defluoridation guided by:dr. mahmood moothedath dr. azeela ahammed

GOOD MORNING

DEFLUORIDATION

Guided by:Dr. Mahmood moothedath Dr. Azeela ahammed

CONTENTS Introduction Source of fluoride Epidemiology Fluorosis Definition of defluoridation Classification Technique of defluoridation Defluoridation programmes in india Conclusion

IntroductionIn our country endemic fluoride belts with fluoride

content in water more than 4.00ppmAll ground water sources are not always safe,some of

these have problem such as excess salinity,iron,nitrate.

In india the first work on defluoridation was done by the “National Environmental Engineering Research Institute at Nagpur in 1961.

The most obvious way of reducing exposure to water-borne fluoride is to change the water supply to one containing acceptable level of fluoride

In particular, canned fish such as salmon & sardines have a fluoride content of up to 20-40mg/kg

Fluoride is also present in organic combination in certain compound used as drugs&general anesthetics,which may release ionic fluoride.

Fluoride is rapidly released into tea infusion ,it within 5-10min.tea made from instant tea powder result in almost twice as much fluoride in the extract as in regular brewed tea.

Water is the most important single source of fluoride,

Sources of fluoride

(cont..)Mineral water contain considerably higher

concentration,from1.5-7ppm ,depending on the geological location of the source.

EpidemiologyIn India the first work on defluoridation was done by the

national environmental engineering research institute at nagpur in 1961

In our country the states having high fluoride level are Punjab,Haryana,Rajasthan,Madhya pradesh etc..

1945,the world’s first artificial fluoridation plant was started at Grand Rapid ,USA.

1969 WHO advocated that 1ppm of fluoride in community water supplies was a practical & effective public health measure.

FluorosisEndemic disease in geographic area where the content of

fluoride ion in the drinking water exceeds 2ppm.Occur symmetrically within the dental arches,the

premolar is usually affected followed by 2nd molar,maxillary incisor,canine,1st molar,mandibular incisors.

Characterized clinically by lusterless,opaque,white patches in the enamel which may become mottled area or may become yellow or brown

Dental fluorosisis a developmental disturbance of dental enamel caused

by excessive exposure to high concentration of fluoride during tooth development.

These teeth present cosmetic problems & they are highly resistant to carious attack

Skeletal fluorosisIs a bone disease caused by excessive consumption of

fluoride. In advanced cases,skeletal fluorosis causes pain&damage to bones & joints.

In India the most common cause of fluorosis is fluoridated water derived from deep bore wells.

In India the disease was first reported by VISHWANATHAN to be prevalent in residents of MADRAS PRESIDENCY in 1933.

DefluoridationIs the process of removing excess

naturally occuring fluoride from drinking water in order to reduce

the prevalance & severity of dental fluorosis

ClassificationDefluoridation methods are divided into three

basic types depending upon the mode of action

1. Based on some kind of chemical reaction with fluoride:Nalgonda technique,Lime

2. Based on adsorption process:activated alumina,tamarind gel,burnt clay

3. Based on ion exchange process:cation/anion exchange resin

Technique

Nalgonda techniqueKrass processActivated aluminaContact precipitationSynthetic tricalcium phoshateIon exchange resinElectro chemical method

Nalgonda techniqueUsed for community $ domestic water suppliesAddition of- sodium aluminate bleaching powder lime ↓ Flocculation ↓ Sedimentation ↓ Filteration

Mechanism1.Rapid mix: coagulant is rapidly & uniformly dispersed

throughout a single or multiple phase system mixed for 30-60s with a speed of 10-20rpm.

-microflocs are formed which prevent localisation of concentration&premature formation of hydroxide due to proper utilisation of chemical coagulant.

2.Flocculation: formation of settable particles.3. Sedimentation:separation of water by gravitational

setting of suspended particles that are heavier than water.

Factors depending;Size & shape,density & nature of particlesViscosity density & temperature of H2OSurface over flow rateEffective depth of setting zone

4.Filteration: process of separating suspended & colloidal particles by passage through porous media.

- flocculated water filtered through FILLENS EARTH CANDLES.

