In the News
Heather Cooley on reasons for and against desalination
Water expert Heather Cooley spoke with EarthSky about
promises and problems of desalination in California.
by Beth Lebwohl
EarthSky.org, 8/4/11
Desalination is the process of taking the salt out of ocean water to
convert it into drinking water. An EarthSky listener asked why
desalination isn’t in greater use in U.S. coastal regions – like
California – where water scarcity is an issue. As yet, no full-scale
desalination plant – that is, a plant that produces millions of
gallons of freshwater per day – has been built there.
EarthSky spoke to Heather Cooley, co-director of the water program
at the Pacific Institute. She told us the answer is complicated.
Desalination has one huge plus, she said – it relies on plentiful
seawater. She said:
It’s not dependent on local climate conditions. In addition, water
produced from seawater desalination is very high quality.
But, she added, desalination can have drawbacks. For instance, she
said, desalination plants can cost millions to billions of dollars
to build.
A lot of the cost is also in operating the facility. It’s also very
energy intensive, which raises questions about the cost, but also
about greenhouse gases.
Cooley explained that it takes a lot of power to run a desalination
plant because seawater, in order to be purified, is typically pushed
through filters, or “membranes,” at very high pressure. She said:
It’s very expensive, considerably more expensive than other water
supply options, or conservation measures.
But, she said, the advantages and drawbacks of desalination will
likely shift as water scarcity on Earth increases in the 21st
century, and desalination technology improves.
Cooley added that desalination also has environmental impacts which
aren’t particularly well understood – for example, impacts on ocean
life near water intake vents.
I think a lot is not known, especially on the environmental impacts
globally.
To learn more, Cooley is launching an in-depth study on desalination
around the world, which the Pacific Institute plans to publish in
the summer of 2012. Cooley said that she did a previous study in
2006, when plans to build about 20 desalination plants were on the
table in water-scarce California. As of 2011, only one plant had
opened (in Sand City, California). She said:
It’s small. Some of the ones they’re considering in Southern
California are on the order of 50 million gallons per day. In some
cases they’re considering some that are 75-100 million gallons per
day. The one in Sand City was considerably less than a million
gallons per day, considerably less. Some of the issues in terms of
the bigger plants – there are a lot of groups opposing them – some
of the issues are related to open-ocean intakes in particular. That
particular facility in Sand City is using sub-surface intakes, which
have fewer environmental impacts.
That is, the Sand City plant is drawing its water from pipes
underground, and using sand as an initial-stage filter. Most of the
time, desalination plants, especially bigger ones, don’t have that
luxury. They have to draw their water from the open ocean, which can
pull in plants and animals, and are thought to possibly disrupt the
coastal ecosystem.
That’s one of the things we’re trying to tease out in our [new]
analysis – why did that plant in Sand City get built, what are the
concerns with the larger facilities that are being proposed.
Ground was broken for another desalination project in California,
the Carlsbad Desalination project, in 2009. The plant was conceived
as a facility to desalinate upwards of 50 million gallons of
seawater a day, and serve residents of Carlsbad, California within
the next few years. The project took ten years of planning, and five
years in the state’s permitting process. There has been legal
wrangling, and permits are currently poised to lapse, according to
Heather Cooley. In contrast, an even larger project in Israel had a
significantly quicker turnaround for approval: about a year. Water
demand in the Middle East is possibly more intense than it is in the
United States. As Heather Cooley pointed out:
Seawater desalination is in use around the world. It’s been most
successful in areas that have very little water, like the Middle
East, and very low cost of energy, again, the Middle East would be
an example of that.
The majority of the world’s 13,000 or so desalination plants are
located in the Middle East. Cooley added that, looking beyond money
and energy, desalination’s environmental impacts offer another
obstacle to their construction in the United States. She said these
impacts haven’t been very well studied – impacts on marine life near
ocean water intake vents, for example. Cooley said:
There are plants that have been operating for a very long time, but
it’s generally in areas where environmental concerns were very low,
and so there hasn’t been a lot of long-term monitoring in those
particular facilities. So with some of the new plants, they are
being built in areas where environmental concerns are much higher.
EarthSky also spoke with Yoram Cohen, a global desalination expert
at UCLA who has worked with desalination experts in both Australia
and Israel. He said the expense and slow progress of developing
desalination plants in California is in part due to political,
policy and other obstacles. That said, both water experts agree that
desalination needs to be studied further.
Both Cooley and Cohen say desalination is not the magic bullet
answer to all our water troubles. Cohen said we need to focus on
what he called an “integrated approach” to developing water
solutions around the globe. In other words, in some places, using
more recycled water than desalinated water might work. In other
cases, the balance might have to be reversed. Cooley echoed the
sentiment:
It’s true in the United States, it’s true in California, it’s true
globally. We have enormous water supply problems, and as population
grows, as economies grow, are potentially going to become more
severe. Climate change is a very big issue, and that will impact the
supply and demand for water.
It’s very important that we look at all the options – I know that
some people like to focus just on the technology. But we need to
look at all the water supply and conservation options available and
try to find solutions that are the most cost effective, have the
least environmental impact, and are sustainable.