Membrane processes refer to physical methods for separating a solvent from its dissolved salts using semipermeable membranes. These processes have made great progress in recent years. The history of using membranes for filtration dates back to the early 20th century.

The process of ion exchange has been used since ancient times. Eratosthenes Thallis used this process to contact salt water with soil to produce fresh water. In 1845, Thomson showed that when water containing ammonium sulfate was passed through soil, calcium sulfate would be produced in the effluent.

Softening processes are used to reduce water hardness. Using chemicals, water hardness undergoes chemical reactions and precipitates. As a result, water hardness is reduced. Water hardness is due to the presence of carbonates, sulfates, chlorides, and nitrates of the metals calcium, magnesium, iron, and aluminum.

Water transmission systems include the channels necessary to transport water from one point to another. In most cases, it is necessary to transport water from its source to a treatment facility and from there to consumers. Pumping is used to provide the energy necessary to move the water from the beginning to the end of the transmission system. Pumping stations are usually located at the raw water intake, treatment plant and distribution network.

The impact of plastic pipes on water quality in household plumbing and water distribution systems causes leakage of metals such as lead into drinking water. Lead, as the most widespread heavy and toxic element in the environment, is naturally present in river water at a level of 1 to 10 micrograms per liter. Lead compounds enter water sources as a result of mining, battery manufacturing, fossil fuel, paint, and glass and enamel industries.

Preliminary treatment is performed to optimize the use of membranes and increase membrane operating time. During this operation, water is prepared to pass through the membrane.

Osmosis is the movement of a solvent from a dilute solution to a concentrated solution through a semipermeable membrane. Reverse osmosis is a widely used separation technique with a variety of applications. Desalination of seawater and separation of organic and toxic substances from industrial wastewater are two important applications of this technology.

Water is the source of life and the continuation of life for living organisms, as well as a fundamental factor in the emergence of human communities and civilizations. Today, the total volume of the Earth's water, which is the source of life for all organisms, has remained almost constant and unchanging since its formation. These water resources were created about 4.5 billion years ago.

Pure water does not exist in nature due to its high solubility and contains various impurities. Water impurities are classified into three general categories: dissolved solids, suspended and colloidal solids, and gases.