fluoride pollution in groundwater123.pdf

1. Groundwater Fluoride Pollution

Ali Shah

2. Geology

Q Fluoride is the most electronegative of all chemical elements.

Q It is 17% in the order of frequency of occurrence of the elements.

Q The average crustal abundance is 300 mg/kg.

Q Mostly granite and granitic gneiss terrain.

O Apatite (Ca10(PO4)6F2)one of the major fluoride minerals.

Q Fluoride as complex hydroxy-silicates and hydroxyalumino-silicates, in
which the hydroxyl ions (OH) may be largely replaced by fluoride, as
observed in amphiboles and minerals of the mica family (biotite and

muscovite).

O Fluoride in the ground/surface water derives from the weathering and
subsequent leaching of fluoride-bearing minerals in rocks and soils like

3. Q Fluoride is one such ion that causes health problems in people living in
more than 25 nations around the world. Fluoride concentration of at least
0.6 mg/l is required for human consumption as it will help to have stronger
teeth and bones.

Q Consumption of water with fluoride concentration above 1.5 mg/l results
in acute to chronic dental fluorosis where the tooth become coloured from
yellow to brown. Skeletal fluorosis which causes weakness and bending of
the bones also results due to long term consumption of water containing
high fluoride.

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Q Several rocks have fluoride bearing minerals like apatite, fluorite, biotite
and hornblende. The weathering of these rocks and infiltration of rainfall
through it increases fluoride concentration in groundwater.

Q WHO drinking water 1-1.5 mg/l.
Q Fluoride does not exhibit any colour, taste or smell
en re: i n

4. Fluoride Hydrogeochemistry

Q The high HCO, bearing water has alkaline nature, which favours
the higher mobility of F- ions in the groundwater. Solubility of
fluoride in soils is highly variable and has the tendency to be
higher at pH > 6. Higher F- concentration observed to have higher
pH values.

CaF,+ 2HCO; = CaCO,+ 2F-+ H,0 + CO,
CaF,+ 2NaHCO, = CaCO,+2Na* + 2F-+ H,O + CO,

Q Fluoride rich groundwater in many parts of the world are often of
Na-HCO, type with low Ca?* concentrations and neutral to alkaline
pH values. Several studies have demonstrated positive correlations
between F- and both HCO, and Na* in high F- groundwater as well
as an inverse relationship between F and Ca ” concentrations in

5. Fluoride (mg/l) fects on human body

Below 0.5 Dental Caries

0.5 to 1.0 Protection against dental
caries. Takes care of bone
and teeth

1.5 to 3.0 Dental fluorosis

3 to 10 Skeletal fluorosis (adverse
changes in bone structure)

10 or more Crippling skeletal fluorosis

and severe osteoclerosis
IS

6. Fluorosis

Excess fluoride in the
body
(above 1.5 — 2 ppm)

Skeletal Fluorosis Dental Fluorosis

19 states in India have groundwater that is rich in
fluoride

7. Over 6.6 crore Indians are affected
by fluorosis

(slight OI of teeth)

(obvious mottling of teeth)

(severe mottling of teeth)

8. ‘© Fivoronts is endemic in 19 sites of india. 6$ maton
people, Inchung sx mann cen. are today afec.
© Fluoride levels in India’s groundwater vary from 1 mg
10 48 mp (The World Health Organization guideane for
mann permease teve of Rute in nnung mater m
15 gh)

2° À 1999 say by New Dats-pased Fcrosis Research
no fura Oevetopmens Foundation nas derung 39.1
Proben ALES with orde het above 1 mA

22
Rap mms

© A 1997 study by the Rajasthan Voluntary Health
‘Association shows that almost 35.000 people in the state.
Late comme wate Raving more than 10 mgt of Mande

uoreni in varios drei, ofthe state: 63.4 per com in
‘Sarswara. 772 por contin Dungarpur, and 725 par cert
Va

e A recent wie paper prepared by the Gujarat govern.
(mark, Water quay problems im Capra shown a 2826
ges have Rande ever above 13 mot

‘© Out ofthe total 1.182 witages in Anata Pradeun, 624
‘Raw righ ondo no ng water

foto witage Tampa of Manga district in Maanya
Proc 74.4 per cera o chan an agote cents tom
09% 20 reve dental matting. and 312 percent are athe

10. 119
Kolar in KARNATAKA

Moo arc ans

| CES

92 m9N
Koraput in ORISSA

© A 1997 study by the Rajasthan Voluntary Health
Association shows,

Banswara, 77.2 per cont in Dungarpur, and 72.5 por cent in
Udaipur.

© Arocent white paper prepared by the Gujarat govern-
ment, Water quality problems in Gujarat. shows that 2.826
vitages have fluoride levels above 1.5 mg.

© Out of the total 1,152 villages in Andhra Pradesh, 624
have high fluoride in the drinking water

+ In village Tilsipani of Mandia district in Madhya
Pradesh, 74.4 per cent of children and adolescents below
age 20 have dental motting. and 51.2 por cent are afflicted
with genu vakgum (knock knees).

® Groundwater surveys in Unnao district of ur conducted

11. Defluoridation process

Q Numerous exsitu methods are available for defluoridation of water
either at household or community level.

O Activated charcoal and activated alumina are the widely used
adsorbents. Brick, bone char, fly ash, red mud, rice husk, kaolinite,
bentonite, ceramic etc. are some of the other absorbents capable of
effectively removing fluoride from groundwater.

Q The effective removal of fluoride by these absorbents depends on
the initial concentration of fluoride, pH, contact time, type of
absorbent and its size. Nalgonda technique which is a well known
technique uses alum, lime and bleaching powder followed by rapid
mixing, flocculation, sedimentation and filtration.