Salt evaporation pond

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Salt evaporation pond in Ile de Re, France MaraisSalant.JPG
Salt evaporation pond in Île de Ré, France

A salt evaporation pond is a shallow artificial salt pan designed to extract salts from sea water or other brines. Natural salt pans are geological formations that are also created by water evaporating and leaving behind salts. Some salt evaporation ponds are only slightly modified from their natural version, such as the ponds on Great Inagua in the Bahamas, or the ponds in Jasiira, a few kilometres south of Mogadishu, where seawater is trapped and left to evaporate in the sun.


The seawater or brine is fed into large ponds and water is drawn out through natural evaporation which allows the salt to be subsequently harvested.

The ponds also provide a productive resting and feeding ground for many species of waterbirds, which may include endangered species. [1] The ponds are commonly separated by levees. Salt evaporation ponds may also be called salterns, salt works or salt pans.

Algae and color

San Francisco Bay salt ponds Salt ponds SF Bay (dro!d).jpg
San Francisco Bay salt ponds

Due to variable algal concentrations, vivid colors (from pale green to bright red) are created in the evaporation ponds. The color indicates the salinity of the ponds. Microorganisms change their hues as the salinity of the pond increases. In low- to mid-salinity ponds, green algae such as Dunaliella salina are predominant, although these algae can also take on an orange hue. In middle- to high-salinity ponds, Halobacteria, which is actually a group of halophilic Archaea (sometimes called Haloarchaea), shift the colour to pink, red and orange. Other bacteria such as Stichococcus also contribute tints.[ citation needed ]


Notable salt ponds include:

Until World War II, salt was extracted from sea water in a unique way in Egypt near Alexandria. [8] Posts were set out on the salt pans and covered with several feet of sea water. In time the sea water evaporated, leaving the salt behind on the post, where it was easier to harvest.


Salt pans are shallow open, often metal, pans used to evaporate brine. They are usually found close to the source of the salt. For example, pans used in the solar evaporation of salt from sea water are usually found on the coast, while those used to extract salt from solution-mined brine will be found near to the brine shaft. In this case, extra heat is often provided by lighting fires underneath.

See also

Related Research Articles

The halophiles, named after the Greek word for "salt-loving", are extremophiles that thrive in high salt concentrations. While most halophiles are classified into the domain Archaea, there are also bacterial halophiles and some eukaryotic species, such as the alga Dunaliella salina and fungus Wallemia ichthyophaga. Some well-known species give off a red color from carotenoid compounds, notably bacteriorhodopsin. Halophiles can be found in water bodies with salt concentration more than five times greater than that of the ocean, such as the Great Salt Lake in Utah, Owens Lake in California, the Dead Sea, and in evaporation ponds. They are theorized to be a possible candidate for extremophiles living in the salty subsurface water ocean of Jupiter's Europa and other similar moons.

Lithium carbonate Chemical compound

Lithium carbonate is an inorganic compound, the lithium salt of carbonate with the formula Li
. This white salt is widely used in the processing of metal oxides, and as a drug for the treatment of mood disorders.

Brine A highly concentrated solution of a salt in water

Brine is a high-concentration solution of salt (NaCl) in water (H2O). In diverse contexts, brine may refer to the salt solutions ranging from about 3.5% (a typical concentration of seawater, on the lower end of that of solutions used for brining foods) up to about 26% (a typical saturated solution, depending on temperature). Brine forms naturally due to evaporation of ground saline water but it is also generated in the mining of sodium chloride. Brine is used for food processing and cooking (pickling and brining), for de-icing of roads and other structures, and in a number of technological processes. It is also a by-product of many industrial processes, such as desalination, so it requires wastewater treatment for proper disposal or further utilization (fresh water recovery).

Sea salt Salt produced from the evaporation of seawater

Sea salt is salt that is produced by the evaporation of seawater. It is used as a seasoning in foods, cooking, cosmetics and for preserving food. It is also called bay salt, solar salt, or simply salt. Like mined rock salt, production of sea salt has been dated to prehistoric times.

Seawater Water from a sea or an ocean

Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5%. This means that every kilogram of seawater has approximately 35 grams (1.2 oz) of dissolved salts. Average density at the surface is 1.025 kg/l. Seawater is denser than both fresh water and pure water because the dissolved salts increase the mass by a larger proportion than the volume. In comparison, most human physiological saline levels are approximately one quarter of this, for example blood is 9g/l. The freezing point of seawater decreases as salt concentration increases. At typical salinity, it freezes at about −2 °C (28 °F). The coldest seawater still in the liquid state ever recorded was found in 2010, in a stream under an Antarctic glacier: the measured temperature was −2.6 °C (27.3 °F). Seawater pH is typically limited to a range between 7.5 and 8.4. However, there is no universally accepted reference pH-scale for seawater and the difference between measurements based on different reference scales may be up to 0.14 units.

Salt pan (geology) Flat expanse of ground covered with salt and other minerals

Natural salt pans or salt flats are flat expanses of ground covered with salt and other minerals, usually shining white under the sun. They are found in deserts and are natural formations.

Lake Grassmere / Kapara Te Hau

Lake Grassmere / Kapara Te Hau is a New Zealand lake in the northeastern South Island, close to Cook Strait. The lake is used for the production of salt.

