Methods of deflouridation

1. Defluoridation of Water

2. Lesson Plan
• Subject: Public Health Dentistry
• Topic: Defluoridation of Water
• Name of teacher: Dr. Rekha P. Shenoy
• Date: 20.09.2021
• Duration: 60 minutes
• Time: 09.30 am to 10.30 am
• TL Method: Interactive Lecture
• Media: LCD, Blackboard

3. Sl. No. Specific Learning
Objective
Content Duration
1. Students should be able to
state the definition of
defluoridation and the need
for defluoridation. They
should be able to describe
the Nalgonda technique of
defluoridation in detail.
1. Introduction
2. Methods of
defluoridation of water
3. Nalgonda technique
4. Summary
5. Conclusion
30 minutes

4. Index:
◼ Introduction
◼ Methods of defluoridation of water
◼ Nalgonda technique
◼ Summary
◼ Conclusion

5. Introduction
Fluoride (F)
• is a double-edged sword
• at an optimal level, reduces incidence of dental caries
• at higher levels (during developmental stages), can
cause adverse effects like dental and skeletal fluorosis

6. Defluoridation of water
is defined as “a downward adjustment of F
ion concentration in a public drinking water supply so
that the level of F is maintained at the normal
physiological limit of 1 ppm to prevent dental caries
with minimum possibility of causing dental fluorosis”

7. Methods of Defluoridation
Two basic types:
▪ based on chemical reaction / addition of chemicals to
water during treatment
▪ based on ion exchange process or adsorption

8. ◼ Based on chemical reaction / addition of
chemicals to water during treatment:
1. Lime:
Lime + water containing Mg salts in sufficient
quantity → F absorbed on Mg hydroxide flocs =
F removed
2. Nalgonda technique:
Substances used:
- lime, bleaching powder, alum

9. The Nalgonda technique of
Defluoridation
• useful for domestic and community water supplies
• the process comprises addition in sequence of lime,
bleaching powder and filter alum to the water followed
by flocculation, sedimentation and filtration

10. ◼ Aluminium salt is responsible for removal of fluoride
ions from water.
◼ Lime makes the water alkaline and facilitates formation
of dense flocs for rapid settling
◼ Bleaching powder is added for disinfection purposes

11. Mechanism of defluoridation by Nalgonda
technique:
o Rapid mix
-- rapid and uniform dispersion of coagulant,
formation of microflocs
o Flocculation
-- gentle, prolonged mixing

12. o Sedimentation
-- separation of suspended particles from water by
gravitational setting
o Filtration
-- separation of suspended and colloidal impurities
from water by passage through porous media
o Disinfection

13. Salient features:
• no handling of caustic acids and alkalies
• readily available chemicals used in conventional
municipal water treatment required
• adaptable to domestic use

14. • simplicity of design, construction, operation and
maintenance
• highly efficient removal of Fluoride from 1.5 – 20 mg/l
to desirable levels
• little wastage of water
• needs minimum of mechanical and electrical equipment

15. Advantages:
• simple technique
• economical
• can be adapted at domestic and community levels

16. DOMESTIC USE
COMMUNITY
DEFLUORIDATION
PLANT

17. ◼ Based on adsorption process:
Materials used include –
Bone charcoal, Processed bone, Tricalcium
phosphate, Activated Carbons, Activated
Magnesia, Activated Alumina, Burnt clay, Plant
materials, Serpentine, Hydroxyapatite, Tamarind
gel

18. ◼ Based on ion exchange mechanism:
1. Anion exchange resins:
- by hydroxyl cycle or chloride cycle
2. Cation exchange resins:
- Defluoron 1, Defluoron 2, Carbion, Magnesia

19. Summary
◼ Defluoridation of water can be achieved through many
methods where high fluoride levels are naturally
present in drinking water

20. Conclusion
◼ Defluoridation of water is an important means of
providing potable water in areas with naturally
occurring high fluoride levels in drinking water
◼ It is a cost-effective method of defluoridating water
and can be easily implemented

21. Assignment
◼ Define defluoridation of water. (3)
◼ Classify methods of defluoridation of water. (3)
◼ Write in detail on the Nalgonda technique. (3/5)
◼ Name some indigenous materials used in water
defluoridation. (3)

22. Reference
• Soben Peter. Essentials of Public Health Dentistry. 6th
edition. June 2017.

23. Thank you