Since approximately 71% of the earth’s surface is water, it’s amazing to think that many countries across the globe are suffering from a fresh water shortage. Indeed, drought conditions throughout much of California continue to be serious enough that experts are constantly searching for solutions.
The problem is that only a tiny percentage of the world’s water is fresh to begin with — approximately 2.5%. Of that tiny amount, around 69% is frozen in ice caps and glaciers, sources that are dangerously finite. Since humans, and a significant population of the planet’s animal and plant population, cannot survive on saltwater, people have long looked to the sea as a potential source for the drinking water they require. The only hurdle we have to overcome, is figuring out how to remove the salt from the water before we drink it.
Desalination plants and procedures could be the solution we’ve been searching for in order to provide a drought-proof water supply to the masses. What’s more, as we continue to explore the capabilities of desalination water plants, we find that there are numerous opportunities available that might allow us to transform seawater into fresh water on a huge scale.
What Is Desalination?
Put simply, the term “desalination” refers to the removal of dissolved minerals and salts from brackish water or seawater. To some, the concept is also known as “desalting”, and it produces fresh water from a source that otherwise would not be consumable. The primary technology desalination plants use today is “reverse osmosis”, a system that uses semi-permeable membranes as a way of removing impurities and salts, similarly to passing a substance through a sieve.
Desalination is not a new concept by any means – it has been used by sailors and other individuals for hundreds of years. In fact, the sun has been desalinating forever – using the process of evaporation to produce rain. Our current drought conditions have lead to an increase in interest towards desalination, as scientists search for effective methods of providing fresh water to regions where its availability is limited, or waning. Today, one of mankind’s earliest forms of water treatment is evolving through ever-improving technology to become a more popular solution for people everywhere.
How Do Desalination Plants Work?
The primary focus behind desalination plants is to remove salt, debris, and other minerals from large quantities of water, leaving clean water behind. At this point, there are a number of different kinds of water desalination processes available, including the most popular solution – reverse osmosis, as well as other options such as electro dialysis and thermal distillation.
Reverse osmosis works by pushing water through a thin membrane that traps unwanted minerals and salt, typically removing anywhere in the region of 95-99% of unwanted materials from drinking water. Before the water is forced through the membrane, with microscopic pores only large enough to allow water molecules to pass through, it is generally pretreated, and moved through other micro filters intended to remove larger particles. The process involves a number of critical stages:
- Pre-treatment uses coagulation, sedimentation, and other methods to remove bacteria, suspended solids, and other contaminants that might clog the membrane.
- High-pressure pumps ranging in power according to specific types of water, force the water through a membrane made up of composite polymers, and into a tube for collection.
- Post-treatment often adjusts the pH of the water and ensures disinfection before adding it to the remaining municipal water supply.
One negative of reverse osmosis is that it is still possible for herbicides, pesticides and other chemicals to pass through the membrane – making additional treatments necessary. What’s more, the same membrane may remove other healthy minerals from water that could be beneficial.
Other Desalination Methods
Aside from reverse osmosis, there are a number of other options for desalination available. For example, thermal distillation uses heat to remove minerals. By bringing salt water to a boil, the water vaporizes and leaves the salt behind. From that point, the vapor can condense into an alternate container for collection. Alternatively, electro dialysis utilizes the electrical charge in salt ions to separate them from the water. During this process, pre-treated water goes into a membrane stack. Negative and positive electrodes are placed on either side of the stack to run electrical currents through the water, trapping the salt ions and leaving fresh water behind.
As technology continues to evolve, we will no doubt discover new and more efficient methods of desalination. At this point, it seems as though the process could offer an incredible solution to the problem of our limited fresh water supply.