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After reading this article you will learn about the meaning and habitats of brackish water.
Meaning of Brackish Water:
Brackish water is water that has more salinity than fresh water, but not as much as seawater. It may result from mixing of seawater with fresh water, as in estuaries, or it may occur in brackish fossil aquifers. The word comes from the Middle Dutch root “brak”, meaning “salten” or “salty”.
Certain human activities can produce brackish water, in particular certain civil engineering projects such as dikes and the flooding of coastal marshland to produce brackish water pools for freshwater prawn farming.
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Brackish water is also the primary waste product of the salinity gradient power process. Because brackish water is hostile to the growth of most terrestrial plant species, without appropriate management it is damaging to the environment.
Technically, brackish water contains between 0.5 and 30 grams of salt per litre—more often expressed as 0.5 to 30 parts per thousand (ppt or %c). Thus, brackish covers a range of salinity regimes and is not considered a precisely defined condition. It is characteristic of many brackish surface waters that their salinity can vary considerably over space and/or time.
Habitats of Brackish Water:
Brackish water or briny water is water that has more salinity than fresh water, but not as much as seawater. It may result from mixing of seawater with fresh water, as in estuaries, or it may occur in brackish fossil aquifers.
Certain human activities can produce brackish water, in particular certain civil engineering projects such as dikes and the flooding of coastal marshland to produce brackish water pools for freshwater prawn farming.
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Brackish water is also the primary waste product of the salinity gradient power process. Because brackish water is hostile to the growth of most terrestrial plant species, without appropriate management it is damaging to the environment.
Technically, brackish water contains between 0.5 and 30 grams of salt per litre—more often expressed as 0.5 to 30 parts per thousand (ppt or %c). Thus, brackish covers a range of salinity regimes and is not considered a precisely defined condition. It is characteristic of many brackish surface waters that their salinity can vary considerably over space and/or time.
Water Salinity based on Dissolved Salts:
1. Estuaries:
Brackish water condition commonly occurs when fresh water meets sea water. In fact, the most extensive brackish water habitats worldwide are estuaries, where a river meets the sea. This type of ecological succession from fresh water to marine ecosystem is typical of river estuaries.
River estuaries form important staging points during the migration of anadromous and catadromous fish species, such as salmon and eels, giving them time to form social groups and to adjust to the changes in salinity.
Salmon are anadromous, meaning they live in the sea but ascend rivers to spawn; eels are catadromous, living in rivers and streams, but returning to the sea to breed. Besides the species that migrate through estuaries, there are many other fish that use them as “nursery grounds” for spawning or as places young fish can feed and grow before moving elsewhere.
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Estuaries are also commonly used as fishing grounds, and as places for fish farming or ranching.
2. Mangroves:
Another important brackish water habitat is the mangrove swamp or mangal. Many, though not all, mangrove swamps fringe estuaries and lagoons where the salinity changes with each tide.
Among the most specialised residents of mangrove forests are mud-skippers, fish that forage for food on land, and archer fish, perch-like fish that “spit” at insects and other small animals living in the trees, knocking them into the water where they can be eaten.
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Like estuaries, mangrove swamps are extremely important breeding grounds for many fish, with species such as snappers, halfbeaks, and tarpon spawning or maturing among them.
Besides fish, numerous other animals use mangroves, including such specialists as the saltwater, crocodile, American crocodile proboscis monkey, diamondback terrapin, and the crab-eating frog, Fejervaryaconcrivora (formerly Ranacancrivora). Mangroves represent important nesting site for numerous birds groups such as herons, storks, spoonbills, ibises, kingfishers, shorebirds and seabirds.
Although often plagued with mosquitoes and other insects that make them unpleasant for humans, mangrove swamps are very important buffer zones between land and sea, and are a natural defense against hurricane and tsunami damage in particular. The Sundarbans and Bhitarkanika mangroves are two of the large mangrove forests in the world, both on the coast of the Bay of Bengal.
3. Seas and Lakes:
Some seas and lakes are brackish. The Baltic Sea is a brackish sea adjoining the North Sea. Originally the confluence of two major river systems prior to the Pleistocene, since that it has been flooded by the North Sea but still receives so much freshwater from the adjacent lands that the water is brackish.
Because the salt water coming in from the sea is denser than freshwater, the water in the Baltic is stratified, with salt water at the bottom and freshwater at the top. Limited mixing occurs because of the lack of tides and storms, with the result that the fish fauna at the surface is freshwater in composition while that lower down in more marine.
Cod are an example of a species only found in deep water in the Baltic, while pike are confined to the less saline surface waters.
The Caspian Sea is the world’s largest lake and contains brackish water with a salinity about one-third that of normal seawater. The Caspian is famous for its peculiar animal fauna, including one of the few non-marine seals (the Caspian seal) and the great sturgeons, a major source of caviar.
In the Black Sea the surface water is brackish with an average salinity of about 17-18 parts per thousand compared to 30 to 40 for the oceans. The deep, anoxic water of the Black Sea originates from warm, salty water of the Mediterranean.
Reverse Osmosis systems can be used to remove both salts and organic materials from brackish water, enabling communities with limited fresh water to increase potable water for their inhabitants. Long lasting, highly efficient membranes reduce demineralization and desalination costs.
For the preservation of the effectiveness and life span of a Reverse Osmosis (RO) installation, a sufficient pre-treatment is required. A proper selection of pre-treatment methods for feed water will improve affectivity and extend the life span of the system by preventing or minimizing bio-fouling, scaling and membrane plugging.
To perform an uninterrupted and reliable pre-treatment of the feed water a special approach is used. A pre-treatment that is not geared to the installation may cause a system overload. When this occurs the system parts need cleaning much more often to restore productivity and salt retention. Cleaning costs, system performance and standstill time are very significant in that situation.
The kind of pre-treatment system that is used greatly depends on feed water quality. Consequentially, sufficient feed water pre-treatment is dependent on:
i. The source of the feed water
ii. The composition of the feed water
iii. The function of the feed water
When the source of the feed water that needs treatment is specified, a complete and exact water analysis is performed. This action is an important step for the design of a pre- treatment system and the entire Reverse Osmosis system, because this often determines the type and size of the pre-treatment.
i. Water Treatment Systems
ii. Reverse Osmosis Systems
a. Technical Specifications
iii. Nano filtration
a. Technical Specifications
iv. Ultrafiltration/Microfiltration
v. Electro ionization (EDI)
vi. Carbon Filtration
vii. Multimedia Filtration A
viii. Disinfection and Sterilization
a. Ozone Systems
b. UV Systems
ix. Water Types Treated
a. Salt water
b. Brackish water
c. Effluent
d. Potable water
e. Process water
x. Applications
a. Power plants
b. Beverage
c. Drinking water
d. Pharmaceutical water
xi. Components and Supplies
a. Membranes
b. Filters
c. Pumps.
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