Many human activities require significant amounts of water, making desalination of water a critical procedure in the survival of the human race. From drinking, sanitation, agriculture, and electricity generation, there is no end to the list of the number of ways through which water is used. Many people across the globe are lucky to be located near sources of usable water. Unfortunately, the majority of the earth’s water, which is in the oceans, is not usable because of its salty nature.
The fact that oceans cover over 70% of the earth means that majority of the water available cannot be used as it is. Salty water is unsuitable for many applications, including drinking, which is essential for human survival. The salt in water must be eliminated through desalination to make it more useful. There are various methods of desalination, with some being more intensive than others.
Methods of Desalination
This is the oldest method of water desalination has been around for thousands of years. This method involves boiling the water to produce steam leaving the salt behind. The evaporated water is then cooled down to produce fresh, non-salty water. One of the major cons of this method of desalination is that it is energy-intensive.
Significant amounts of energy are needed during vaporization. Fortunately, with modern technologies, it is possible to reduce the amount of energy needed during the whole process. Low-pressure vessels are used to reduce the boiling point of the water, ensuring less energy consumption during vaporization.
This method utilizes electric currents to separate water and salt. An electric current is typically used to drive ions across a membrane that is selectively permeable, carrying the salt ions with it. The membrane used only allows the dissociated salt ions to pass through, leaving fresh water behind. The energy consumed through this method depends on the amount of salt that is initially present in the water.
This method is easy and cheap to apply for salty water, whose salty concentration is not too high. However, the electrical desalination of seawater consumes too much energy. The cost outweighs the benefits meaning that seawater should be desalinated using any other method apart from this one.
This method has many similarities with electrical desalination. The method is implemented by using pressure to drive water through a selectively permeable membrane. The membrane allows freshwater to pass through it, leaving the salt behind. Just like electrical desalination, the amount of energy used depends on the amount of salt present in water. This means that this method is not suitable for purifying seawater because the salt content is too high.
It is impossible for any living thing to survive without water. That said, technologies aimed at creating fresh and usable water are very important, especially to the human race. Unfortunately, no matter the method of desalination chosen, the energy required remains tremendous. The world desalinates around 12 billion gallons of water every day and consumes a minimum of 84 million kWh of energy per 1000 gallons of water.