Editing Desalination (section)

=== Distillation ===

====Solar distillation====
[[Solar distillation]] mimics the natural water cycle, in which the sun heats sea water enough for evaporation to occur.<ref name=Khawaji /> After evaporation, the water vapor is condensed onto a cool surface.<ref name=Khawaji /> There are two types of solar desalination. The first type uses photovoltaic cells to convert solar energy to electrical energy to power desalination. The second type converts solar energy to heat, and is known as solar thermal powered desalination.

====Natural evaporation====
Water can evaporate through several other physical effects besides [[solar irradiation]]. These effects have been included in a multidisciplinary desalination methodology in the [[IBTS Greenhouse]]. The IBTS is an industrial desalination (power)plant on one side and a greenhouse operating with the natural water cycle (scaled down 1:10) on the other side. The various processes of evaporation and condensation are hosted in low-tech utilities, partly underground and the architectural shape of the building itself. This integrated biotectural system is most suitable for large scale [[desert greening]] as it has a km<sup>2</sup> footprint for the water distillation and the same for landscape transformation in desert greening, respectively the regeneration of natural fresh water cycles.{{citation needed|date=March 2021}}

====Vacuum distillation====
In [[vacuum distillation]] atmospheric pressure is reduced, thus lowering the temperature required to evaporate the water. 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 evaporation]]s.<ref name=Khawaji>{{cite journal|last1=Khawaji|first1=Akili D.|last2=Kutubkhanah|first2=Ibrahim K.|last3=Wie|first3=Jong-Mihn|title=Advances in seawater desalination technologies|journal=Desalination|volume=221|issue=1–3|pages=47–69|doi=10.1016/j.desal.2007.01.067|date=March 2008|bibcode=2008Desal.221...47K }}</ref> Each subsequent flash process uses energy released from the condensation of the water vapor from the previous step.<ref name=Khawaji />

====Multiple-effect distillation====
[[Multiple-effect distillation]] (MED) works through a series of steps called "effects".<ref name=Khawaji /> 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.<ref name=Khawaji />  To increase efficiency, the steam used to heat the sea water can be taken from nearby power plants.<ref name=Khawaji /> Although this method is the most thermodynamically efficient among methods powered by heat,<ref name=WarsingerEntropy>{{cite journal|last1=Warsinger|first1=David M.|last2=Mistry|first2= Karan H.|last3=Nayar|first3=Kishor G.|last4=Chung|first4=Hyung Won|last5=Lienhard V|first5=John H.|title=Entropy Generation of Desalination Powered by Variable Temperature Waste Heat|journal=Entropy|volume=17|issue=12|pages=7530–7566|doi=10.3390/e17117530|date=2015|bibcode=2015Entrp..17.7530W|url=http://dspace.mit.edu/bitstream/1721.1/100423/1/Entropy%20Generation%20of%20Desalination%20Powered%20by%20Variable%20Temperature%20Waste%20Heat%2c%20Warsinger.pdf|doi-access=free}}</ref> a few limitations exist such as a max temperature and max number of effects.<ref name="Al-Shammiri">{{cite journal|title=Multi-effect distillation plants: state of the art|last2=Safar|first2=M.|date=November 1999|journal=Desalination|volume=126|issue=1–3|pages=45–59|doi=10.1016/S0011-9164(99)00154-X|last1=Al-Shammiri|first1=M.|bibcode=1999Desal.126...45A }}</ref>

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

==== Membrane distillation ====
[[Membrane distillation]] uses a temperature difference across a membrane to evaporate vapor from a brine solution and condense pure water on the colder side.<ref name="WarsingerFramework">{{cite journal|last1=Warsinger|first1=David M.|last2=Tow|first2=Emily W.|last3=Swaminathan|first3=Jaichander|last4=Lienhard V|first4=John H.|date=2017|title=Theoretical framework for predicting inorganic fouling in membrane distillation and experimental validation with calcium sulfate|url=https://dspace.mit.edu/bitstream/1721.1/107916/1/Theoretical%20framework%20for%20predicting%20inorganic%20fouling%20in%20membrane%20distillation%20and%20experimental%20validation%20with%20calcium%20sulfate-%20warsinger%20preprint.pdf|journal=Journal of Membrane Science|volume=528|pages=381–390|doi=10.1016/j.memsci.2017.01.031|doi-access=free}}</ref> The design of the membrane can have a significant effect on efficiency and durability. A study found that a membrane created via co-axial [[electrospinning]] of [[Polyvinylidene fluoride|PVDF]]-[[Hexafluoropropylene|HFP]] and [[Aerogel|silica aerogel]] was able to filter 99.99% of salt after continuous 30-day usage.<ref>{{Cite web|last=Irving|first=Michael|date=July 6, 2021|title=Mixed up membrane desalinates water with 99.99 percent efficiency|url=https://newatlas.com/materials/desalination-membrane-coaxial-electrospinning-nanofibers/|url-status=live|access-date=2021-07-07|website=New Atlas|language=en-US|archive-url=https://web.archive.org/web/20210706034413/https://newatlas.com/materials/desalination-membrane-coaxial-electrospinning-nanofibers/ |archive-date=July 6, 2021 }}</ref>