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Coastal A-Z
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Seawater Desalination
Issue Summary
FORWARD
 There are numerous
proposals to build desalination facilities on California's coast and
estuaries. Desalination facilities have also been proposed in several other
states including Texas and Hawaii and a facility
was recently built in Tampa, Florida. This discussion
and issue summary is for Surfrider Foundation
activists who wish to become informed regarding desalination and participate
in review of a planned desalination plant. We hope this background paper
highlights some of the issues of concern when evaluating the prudence of
building a desalination facility in your area. Also, we hope this provides a
little "food for thought" when considering alternatives to
desalination, or alternative technology and practices for implementing
desalination.
OVERVIEW
Producing drinking water from seawater has been technologically achievable
for several decades. Until recently, however, application of seawater
desalination ("desal") on a large scale has been primarily limited
to arid regions of the world that have a cheap supply of energy, such as in
the Middle East. Saudi Arabia produces 30% of
the world's output of desalinated seawater. The cost of energy is important
due to the fact that the two primary technologies used for desalination,
distillation and reverse osmosis, require a lot of energy, either to boil and
then re-condense water (distillation) or to force water molecules through
semi-permeable membranes at high pressure (reverse osmosis).
Advances in reverse osmosis membrane technology have recently reduced the
cost of producing water from approximately $2,000 per acre-foot in 1990 (1
acre-foot equals approximately 326,000 gallons, or the average use a
household in a year) to about $800 per acre-foot.1 In southern California, the Metropolitan
Water District is offering local water agencies subsidies of up to $250 per
acre-foot to implement desalination projects. This subsidy reduces the cost
of producing desalinated drinking water and makes desalination facilities
more economically viable for local water agencies. However, the subsidies
only defray costs and do not reduce the cumulative costs in the region.
Furthermore, many of these subsidies are not intended for research and
development, and consequently will not directly lower the overall cost of
producing freshwater through desalination over time.
A desal facility using reverse osmosis technology forces seawater through
membranes with tiny pores large enough to pass water molecules but too small
for salt molecules. For every 2 gallons of seawater introduced, about 1
gallon of drinking water is produced and 1 gallon of concentrated brine
(about twice the normal salt concentration of seawater) is returned to the
ocean.
Several seawater desal facilities have recently been proposed in California,
Hawaii and Texas and a large facility has been constructed to produce 25
million gallons per day (mgd) of drinking water in
Tampa, Florida. The Florida project is
experiencing technical difficulties that are impairing full production and
clouding the economic and environmental post-operation analysis. In California, a State
Desalination Task Force has reviewed desalination and has created draft issue
papers and a final report.
http://www.owue.water.ca.gov/recycle/desal/desal.cfm
The California Coastal Commission has also prepared a report on desalination
and associated California Coastal Act applicability.
http://www.coastal.ca.gov/energy/14a-3-2004-desalination.pdf
Simultaneously, several California state and local
government agencies are currently grappling with the numerous regulatory
issues confronting permit applications for coastal desalination facilities.
Some of these same agencies also have regulatory authority and/or budgetary
discretion over implementing alternative technologies and rules to provide
additional water -- primarily through wastewater reclamation and/or
conservation.
The stated benefit of desal is primarily a reliable flow of freshwater to
supplement other sources that will not supply growing populations.
Desalination may also include the environmental benefit of reducing our
unsustainable reliance and over-drafting of rivers, streams and aquifers,
thereby reducing the adverse environmental impacts on those resources. Also, a constant
flow of freshwater from desalination could avoid the environmental disruption
of building more dams for storage. However, to ensure these potential
environmental benefits come to fruition could require complex legal
mechanisms and each project proposal might involve different complications.
Desal facilities can have several potential negative environmental impacts,
depending upon where they are located, how they are designed and operated,
and the end use of the produced water. In some cases,
there are also concerns about "privatizing" what has
always been a public resource, as well as additional complications if a
private owner is a foreign entity. Listed below are some of the potential
negative impacts of desal projects:
ISSUE SUMMARY
1. Seawater Intake.
There are several alternatives for gathering the "source" water for
desalination: intake pipes in the ocean, beach wells (seawater aquifers) and
intake galleries (collection systems buried beneath nearshore
sediment). Unless the seawater intake is gathered from beach wells or
galleries there is an inevitable destruction of marine life (fish and smaller
marine life like eggs and larvae) as the water is drawn into the desal plant.
