January 2008 Updates This ppt was originally arsenic & fluoride and now they have been split Formatted to be consistent with other PowerPoint presentations Added Slide 4 – map of fluoride affected countries Added Slide 9 – fluoride mitigation options Added Slides 11 – 18 on removal technologies

Fluoride in Drinking Water

Presentation Outline Fluoride around the world Guidelines Health effects Fluoride removal Mitigation options

Source: UNICEF Fluoride in water: An overview Countries with Excess Fluoride in Drinking Water

Fluoride in Water Naturally occurring fluoride is released from rocks and minerals as they erode over time Also released through volcanic activity or marine aerosols Industrial activities also release fluoride: –mining –phosphate fertilizer manufacturing –coal fired power Usually tightly bound in soil, but when this level is above what the soil can retain, inorganic fluorides can be leached into the groundwater or taken up by plants

Harmful Levels WHO guidelines specify that fluoride levels be no higher than 1.5 mg/L drinking water However, levels of 0.6 mg/L have been suggested as being a problematic in areas of hot dry climate Source: Source: /wes_1428.htm?q=printme

Fluoride Guidelines DoseSymptoms < 0.5 mg/LSusceptibility to dental caries mg/LLower dental caries mg/LDental fluorosis > 4 mg/LDental and skeletal fluorosis >10 mg/LCrippling fluorosis

Health Effects Low levels can prevent dental caries Excess fluoride can cause fluorosis –Dental fluorosis –Skeletal fluorosis –Acute fluorosis Fluorosis is further aggravated by calcium and vitamin D deficiencies (Source: Source:

Alternative Fluoride- Free Sources Defluoridation Technologies Low fluoride groundwater Improved Dug wells Rainwater harvesting Surface water treatment Fluoride Mitigation Mitigation Options

Theory of Fluoride Removal 1.Adsorption/Ion Exchange: Through adsorption, fluoride ions are collected on the surface of the adsorbent; in ion exchange, fluoride ions would be removed from solution onto the ion exchange resin in exchange for a less problematic ion. 2.Chemical: By chemical reaction with fluoride, the fluoride is bound in the solution, it would then require removal from solution. 3.Precipitation/Sedimentation: Employed along with chemical reaction to remove particles, such as flocculants, from solution. 4.Filtration: This method can be used in to remove particles, such as flocculants or bacteria from solution

Fluoride Removal Technologies Activated alumina Nalgonda technique Bone charcoal Clay Contact precipitation

Activated Alumina Fluoride is adsorbed onto the surface of aluminium oxide grains Column becomes saturated Regeneration of media is necessary after saturation Cost –Evidence from India, China, & Thailand show process can be low cost in some communities –Chemical cost may be prohibitive in other markets Source: WHO Fluoride in Drinking-water, 2006

Nalgonda Technique Add pre-determined quantities of alum and lime- stir vigorously Allow flocs to settle for two hours before decanting clean water Creates toxic sludge – need to dispose of properly Developed in India, implemented in Tanzania Household or community level technology Source: WHO Fluoride in Drinking-water, 2006

Bone Charcoal Brackish, porous, granular media (calcium phosphate) acts as removal agent for fluoride Prepare media by heating ground bone in kiln-like environment with limited entrance of atmospheric oxygen Source: WHO Fluoride in Drinking-water, 2006 Quality must be assured otherwise treated water may taste and smell like rotten meat May not be culturally appropriate in some regions Regeneration of media is not cost-effective

Clay Brick pieces most commonly used –Aluminium oxide is activated during firing in kiln –Fluoride is removed by brick pieces –Flow of filter is in upwards direction –Column filter from Sri Lanka illustrated w/ layered brick chips, pebbles and coconut shells Often not cost-effective to regenerate media after saturation Low removal efficiencies Source: WHO Fluoride in Drinking-water, 2006

Contact Precipitation Promising technology Add calcium and phosphate compounds Contact time should be minutes Pass water through a saturated bone charcoal medium Bone charcoal acts as a catalyst for removal of fluoride and filters out precipitate Household or community level technology Source: WHO Fluoride in Drinking-water, 2006

Contact Precipitation Relatively low daily work load High reliability without need for surveillance of flow or effluent concentration High removal efficiency, even with high concentrations of fluoride in water Low operating cost No health risk in the case of misuse or over- dosage of chemicals Source: WHO Fluoride in Drinking-water, 2006

Comparison of Advantages of the Most Promising Defluoridation Methods Source: WHO Fluoride in Drinking-water, 2006