Environmental Engineering Reference
In-Depth Information
17.7.8 Recent Developments in Materials for Deluoridation ..................................... 339
17.7.8.1 Nanomaterials for Fluoride Removal ................................................... 340
17.7.8.2 Magnetic Nanoparticles ......................................................................... 342
17.7.8.3 Regeneration of Adsorbents .................................................................. 343
17.7.8.4 Disposal of Adsorbent ............................................................................ 343
17.7.8.5 Green Chemical Approach .................................................................... 346
17.8 Future Prospects and Outlook ......................................................................................... 350
17.9 Summary ............................................................................................................................. 350
References ..................................................................................................................................... 351
17.1 Introduction
Fluoride is one of the most abundant water contaminants occurring in groundwater as
it poses severe problems in safe drinking water supplies. According to United Nations
Educational, Scientiic and Cultural Organization estimates (January 2007), >200 million
people use luoride-contaminated groundwater for drinking, with luoride concentrations
of more than the World Health Organization (WHO)-recommended value of 1.5 mg/L.
The 1984 WHO guidelines mention that in areas with a warm/arid climate, the optimal
luoride concentration in drinking water should be <1 mg/L (1 ppm), while in cooler cli-
mate regions it could be acceptable up to 1.2 mg/L. This differentiation is based on the
fact that perspiration occurs more in hot weather and consequently more drinking water
is generally consumed. The WHO has set a guideline value (permissible upper limit) for
luoride in drinking water at 1.5 mg/L. There is minor deviation from this value for dif-
ferent countries.
The sources of luoride in water are both natural and anthropogenic; however, the major-
ity of luoride in groundwater is of geogenic origin. Weathering of luoride-rich minerals
such as limestone, sandstone, and granite results in the release of luoride in groundwater.
The extent of luoride contamination in groundwater depends on water geochemistry and
temporal factors. The widespread occurrence of luoride above the prescribed limits in
groundwater has been reported from >30 nations around the globe, among which India,
South Africa, China, Sri Lanka, Kenya, Nigeria, and Mexico are among the worst affected.
In India alone, >60 million people from >17 states are considered at risk due to the con-
sumption of luoride-contaminated groundwater. Long-term consumption of luoride-rich
water results in a disease termed luorosis, which can be categorized as dental or skeletal
luorosis. Besides, other clinical manifestations including gastrointestinal problems, aller-
gies, neurological disorders anemia, and urinary tract problems due to prolonged expo-
sure of luoride are well documented. An estimated 25-65 million people are affected with
dental, skeletal, and/or nonskeletal luorosis in India, with a wide range of luoride con-
centration of 1-48 mg/L in groundwater (Ayoob et al., 2008). As per a WHO estimate, the
disability affected life years (DALY) value because of skeletal luorosis could be as high as
17 per 1000 population in India. With depleting surface water sources and increasing water
demand, the groundwater sources are under stress leading to further increase of luoride
concentration as well as higher intake.