"Impingement" is the term for the mortality of larger animals that
are trapped and killed on the intake screens, and "entrainment"
refers to smaller organisms (e.g., larvae and eggs) that slip through the
screens and are killed once they enter either the reverse osmosis membranes
of the desal plant or the cooling condensers of an adjacent electric
generating plant.
One of the reasons that desal plants are often
proposed for co-location with coastal electric generating plants is that they
take advantage of the existing cooling water intake and outfall pipes. Desal
"source" or "feed" water is typically taken off of the
discharge (hot) side of the power plant cooling water system and the
concentrated brine is discharged by mixing it with the remaining cooling
water return to the ocean. In this way, no additional seawater is drawn from
the ocean, and proponents argue that no "additional" marine life
mortality is attributed to the desal process. However, although there is some
debate about the degree to which sea life survives the trip through a power
plant cooling system, any sea life that did survive would then be destroyed
by the filtration and reverse osmosis steps of the desal process.
Furthermore, because of the energy-intensive nature of desalination plants,
co-location of these plants could mean that the generator is in use when it
otherwise wouldn't be. The more the generator runs, the more water it takes
for cooling, the more fish that die. The cumulative energy demands of
desalination facilities will translate into additional electric generator
output to supply the desal facilities.
The US Environmental Protection Agency, under a court order, is currently
reviewing the rules on cooling water intakes for power plants. Cooling water
intakes are regulated under the authority of the Clean Water Act Section 316
(b), and the EPA is reviewing whether
"once-through" cooling meets the "best technology
available" standards mandated by that Act. Generators could be
compelled, at least in many circumstances, to retrofit the plant with cooling
towers that recycle water. These towers cool the water with forced air from
large fans. This technology would either eliminate or dramatically reduce the
marine life mortality and cumulative impacts on marine ecosystems from
once-through cooling.
Furthermore, under the "consistency" authority granted the states through
their participation and compliance with the federal Coastal Zone Management
Act, coastal states may review permits granted by federal agencies. The state
agency in charge of the coastal zone management plan can then deny the
federal permit if it is found to be inconsistent with the state's management
plan. In the present case, this means that the coastal management authority
could either deny the cooling water intake and/or discharge permits for the
co-located generator or desalination facility.
2. Estuaries vs. Ocean Source
Water. There has been a dramatic loss of estuarine habitat in
California especially in
the southern region of the state. Most of our coastal wetlands and estuaries
have been filled and developed or are highly degraded from pollution and
unnatural sediment loading. Consequently, estuarine habitat is a precious
commodity and this creates heightened threats to aquatic and terrestrial life
that depend on estuaries for some stage of their life history (e.g., birds,
fish, invertebrates, etc).
Therefore, desalination facilities that rely on estuarine "source"
water should be viewed with heightened scrutiny. Many of the entrainment and
impingement issues that impact marine life and healthy marine ecosystems are
arguably made worse when they impact estuarine species and the intricate
ecological balance of estuarine ecosystems.
3. Brine Discharge.
Seawater contains about 35,000 parts per million (ppm)
salt. During the reverse osmosis process, water
molecules are forced through membranes while the salt particles are retained
by the membrane and end up in a "reject stream" that is about twice
as salty (70,000 ppm) as seawater. If this were
discharged directly back into the ocean or into a coastal estuary there would
likely be some negative impacts to sea life in that immediate area of the
discharge. If a desal plant is located next to a power plant, they can mix
this brine water with the higher volumes of "hot" cooling water
that are being returned to the ocean. This dilutes the brine and marginally
lowers the discharge temperature so there is arguably less of an impact on
sea life. In the same vein, desalination plants might be co-located with
wastewater treatment facilities, or connected by pipes, so the brine could be
mixed with the freshwater discharge and possibly reach a salt concentration
and temperature closer to ambient ocean conditions.
