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Indian Institute of Science (2008)

A Magnesia Based Sustainable Method For De-Fluoridation Of Contaminated Groundwater

Pemmaraju, Mamatha

Titre : A Magnesia Based Sustainable Method For De-Fluoridation Of Contaminated Groundwater

Auteur  : Pemmaraju, Mamatha

Organisme de soutenance : Indian Institute of Science

Grade : Doctoral PhD 2008

Résumé partiel
Groundwater is a major and sometimes lone source of drinking water worldwide. The chemical composition of groundwater is a combined product of the composition of water that enters the aquifer and its reaction with various minerals present in the soil and rock mass, which alter the water composition with time and space. Some important factors influencing groundwater quality are (1) physiochemical characteristics o the rocks through which the water circulates ; (2) geology of the location ; (3) climate of the area ; (4) role of microorganisms, which includes oxidative and reductive biodegradation of organic matter ; (5)chemical, physical, and mineralogical characteristics of the overburden soils through which the rainwater percolates ; and (6) human intrusion affecting the hydrological cycle and degradation in water quality through utilization of water for agricultural and industrial activities. By far the most serious naturally occurring groundwater-quality problem in India derives from high fluoride, arsenic and iron concentrations which are dissolved from the bedrocks by geochemical processes. Presence of excess fluoride in groundwater is identified as a naturally occurring health hazard by the World Health Organization (WHO). Prolonged ingestion of fluoride beyond certain permissible limit leads to ffluorosis, one of the common water-related diseases recognized by the WHO and the United Nations Children’s Fund (UNICEF). Endemic fluorosis is now known to be global in scope, occurring on all continents and affecting many millions of people. According to estimates made in the early 1980s, around 260 million people in 30 countries worldwide were drinking water with more than 1 ppm of fluoride. The ultimate source of fluoride in water, soil or biosphere is associated with its distribution in rocks and its dispersion in groundwater. The three most important minerals of fluoride are fluorite (CaF2), cryolite (Na3AlF6) and fluorapatite (Ca5(PO4)3F) ; cryolite is a rare mineral where as by far the largest amount of fluorine in the earth’s crust is in the form of fluorapatite (about 3.5% by weight of fluorine) which is processed almost exclusively for its phosphate content. Fluoride substitutes readily in hydroxyl positions in late-formed minerals in igneous rocks, and in primary minerals especially micas (such as biotites) and amphiboles (such as hornblende).

Mots clés : Water Supply ; Underground Water ; Defluoridation ; Magnesia Defluoridation ; Fluoride Geochemistry ; Magnesia - Fluoride Retention ; Fluoride Bearing Sludge ; Fluoride-Contaminated Water ; De-fluoridation ; Groundwater Quality ; Fluoride Sludge ; Magnesium Oxide


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