Salt Water Filtration

Desalination, a form of salt water filtration of seawater or brackish groundwater or river water for a public safe water supply is increasingly being acknowledged or adopted around the world in areas where the need has been increasing beyond sustainable supply.
Rapidly increasing populations are also placing pressure on present water sources, forcing governments to turn to salt water filtration to provide additional water supplies when existing sources are fully needed. There is also potential for salt water filtration to process already treated wastewater, usually returned to the environment, to a higher quality level for utilization in industry or mining processing, thus taking industrial need away from public water supplies. An additional benefit of this would be decreasing the volume of treated wastewater disposed to the environment. This option can make water at a lower cost of treating sea water in many cases.
Salt water filtration for most public supply is already used in fairly extensive areas such as the Middle East and North Africa, the Caribbean, Southern Europe and now in China, Singapore and the USA.
A desalination plant which uses salt water filtration essentially divides saline water into two streams: one with a low concentration of dissolved salts (the fresh water stream) and the other containing the remaining dissolved salts (the concentrate or brine stream). The plant needs energy to work and can use a numerous amount of different technologies for the division of the saline water. The amount of the feed water discharged to waste in the brine stream varies from 20 -70 % of the feed flow, relying on the technology used and the salt content of the feed water.
Salt water filtration is becoming more economically usable as the technology develops. Desalination plants can be given a wide range of outputs to provide small isolated communities or to contribute fairly enough to water supplies for large cities and even for irrigation (Spain, United Arab Emirates).
One of the processes for salt water filtration is reverse osmosis (RO). It is a membrane division process in which the water from a pressurized saline solution is segregated from the dissolved material by flowing through a membrane. No fire is needed for this separation. The major energy needed for desalination salt water filtration is for pressurizing the feed water. In principle, the saline feed water is pumped into a closed container where it is pressurized to overcome the osmotic pressure of the solution before diffusing through the membrane. As a portion of the water moves through the membrane, the remaining feed water heightens in salt content. This portion of this feed water is then discharged without going through the membrane.
A distinct benefit of salt water filtration of seawater is that it is climate proof and can continue to operate at full capacity even if declining rainfall means dam storages and rivers are draining and groundwater dwindling. However, salt water filtration needs stringent marine environment management.