The impacts on marine life are, for the most part, dislocation of indigenous
populations. For instance, the marine life normally found in the area of the
discharge (the Zone of Initial Dilution or ZID) might be displaced and the
area re-inhabited by organisms more tolerant to dynamic salt concentrations
and temperatures (e.g., estuarine species). Furthermore, the concentration of
dead marine life in the discharge may attract an uncommon congregation of
filter feeders and other scavengers. In short, the natural ecosystem is
disrupted, but this does not necessarily lead to lower biomass in the area.
However, this would be a site-specific determination and would depend on
variables like ocean current, depth, and maybe most importantly, how close
the discharge is to sensitive and essential fish habitat.
4. Building on the Coast.
Although desal plants are not nearly as huge or ugly as power plants, they
are an industrial facility that some people may object to. Being located
along the coast, the structures may impair views, block coastal access,
result in the filling of wetlands, or otherwise negatively impact the
experience of going to the beach.
5. Growth Inducement?
If the water produced from desal is used to reduce our reliance on imported
water and more water then ends up being retained in water source areas to
help sustain the environment there, then desal may produce a net
environmental benefit. If, on the other hand, the water not taken from these
rivers is diverted to other users and the river doesn't benefit, desal may
not result in a net environmental benefit. And if the desal plant fuels new
growth along the coast rather than just replacing imported water, it may
contribute to environmental degradation. This question of whether water is
for "replacement" or "new source" is at the heart of the
question of "growth inducement."
It is also important to note that many of the current proposals are located
in areas with dramatic surface run-off problems and limited sewage treatment
capacity. Adding a "new" source of freshwater to this system will
arguably exacerbate an already difficult problem to as the produced water is
used and becomes wastewater and urban runoff.
These direct and indirect concerns about growth inducement are difficult, if
not impossible, to quantify and analyze without the project proponent
identifying the "end user" of the water supply. It is therefore
important the any Environmental Impact Report (EIR) or other environmental
analysis of the project identify the end user(s). The EIR should also
evaluate project alternatives that may have less environmental impact,
including water conservation and recycling.
6. Cost and Power Use.
Desal is an expensive way to make water and uses a lot of electricity. Water
most be pumped through special membranes at about 900 pounds per square inch
(psi) pressure to remove the salt, then the water
often must often be pumped several miles to a water distribution network.
Depending on the specific project proposed, water costs to consumers may go
up at least 30% and could more than double. The required electrical energy is
often produced by fossil fuel burning power plants that cause air pollution.
7. Dependance
on Power Plants. As mentioned above, there are logical
reasons to locate desal facilities next to power plants. But power plants are
under pressure to eliminate their use of "once through" cooling
water that kills fish. See http://www.epa.gov/waterscience/316b/
for more information on this topic. Power plants may be required by the U.S.
EPA to install a "closed loop" cooling system that reduces the
amount of seawater intake and fish kill by 90% or more. Some may convert to
an air cooling system that uses no water or a recirculating
cooling water system that uses a cooling tower and reduces seawater intake by
90% or more. If these changes take place, it may no longer make sense to locate
the desal plant next to the power plant. In fact, it may no longer make sense
to locate power plants along the coast. Looking at this
another way, if a desal plant is installed at an existing coastal
power plant facility, that may not be a good investment if the power plant
cooling system that is the basis for the desal plant is removed or modified.
From the power company's perspective, if a desal plant is built next to a
power plant, that may represent a disincentive to upgrade the power plant's
cooling system.
8. Alternative Sources of Potable
Water: As with any social choice, the determination to
implement desalination facilities should be compared with other alternatives.
Some of the possible alternatives include improved water conservation and
greater implementation of wastewater reclamation.
Although water agencies are constantly struggling to provide citizens with
affordable and reliable drinking water, it is evident that we still do not
use water very efficiently. This is directly apparent in the amount of urban
runoff that we see every day. There is some concern that desal will reduce
the drive to use existing sources of water efficiently, and consequently
negatively impact programs to advocate for water conservation. The southern California region has
experienced dramatic population growth over the past several years. Yet, the
demand for water has remained relatively constant in large part because of
efforts at water conservation. These current conservation efforts are
arguably only scratching the surface of what could be a much broader effort
in the southern California region, and other
areas of the country may not be employing these strategies at all.
