Desalination: A Promising Solution to Drought or Just Another Misguided Stab In the Dark?
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*** Re-Posted from “One-Green-Planet” ***
All of terrestrial life depends on freshwater. From densely populated cities to rural communities, farmland and forestland, and domestic and wild animals, all are in need of clean water to sustain them. Miraculously, just a small percentage of the water on earth is actually available as freshwater.
According to the U.S. Geological Service, only about 2.5 percent of all the water on planet earth is freshwater. And only 1.2 percent of that is most easily accessible on the earth’s surface in the form of lakes, rivers, swamps, soil moisture, and permafrost. An additional 30.1 percent exists as groundwater while the majority of this freshwater, 68.7 percent to be exact, is locked up as frozen glaciers and ice caps.
It is in our best interest to treat freshwater supplies with the utmost respect, and yet we’re losing out on this invaluable resource due to our own ignorance and negligence.
So, what can we do to save our water? There are, luckily, a variety of solutions. From education and conservation to emerging technologies, we are hatching up a plethora of solutions to our water woes. One of the strategies that many countries are using is desalination where salt water is essentially converted into freshwater. There’s plenty of salt water on the planet, as we know, so this sounds like a fabulous idea. Or is it?
Getting freshwater From Saltwater – How?
Desalination is a process that converts salt water to freshwater by removing salts and other minerals, leaving behind freshwater, potable water. While there are a variety of methods to accomplish this task, they can be grouped mainly into two types.
The first method, thermal desalination, involves the heating of saline water. Salts are left behind while freshwater is converted to steam and is collected, ultimately to condense back into water that is now saline-free and ready for use in an instance where freshwater is desired.
The second type of desalination involves the use of membranes to separate salt and other minerals from water. Pressure or electric currents may be used to drive saline water through a membrane which acts as a filter. Freshwater ends up on one side of the membrane while saline water stays on the other side as a form of waste.
Of course, these are very, very basic descriptions of some pretty complex and evolving technologies. But they do offer a quick insight into what the process of desalination looks like in most settings around the world. For some individuals, this is the technology used to provide them with clean drinking water.
Where Are Desalination Plants Working Now?
Desalination is a technology that has been around for quite some time and is seeing improved growth around the world in the face of increasing water demands. Since 2003, Saudi Arabia, the United Arab Emirates and Spain have led the world in desalination capacities. As of 2013, there were over 17,000 desalination plants worldwide in roughly 150 countries, providing more than 300 million people with at least some of their daily freshwater needs.
Israel is one successful case-study when it comes to the value of desalination. The nation currently has a quarter of its freshwater needs met through four desalination plants that treat mainly brackish well water (water that is part salt/part fresh). Israel’s desalination plants currently produce 130 million gallons of potable water a year and they are aiming to increase that number to 200 million gallons a year by 2020. While aggressive conservation efforts also helped ease the impact of severe drought, desalination has certainly been an important piece of solving a water crises.
As countries all over the world increase their capacity for desalination plants, drought-stricken areas like the United States southwest are taking note and investing in this technology. In fact, construction on the Western hemisphere’s largest desalination plant is nearly complete in San Diego, California and is expected to open for operation later this year. In the face of severe drought, desalination is becoming a much more appetizing option for this region to put its plentiful access to seawater to good use and to alleviate some of the pressures that developed and agricultural areas are placing on freshwater sources.
Is This The Answer to Water Shortages Worldwide?
Whether or not desalination is the savior for water woes is a complex debate and answers will probably vary depending on who you are asking. You’ll find there are activists, scientists, public agencies, governments, and citizens on both sides of the debate.
The first input that comes to mind when you think of desalination is probably the saline water that’s being treated, right? Depending on the source of this saline water, there may be a variety of detrimental impacts to the local ecology to consider when it comes to desalination operations.
Some desalination plants use direct intake methods to gather saline water, meaning they extract water directly from the water column, either from the surface or at greater depths in the ocean. The problem with this extraction method is that, in addition to taking in saltwater that can become a viable freshwater source, a host of marine life is also sucked up in the process. Algae, plankton, jellyfish, fish, and larva of many species can all easily be killed with this direct intake method for harvesting sea water.
