Membrane technology has been dominating the desalination and brackish water treatment. Brackish water reverse osmosis processes account for much of the global capacity of desalination plants. The reverse osmosis is possible through high rejection water membranes. Read this article to know more about the reverse osmosis process.
What is the reverse osmosis process?
Reverse osmosis is a process that separates the pure solvent from the solute with the help of membranes. In short, it is the process that forces the solvent from high solute concentration via a membrane to low solute concentration through pressure application on osmotic pressure. This method is just the reverse of the usual osmosis process which is the solvent movement from the place of low solute concentration to the place of high solute concentration but here external pressure is not applied. In this process, membranes are semi-permeable.
The reverse osmosis process is known best for its usage in desalination but is also used in purifying fresh water for industrial, domestic and medical applications since the 1970s. The same setup as the osmosis process is needed in reverse osmosis where the pressure is applied. In this scenario, two forces influence the water movement – a) pressure that is caused by solute concentration difference in between the compartments (it is osmotic pressure) and b) Pressure applied externally.
What are some of the important applications of reverse osmosis systems?
You can find vital applications of the reverse osmosis method. Have a look at those:
a) Purification of Drinking water
Most household drinking water purification systems throughout the world include reverse osmosis methods. It is used to improve the water for cooking as well as drinking. Such kind of systems consist of some steps:
> The sediment filter present in the system traps the particles that include calcium carbonate and rust. A second sediment filter is optional with little pores.
> Consists of an activated carbon filter that traps the organic chemical that can harm TFC reverse osmosis water membranes
> A RO (reverse osmosis) filter – thin film composite membrane
> The second filter of carbon may be present that can capture the chemicals which are not eliminated through RO membranes.
> Ultra-violet lamps may be there to disinfect the microbes
Many portable reverse osmosis water processors are available for personal water purification in many areas. To make them work efficiently, water feeding in these units can work best but under 40 psi pressure or greater than that too. The portable reverse osmosis water processors are used majorly by the people living in rural areas where access to clean water is quite far away from the water pipes. Even travellers on island camping or fishing use these water processors along with ultraviolet sterilizers. If we talk about bottled mineral water production, water passes via a reverse osmosis water processor to eliminate pollutants along with microorganisms. The whole RO process may consist of some additional stages of treatment that may use ozone or ultra-violet to avoid microbiological contamination.
b) Food industry
In addition to the desalination process, reverse osmosis is much more cost-efficient to concentrate food liquids like fruit juices than the traditional heat-treatment methods. The benefits of having RO systems installed include: less operating cost with the capacity to prevent usage of heat treatment process makes RO apt especially for heat-sensitive substances such as enzymes and protein.
c)For Dialysis:
The reverse osmosis process is quite the same as the procedure used in dialysis, used by those people having kidney failure. Blood passes from the body through the catheter across the filter to a dialysis machine.
d) In washing cars
Reverse osmosis is sometimes used for car washing at the time of the last vehicle rinsing to avoid water spotting on vehicles. RO method helps in displacing heavy mineral reclamation water and it also enables the operator of car washing to lessen the need for vehicle drying tools like air blowers.
e) Filtering brackish water
The reverse osmosis process is the perfect method to filter brackish water from a well or tap. With the correct RO filtration system and high rejection water membranes, you can turn brackish water into drinkable water which can be free of salt.
Membranes used for reverse osmosis:
Membranes that are used for the reverse osmosis process have a layer of thick barrier made of polymer matrix where most of the separation happens. In almost every case, the reverse osmosis membranes are specially designed for allowing just water to pass via dense layers. This helps in warding off the solutes passage like salt ions. This method needs exertion of high pressure on the membrane’s high concentration side (that is around 2 bar to 17 bar or 3- psi to 250 psi) for both fresh as well as brackish water. For seawater, it is – 40 bar to 70 bar or 600 psi to–1000 psi.
In the industry of water treatment, there is a list of kinds of contaminants, about their sizes & which pass via several kinds of membranes. Usually, the pore size of membranes varies from 1 – 50000 angstroms but that depends on the kind of filter used. Reverse osmosis is the last stage of membrane filtration that eliminates the particles which are larger than 1 Å.
What are brackish water membranes?
The reverse osmosis filtration method is the common kind of filtration used for desalination for reducing total dissolved solids in water. This process depends on the pressure that forces water via a reverse osmosis water membrane. This membrane helps in isolating water from impurities. Reverse osmosis membranes are used for desalination purposes and can also be used for wastewater treatment, elimination of trace calcium, phosphates, and some other substances, water reuse etc.
Brackish water has salinity more than freshwater but not like seawater. The brackish water membranes or high rejection water membranes are used in various applications that include potable water, desalination, industrial process water and so on.
So, you must have got a brief knowledge about the reverse osmosis process and its applications. People always want water free of contaminants that include chemicals, metal etc. Every filtration system must include the reverse osmosis method.