History of salt

Salt, also referred to as table salt or by its chemical formula NaCl, is an ionic compound made of sodium and chloride ions. All life has evolved to depend on its chemical properties to survive. It has been used by humans for thousands of years, from food preservation to seasoning. Salt's ability to preserve food was a founding contributor to the development of civilization. It helped eliminate dependence on seasonal availability of food, and made it possible to transport food over large distances. However, salt was often difficult to obtain, so it was a highly valued trade item, and was considered a form of currency by certain people. Many salt roads, such as the via Salaria in Italy, had been established by the Bronze Age.

Searles Lake

Searles Lake is an endorheic dry lake in the Searles Valley of the Mojave Desert, in northwestern San Bernardino County, California. The lake in the past was also called Slate Range Lake and Borax Lake.

<i>Fleur de sel</i>

Fleur de sel or flor de sal is a salt that forms as a thin, delicate crust on the surface of seawater as it evaporates. Fleur de sel has been collected since ancient times, and was traditionally used as a purgative and salve. It is now used as a finishing salt to flavor and garnish food. The name comes from the flower-like patterns of crystals in the salt crust.

Saltern Area or installation for making salt

A saltern is an area or installation for making salt. Salterns include modern salt-making works (saltworks), as well as hypersaline waters that usually contain high concentrations of halophilic microorganisms, primarily haloarchaea but also other halophiles including algae and bacteria.

Osmotic power Energy available from the difference in the salt concentration between seawater and river water

Osmotic power, salinity gradient power or blue energy is the energy available from the difference in the salt concentration between seawater and river water. Two practical methods for this are reverse electrodialysis (RED) and pressure retarded osmosis (PRO). Both processes rely on osmosis with membranes. The key waste product is brackish water. This byproduct is the result of natural forces that are being harnessed: the flow of fresh water into seas that are made up of salt water.

Open-pan salt making

Open-pan salt making is a method of salt production wherein salt is extracted from brine using open pans.

Salar de Atacama

Salar de Atacama is the largest salt flat in Chile. It is located 55 km (34 mi) south of San Pedro de Atacama, is surrounded by mountains, and has no drainage outlets. In the east it is enclosed by the main chain of the Andes, while to the west lies a secondary mountain range of the Andes called Cordillera de Domeyko. Large volcanoes dominate the landscape, including the Licancabur, Acamarachi, Aguas Calientes and the Láscar. The last is one of the most active volcanoes in Chile. All of them are located along the eastern side of the Salar de Atacama, forming a generally north-south trending line of volcanoes that separate it from smaller endorheic basins.

<i>Haloquadratum</i> Genus of archaea

Haloquadratum is a genus of archaean, belonging to the family Halobacteriaceae. The first species to be identified in this group, Haloquadratum walsbyi, is unusual in that its cells are shaped like square, flat boxes.

Bittern, or nigari, is the salt solution formed when halite precipitates from seawater or brines. Bitterns contain magnesium, calcium, and potassium ions as well as chloride, sulfate, iodide, and other ions.

A seawater greenhouse is a greenhouse structure that enables the growth of crops and the production of fresh water in arid regions which constitute about one third of the earth's land area. This in response to the global water scarcity and peak water and the salt-infecting soil. The system uses seawater and solar energy. It uses a similar structure to the pad-and-fan greenhouse, but with additional evaporators and condensers. The seawater is pumped into the greenhouse to create a cool and humid environment, the optimal conditions for the cultivation of temperate crops. The freshwater is produced in a condensed state created by the solar desalination principle, which removes salt and impurities. Finally, the remaining humidified air is expelled from the greenhouse and used to improve growing conditions for outdoor plants.

Bromine production in the United States

Bromine production in the United States of 225,000 tonnes in 2013 made that country the second-largest producer of bromine, after Israel. The US supplied 29 percent of world production. Since 2007, all US bromine has been produced by two companies in southern Arkansas, which extract bromine from brine pumped from the Smackover Formation. At an advertised price of US$3.50 to US$3.90 per kg, the US 2013 US production would have a value of roughly US$800 million.

Brine mining is the extraction of useful materials which are naturally dissolved in brine. The brine may be seawater, other surface water, groundwater, or hyper-saline solutions from several industries. It differs from solution mining or in-situ leaching in that those methods inject water or chemicals to dissolve materials which are in a solid state; in brine mining, the materials are already dissolved.

San Francisco Bay Salt Ponds Salt evaporation ponds in the San Francisco Bay in California

The San Francisco Bay Salt Ponds are an approximately 16,500-acre (6,700 ha) part of the San Francisco Bay that have been used as salt evaporation ponds since the California Gold Rush era. Most of the ponds were once wetlands in the cities of Redwood City, Newark, Hayward and other parts of the bay.


  1. Athearn, Nicole D.; Takekawa, John Y.; and Shinn, Joel M. (2009) Avian response to early tidal salt marsh restoration at former commercial salt evaporation ponds in San Francisco Bay, California, USA, Natural Resources and Environmental Issues: Vol. 15, Article 14.
  2. Napa Salt Pond Complex Archived 2011-08-19 at the Wayback Machine , The Bay Institute
  3. Salt ponds, South San Francisco Bay, NASA Earth Observatory
  4. "NASA Helps Reclaim 15,100 Acres Of San Francisco Bay Salt Ponds". Space Daily. Moffett Field. July 14, 2003.
  5. "Archived copy". Archived from the original on 2011-08-07. Retrieved 2011-08-09.CS1 maint: archived copy as title (link)
  6. "The Salt Works". 19 July 2011.
  7. "Baleni Cultural Camp". African Ivory Route. Transfrontier Parks Destinations. Retrieved 11 September 2019.
  8. Salt, Grown On Sticks Harvested From Sea, Popular Science, March 1933