deflouridation: importance and techniques
TRANSCRIPT
-
7/29/2019 Deflouridation: Importance and Techniques
1/20
IMPORTANCE ANDTECHNIQUES
DEFLUORIDATION
PRESENTED BY:
SANKET AGRAWAL
M.TECH 1ST YEAR, ENVIRONMENT ENGG.
ADVANCED WATER AND WASTEWATER TREATMENT
-
7/29/2019 Deflouridation: Importance and Techniques
2/20
DEFLUORIDATION: IMPORTANCE
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 forabout one-sixth of humanity on this planet.
-
7/29/2019 Deflouridation: Importance and Techniques
3/20
CHEMICAL PROFILE
One Electron short to Inert gas configuration.
Most Electronegative and Reactive of all elements.Pale Yellow-Green Irritating gas.
0.3g/kg of Earths crust.
GEOCHEMISTRYRAIN WATER
CO2 FROM SOIL &AIR
LEACH SALTS (NaCl,NaHCO3)
FLOURIDE-BEARINGCOMPOUNDS via
FERTILIZERS
The alkaline water can mobilize F from soil ,
weathered rocks and CaF2.CaF2 + 2HCO3 CaCO3 + 2F + H2O + CO2
CaF2 has solubility product ofKsp= [F]2[Ca2+] = 4.0 1011
Waters with low content of calcium should have
high fluoride concentration.
-
7/29/2019 Deflouridation: Importance and Techniques
4/20
SOURCES OF FLUORIDE
NATURAL
CHIEF SOURCE: PARENT ROCK
(GRANITE ROCK 20-3600ppm)
SOIL
200-300ppm
FERTILISERS
FOOD
HIGH IN TEA PLANTS
1000 TIMES THAT OFSOIL
WATERHIGHEST: 2800ppm
SURFACE: 0.1-0.3
SEA WATER: 1.2-1.5
OTHER
INDUSTRIES
POWER PLANTS
CIGARATTES:236ppm
TEFLON-LINEDCOOKWARES:
3ppm
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.
-
7/29/2019 Deflouridation: Importance and Techniques
5/20
GLOBAL SCENARIO
Affected (poisoned) morethan 25 nations across the
world.
More than 200 million
people across the globe are atrisk 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 of1.5 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.)
-
7/29/2019 Deflouridation: Importance and Techniques
6/20
INDIAN SCENARIO
20 States affected.
Affecting more than 66 million peopleincluding 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 fluorideconcentration up to 44ppm and 23ppm,
resp.
Delhi has natural maximum fluoride concentration of
32ppm.
-
7/29/2019 Deflouridation: Importance and Techniques
7/20
EFFECTS
Dental Effects
DENTAL CARIES
DENTALFLUOROSIS
Skeletal
Effects
SKELETALFLUOROSIS
Other AdverseEffects
CARCINOGENICITY
GASTROINTESTINALEFFECTS
EFFECTS OF FLUORIDE
Fluoride has both beneficial and detrimental effects on human health with
only a narrow range between intakes that are associated with these
effects.
-
7/29/2019 Deflouridation: Importance and Techniques
8/20
DENTAL CARIES(Tooth Decay)
Dental caries is an infectious and multifactorial
disease causing demineralization of inorganiccomponents of teeth. Untreated caries can lead to:
Incapacitating pain
Bacterial infection
Tooth extraction
Loss of dental function.
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.
Fluoride aids the calcium and phosphate ions chemical reaction producing
a crystal surface much less soluble in acid enhancing remineralization.
-
7/29/2019 Deflouridation: Importance and Techniques
9/20
DENTAL FLUOROSIS
Irreversible toxic effect on the tooth
forming cells
It ranges from barely visible whitestriations on the teeth through to gross
defects and staining of the enamel.
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 and prone to wear.
MECHANISM
EFFECTS
unfavorable effects on individuals personality.
It is hard to smile for a person with dental fluorosis.
Inferiority complex, likely to experience embarrassment, isolation and discrimination.
Can lead to deep psychological depression.
-
7/29/2019 Deflouridation: Importance and Techniques
10/20
SKELETAL FLUOROSIS
Fluoride replaces the hydroxyl ion from hydroxyapatite, a mineral phase during formation
of bone forming hydroxyfluorapatite, altering the mineral structure of bones this leads
to the formation of denser bones which are more fragile and brittle.
Occurrence of fluorosis depends upon many factors like nutritional status and diet, climate,
amount of exposure, source of fluoride intake, etc. (observed even in range of0.4-1.4ppm)
Physical Effects: kyphosis, scoliosis, paralysis, deafness, Genu vaum (bow legs),
etc.
Social Effects: loss of work & livelihoods, psychological trauma, impaired
marriage possibilities for girls, inability to meet high medical costs and above
all, the loss of will to live.
