IMPORTANCE AND TECHNIQUES
PRESENTED BY: SANKET AGRAWAL M.TECH 1ST YEAR, ENVIRONMENT ENGG. ADVANCED WATER AND WASTEWATER TREATMENT
Though water is regarded as a “human right” rather than a “human need,” the access to “closer and cleaner drinking water” is still a distant dream for about one-sixth of humanity on this planet.
•One Electron short to Inert gas configuration. •Most Electronegative and Reactive of all elements. •Pale Yellow-Green Irritating gas. •0.3g/kg of Earth’s crust.
•The alkaline water can mobilize F− from soil , weathered rocks and CaF2. CaF2 + 2HCO−3 → CaCO3 + 2F− + H2O + CO2
CO2 FROM SOIL & AIR
LEACH SALTS (NaCl, NaHCO3)
•CaF2 has solubility product of
Ksp= [F−]2[Ca2+] = 4.0 × 10−11
•Waters with low content of calcium should have high fluoride concentration.
FLOURIDE-BEARING COMPOUNDS via FERTILIZERS
SOURCES OF FLUORIDE
CHIEF SOURCE: PARENT ROCK
(GRANITE ROCK 20-3600ppm)
INDUSTRIES POWER PLANTS
HIGH IN TEA PLANTS 1000 TIMES THAT OF SOIL
HIGHEST: 2800ppm SURFACE: 0.1-0.3
CIGARATTES: 236ppm TEFLON-LINED COOKWARES: 3ppm
SEA WATER: 1.2-1.5
•Average dietary intake of fluoride for adults living in area with 1.0ppm fluoride in water is b/w 0.02-0.048mg/kg/day. •The presence of diet rich in calcium reduces the fluoride absorption in human.
•Affected (poisoned) more than 25 nations across the world. •More than 200 million people across the globe are at risk of fluorosis. • China more than 1/10th of population affected by fluorosis. • In Mexico, 5 million people(6% population) affected. • In Ethiopian Rift Valley fluoride conc. in range of 1.5 to 177 ppm encountered. • Tanzania (8-12.7ppm) most severely affected country. (Acc. to WHO (1-1.5ppm)standards nearly 30% water sources are unfit.)
• 20 States affected. •Affecting more than 66 million people including 6 million children under 14 years age. •One of the most alarming public health problem of the country. •Rajasthan, Andhra Pradesh and Assam are most endemic. •People of Rajasthan and Assam are forced to consume water with fluoride concentration up to 44ppm and 23ppm, resp.
•Delhi has natural maximum fluoride concentration of 32ppm.
EFFECTS OF FLUORIDE
Other Adverse Effects
Fluoride has both beneficial and detrimental effects on human health with only a narrow range between intakes that are associated with these effects.
DENTAL CARIES(Tooth Decay)
Dental caries is an infectious and multifactorial disease causing demineralization of inorganic components of teeth. Untreated caries can lead to:
• Incapacitating pain •Bacterial infection •Tooth extraction •Loss of dental function. Fluoride aids the calcium and phosphate ions chemical reaction producing a crystal surface much less soluble in acid enhancing remineralization. •WHO permissible limits for preventing Dental Caries is 0.5-1.2ppm. •CDC hails water fluoridation as one of the ten most important public health measures currently available. •Globally, the population consuming fluoridated drinking water were estimated as about 355 million in 2005.
•Irreversible toxic effect on the tooth forming cells •It ranges from barely visible white striations on the teeth through to gross defects and staining of the enamel. MECHANISM
•The calcium rich constituents of teeth, viz. enamel and dentin, have strong affinity for fluoride during the formation of teeth. •Fluoride combines with calcium forming calcium fluoroapatite crystals during mineralization. •So, as fluoride accumulates, calcium is lost from the teeth. •Due to loss of calcium, enamel becomes more porous, discolored...
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