WHAT IS REVERSE OSMOSIS?
Reverse Osmosis is not a new concept. Its process was first observed in 1748 by Jean-Antoine Nollet who used a pig’s bladder as a membrane. Do you know why was it put into use and for what purpose?
Reverse Osmosis is the most popular technique used to purify water. It was mainly used for the desalination of seawater in the year 1950. At that time the process was quite slow and limited to certain laboratories but as the years passed by and due to advancements in technology, this process is now commonly used in almost every field including industrial, commercial, residential, and for scientific purposes.
As we have been witnessing pollution everywhere because of the increasing population, it is the need of an hour that we use this technique for the betterment.
Reverse Osmosis Principle
When pressure greater than the osmotic pressure is applied on the higher concentration side, solvent molecules start moving from the higher concentration side to the lower concentration side via a semi-permeable membrane. This thin membrane separates impurities from water.
As the name suggests, it is done by reversing the principle of osmosis. This principle applies to reverse osmosis plants as well. They absorb nutrients and water from the soil.
Do you know how this principle works for humans and animals? Kidneys use osmosis to absorb water from the blood.
In an RO system, pressure from a pump overcomes natural osmotic pressure thereby forcing feedwater containing salts and other impurities to remove a high percentage of impurities from the water. The separated salts and impurities get collected above the membrane and are passed from the system to the drain.
In the commercial and industrial world, 75% of feedwater is clean and purified.
RO uses cross filtration where it crosses the system with two outlets: – one outlet is for filtered water and the other one is for contaminated water.
Sometimes, all the contaminated water gets collected in one place and if we don’t keep maintenance of this, it looks filthy. So, to overcome this problem, this cross-flow filtration allows water to sweep away contaminant buildup and therefore keeps the membrane’s surface clean.
Reverse Osmosis process
The process of Reverse Osmosis involves 4 stages. These include: –
- A sediment pre-filter
- A carbon block pre-filter (optional)
- A reverse osmosis membrane
- A carbon block post-filter (Or any other post filtration method or disinfection method)
Stage 1
The first stage is highly crucial to carry out the other stages. It forms the bases for the other stages. So, in this stage, it uses pre-filter to separate larger solid impurities like sediments and dirt present in the water.
Stage 2
After the removal of larger impurities, stage 2 has the carbon filter and its use is of utmost importance. While the water is being processed after it has gone through stage 1, the carbon filter removes chlorine, odors present in the water, sediments, and volatile organic compounds (VOCs). Other contaminants like household waste, and pipe waste can also come in contact with the system but the carbon filter does its duty and gives us potable water.
Stage 3
This is the utmost important stage of all stages in the Reverse Osmosis process because it involves the purification stage. In this stage, pressure is applied to water so that it passes through fine membranes to drain out the clean water. This stage eliminates all the contaminants including total dissolved solids (TDS).
There is a cross-section tube in the system, a semi-permeable membrane, and porous layers. They all work as filtration as the pressure moves the water through the membrane. As the water molecules pass through the system, it keeps removing the bacteria.
Stage 4
This stage involves the final filtration. Sometimes a chemical dosing or disinfection method is used after the RO stage. Then, at last, the clean water gets deposited into the water tank reserve or sent directly into the pipes for use
This overall process eliminates the bacteria and contaminants in water by 97%. It also gets rid of calcium and magnesium which are too harmful to the body.
Advantages of Reverse Osmosis
1. Fewer chemicals involved-
We see that in many technologies, we require chemicals to get the work done but, in this system, fewer chemical reagents are required, no acid-base treatment, no chemical waste liquid, and zero environmental pollution.
2. Advancements in technology help to reduce energy consumption-
Energy recovery devices now allow most of the wasted energy to be brought back into the process, making the RO process energy efficient if designed properly.
3. Can treat any water quality-
There is nothing any particular water quality that this system needs. It can treat a wide range of qualities like brackish water treatment, seawater RO treatment, and freshwater with minimal salt content.
Disadvantages of Reverse Osmosis
1. Not easy to install and maintain-
It doesn’t involve a single stage. Before and after the installation of RO, you have to upkeep every single system so that the life of the RO may remain longer. You have to check whether its filter is working and you have to go for filter replacements after every 6 months or 1 year.
2. Costly-
An RO is considered more costly than any other water technology. However, this technology is the most trusted technology adopted by every household and industry. Because every person prefers healthy life to a cost.
3. Removes all minerals-
Sometimes, RO removes all minerals whether it is good or bad. It drains consumable calcium and magnesium also. Drinking water low in calcium and magnesium may invite various health disorders, especially in children, pregnancy disorders, cancer, and premature deaths in infants. But according to several reports, most of the minerals in our body are added via water only and if these are absent in water, then we may lack certain minerals which are required to keep us healthy.
Conclusion
It can be agreed that RO is not the perfect purification method but it is the most trusted system in many countries. Despite its disadvantages, people still prefer to adopt this technology because of its safe and hygienic drinking water.