 2017. https://www.ocregister.com/2017/10/19/fight-overposeidon-desalination-plant-could-get-personal-today/ Vega, P. (2018, July 12). Environmentalists plan to protest proposed Poseidon desalination plant. TCA Regional News, p. TCA Regional News, Jul 12, 2018.

Wang, Yi-Ning, Goh, Kunli, Li, Xuesong, Setiawan, Laurentia, & Wang, Rong. (2018).

Membranes and processes for forward osmosis-based desalination: Recent advances and future prospects. Desalination, 434, 81-99. https://doi.org/10.1016/j.desal.2017.10.028 Wisckol, M. (2018, May 01). Poseidon desalination plant: What to know about its pros and cons for southern california water. TCA Regional News Gille, D. (2003). Seawater intakes for desalination plants. Desalination, 156(1), 249-256. https://doi.org/10.1016/S0011-9164(03)00347-3.

Kate Kershner. (2008) "How Reverse Osmosis Works" 8 May 2008.

HowStuffWorks.com. https://science.howstuffworks.com/reverse-osmosis.htm. 31 July 2018.

Fikes, B. J. (2015, December 13). State's biggest desal plant to open: What it means. The San Diego Union Tribune. Retrieved August 1, 2018, from http://www.sandiegouniontribune.com/news/environment/sdut-poseidon-waterdesalination-carlsbad-opening-2015dec13-htmlstory.html