Water covers almost three fourths of the earth. But of this massive amount, freshwater only accounts for approximately three percent, found in lakes and rivers, glaciers, and underground aquifers. Saline, or salt water, makes up the remaining 97 percent.
We need potable (e.g, drinking) water to survive. But the earth’s population grows by about 85 million people every year and fresh water demand increases at twice that rate. Diminished potable water doesn’t just threaten dehydration-it encourages preventable diseases that claim an estimated 42,000 people each week.
Some researchers have turned to desalination-the transformation of ocean water into potable water-as a possible solution. In this blog, we explore the science and possibilities of desalination.
The Desalination Process
Desalination doesn’t just remove salt-it also removes other dissolved minerals that pollute brackish water and treated waste water. Technicians typically accomplish this task through one of the following methods:
- Distillation: This method mimics the natural water cycle in which water evaporates, leaving impurities behind, and then condenses in a purer form. Distillation plants artificially heat and cool water to speed up this process.
- Electrodialysis: By using an electrical current, electrodialysis forces water through a filter to strain out unwanted particles.
- Reverse Osmosis (RO): RO systems also use filters to clean the water, but technicians use pressure rather than electricity to produce movement.
The Problems with Desalination
Unfortunately, these methods each have drawbacks that prevent large-scale desalination. Some of the common issues are as follows:
- Distillation: Because distillation relies on forced heating and cooling, it uses enormous amounts of energy. This makes distillation impractical on a large scale due to the accompanying costs.
- Electrodialysis: This process effectively removes salt and other large particles. However, it cannot remove microparticles. Micro-particles found in water include bacteria and dirt that could prove harmful if ingested.
- Reverse Osmosis (RO): (RO) uses significantly less energy than other forms of desalination. However, few commercial plants exist because the process uses three times as much energy as freshwater treatment.
Desalination by RO produces two main byproducts-high-quality purified water and water with twice the concentration of salt and particles as seawater. Irresponsible disposal of RO’s waste product could negatively impact the marine environment because such wastes do not naturally dilute in the ocean.
The Future of Desalination
Energy consumption and prohibitive costs remain the largest obstacles to large-scale desalination. In fact, experts exhort people to try conservation and reuse before resorting to desalination.
ry conservation and reuse before resorting to desalination.
However, there’s now a greater interest in the desalination processes. Gulf countries, such as Saudi Arabia and Kuwait, have used desalination to produce potable water for decades. At the same time, most of these nations use the distillation method, which carries a high energy cost.
In 2011, Israel completed its fifth RO desalination plant. These plants supply Israel with 500 million cubic meters of water each year (for scale, a cubic meter of water represents approximately 1,000 liters).
Several other nations have also made strides in desalination, including Singapore and Spain. Many countries employ desalination because there are no other viable options for producing potable water.
The Gulf countries have few other water sources. Israel was already reusing all its waste water before it began using desalination. Singapore relied heavily on Malaysia for its water and sought independence. Spain struggled to meet the demands of agriculture and tourism without alternative water sources.
In the future, water professionals may make RO systems more economical on a large scale. Researchers also investigate the practicality of refining other desalination methods for future use.
On a small scale, reverse osmosis cannot desalinate seawater (yet), but it can supply you and your family with delicious, clean water straight from your tap. Talk to a water professional about installing a new system today.
For more information about water purification and the future of potable water, read our other blog posts.