Water reclamation is the practice of treating wastewater to
allow re-use the water. Although there has been considerable
controversy surrounding the use of reclaimed water as a source of drinking
water, there are more and more examples of successful programs that either
use this water for irrigation (offsetting the need to use drinking water for
this purpose), or for injection into groundwater aquifers (reducing the
negative impacts from overdrafting our aquifers
and/or reserving this water for potable uses in the future). Besides
providing a reasonable alternative to desalination, widespread implementation
of reclamation could dramatically reduce the amount of partially treated or
untreated wastewater being discharged into the ocean.
In addition, in many places we have either over-used or polluted our
groundwater. If desal should reduce our dependency on groundwater, we may be
less inclined to properly manage or clean up our ground water resources. On a
similar note, reverse osmosis technology has been proposed as a means for
cleaning up polluted groundwater. While this may seem attractive at first
glance, it should not be used as a tool to justify continued pollution.
In conclusion, reviewing alternatives to desal should not only consider the
dramatically lower cost of conservation and reclamation, but should also
account for the benefits of reducing the pollution reaching our waterways
through urban runoff and sewage discharge.
9. Private Ownership:
The California Coastal Commission report on desalination raises a number of
concerns regarding private ownership of desalination facilities. Historically,
the ocean has been regarded as a public resource to be utilized and enjoyed
by all people and animals in a sustainable, non-extractive manner. Using the
ocean as a source of drinking water (clearly an extractive use) changes all
that. While one desal facility may not have a significant effect on the
ocean, many such facilities (see cumulative impacts discussion below) may
have detrimental effects.
Typically, most of the water supply infrastructure in the United States is owned and
operated by public or semi-public agencies. Quality of the water, reliability
of the water supply system, and the price of the delivered water are all
subject to the scrutiny of various regulatory agencies, local governmental
bodies, and the general public. A water supply system operated by a private
company (perhaps a multinational company) may not be subject to the same
restrictions. Their profit goals may encourage rate increases, reductions in
quality, and promotion of more water use, as opposed to calls for more water
conservation and recycling.
The subject of ownership by a multinational private company raises additional
concerns regarding potential challenges to US laws that a multinational
corporation might regard as restrictions on "free trade" or an
undue limitation on their ability to make a profit.
10. Cumulative Impacts:
An environmental analysis conducted under CEQA (California Environmental
Quality Act) or NEPA (National Environmental Quality Act) should include an
assessment of the cumulative impacts of not only the proposed project, but
also other proposed projects (and existing facilities) in the area. These
impacts would include the cumulative entrainment/impingement bioregion
impacts, cumulative energy consumption impacts, cumulative growth-related
impacts, and cumulative wastewater & urban runoff impacts, among others.
This is especially import in areas where existing air quality, water quality
or ecosystem health in already compromised. In California, 18 new
desalination facilities have been proposed, with a cumulative production
capacity of 187 million gallons per day. Some facilities are with a few miles
of each other, potentially impacting the same bioregion of the ocean and/or
other common environmental resources. These projects should not be reviewed
in a vacuum.
CONCLUSION
With the rise of interest in desalination, partly caused by improvements in
reverse osmosis technology, there is a wealth of information coming to the
forefront. This fast growing interest in desalination has also caused
government agencies and non-governmental organizations to quickly begin
discussions about policy that will guide the implementation of this
technology. We suggest that any review of local proposals include a thorough
research of all of the issues outlined above. We have provided a list of
reference sites to start your research. Please feel free to contact Joe Geever or Rick Wilson at
the Surfrider Foundation National Headquarters if
you have questions or recommendations about the discussion surrounding desalination.
REFERENCES
Information of desalination from California Department of Water Resources
Water Desalination Task Force
http://www.owue.water.ca.gov/recycle/desal/desal.cfm
California Coastal Commission report (March 2004) "Seawater Desalination
and the California Coastal Act"
http://www.coastal.ca.gov/energy/14a-3-2004-desalination.pdf
USEPA Guidance on cooling water intake structures http://www.epa.gov/waterscience/316b/
The United States Desalination Coalition http://www.usdesal.org/
1 U.S. Desalination
Coalition, 2003.
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