Reverse osmosis (RO) is a filtration technology for water purification that removes dissolved impurities using a tightly coiled, semi-permeable membrane. Pressure applied before the membrane causes the fluid to flow from a zone of high solute concentration to a region of low solute concentration, overcoming natural osmotic pressure and redirecting dissolved impurities, resulting in fine filtration of water or any solution. Similar to a paper towel roll, the membrane is made up of numerous layers of wound material. The water flows from the membrane's outer layers to its interior layers.

While the pure water travels through the layers into the center permeate rube, the contaminated water is pushed and exits the membrane on the opposing side of the incoming water. As the fluid spirals through the numerous tightly wrapped layers of the membrane and into the inner permeate tube, all micro-contaminants are separated and removed, and the purified water is collected for usage.

COMMERCIAL RO: THE PROCESS

The RO membrane functions as a filter, allowing only water molecules to flow through while preventing dissolved contaminants from passing through. To counteract the osmotic pressure of the membrane and drive the pure water molecules through it, high pressure is applied to the impure water. Almost all dissolved chemicals, minerals, and salts, as well as heavy metals, large molecular weight organic pollutants, and microbes, are removed by RO. The water that results is 95-99 percent clean. Typically, wastewater is disposed of through the municipal sewer system.

A reverse osmosis system's capacity is determined by various factors, including:

• Temperature of the water
• The dissolved solids concentration in the input water
• The feed water is operated at a constant pressure.

Taking an example of sugar industry,

1 Begin with two cups, one with ordinary water and the other with water and sugar dissolved in it. The U-tube, which is a beaker fashioned in a U-shape, is then utilized.

2 Imagine a piece in the middle of the tube, cutting the U in half. Our "semipermeable membrane" is a thin plastic with a billion microscopic holes that let water vapor pass through while keeping liquid out.

3.Plain water is poured into one arm of the U-tube, while sugar water is pumped into the other. The osmosis process starts at this point. As plain water passes through, the volume of liquid in the sugar water arm will gradually grow, equating the sugar-to-water ratio on both sides of the arm.

4.This is because the water has reached a state of equilibrium. Because one side of the arm is clogged with sugar, clean water from the other side decides to migrate over to equalize the concentration or until the osmotic pressure (the pressure that occurs as molecules travel) is attained.

5.A lower-concentrate solution will filter its solvent to a higher-concentrate solution through osmosis. In reverse osmosis, we simply reverse the process by filtering our solvent out of the high concentrate solution and into the lower concentrate solution. Rather than achieving a better balance of solvent and solute in both solutions, it separates the solute from the solvent (the sugar from water).

6.Because solutions do not want to accomplish this, pressure is introduced to the equation to cause reverse osmosis to occur. Water is forced to travel through the membrane by pressure, which removes contaminants from the water.

RO: APPLICATIONS

Purification of Municipal Water

Municipal water is used for both home and commercial purposes. In industry, the requirement for high-quality water extends far beyond cooking and washing. The food and beverage business pursues quality control so that a soda's or recipe's flavor remains constant no matter where it is consumed. The pharmaceutical and chemical industries are both adversely affected by poor water quality due to microbial contamination, chemical residue, salinity, and other factors. Commercial reverse osmosis systems are widely used in municipal water purification to ensure high-quality water.

Desalination of Seawater

Oceans and seas with salt levels of up to 35,000 mg/l are the only source of water for many populated places. This high salinity water is also used in marine industrial applications, off-shore drilling, maritime transit, and cruise ships. Continuous usage of high-salt water can harm marine equipment and render it unsafe for human consumption. As a result, the marine industries build high-pressure commercial reverse osmosis systems with specific membranes to remove the salt content from saltwater. It aids in desalination as well as chemical and bacterial pollution reduction.

Desalination of Brackish Water

Brackish water is a mixture of fresh and salt water that contains 1,000 to 15,000 mg/L of dissolved salts. Water with a salinity of less than 500 mg/L is recommended for industrial and potable water applications, according to the WHO. Desalination of brackish water is also done using the reverse osmosis (RO) method.

Boiler Feed Water

Hard water is a problem for industrial boilers. Scaling, thermal transfer defects, greater downtime for cleaning, and a shorter boiler vessel life cycle are all concerns caused by using hard water at high temperatures. As a result, only softened water should be used to supply and feed the boiler system. Industries such as mechanical, chemical, pharmaceutical, and lumber/pulp use reverse osmosis systems for pre-boiling water treatment/conditioning to attain this purpose.

Wastewater Treatment

One of the water purification procedures used in the water treatment industry is reverse osmosis. Chemical, bacterial, and dissolved contaminants are frequently removed using reverse osmosis as the final step. In the wastewater industry, reverse osmosis (RO) systems are used for tertiary water treatment. Similarly, before being disposed of, industrial wastewater is processed with a reverse osmosis (RO) system. Reverse osmosis systems are used in industrial grey water treatment, blackwater treatment, and other applications.

Spot-free Rinse

Salt-free water is frequently required in industrial manufacturing, equipment cleaning, and even commercial applications such as car washing, surface rinsing, and so on. Due to the presence of chemicals or magnesium and calcium salts in hard water, it causes scaling, hard surface patches, and even surface bleaching. To reduce equipment damage and extend the product lifecycle, the rinse water is filtered using reverse osmosis systems.