Thank you to Mo Wise for contributing to this article.
Water in the West is a complicated and constantly changing. With the Pacific to the west and arid country to the east, California’s water needs are massive. Don’t let the lush golf courses, dense lines of palm trees, and balmy weather fool you, most of coastal SoCal is desert. California receives the majority of its drinking water from the Sierra Nevada snowpack and Colorado River. Many local districts also utilize groundwater wells and recycle water for irrigation. As the climate shifts to include more unseasonably warm months, water sources are changing, with some sources running dry, prompting a need to become more creative in sourcing our water. Water scarcity is now recognized as a global challenge in all areas, as we continue to deplete our resources, highlighting the urgent need for a more sustainable water management source. Desalination offers several advantages; however, there are adverse environmental impacts that could eventually affect the coastline and its surrounding areas. One possible solution is desalination. It’s a very debated topic, so why don’t we dive into the discussion?
What is Desalination?
Desalination is the process of removing salts from saltwater/brackish water and creating fresh water that can be used for drinking, irrigation, or industry. There are multiple ways to desalinate water, mostly through thermal desalination or membrane separation. Both take quite a bit of energy but create clean, potable water. Let’s take a closer look at each broad category.
Thermal Distillation, is the process of separating freshwater from saltwater.
It includes two major methods used globally, Multi-Stage Flash (MSF) and Multi-Effect Distillation (MED). In the process of MSF, seawater is heated to the point where it turns into steam at progressively lower pressure levels, and by the end, the steam is condensed into pure water. MED uses the same process, but is more efficient as it uses the heat from previous stages in the cycle to power the next, till the seawater turns to steam and is condensed into pure water. Think of Thermal Distillation as using the processes of evaporation and condensation to get pure water.
Membrane separation uses pressure and filters. We see Reverse Osmosis (RO) being used as one of the most widely used membrane separation techniques. This technology pushes seawater through a semipermeable membrane, filtering out salts and impurities while allowing pure water to pass.
Why are we considering desalination?
As population, agriculture and industry increases there is also an increase in water usage. Many coastal water agencies rely on up to 100% imported water to fulfill their community’s water needs. Desalination plants offer a local source of water, which increases water reliability. The bottom line is we need water and with an increasing population and decreasing freshwater resources, desalination is a strong option for coastal communities, but the process does have unfavorable trade-offs. Environmental Impact Assessments (EIAs) are vital as countries continue to evaluate desalination facilities as reliable source for freshwater. Other options, such as direct reuse (from wastewater) and stormwater capture, are also topics of discussion as sustainable alternatives to desalination.
PROS & CONS of Desalination:
PROS:
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Longterm Reliable Water Supply
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Helps to Drought Proof Cities
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Supports growing populations
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Water security
CONS:
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Energy-intensive (Thermal is an expensive process)
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Harms marine ecosystems
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Harms the coastal water quality
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High production cost
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Large carbon footprint
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Limited Accessibility
ACTION: How to incorporate desalination mindfully
Desalination offers a promising solution to global water scarcity; however, it presents significant environmental challenges.The most pressing concern is energy consumption. Traditional desalination technologies often rely on natural gas–fired power plants to generate the electricity. This dependence on fossil fuels undermines long-term sustainability practices by increasing greenhouse gas emissions. The process of reverse osmosis and thermal desalination plants uses natural gas-fired power plants to generate electricity. The tradeoffs: Increases local emissions and creates highly concentrated saltwater that affects marine life. New projects are experimenting with solar-powered reverse osmosis, wind-assisted, and hybrid systems, intended to remedy water scarcity without the tradeoff of increasing climate change. If people can find more sustainable desalination plant options (running on sustainable energy and creating less highly concentrated saltwater), there could be a net benefit.
The other main challenge with desalination is the large amount of leftover brine it produces. To help protect marine life, many facilities mitigate this by blending brine with treated wastewater before releasing it, resulting in minimal effects on the marine environment. It’s also important that seawater intake systems are designed with ecological sensitivity in mind. Open-surface intake pipes should be avoided whenever possible to minimize the disruption of the marine environment. Avoiding surface intake systems is a critical part of sustainable practice.
Luckily, innovation is beginning to shift this trajectory. New projects are experimenting with renewable-powered desalination systems, including solar-powered reverse osmosis, wind-assisted, and hybrid models. The goal is to produce clean, safe drinking water without worsening climate change—a balance that is both urgent and achievable. While desalination can be part of the solution, it should not be the only approach. Water conservation, wastewater recycling, and stormwater capture are equally important strategies that reduce pressure on both the environment and the need for energy-intensive desalination plants. They are less expensive, have significantly better environmental benefits, and reduce environmental pollution that desalination cannot offer. As communities continue to experiment and test new ways for long-term sustainable water management practices, desalination may help bridge the gap between the growing water needs. Using both innovation and conservation together in tandem will move areas toward more sustainable developments and solutions. At the end of the day, the goal is not just to provide more water, but we need to look to building systems that mindfully collect our most valuable resource.
