Ocean-Water Desalination:
A Solution or a Problem?
What is desalination?
Desalination is the process of removing salts and other minerals from otherwise
undrinkable water to produce freshwater for human consumption and other uses.
To produce this fresh water, desalination facilities withdraw enormous amounts ofbrackish or seawater through large pipes along (“surface”) or beneath the seafloor(“subsurface”).
What happens to the remaining water and salt that is removed?
Extracted salts, minerals, and a percentage
of source water mix to form a hyper saline
slurry commonly referred to as brine. Brine
has a much higher salt concentrationcompared to salt water, which creates
disposal challenges.
Brine waste is commonly disposed of in theocean. To reduce environmental impacts
during disposal, brine can be mixed with
Desalination plant in Lanzarote, Canary Islands.
other water sources to reduce salinity and/ordischarged through diffusers. Diffusers
stimulate brine mixing with ocean water and are used to disperse brine at several
different discharge points from desalination facilities.
What are the environmental impacts of desalination?
Most forms of desalination are energy-intensive. Desalination has the potential toincrease fossil fuel dependence, increase greenhouse gas emissions, and exacerbate
climate change if renewable energy sources are not used for freshwater production.
Desalination surface water intakes are a huge threat to marine life. Mature fish, larvae,
and other marine life can be significantly injured or killed when they become trapped orsucked into open water surface intake pipes.
The State Water Resources Control Board estimates that open ocean intakes used bycoastal power plants in California kill 70 billion fish larvae and other marine life on anannual basis. These same open ocean intakes are being proposed for use atdesalination plants throughout California.
Brine waste also poses a potential threat to marine life and water quality, as it contains
dangerously high concentration of salts and other minerals. Because of its high density
and salinity, brine waste can accumulate in and around disposal areas smotheringbottom dwelling species and significantly altering coastal ecosystems.
Why isn’t desalination the solution to our water problems?
Desalination’s energy-intensive process is expensive and environmentally harmful,
making it a costly strategy to bolster regional water supplies. The average price peracre foot of desalinated water is often 2-4 times more expensive than other water
sources.
Ocean desalination is not efficient. It requires roughly two gallons of ocean water for
every one gallon of freshwater produced. This means one large desalination facility is
not going to solve regional water supply problems.
Are there alternatives to desalination?
Water conservation, water use efficiency, storm water capture and reuse, and recycledwater expansion are proven effective strategies to increase regional water supplies
and often cost less than desalination. In addition, these alternatives provide pollution
abatement, habitat restoration, and flood control benefits, which are commonly
overlooked during cost/benefit assessments.
What is Heal the Bay’s stance on desalination?
Before desalination is even explored, it is important that water conservation, water use
efficiency, storm water capture andreuse, and recycled water
expansion are maximized.
Each day roughly 10 million
gallons of urban runoff flows
through Los Angeles County
stormdrains, picking up pollutantsand eventually reaching the ocean
without the benefit of anytreatment. That volume raises to10 billion gallons during a rain.
Capturing, treating, and reusing
this water could be a significant
Why dump highly treated wastewater from Hyperion into the sea insteadof using it to recharge local aquifers?
local water source.
Hyperion Wastewater Treatment
Facility releases more than 250 million gallons of treated water into Santa Monica Bay
every day. If all of Hyperion’s water was treated to a higher standard and reused, it
could substantially reduce the region’s reliance on imported sources while
simultaneously creating a new source of local water in the region.
If desalination is pursued as a freshwater source, it must use the best available
technology to minimize marine life impacts. The State Water Resources Control Board
recently adopted a desalination policy requiring desalination plants in California to use
subsurface intakes, or minimize their marine life impacts via surface intakes to a levelconsistent with subsurface intakes.
The marine impacts from ocean desalination facilities can be significant; we want toensure that these impacts are avoided at all costs.