1 DEFLUORIDATION Defluoridation is defined as, - PowerPoint Presentation

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2. DEFLUORIDATION

3. Defluoridation is defined as, “the downward adjustment of level of fluoride in drinking water to the optimal level‟.

4. The recommended optimum level of fluoride in drinking water is 1 ppm (WHO 1963). Optimum level of fluoride that can be consumed by normal adult is 1 mg/day. ` The maximum allowable level of fluoride in drinking water.According to WHO = 1- 1.5 ppmAccording to BIS = 0.6-1.2 ppm (the less the better)According to ICMR = 1PPM4REGULATIONS FOR DRINKING WATER FLUORIDE LEVELS

5. The 1984 WHO guidelines suggested that in areas with a warm climate the optimal fluoride concentration in drinking water should remain below 1 mg/l (1ppm or part per million), while in cooler climates it could go up to 1.2 mg/l. 5Piddennavar Renuka, Krishnappa Pushpanjali. Review on Defluoridation Techniques of Water.The International Journal Of Engineering And Science 2013;2(3):86-94.

6. Locating alternative sources of safe water. Bringing in water from a distant, safe source. Removal of fluoride from water (defluoridation), using suitable techniques. Prevention of industrial fluorosis.Rain water harvesting.Constructing check dams, which raise the ground water level and decrease ground water F- concentration by dilution.Blending high fluoride with low fluoride water.Dual water sources.6Strategies to Provide water with optimal fluoride concentration

7. EconomicEfficient Consistency in performance over a prolonged periodSimple technique, where unskilled personnel can operate the plantRaw materials should be readily availableAcceptable to the communityShould not impart bad taste and odor to the treated waterShould not change pH of water7Ideal requirements of defluoridation techniques

8. Adsorption techniqueIon-exchange techniquePrecipitation techniqueOther techniques8DEFLUORIDATION TECHNIQUES

9. AdsorptionIon-exchangePrecipitationOthers-Carbon materials, -Activated Alumina, -Magnesia, -Tricalcium phosphate, -Calcite, -Hydroxy apatite, -Wood, -Lignite, -Activated char coal, -Bone char, -Processed bone, -Nut shells, -Avaram bark, -Paddy husk, -Coffee husk, -Tea waste, -Jute waste, -Coir pitch, -Fly ash, -Bauxite, -SerpentineAnion exchange resins: -NCL poly anion resin, -Tulsion A27, -Lewatit-MIH-59, -Amberlite IRA-400, -Deacedite FF-IP, -Waso resin-14, -Polystyrene. Cation exchange resins: Defluoron-1, Defluoron-2, Carbion -Lime, -Alum, -Lime & Alum (Nalgonda technique), -Alum flock blanket method, -Poly Aluminium Chloride (PAC), -Poly Aluminium -Hydroxy Sulphate (PAHS), -Brushite-Electrochemical method (Aluminium electrode), -Electro dialysis, -Electrolysis, -Reverse Osmosis9Materials used in different defluoridation techniques

10. This technique functions on the adsorption of fluoride ions onto the surface of an active agent. Activated alumina, activated carbon and bone char were among the highly tested adsorbing agents. 10 DEFLUORIDATION BY ADSORPTION

11. 1. Activated AluminaApplication of domestic defluoridation plants based on activated alumina has been launched by UNICEF in rural India -- famously known as ‘Prasanthi technique’. The F removing efficiency of activated alumina gets affected by hardness and surface loading.The ph is maintained between 5 and 611

12. • This process can remove fluoride up to 90%• Effective and economical• It requires minimum contact time for maximum defluoridation• It is indigenously available and cheap• Percentage of regeneration is considerably high.Advantages

13. Disadvantages :Adsorption of fluoride is possible only at specific pH range, needing pre-and post- pH adjustment of water. Frequent activation of Alumina is needed, which make the technique expensive. Generates concentrated fluoride solution, causing disposal problems. Disposal of fluoride laden sludge is also a problem Skilled personnel are required for plant operation13