Maintenacnce of nalgonda filtersReqiures a skilled operation50 steel filters required- costing Rs;35,000/-ADVANTAGE; Low cost investment Low cost maintenance

Salient features No regeneration of mediaNo handing of acids & alkaliesAdaptable for domestic useOnly readily available chemicals used in conventional

municipal water treatment are required.Highly efficient removal of fluoride to desirable levelLittle wastage of water- least disposal problem. Needs minimum of mechanical & electrical equipment.

Indication for adopting nalgonda techniqe.Absence of alternate,acceptable low fluoride source

within transportable distanceTotal dissolved salts<1500mg/dlRaw water fluoride ranging-1.5mg-20mg/dl

Krass processIn this process of defluoridation , the water is passed

through a prepared media ,30 to 60 cms thick. The media,grounded material in powder form, is supported on graded support material consisting of coarse sand resting on fine to coarse gravel media,

Similar to rapid sand-filters used in water treatment plant which also facilitates collection and withdrawal of treated water.

Salient featuresLow cost techniqueCan be sited at anywhere suitable to userEasy to handle by rural populationOnly unskilled persons is requiredDoes not affect the taste of waterFilter bed recharging using alum solutionCan be recharged for 30-40 cycles and then discarded

ComparisonNalgonda technique1.Water to be treated is to

be tested more frequentiy as dose of alum and lime required varies with fluoride and alkalinity con.

2. Total dissolved salt in the treated water increased in NT

Krass process. KDP is not affected by

fluoride and alkalinity con. In input water.

.Decresed in TDS con. has been noticed

3. Excess residual aluminium which is a neurotoxin has been observed in treated water

4. Gentle agitation for a minimum of 10min is a critical part of the process which makes it some what cumbersome & generally it is not properly followed while operating DDU.

. Does not add any aluminium during the treatment, only traces of aluminium present in the input have been observed in treated water

. KDP is very simple to understand & operate

Precipitation methodIt is cheap & is used extensively in IndiaThough lime softening accomplishes fluoride removal,it

has high initial costLarge dosage & alkaline pH of the treated water renders

it unsuitable for field applicationRESOURCE: Alkali Chlorine Aluminium sulphate

Activated aluminaAA is a granular, highly porous material consisting

essentially of aluminium trihydrate.It is widely used as a commercial desiccant & in many gas

drying process.High potential of AA for fluoride uptake, an initial con.of

5mg/l was effectively brought down to 1.4mg/l before regeneration & to .5mg/l on regeneration with 2NHCl.

Use of AA in a continous flow fluoridized system is an economical & efficient method for defluoridating water.

The process could reduce the fluoride level down to.1mg/l . The operational,control & maintenance problem mainly clogging of bed may be averted in this method.

RESOURCE: Activated alumina NaoH Nacl filter alum

Salient featuresIt requires minimum contact time for maximum

defluoridationDoes not affect the taste of waterPercentage of regeneration is considerably highThere is very little attritional loss during the regeneration

at the initial stage of operationIts defluoridation capacity is independent of

temperature.It is indigenously available & cheap.

Bone charThe uptake of fluoride onto the surface of bone was one

of the early method suggested for defluoridation of waterThe process was reportedly one of the ion exchange

method in which carbonate radical of the apatite comprising bone was replaced by fluoride to form an insoluble fluoroapatite

Bone char produced by carbonizing bone at temp of 1100-16000c had superior qualities than those of unprocessed bone & hence replaced bone as defluoridating agent

Salient featuresThe fluoride removal capacity of the product is 1000mg/l

Contact precipitationIt is a technique by which fluoride is removed from the

water through the addition of calcium & phosphate compound & then bringing the water in contact with an already saturated bone charcoal medium.

Synthetic tricalcium phosphateThe product is prepared by reacting phosphoric acid with

lime.The medium is regenerated with 1% Na0H solution

followed by a mild acid rinse

Salient features: it has a capacity to remove 700mg/l

Ion exchange resinCommercially produced resin. It is expensive&

uneconomicalCation exchange resin impregnable with alum solution

have been found to act as defluoridating agentAVARAM BARK based cation exchange resin had been

reported to work effectively in removing fluoride from water

DISADVANTAGE; maintenances of the plant required skilled operation.