The impact of ocean water extraction on local marine life is not well understood, however, experts will note there are a variety of ways to skate around issues like this. One such method is indirect intake where pipes are buried in the substrate and intake water that is actually filtered down through the sand first. Marine life damage is largely eliminated using this method. Physical barriers to intake pipes may also be utilized where screens or meshes are able to keep smaller marine creatures out of the intake pipes. And behavioral deterrents, like bubble screens and strobe lights, are another option to discourage marine animals from swimming too close to intake systems where they become trapped.
Saline water that is being harvested for desalination projects are not the only issue creating ecological impacts for this water treatment system. The output of wastewater is another issue that critics point out when it comes to desalination. Water discharged from desalination plants has a higher level of saline than the body of water it is entering. While some creatures can tolerate change in salinity, others cannot and may be killed on contact. Discharging water that has been heated in the desalination process can also cause temperature spikes and stress to any aquatic life in a close radius. And, the water discharged from desalination operations may also have an altered chemical composition given the added antifouling agents, heavy metals, chlorine, antiscaling chemicals, and cleaning solutions used in the process. All have a potential to detrimentally impact the local ecology surrounding a desalination operation.
Some solutions for wastewater from desalination operations already exist. Because saline water is more likely to sink and move along the ocean bottom, discharging it upward can help promote mixing of wastewater more quickly to disperse salinity and weaken the impacts that concentrated salt levels can cause. Additionally, plants can invest in technology to lessen the amount of chemicals they use in the treatment process, and even attempt to let wastewater evaporate, leaving behind only solid waste for plant operators to dispose of. These may not be perfect solutions, but they are attempts to make desalination operations more friendly to the local ecology.
One major difficulty with fully embracing desalination has to do with the major energy inputs the technology requires. Costs attributed to desalination depend largely on energy costs which can and do fluctuate from year to year. Roughly 60 percent of the cost of operating a thermal desalination plant comes from the energy costs to operate the plant, while 36 percent of the cost to run a reverse osmosis plant comes from the energy it uses.
Greenhouse gas emissions associated with desalination plants depend heavily on the type of energy utilized. In an area where fossil fuels are burned to make electricity, emissions associated with desalination will be higher. Additionally, if a desalination plant relies heavily on hydroelectric power, a drought in the area may increase the cost of energy from the electric plant and thus the cost to run the desalination plant.
As with any new and growing technology, there can be an expected higher cost than the conventional way of doing things. Desalination is no exception. Using San Diego County as an example, we can see just how much more expensive desalination is than other methods of providing freshwater. The cost to save an acre-foot of water through conservation and user education around efficiency may fall anywhere between $150 and $,1000. Importing an acre-foot of water may cost somewhere between $875 and $975. Recycling an acre-foot of potable water has a range in cost between $1,200 and $1,800. And providing an acre-foot of freshwater through seawater desalination would cost between $1,800 and $2,800. As local agencies and governments come up against budget cuts and financing difficulties, it may be impossible to justify this technology in the face of cheaper options that provide the same results.
Citizens will see an increase in their water bill as more of their freshwater is sourced from expensive desalination processes. This rise in basic living costs in the face of economic hardship may be difficult to justify, especially for a resource as important as freshwater. Desalination is certainly not a cost-saving choice.
Is It A Go?
It is certainly important to note the improvements that technology like desalination can provide to society. Especially as we are faced with increased challenges to meet the needs of a growing population, it is important to have a variety of options available to us.
While desalination is certainly an amazing option to convert water that was once too salty for human-use into something that can quench thirsts, maintain sanitation, and irrigate agriculture, one may be left wondering if the cost is really worth it. There are still many improvements left to be made to make this a more environmentally friendly option. As it stands, it is not without some major drawbacks when it comes to local ecology destruction, energy use, and greenhouse gas emissions. And it is certainly a very expensive option when you consider how little money it would take to simply educate the masses on how to conserve water.
Desalination is a wonderful testament to the human mind and inventive capacity, but it may simply be a very advanced and expensive method for maintaining our ignorance to the natural world with exist within. We may be able to provide freshwater in places where it didn’t previously exist, but what’s the point if people continue to remain ignorant to how to better use the water we already have? In the face of a crisis this may certainly be a valuable technology, but we have not even yet begun to address some of the issues that are causing our water shortages in the first place. And that’s an issue we need to work out through education and conversation around sustainability rather than throwing money into more expensive technology.
Lead Image Source: JohnKay/Flickr