1. Defluoridation by Adsorption
Presented By:
Emily Stewart, Rachel Sparks, Sajeev E.M., & Erin Kennedy

2. Agenda Problem Statement Groundwater Situation in Odisha
Defluoridation Methods
Preliminary Analysis
Specifics on Adsorption Technique
Common Adsorption Materials
Selection Criteria & Recommendation
Additional Questions & Information Required

3. The Problem India’s economy dependent on agriculture
There has been a shift from seasonal to year-round cropping to address food security
Groundwater used to supplement irrigation
Quality and quantity of groundwater degraded by natural and human activities
Detrimental effect on the quality of crops and public health

4. Solution Methodology Define area of study
Amount of groundwater used for irrigation
Extraction methods
Chemical composition of water
Type and intensity of cropping
Effects of contaminated water on crops and health
Suggest point/on-farm treatment methods

5. Groundwater in Odisha
Total usable groundwater resource = 12.6 BCM (12.6x1012 L),
Around 390,000 groundwater structures employed for irrigation, 2004
Dug well (92%)
Shallow tube well (4%)
Filter point tuber well (3%)
4.7 BCM of groundwater was used for irrigation in 2001
Projections indicate groundwater use for irrigation could rise to 9.4 BCM by 2050

6. Groundwater in Odisha cont.
Groundwater affected by:
High fluoride concentration (>1.5 mg/L)
High iron concentrations (>1 mg/L)
High nitrate concentrations (>45 mg/L)
Presence of these pollutants in groundwater causes health issues and affects the quality/yield of crops
Study focuses on treating high fluoride concentrations in ground water

7. Defluoridation Methods
Common methods include:
Adsorption and ion exchange
Precipitation
Membrane filtration process
Distillation
Membrane filtration and distillation are advanced and not deployable in developing countries
Conduct preliminary analysis to select treatment method

8. Preliminary Analysis Green – Most suitable
Orange – Average suitability
Red – Not suitable

9. Adsorption Through Ion Exchange
Process involves passage of water through a contact bed where fluoride is removed by ion exchange or surface chemical reaction with solid bed matrix
Water is filtered down through column packed with an ion exchange resin
When adsorbent becomes saturated with fluoride ions (F-), material must be backwashed (recharged) with a mild acid or alkali solution to clear and regenerate it
Exchange reaction:
AB + CF  AF +CB where A and C are cations and B and F are anions
Double replacement occurs with the fluoride anions exchanged leaving the remaining water with less fluoride.

10. Adsorption Apparatus (Drinking Water Treatment)

11. Common Adsorption Materials
Dosage
Cost
Advantage
Disadvantage
Activated Alumina (Al2O3)
100 mg alumina/mg F (1200 g F/m3)
pH of 6.5
$700-$1400 per metric ton
85-95% effective
Lots of past experience in this type of technique (therefore lots of literature on how-to)
Usable at household & community level
Low energy consumption
High capacity
Periodic regeneration of material required
Slightly more expensive than other materials
Suitable grade may not be readily available in Odisha
Training on handling of materials required
Bone Char
1000 g F/m3
pH > 7
Locally available
Low cost
Good capacity
Low efficiency
Affected by high alkalinity
May not be culturally acceptable (possibly animal bones more acceptable?)
For drinking: if improperly prepared, imparts taste and odor to treated water
Activated Alumina:
Bauxite:
Activated Carbon:
Red Mud:

12. Common Adsorption Materials cont.
Dosage
Cost
Advantage
Disadvantage
Bauxite
(Al(OH)3)
“red mud” is a solid waste from refining of bauxite
Effective in pH range 5-7, max effectiveness at pH of 6.4; (not effective above pH of 10)
$20-$30 per ton
Locally available
Likely low cost – will need further research into actual cost
Adsorption highly dependent on concentrations of other anions (sulphate (SO42-), nitrate (NO3-), and phosphate (PO43-)) due to competition with each other for aluminum based materials.
Limited literature available Sujana.
Activated Carbon
Variable dosage
Most effective at pH < 3
>90% effective
Usable at household & community level
Many interferences
Large changes in pH before & after treatment
Relatively high cost
Medium operator skill level

13. Common Adsorption Materials cont.
Dosage
Cost
Advantage
Disadvantage
Coconut Shells & Paddy Husk Charcoal (specific types of activated carbons)
Variable dosage
Effective at low pH (1.7 in experiment)
Low cost
Local availability
Usable at household and possibly small community level
Effectiveness of coconut fiber charcoal significantly increased with zirconium ion impregnation.
Not effective at commercial level (depending on size of farm, it may not be appropriate)
Varying effectiveness

14. Selection Criteria & Recommendation
Activated Alumina
Key Selection Criteria
Use of treated water
Cost of method
Effectiveness
Problems due to break point
Effect of other chemicals
Size and capacity of method
Quality of water (high pH issues and other chemicals)
Social acceptance
Reasons
Used mostly for drinking water, but seems feasible to increase capacity for irrigation
Relatively low cost
Effective (85-95%) at pH of 6.5
Material available locally
Easy to implement
Socially acceptable, but training necessary on handling of chemicals

15. Additional Questions / Info Required
Chemical composition of groundwater? Effect of interference due to other contaminants?
Factors affecting fluoride uptake capacity:
Grade of activated alumina
Particle size
Water chemistry: pH, alkalinity, fluoride concentration (effective range of process), temperature
Exact source of irrigation water at specific farms? Groundwater or surface water or both?
Does Odisha (and specifically the local community we are working with) treat water for irrigation? How much do they treat water for drinking water requirements?

16. Additional Questions / Info Required
What volume of treated water is needed?
Irrigation water rotation between surface and treated groundwater may still be a possible option.
What time is available/acceptable for treatment?
Additional costs: apparatus materials, regeneration chemicals, maintenance tools/materials, preliminary treatment chemicals, testing equipment?
Type and intensity of crops?
Further information on exact effect of fluoride on crops: stunting growth/damaging of crops or indirect damage to health from human consumption of crops?