Sometimes when you help yourself to a glass of water at home, do you wonder how water was purified during your childhood? Today we have RO water purification systems and UV water purifiers at home that offer safe drinking water in a matter of minutes, but a few decades ago, using traditional water purification methods was commonplace.
Let us learn more about how the process of purifying water has evolved over the years.
Before modern water purification systems were introduced, India and many other developing countries used ceramic filters and cloth filters to obtain clean water from wells and other water bodies. This was meant only to remove the physical contaminants that can be visible to the eyes.
Another well-known technique is boiling water. Many people still rely on boiling water as it is an effective method for removing certain microbial contamination. However, boiling can be effective only when boiled for a specific time, and chemical contaminants will remain in the water.
Boiling the water for drinking does not ensure the complete removal of pathogens and other bacteria that can evade high temperatures. Hence, modern water purification methods that use multiple filtration and purification processes can be used to treat water.
Below is the working of a modern water purification system:
The use of Ultraviolet (UV) light disinfection can aid in the removal of microbiological contaminants. The water from sources such as rainwater tanks, streams, and borewells can be treated using UV disinfection. 
However, in many cases, UV light systems alone may not be the right choice for removing chemical contaminants from the water. This also includes organic and inorganic contaminants like calcium, magnesium, sodium chloride, copper, chromium, and others. 
Hence, Reverse Osmosis (RO), along with other filtration methods, is used to treat water made fit for consumption, as shown below:
The first step in water purification systems is microfiltration, where the membrane’s pore size is 0.1 micrometre. This separation technique removes micro-sized particles, like bacteria, yeast cells, colloids, and smoke particles, from suspensions or gases. 
This pore size of about 0.01 micrometre is vital for filtering out viruses, which are more minute than total suspended solids. 
In this step, the membrane’s pore size is about 0.001 micrometre. This membrane’s pore size effectively filters a majority of organic molecules and some ions, most commonly found in hard water or well water. 
In reverse osmosis, the pore size of the semi-permeable membrane is approximately 0.0001 micrometres. This eliminates the chemical impurities in the water, resulting in purified drinking water. 
In the purest sense, reverse osmosis technology is not a filtration method. Unlike the other filtration methods, RO works on osmotic pressure. This forces the water from the contaminated side of the solution through the semi-permeable membrane. The process leaves behind the dissolved salts, ensuring safe, filtered water. 
With the 8-stage purification system and the dual protection of RO+ Silver Charged Membrane Technology, A. O. Smith water purifiers ensure pure Baby Safe drinking water.