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Fluoride contamination in groundwater

A recent study by the National Remote Sensing Centre (NRSC) has highlighted significant fluoride contamination in groundwater across India. 

Fluoride

  • Fluoride is an inorganic, single-atom anion of the element fluorine with chemical formula F−.
  • Fluoride salts are usually white or colorless, have a bitter taste, and are odorless.
  • It is found naturally in groundwater, and comes from the Earth’s crust (0.06-0.09%). 
  • It enters the water through the leaching and dissolution of fluoride-bearing minerals in underground aquifers.
  • According to WHO, the safe limit for fluoride in drinking water is 1.50 mg/litre, and levels above this are considered unsafe.

Key Findings of the Study  

  • Fluoride Contamination in Groundwater
    • Western India: Groundwater in western Indian regions, characterized by arid and dry climates, generally has higher fluoride concentrations.
      • Highest pre-monsoon and post-monsoon fluoride concentrations: Rajasthan recorded the highest levels of fluoride in groundwater during both pre-monsoon and post-monsoon periods.
        • Its Pre-monsoon concentration was 1.41 mg/litre and post-monsoon was 1.44 mg/litre, close to the maximum permissible limit.
      • Jaisalmer district worst affected: The Jaisalmer district in Rajasthan exhibited the worst fluoride contamination.
    • Southern India:  
      • Several other states, including Karnataka, Tamil Nadu, and Jharkhand also showed post-monsoon fluoride levels higher than the permissible limit.
    • Eastern India: Jharkhand, Bihar, and Chhattisgarh have elevated fluoride levels.
  • Seasonal Variation in Contamination
    • The highest levels of fluoride contamination in groundwater were observed during the dry, pre-monsoon months (March-May).
      • During this period, fluoride levels were 8.65% above the permissible limit.
    • Post-monsoon months also showed significant contamination, with levels 7.1% above normal.
  • Risk of Fluorosis
    • Skeletal fluorosis: Even a 2% fluoride concentration in groundwater poses a significant risk of skeletal fluorosis.
      • Skeletal fluorosis is a bone disease caused by too much fluoride in the body, which makes the bones weak.
    • Dental decay: This risk increases if fluoride levels reach 40% in groundwater.
  • Factors Affecting Fluoride Contamination
    • Geology: The type of rocks and soil in an area can influence fluoride levels.
    • Climate:.Arid and dry regions, especially in western India, are more prone to high fluoride levels compared to humid areas.
    • Season: Fluoride levels tend to be higher during dry, pre-monsoon months.

Fluoride Remediation Using Biochars

  • Fluoride remediation is defined as the process in which excess fluoride is removed from the water. 
  • Biochars:  it is a charcoal like material which is made by heating biomass in a low oxygen environment. 
    • The process of heating organic substances at high temperatures is called”pyrolysi”. 
    • Working of Biochars
      • Absorption: porous structure of biochars help in absorbing fluoride ions from water. 
      • Ion Exchange: In biochars, fluoride ions are exchanged with other ions.
      • Precipitation: In some cases, fluoride ions react with compounds to form insoluble fluoride compounds that precipitate out of the water.






POSTED ON 20-08-2024 BY ADMIN
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