As the world searches for technological solutions to its problems, it has sharpened its focus on desalination to respond to climate change and dwindling fresh water. Many people think the issue is simply financial. How do we obtain drinking water at the lowest possible cost? But what if your water source is going, going, gone forever? This is when support for desalination is strongest.
Bloomberg reports the desalination industry is booming and growing by 15% per year. A February 13, 2013 article states, “As the global population soars by about 74 million people a year, water shortages are becoming more severe….At current rates of growth, the demand for water worldwide may exceed supplies by 40 percent by 2030, according to the World Bank sponsored 2030 Water Resources Group.”
The areas with greatest demand for water are countries that view it as key to further economic growth such as Saudi Arabia, China, Spain and the U.S. The next greatest demand is in countries whose populations are growing and where demand will clearly outstrip the supply of available water such as China, India, and Pakistan. These governments are willing to pay premiums to insure the future availability of water.
The economics clearly favor fresh ground water where the cost averages around 20 cents per cubic meter of water. The lowest comparable price for desalinated water is somewhere around 50 cents per cubic meter. This is a considerable improvement in cost as a result of newer, cheaper methods of desalination that used to cost multiple dollars to produce the same amount of water.
Historic processes include distillation, reverse osmosis (RO), electrodialysis, and vacuum freezing. Of these, distillation and reverse osmosis are most in demand by local governments. Cost reduction tends to focus on the reduction of the energy to run a desalination plant. Historically energy has represented between 44% and 60% of the cost of desalination. Co-locating desalination and energy plants reduces costs. Trying to transport the resulting water through pipelines to distant locations that are poor, deep in the interior of a continent or at higher elevations is cost prohibitive. This keeps desalination as economic mainly for coastal areas.
Distillation as a process involves evaporating input water and then compressing and condensing the vapor to release heat. The resulting heat is then used for further evaporation of the input water. The condensation separates the salt and impurities from the fresh water that remains. This often will include sequential stages each of which is at a lower pressure.
Reverse osmosis begins with treatment of seawater to remove particles that would clog membranes. Then the seawater is pumped at high pressure through membranes that separate the salt from the water. The water can be improved by having multiple stages of membranes.
Farsighted communities are exploring future sources of fresh water. Opponents of desalination point to environmental damage in the ocean and surrounding areas close to the desalination plants and collocated power plants. They are progressively adding additional requirements to plans for these facilities to address areas of concern.
Unfortunately, we are not going to restrain industrial or population growth anytime soon. We also have not yet found a renewable or clean power source to be used to power these desalination plants. But the reality remains that concerns of environmental damage become less important as water shortages begin to occur. Governments act to eliminate shortages when fresh drinking water and water for farming and industry are disappearing.
It is incumbent on each of us to consider our own areas and the likelihood of experienced dwindling water. Water conservation requirements should be instituted now, before shortages become acute. This will postpone requirements for desalination plants. The longer the need is managed, the more time is allowed for further development of the technologies and the cheaper and greener the solutions will become.
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