Applications and Desalination of Reverse Osmosis

Today we are going to discuss about the applications and desalination of reverse osmosis. Around the world, household drinking water purification systems, including a reverse osmosis step, are commonly used for improving water for drinking and cooking. Such systems typically include a number of steps:

• A sediment filter to trap particles, including rust and calcium carbonate.
• Optionally, a second sediment filter with smaller pores.
• An activated carbon filter to trap organic chemicals and chlorine, which will attack and degrade TFC reverse osmosis membranes.
• A reverse osmosis (RO) filter, which is a thin film composite membrane (TFM or TFC).
• Optionally, a second carbon filter to capture those chemicals not removed by the RO membrane.
• Optionally a ultra-violet lamp for sterilizing any microbes that may escape filtering by the reverse osmosis membrane.

In some systems, the carbon pre-filter is omitted, and cellulose triacetate membrane (CTA) is used. The CTA membrane is prone to rotting unless protected by chlorinated water, while the TFC membrane is prone to breaking down under the influence of chlorine. In CTA systems, a carbon post filter is needed to remove chlorine from the final product, water.

Portable reverse osmosis (RO) water processors are sold for personal water purification in various locations. To work effectively, the water feeding to these units should be under some pressure (40 psi or greater is the norm).

Portable RO water processors can be used by people who live in rural areas without clean water, far away from the city’s water pipes. Rural people filter river or ocean water themselves, as the device is easy to use (saline water may need special membranes).

Some travelers on long boating, fishing, or island camping trips, or in countries where the local water supply is polluted or substandard, use RO water processors coupled with one or more UV sterilizers.

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RO systems are also now extensively used by marine aquarium enthusiasts. In the production of bottled mineral water, the water passes through an RO water processor to remove pollutants and microorganisms.

In European countries, though, such processing of Natural Mineral Water (as defined by a European Directive) is not allowed under European law. In practice, a fraction of the living bacteria can and do pass through RO membranes through minor imperfections, or bypass the membrane entirely through tiny leaks in surrounding seals.

Thus, complete RO systems may include additional water treatment stages that use ultraviolet light or ozone to prevent microbiological contamination.

In the United States military, Reverse Osmosis Water Purification Units are used on the battlefield and in training. Capacities range from 1,500 to 150,000 imperial gallons (6,800 to 680,000 l) per day, depending on the need.

The most common of these are the 600 and 3,000 gallons per hour units; both are able to purify salt water and water contaminated with chemical, biological, radiological, and nuclear agents from the water.

During 24-hour period, at normal operating parameters, one unit can produce 12,000 to 60,000 imperial gallons (55,000 to 270,000 l) of water, with a required 4-hour maintenance window to check systems, pumps, RO elements and the engine generator.

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