-
7/29/2019 Deflouridation: Importance and Techniques
11/20
DEFLUORIDATION TECHNIQUES
The lack of excess to clean water denies the most essential of allrights, the right to life
-
7/29/2019 Deflouridation: Importance and Techniques
12/20
CLASSIFICATION
COAGULATIONTECHNIQUES
PRECIPITATION
(LIME , CaSO4)
COPRECIPITATION
(BY ALUM & LIME)
ADSORPTION/ION EXCHANGE
BY BONE, BONECHAR,CLAYS
ACTIVATEDALUMINA
ELECTROCHEMICALMETHODS
ELECROCOAGULA-TION
ELECTROSORPTION
MEMBRANEMETHODS
REVERSEOSMOSIS
ELECTRODIALYSIS
NANO FILTRATION
DEFLUORIDATION TECHNIQUES
-
7/29/2019 Deflouridation: Importance and Techniques
13/20
NALGONDA TECHNIQUE
(Alum-lime Co-precipitation)
It involves addition of alum, lime, and bleaching
powder to raw water.Sodium aluminates or lime hastens the
settlement of precipitate and bleaching powder
insures disinfection.
Fluoride get adsorbed on sticky gelatinous
Al(OH)3 flocs during sweep coagulation.
Al+3 +H2O Polynuclear-Hydroxo Complexes + H+
H+ ions will neutralize the alkalinity.
If initial alkalinity is low there will be further
reduction buffering capacity destroyed pH
drop rapidly.
But alkalinity is must for hydroxide floc
formation.
Hence artificial alkalinity in the form of lime or
soda ash is added with the alum.Fig. Domestic Treatment
Precipitation Settling Filtration
-
7/29/2019 Deflouridation: Importance and Techniques
14/20
ADVANTAGES
The absence of regeneration of media
Use of readily available chemicals.
Easy operation and maintenance.
Low cost chemicals used.
Simultaneous removal of color, odor, turbidity, bacteria, and organic
contaminants.
DISADVANTAGES
Did not achieve a great degree of success in field applications both as
hand-pump-based units and as smaller domestic units.
Medium efficiency (
70%).Large dose requirement of aluminum sulfate (7001200 mg/L).
Difficulty in controlling alum and lime dosages for different sources.
High hardness of the treated water.
Increased pH.
-
7/29/2019 Deflouridation: Importance and Techniques
15/20
ELECTRODIALYSIS
The removal of ionic components from aqueous solution through ion
exchange membranes is carried out under the driving force of anelectrical field.
C(-) A(+) A(+)
CONCENTRATECONCENTRATE
-
7/29/2019 Deflouridation: Importance and Techniques
16/20
SELECTION OF ELECTRODIALYSIS MEMBRANE
Permselectivity,A low water transport number,
Reasonably good electrical conductivity,
Good chemical resistance especially to oxidation,
Adequate mechanical strength,
Dimensional stability.
Perfluorosulfonic acid polymer: Nonporous ,Isotropic, 50500 Poly(styrene-co-divinylbenzene ): Nonporous, Isotropic, 100500
ACS-CMX membranes: Monovalent Anion Permselective
MEMBRANES USED
-
7/29/2019 Deflouridation: Importance and Techniques
17/20
EFFICIENCY
Current efficiency is a measure of how effective ions are transported
across the ion exchange membranes for a given applied current.
5000 mg/L TDS and fluoride up to 15 mg/L can be reduced to600 mg/L
TDS and
-
7/29/2019 Deflouridation: Importance and Techniques
18/20
ADVANTAGES
Simultaneous defluoridation and desalination of brackish water.
Commercially established.More economical than pressure driven processes.
More resistant to fouling ( Electrodialysis Reversal Systems).
High capacity.
Less space requirement.
LIMITATIONS
Require high degree ofpretreatment.
Ineffective in removing low-molecular-mass non-charged compounds.Not suitable for waters oflow salinity (conductivity < 0.5 Ms).
Disposal of concentrate: (Dilution in saline water, deep well storage,
combustion, industrial reuse, etc.)
-
7/29/2019 Deflouridation: Importance and Techniques
19/20
REFERENCES
Ayoob, S. & Gupta, A.K. (2006) Fluoride in Drinking Water: A Review on
the Status and Stress Effects. Critical Rev. Environ. Sci. Technol.
Ayoob, S., Gupta, A.K. & Venugopal, T.B. (2008)A conceptual overview
on sustainable technologies for defluoridation of drinking water, Critical
Rev. Environ. Sci. Technol.
Frederick B. &Daniel E.(2009) Defining the concentrate disposal problemand identifying potential solutions. Critical Rev. Environ. Sci. Technol.
Turnbull S., Benning F., G. W. Feldmann, Linch L., Mc Harness, &
Richards S.Analysis and disposal of fluorine. Industrial and engineering
chemistry. Vol.39, No.3.
Adhikary, S.K., Tipnis, U.K., Harkare, W.P., and Govindan, K.P. 1989.
Defluoridation During Desalination of Brackish Water by Electrodialysis.
Desalination,71, 301312
Electrodialysis Source: http://en.wikipedia.org/w/index.php?
oldid=498361104.
-
7/29/2019 Deflouridation: Importance and Techniques
20/20
Thank You