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In the water body, when the fluorine content is greater than the standard, it is called fluorine exceedance, also known as high fluoride water. Dissolved solids content of 1500mg l, it is called brackish water. Fluorine is a non-metallic chemical element, ranked ninth in the periodic table, belonging to the main group of elements of the seventh group of the second period, the chemical properties are very active, almost can not exist alone, in nature are in the state of various compounds, widely found in rocks, soil, oceans, the distribution on the earth is quite extensive.
When the fluoride is high, it is easy to cause fluorosis. Fluorine is still widely used in daily life, including medicine, chemical industry, aerospace, atomic energy and other applications. For example, sodium fluoride itself is a toxic substance, but it can also be used as a drug or insecticide.
Endemic fluorosis is because people live in this high fluoride environment, long-term excessive intake of fluoride causes changes in chronic poisoning of the body, mainly affecting the hard tissues of the human body, including teeth, bones, and damage to some other soft tissues, of course, the most obvious clinical manifestations are dental fluorosis and skeletal fluorosis. Fluoride can damage teeth not only aesthetically, but also chewing and digestion. Skeletal fluorosis generally occurs in adults, but it can also occur in children.
The earliest changes in skeletal fluorosis include bone bending, such as the inability to stretch the arm, which affects life and labor. Endemic fluorosis is very harmful, not only to the patient to bring pain, but also to affect the local economic development, fluoride into the body makes excessive calcium deposited on the blood vessels, resulting in vascular calcification, causing arteriosclerosis. Drinking high-fluoride water can easily cause fluorosis.
In China, except for Shanghai, Hainan and Taiwan, fluorosis has not been found so far, and other provinces, municipalities and autonomous regions have endemic fluorosis epidemics of varying degrees. At present, 77 of the 101 counties in Inner Mongolia have drinking water fluorosis, and the population living in high-fluoride areas is about 6 million, and there are 1.7 million patients with dental fluorosis. According to incomplete statistics, nearly 30 million people in China drink high-fluoride water.
Brackish water in China is mainly distributed in the northern and eastern coastal areas. More than 38 million people drink brackish water in rural areas. Brackish water is mainly bitter in taste, difficult to drink directly, and long-term drinking leads to gastrointestinal disorders and low immunity.
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The best brand of brackish water desalination Jiefeng environmental protection.
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There is no strict definition of brackish water. In our country, some people call water with a salt content greater than l000mg l brackish water, and some people call chloride content greater than 800mg l or sulfate.
Water with a content greater than 400 mg l is called brackish water. The Americans refer to surface and groundwater with a salt content of 1500 to 5000 mg l as brackish water.
According to China's drinking water quality standards.
The salt content should be less than l000mg l, and surface water and groundwater with a salt content greater than l000mg l should be called brackish water.
Brackish water refers to alkalinity.
Water greater than hardness, with a large amount of neutral salt, and water with a pH value greater than 7. Brackish water in China is mainly distributed in the northern and eastern coastal areas of Zikai. The main characteristic of brackish water is that it has a bitter taste, it is difficult to drink directly, and long-term drinking can lead to gastrointestinal disorders.
Weakened immunity.
Brackish water desalination method.
Broadcast. One: distillation.
Distillation is the process of heating brackish water or seawater to boil and evaporate, and then condensing the steam into fresh water. The distillation method is the earliest desalination method of brackish water, and its main advantages are simple structure, easy operation, and good quality of freshwater. There are many kinds of distillation methods, such as multi-effect evaporation, multi-stage flash evaporation, autoclaved steam distillation, membrane distillation, etc.
2. Electrodialysis.
Electrodialysis uses an ion exchange membrane to separate anions and cations in brine under the action of an electric field.
So as to reduce the salt concentration in the freshwater chamber and obtain a membrane separation technology for freshwater. The electrodialysis device uses the directional migration of ions under the action of the electric field, and achieves the purpose of desalination by selecting the permeable ion exchange membrane. The brackish water desalination technology of electrodialysis is relatively mature, which has the main advantages of simple process, high desalination rate, low cost of water production, convenient operation, and no environmental pollution, but there are shortcomings such as strict water quality requirements and pretreatment of raw water.
In the 50s of the 20th century, the United States and the United Kingdom began to use this method for brackish water desalination, and China used this method for brackish water desalination, industrial pure water and ultrapure water in the 80s of the 20th century.
Fabricate. Three: reverse osmosis method.
Reverse osmosis is to add a higher pressure than natural osmosis to the concentrated solution to the side of the solution, twist the direction of permeation, and press the ions in the solution to the semi-permeable membrane.
On the other hand, this is the opposite of the normal osmosis process in nature, so it is called "reverse osmosis", and this device is called a reverse osmosis device. Reverse osmosis brackish water desalination can remove more than 90% of the solubility from water.
salts and more than 99% colloidal microorganisms and organic matter. Compared with other water treatment methods, it has the advantages of no phase change, normal temperature operation, simple equipment, high efficiency, less land occupation, convenient operation, less energy consumption, wide adaptation range, high degree of automation and water effluent.
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