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Methods

Vacuum distillation
The traditional process used in these operations is vacuum distillation—essentially boiling it to leave impurities behind. In desalination, atmospheric pressure is reduced, thus lowering the required temperature needed. Liquids boil when the vapor pressure equals the ambient pressure and vapor pressure increases with temperature. Effectively, liquids boil at a lower temperature, when the ambient atmospheric pressure is less than usual atmospheric pressure. Thus, because of the reduced pressure, low-temperature "waste" heat from electrical power generation or industrial processes can be employed.

Multi-stage flash distillation
Water is evaporated and separated from sea water through multi-stage flash distillation, which is a series of flash evaporations. Each subsequent flash process utilizes energy released from the condensation of the water vapor from the previous step.
Multiple-effect distillation
Multiple-effect distillation (MED) works through a series of steps called "effects". Incoming water is sprayed onto pipes which are then heated to generate steam. The steam is then used to heat the next batch of incoming sea water. To increase efficiency, the steam used to heat the sea water can be taken from nearby power plants.[7] Although this method is the most thermodynamically efficient among methods powered by heat,[8] a few limitations exist such as a max temperature and max number of effects.

Vapor-compression distillation
Vapor-compression evaporation involves using either a mechanical compressor or a jet stream to compress the vapor present above the liquid.[8] The compressed vapor is then used to provide the heat needed for the evaporation of the rest of the sea water.[7] Since this system only requires power, it is more cost effective if kept at a small scale.

Reverse osmosis
The leading process for desalination in terms of installed capacity and yearly growth is reverse osmosis (RO).[10] The RO membrane processes use semipermeable membranes and applied pressure (on the membrane feed side) to preferentially induce water permeation through the membrane while rejecting salts. Reverse osmosis plant membrane systems typically use less energy than thermal desalination processes.[8] Desalination processes are driven by either thermal (e.g., distillation) or electrical (e.g., RO) as the primary energy types. Energy cost in desalination processes varies considerably depending on water salinity, plant size and process type. At present the cost of seawater desalination, for example, is higher than traditional water sources, but it is expected that costs will continue to decrease with technology improvements that include, but are not limited to, improved efficiency,[11] reduction in plants footprint, improvements to plant operation and optimization, more effective feed pretreatment, and lower cost energy sources.

The Reverse Osmosis process is not maintenance free. Various factors interfere with efficiency: ionic contamination (calcium, magnesium etc.); DOC; bacteria; viruses; colloids & insoluble particulates; biofouling and scaling. In extreme cases the RO membranes are destroyed. To mitigate damage, various pretreatment stages are introduced. Anti-scaling inhibitors include acids and other agents like the organic polymers Polyacrylamide and Polymaleic Acid), Phosphonates and Polyphosphates. Inhibitors for fouling are biocides (as oxidants against bacteria and viruses), like chlorine, ozone, sodium or calcium hypochlorite. At regular intervals, depending on the membrane contamination; fluctuating seawater conditions; or when prompted by monitoring processes, the membranes need to be cleaned, known as emergency or shock-flushing. Flushing is done with inhibitors in a fresh water solution and the system must go offline. This procedure is environmental risky, since contaminated water is diverted into the ocean without treatment. Sensitive marine habitats can be irreversibly damaged.

Freeze-thaw
Freeze-thaw desalination uses freezing to remove fresh water from salt water. Salt water is sprayed during freezing conditions into a pad where an ice-pile builds up. When seasonal conditions warm, naturally desalinated melt water is recovered. This technique relies on extended periods of natural sub-freezing conditions.

A different freeze-thaw method, not weather dependent and invented by Alexander Zarchin, freezes seawater in a vacuum. Under vacuum conditions the ice, desalinated, is melted and diverted for collection and the salt is collected.

Solar evaporation
Solar evaporation mimics the natural water cycle, in which the sun heats the sea water enough for evaporation to occur. After evaporation, the water vapor is condensed onto a cool surface.

Electrodialysis reversal
Electrodialysis utilizes electric potential to move the salts through pairs of charged membranes, which trap salt in alternating channels.

Membrane distillation
Membrane distillation uses a temperature difference across a membrane to evaporate vapor from a salty brine solution and condense pure condensate on the colder side.

Wave-powered desalination
CETO is a wave power technology that desalinates seawater using submerged buoys.[18] Wave-powered desalination plants began operating on Garden Island in Western Australia in 2013 and in Perth in 2015.

Desalination Rubber-lining Piping

• ProjectSohar / Sabiya / Shuaiba / JSTPP / Shuqaiq etc.
• SiteUAE
• DimensionsN/A
• Weight4,121 TON