Dear EarthTalk: With all the talk of desalinization of ocean water for drinking, what do we know about the impacts this might have on climate, ocean salinity and other natural processes? -- Fred Kuepper, via e-mail
Due to its high cost, energy intensiveness and overall ecological footprint, most environmental advocates view desalinization (or desalination) -- the conversion of salty ocean water into fresh water -- as a last resort for providing fresh water to needy populations. Sourcing fresh water from streams, rivers, lakes and underground aquifers and adhering to strict water conservation measures are much more viable for both economic and environmental reasons in most situations, although some desert regions with thirsty and growing populations may not have many such options.
The relationship between desalinization and climate change is complex. Global warming has increased droughts around the world and turned formerly verdant landscapes into near deserts. Some long held fresh water sources are simply no longer reliably available to hundreds of millions of people around the world.
Meanwhile, expanding populations in desert areas are putting intense pressure on existing fresh water supplies, forcing communities to turn to desalinization as the most expedient way to satisfy their collective thirst. But the process of desalinization burns up many more fossil fuels than sourcing the equivalent amount of fresh water from fresh water bodies. As such, the very proliferation of desalinization plants around the world -- some 13,000 already supply fresh water in 120 nations, primarily in the Middle East, North Africa and Caribbean -- is both a reaction to and one of many contributors to global warming.
Beyond the links to climate problems, marine biologists warn that widespread desalinization could take a heavy toll on ocean biodiversity; as such facilities' intake pipes essentially vacuum up and inadvertently kill millions of plankton, fish eggs, fish larvae and other microbial organisms that constitute the base layer of the marine food chain. And, according to Jeffrey Graham of the Scripps Institute of Oceanography's Center for Marine Biotechnology and Biomedicine, the salty sludge leftover after desalinization -- for every gallon of freshwater produced, another gallon of doubly concentrated salt water must be disposed of -- can wreak havoc on marine ecosystems if dumped willy-nilly offshore. "For some desalinization operations," says Graham, "it is thought that the disappearance of some organisms from discharge areas may be related to...the salty outflow."
Of course, as supplies of fresh water dwindle, the economic cost of desalinization -- especially in coastal areas with easy access to ocean water -- begins to look competitive with traditional water sourcing. To date there are about 300 desalinization plants in the United States, with 120 in Florida and less than 40 each in Texas and California. Some 20 additional plants are planned for the coast of California in the coming years, unless environmentalists extolling the virtues of conservation and wielding low-flow shower heads and toilets prevail.
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We are NOT running out of fresh water on this planet. We are merely mis-using the fresh water we have.
Studies are showing that much of North America was covered with beaver dams. Many of our current local rivers and tributaries didn't appear on old maps because they didn't exist. Beaver hunting destroyed our original ecosystem in North America, probably as it had in Europe and other areas in the centuries before. The original ecoystems trapped fresh water efficiently.
Fresh water comes down from the sky in the form of rain. Today, we treat is as a nuissance, diverting it as quickly as possible into rivers, with all of the new problems they generate - massive seasonal flooding, etc...
We have destroyed the ability of the land to absorb and filter the water. We have covered over sensitive land that absorbed water and drew it into underground reservoirs - the aquifers and ground water.
We get rid of smelly and insect filled backwater areas when we actually need more swamps. Instead of flushing it down storm drains, we need to find an alternative way of storing and processing this water back into ancient aquifers or ground water tables where it can be stored until needed.
As for desalination, it would be much preferrable to use brine or brackish water to help cool nuclear power plant coolant fluid and then recover the steam generated to be used for drinking water.
Many coal-fired plants produce excessive steam that could be recovered. In Boston, the steam is used in cogeneration - it heats many buildings in the winter.
The basic problem is that we have broken our ecology. We have to fix what was broken or use technology to replace what is lost - prevent building on unused land, restore ecosystems, cache the water instead of draining it into rivers and streams... And we have a lot of work to do.
1) Desalination uses a lot of energy. Thus, it is often only as "green" as the energy used to create it. That is why most desalination occurs in the Middle East, where water is rare and oil is common. Since oil is cheap, they can afford to burn it for water. However, if you had a green (solar/wind combo) based desalination plant, then it would have very little impact on the environment.
2) Sucking up water kills fish and plankton? Seriously? Unless you put your intake directly in the middle of a coral reef or kelp bed, you are not going to suck up the life of the ocean. Actually, the less sediment and biomass you suck up, the better for the plant, so there is reason NOT to set an intake in a place with high biomass. Since you are removing the water with the biomass, you are not even changing the ratio of biomass in the water. (Put food coloring in your pool and see how many cups of water you have to remove to make the water clear. The last cup will be the same color as the first).
3) Salty sludge is rather toxic to life, but in any desert climate (and let's face it, only desert climates need desalination), there is plenty of space to dump that sludge in land. A non-draining sludge lake in the middle of the desert is hardly an environment killer (there are a few natural ones out there already: GSL, DS, etc). It can't contaminate the ground water where there isn't any to begin with.
