Water is a basic human necessity. We need it to stay hydrated, for irrigation and water recreation among other purposes. It removes contaminated and undesired components or at the very least, reduces their concentration so that it becomes usable for the desired end use.
There are many processes to achieve this but it depends on the purpose of the treatment. The most widely used treatment processes are those that are used to treat water for drinking, particularly municipal drinking water. It uses Pre-chlorination, aeration, coagulation, polyelectrolytes, sedimentation and filtration or a mixture of two or more. These processes are often complicated and require water treatment equipment to be performed correctly.
Reverse Osmosis is the most used form of water treatment. It uses membrane based technology for water treatment and depending on the equipment being used, one can treat from 24 gallons to millions per day.
The water is put through the membrane, which prevents contaminated water, cleaning solutions and undissolved solids from passing through. The membrane is semipermeable and pressure greater than the osmotic pressure is applied to treat the water. Many types of dissolved and suspended species can be removed from the water such as bacteria and it is used in industrial processes as well as in the production of potable water. Another noteworthy part of the process is that the solute is retained on the pressurized side of the membrane while the pure solvent is allowed to pass through to the other side. A shorter explanation would be that applying an external pressure to reverse the natural flow of pure solvent is reverse osmosis.
There are many reverse osmosis solutions available in the market, based on the number of required gallons per day. There are home based point of use reverse osmosis systems, systems for restaurants, aquariums and other SMEs that require up to a 1000 gallons per day and industrial level systems for municipal level plants and industry units that require more than 400,000 gallons per day. Depends on the need, really.