How Reverse Osmosis Works

Millions of RO Customers are curious to know how reverse osmosis works?

The Word Reverse Osmosis or RO’s popularity has sky rocketed in the last 10-15 years.

This technology is so much famous all over the world! When a customer purchases a water filter in the market, then he asks for an RO. Earlier, he wanted a water filter.

Surprised ?

What a BIG change !

How did this happened ??

Lets see the global water purifier market trend!

Reverse Osmosis water purifier demand in Global Water Purifier Markets

Worldwide Reverse Osmosis (RO) market is estimated to be 5.4 billion USD in 2019 & is likely to grow to 8.3 billion USD in 2024 at a CAGR of 8.98%.

Woah ! Isn’t it awesome !

Water purifier market is on fire ! It is fuelled by heavy demand of reverse osmosis purifiers.

Lets start from the word Osmosis. People are clueless about its definition & working.

Suppose water is present in a container with a semi-permeable membrane. Now salt is added in one end of the box.

Salt particles are very bigger. Membranes will not allow salt to pass through it.

Water will flow through the semi-permeable membrane from the more evident end to the one where salt is present. It happens because water concentration at the salt end has decreased. So, Water at the brighter end will rush in to balance the pressure.

This process is known as Osmosis.

How exactly reverse osmosis works?

reverse osmosis working when semi permeable membrane is placed between clear water & salted water.

If we reverse the water flow by external pressure. So, that it flows from salted water end to the clearer end through the membrane.

Then this process is known as reverse osmosis.

Reverse Osmosis Membranes:

The thickness of a RO membrane is 0.0001 microns. They are made up of 3 different layers of materials :

  • Polyamide
  • Polysulfone
  • Polyester
Image showing a RO Membrane sheet made up of 3 layers of Polyamide, Polysulfone & Polyester material

Polyamide(<200 nm) is the barrier layer that removes toxins, salts, nutrients, bacteria & viruses from the water.

It is deposited on top of Polysulfone layer (50 microns), supported by a Polyester fabric base.

These 3 layer materials ensure high filtration & rejection of unwanted water components.

Foldable sheets of RO membrane are rolled up & sealed inside a cylindrical pipe.

The RO cylindrical pipe can be used by home as well as municipality as per the requirement.

Municipality & industries use cylindrical pipe stacks of RO membranes, whereas home water purifiers use a single RO membrane.

Reverse Osmosis Water Filtration System used in Industries & Municipality

What is Reverse Osmosis Water Filtration System?

A reverse osmosis(RO) water filtration system is a combination of multiple filtration technologies like

  • Sedimentation Filter
  • Activated Carbon
  • UF Membrane
  • TDS Controller
  • Ultraviolet lamp
  • RO Membrane

Reverse osmosis works in tandem with all the above technologies.

What is the process of Reverse Osmosis Water Purification?

Let’s start with the process of purification of raw water into pure water at a reverse osmosis water purification plant.

Detailed Process of Reverse Osmosis Water Purification

Step 1: Remove unwanted particles

Dirt, sand & sediment particles can easily damage RO membranes. So, Raw water has to pass through a filter assembly, which prevents water impurities from reaching the reverse osmosis machine.

Step 2: Water Filtration

Water is then sent to 2 different filtration vessels :

  1. Sedimentation vessel
  2. Activated Carbon vessel

Sedimentation  is used to remove water turbidity & increase water transparency.

Higher is the water turbidity, greater is the water quality !

Now, after water transparency is restored to raw water. But as municipal corporations do heavy water chlorination. It becomes tough to remove Chlorine. The excess of Chlorine is very harmful to health.

At this stage , the 2nd carbon filter is used. This contains activated carbon granules.

It remove various unwanted chemicals like chlorine, pesticides & heavy metals from water.

Step 3: RO Membrane role

The question is how reverse osmosis purifies water?

Water is pushed to the RO membrane chamber through low HP motor. RO membranes are as thin as 0.0005 microns. So, water particles greater than the thickness of membranes are unable to pass through it. Bacteria, viruses & other lethal metals are filtered.

Purified RO water collects in a separate tank. Now the storage tank used for RO water collection may also contain pathogens. So, herein Ultraviolet lamp is used for disinfection in the final stage.

The RO rejected water is the wastewater that is not able to pass through the RO membrane. It drains through a separate pipe as it has an extremely high concentration of unwanted minerals & microorganisms.

Step 4: Disinfection of RO water

We may ask the question as to why there is no UV exposure in earlier stages of reverse osmosis.

UV stage requires clean, purified water to function without any hiccups.

If there is UV exposure to salted water, then micro-organisms will stick to the salts & the UV treatment will not yield any results.

RO water after UV disinfection is safe for drinking till the time water is in the storage tank. If the purified water is supplied through a pipe to another tank. Then there is a strong possibility of water getting infected again.

Its no wonder, due to strict health reasons, RO purification system demand is growing everywhere starting from

  • Home
  • Cities
  • Industries

Why need Reverse Osmosis System for home?

Water at home is heavily dependent on the government municipality supply. Sometimes there may be leakage between the supply source & the home connection.

This can contaminate the water with unwanted components like mud & sewer water. This would pose a high risk of serious bacterial & viral infections starting from gastroenteritis, dysentery, diarrhea & Jaundice.

Also, Total Dissolved Solids(TDS) level in supply water is not controllable. It poses a greater threat to human health. Certain unwanted chemicals like Pottasium, Sodium & Chlorides increase the TDS level.

Reverse Osmosis System for home

A portable RO filter system at home has all the necessary components like UF & carbon membrane, RO membrane, Activated Carbon filter & UV lamp.

It has an inbuilt TDS controller, which makes sure that the TDS level in water is automatically controlled.

Herein, RO water filter would function nearly the same way as a RO plant.

A wall hanging pre-sedimentation filter is used for filtering larger water particles which may cause harm to the RO membrane.

This is also used in the case if the water tank in the house is not cleaned at regular intervals. It can invite unwanted floating particles in the RO filter.

Wall hanging pre-sedimentation filter for RO water purifier

Raw water is let in through this pre-sedimentation filter. Water pump sucks in this water & sends them to the RO membrane filter.

Harmful metals & salts are filtered by the RO membrane shown in the image.

RO Membrane used in Reverse Osmosis Water Purifier

Wastewater is pushed to the drainage system which has an extremely high concentration of unwanted water chemicals.

RO purified water is again pushed to pass through Ultra Filtration (UF) membrane & TDS controller.

UF membrane filters out harmful bacteria & viruses while retaining essential water minerals.

Next comes the TDS controller which helps retain water taste & essential minerals, converting hard water into soft water.

UV light kills any remaining pathogens in water while ensuring complete water hygiene.

Ultraviolet(UV) Filter in RO water purifier

Disinfection of water is complete after UV stage & filtered water is stored in the tank for use.

Reverse Osmosis works the same way, in case of a water treatment plant or a portable water purifier.

It is a future-ready dominant technology in the market. The only concern is high wastewater. It is controllable if we make some additional investments. It can be in the form of using more RO membranes to ensure less wastewater.

Companies should work together to make RO technology cheaper & more efficient. It will help increase its reach to every home & safeguard human life.

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