4) The oceans are so great that man made efforts like desalination will never be a significant impact on salinity.
5) Since most desalination plants work through water pressure and screens (not distillation, as most people think), any process that can create enough water pressure can greatly reduce the power required. There are several green options, such as harnesses (wave and tidal) and wind, that can create water pressure just as effectively as they can create electricity. The real issue is cost. There are plenty of ways to create fresh water from salt water, there is just no reason to when there is still so much fresh water and cheap (and dirty) fuel to do it with.
Oakspar77777, I like the comment about using wind, wave and tidal energy to create pressure rather than electricity. I would think that would not only be as efficient but actually more efficient.
If you create electricity then convert that into pressure you have an extra step. There is probably energy lost in that extra step. Remove the extra step and you remove the energy loss.
Solar Towers could be a great way to desalinate and generate electricity using distillation. The open loop creates steam from focused sunlight to generate electricity. The waste steam can be used as drinking water. Or in a closed loop, brackish or briney water can be used to cool the return steam. The heated brine would boil, creating steam to make fresh water.
I am not a great fan desalination that uses filters and osmosis. They usually require activated charcoal or other materials derived from burning large amounts of fossil fuels or creating vast amounts of CO2.
Charcoal is the remnant of wood that is burned. How is that green? The various other ionic filters either use electricity or use materials that require a large expendidure of energy to manufacture, or generate toxic waste materials.
Distillation using a green supply of energy (or waste-energy from a non-green source) is the best solution.
We have thousands of factories in this country that expell vast amounts of waste heat through smoke-stacks. That waste heat could be used to DO things, like desalinate runoff water.
As for concern about ocean life, most of us don't need to use ocean water for desalination. We can trap runoff water from rainstorms and pool it near manufacturing areas of this country, nuclear power plants (from a safe distance), or other power generation facilities that create excessive waste heat that can be harnessed.
In France (and many other countries), Nuclear power plants have to shut down when it gets very hot during the summer, just when the electricity is needed most. The water supplies (rivers and lakes) that the Nuclear power plants use for cooling get too warm and low, and the water they would return would boil the lakes and rivers, leaving them lifeless. If we pool runoff water for these power plants as an alternative cooling supply, they could use that for cooling - generating drinking water from the steam, reducing damage to the environment, and helping us to get electricity in the summer.
While not a fan of Nuclear Power, I think it is in our best interest to reduce its impact on the environment.
In areas of the world (especially Spain and Portugal) there are places that they flood with ocean water. They allow the ocean water to evaporate, leaving behind thick deposits of salt that they market as Fluer de Sel, sea salt. So, places in the middle east that need to desalinate ocean water can do the same - that is desalinate using distillation from solar towers, and then dump the salty sludge on a few acres of the desert where it can be dried to produce salt that can be marketed.
If all of our salt can come from desalinaion, there won't need to be energy intensive and risky salt mining. Also, by marketing and selling this by-product, we are not going to accumulate "waste". The area used is limited in size and reused. The essential balance of salt in the oceans is maintained (unlike salt mining that is steadily increasing ocean salinity).
How is the balance of salt in the oceans maintained if we suck water from the ocean, then dump what's left after desalination on land?
One of the best ways to limit global impact from humans, is to limit the number of humans, and have real rules that put land management before considerations of profit.
Anyone else choosing to not have kids?
that's funny, 3 out of 4 found my comment distasteful. Makes me think people believe we can just go on like nothing's wrong, and that's precisely what's causing the problem. People are unmanageable, keep thinking there's a way around that. There isn't.
and the band played on
While I do not necessarily disagree with the idea to limit human population, it is nearly impossible to do. China has tried to limit the number of children that people can have and they have failed at it miserably.
I think the only real solution and one that would be far easier (granted still quite difficult) would be to just send half the population to Mars while colonizing it. Far off, I know, but much easier to do than changing society and the instincts that we have evolved to reproduce as much as possible.
As to the topic at hand, out in the desert areas of the US they seem to have a very strong stance against waste-to-tap water treatment systems. Why has that idea gained so much negativity? Every drop of water on Earth at some point has been a part of a waste system. Such a system could already be implemented with currently existing infrastructure, with little to no changes.
Wouldn't you think that by desalanization of ocean water would help create more ice up north and south. By decreasing the amount of salt content, wouldn't the water be easier to freeze?
Unless desalinated water is used to re charge the aquifers
you can not solve the true problems of saltifaction of the land mass
Every place upstream that is fertilizing crops excessively
and using both ground water and river water has a reason to buy and pump desalinated water back into their local aquifer . If only to maintain the viability of their local ground and the ability to grow crops.
Without desalination in the mix our ability to maintain viable crop production and healthy rivers is virtually impossible in our current factory farm system.
So in the short term we are facing far more crisis than our esteemed leaders are even willing to consider.
Global warming is not the one that is the most important one to be concerned about today.