14. Among various treatments used, activated carbon is a powerful adsorbent due to large surface area and pore volume.It can be prepared from the different raw materials, such as wood, lignite, coal, bone, petroleum residues, nutshells and also from other low cost/waste materials like the rice-husk, saw dust, coconut shell, tree bark, cotton waste etc.14 2. Activated Carbon

15. It is a highly economic technique with 62 - 66% defluoridation.The optimum time for the adsorption to reach saturation is 9 hours and optimum pH of fluoride solution is between 7 - 7.5. 153. Bone char

16. The efficacy of the plant depends upon temperature and pH of raw water; duration of contact. The efficiency can be improved by pre-treating the raw water with Brushite and Calcium hydroxide. 16

17. The bone char is unhygienic (harbors bacteria).Regular fluoride analysis to check whether the material is exhausted.It is a technique sensitive procedure, charring procedure should be done cautiously. Cultural and religious objections . 17Disadvantages:

18. BRICKPrinciple: same as that of activated alumina. The soil used for brick manufacturing contains Aluminium oxide. During burning operation in the kiln, it gets activated. Replacement of filter media is required once in 3 months if fluoride content in raw water is 2.5 mg/l. The cost of the filter unit is about Rs 600 /-. 18

19. Can not achieve complete defluoridation.All the soils are not rich in Aluminium oxide. Possibility of microbial contamination of brick. 19Limitations:

20. Economical and readily acceptable for the rural communities.Disadvantages:It results a marginal reduction in water fluoride level from 1.8 ppm to 1.5 and 1.4 ppm at the end of 2 days and 4 days respectively, which is practically not significant.The water pH was raised from 7.7 to 8.11 and 8.14 the end of 2 days and 4 days respectively, which is beyond the acceptable limits of alkalinity. 20Mud pot

21. Seeds of the Drumsticks Roots of Vetiver grass Tamarind seeds Mangosteen fruitsRooster feathers21Natural adsorbents

22. Synthetic chemicals, namely, anion and cation exchange resins have been used for fluoride removal.Used in chloride and hydroxy form. These are commercially produced resins which are expensive in most circumstances. a) Carbion : It is a Cation exchange resin of good durability and can be used both on sodium and hydrogen cycle. 22 DEFLUORIDATION BY ION-EXCHANGE

23. De Fluoron –1: 1964 A sulphonated saw dust impregnated with 2% alum solutionDrawbacks : the medium had poor hydraulic properties - cost Defluoran-2:Developed in 1968. It is sulphonated coal & works on the aluminum cycles.Life of medium is 2- 4 yrsThe average fluoride removal capacity of the medium is 484mg F/L23

24. Advantages• Removes fluoride up to 90-95%• It helps in the retention of taste and colour of water intact.

25. Waste produced is very largeExpensive.Regeneration of resin is a problem because it leads to fluoride rich waste, which has to be treated separately before final disposalTreated water has a very low pH and high levels of chlorideThe regeneration and maintenance of plant required skilled operation & personnel which may not be readily available. 25Disadvantages:

26. Major drawbacks of Ion-exchange and adsorption techniques are: The necessary flow through system is often difficult to arrange where there is no piped water supply Gradual exhaustion of the active agent is not easily detected.26

27. Reverse osmosis, electrolysis and electro dialysis are physical methods that are tested for defluoridation of water.Though they are effective in removing fluoride salts from water, there are certain disadvantages that limit their usage on a large scale.Other techniques

28. In reverse osmosis, the hydraulic pressure is exerted on one side of the semi permeable membrane which forces the water across the membrane leaving the salts behind.In electro dialysis, the membranes allow the ions to pass but not the water. The driving force is an electric current which carries the ions through the membranes.

29. • The process is highly effective for fluoride removal• It permits the treatment and disinfection of water in one step• It ensures constant water quality• No chemicals are required and very little maintenance isneeded• Life of membrane is sufficiently long, so problem of regeneration or replacement is encountered less frequently• It works under wide pH range• No interference by other ions is observed• The process works in a simple, reliable automated operatingregime with minimal manpower using compact modular model.Advantages

30. • It removes all the ions present in water. Since though some minerals are essential for proper growth therefore, remineralisation is required after treatment• The process is expensive in comparison to other options• The water becomes acidic and needs pH correction• Lots of water gets wasted as brine• Disposal of brine is a problemDisadvantages

31. Addition of chemicals (coagulants and coagulant aids) and the subsequent precipitation of a sparingly soluble fluoride salt as insoluble fluorapatite.The best example for this technique is Nalgonda technique31 DEFLUORIDATION BY PRECIPITATION

32. Nalgonda techniqueNational Environment Engineering Research Institute (NEERI), Nagpur (1974 )Nalgonda Technique involves addition of Aluminium salts, lime and bleaching powder.Economical and simple method.This technique is extremely useful for both domestic as well as for community water supply.32

33. Aluminium salt responsible for removal of fluoride from water and may be added as Aluminium Sulphate or Aluminium Chloride or Combination. The dose of Aluminium salt increases with increase in the fluoride and alkalinity levels of the raw water. 33

34. The dose of lime is empirically 1/20th that of the dose of Aluminium salt. Lime maintains alkalinity of the solution and facilitates formation of dense flocks for rapid settling. Bleaching powder is added to the raw water at the rate of 3 mg/l for disinfection.34

35. Rapid MixingFlocculationSedimentationFiltrationDisinfection and Distribution35Mechanism of defluoridation by Nalgonda technique

36. 1)Rapid Mixing: Rapid mixing is an operation by which the coagulant is rapidly and uniformly dispersed through out a single or multiple phase system.Duration= 30-60 secSpeed=10-20 rpm 36

37. 2) Flocculation:Settable particles : polymeric aluminium hydroxides (flock) formed.Achieved by gentle and prolonged mixing for 10-15 mins at 2-4 rpm.Besides, bacteria, turbidity, colour, odour, pesticides and organics are also removed. 37

38. 3) Sedimentation: It is separation from the water by gravitational setting of suspended particles that are heavier than water.Factors that affect sedimentation are: size , shape , density and nature of particles.Viscosity , density and temperature of waterSurface over flow rateVelocity of flow38

39. 4) Filtration: Rapid gravity sand filters are suggested to receive coagulated and settled water. In these filters unsettled gelatinous flock is retained. Residual fluorides and bacteria are absorbed on the gelatinous flock retained on the filter bed.The flocculated water is allowed to settle and filter through fullers earth candle overnight. 5) Disinfection and Distribution: The filtered water collected in the storage water tank is chlorinated with bleaching powder before distribution. 39

40. No regeneration of mediaNo handling of caustic acids and alkalis. Readily available chemicals.Adaptable to domestic use. Highly efficient. Effective even when dissolved solids are 1500mg/l and hardness >600 mg/lSimplicity of design, construction, operation and maintenance. No energy except muscle power for domestic equipment.Can be adopted by the common man.40Salient features of Nalgonda technique

41. Simultaneous removal of colour, odour, turbidity, bacteria and organic contaminants.Sludge generated is convertible to alum for use elsewhere. Little wastage of water and least disposal problems. Needs minimum of mechanical and electrical equipment.Can be used as both fill-and-draw and continuous operation system and both at domestic and community level.Low investment and maintenance costs.41

42. Generation of higher quantity of sludge compared to electrochemical defluoridation.The large amount of alum needed to remove fluoride. Careful pH control of treated water is required. High residual aluminium is reported.42Disadvantages :

43. Poly Aluminium chloride: it is evident that for higher concentrations of fluoride, the removal efficiency of fluoride is higher with PAC when compared with Alum.Poly Aluminium Hydroxy Sulphate: is found to require less flocculation time and setting time.43Modifications for Nalgonda technique

44. Conclusion

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