Anion exchange resin were found to be of relatively low capacity for fluoride removal

Anion exchange resin are not economical for removing fluoride from water . Besides, the strong base anion exchange resins impart a taste to the treated water that may not be acceptable to the consumers

Ion exchange filter material

Ion exchange resin system

Electro coagulation Electrochemical methodElectro coagulation process with aluminium bipolar

electrodes was used for defluoridation processThe electrocoagulation process with aluminium bipolar

electrodes permitted the defluoridation of sahara water without adding salts to the treated water.

The basic principle of the process is adsorption of fluoride with freshly precipitated aluminium hydroxide, which is generated by the anodic dissolution of aluminium or its alloys in an electrochemical cell.

Electrochemical cell

Tamarind gelThe con. of fluoride in solution of sodium fluoride of

10mg/l could be brought down to 2mg/l by addition of tamarind gel.

Plant materialsBark of MORINGA olifera & EMBLICA officinalisThe roots of VETIVERIA zizanoidesThe leaves of CYNODON dactylon, these are good

defluoridating agent

Way to remove fluoride from water REVERSE OSMOSIS FILTRATIONACTIVATED ALUMINIUM

DEFLUORIDATING FILTRATIONDISTILLATION FILTRATION

Reverse osmosis filtrationThis is used to purify several types of bottled

water.reverse osmosis system are generally unaffordable for personal use

. DISTILLATION FILTRATION There are commercially available distillation filters that

can be purchased to remove fluoride from water

Activated alumina defluoridating filtrationThey are relatively expensive & require frequent

replacement, but do offer an option for home water filtration

Defluoridation programmes in IndiaThe initial intention of the research project in 1991 was to

develop a hand pump based defluoridation unit that could be maintained by local communities.

Major area of studies are; . Development of hand pump attached defluoridation

unit . Development of domestic defluoridation unit .Screening of AA grades in domestic defluoridation unit .procedure for exhausted AA $ the reuse potential of AA .Safe disposal of spent regenerants

Development of hand pump attached defluoridation unit

A cylindrical defluoridation unit was fabricated $ field tested in MAKKUR,UNNAO district,Uttar Pradesh in 1993.

It was a drum .5mm diameter $ 1.5mm heightThe installation required the raising of hand pump

discharge level with an addition to its normal pedestal $ construction of an elevated platform.users had to go up few steps to operate the handpump.A bypass line was provided to draw the water directly from the handpump for washing $ bathing.

There was no complaint from the users either regarding the design or the palatability of treated water.

Screening of AATwo parameters were considered as important for the

application of AA in defluoridation.One was fluoride uptake capacity expressed as milligram

of fluoride removed per kg of AA $ the second was reuse potential of AA in multiple defluoridation cycles.

The main result from these studies was the improvement $ availability of AA in the desired particle size range.

Domestic defluoridation unitThe first DDU fabricated in the laboratory consisted of

two cylindrical chambers,3kg of AA was taken in the upper chamber which gave a bed depth of 9cm . A flow control device was fixed at the bottom of the upper chamber. So as to have a flow rate of 8-10l per hours.

DDU were initially designed on the assumption that 20 litres of treated water was the daily requirement for cooking and drinking for a family.

Regeneration of exhausted AARegeneration of exhausted AA $ its reuse for multiple cycles is

one of the main advantage of using AA for defluoridationDifferent regenerants used include alum,HCl,H2SO4,NaOH

DIP Regeneration procedure This required the transfer of AA from domestic unit to a

nylon bag dipping the bag in 10l of 1% NaOH for 8 hours with intermittent mixing .After washing once with raw water to remove excess alkali,the bag with AA dipped in 10l.

The main limitation of this method appeared to be intermittent mixing $ the long time required for regeneration

Disposal of spent regenerationRegeneration of AA generates spent alkali $ acid having

extreme pH.spent alkali regenerant would also be having high fluoride concentration.

DIFFERENT METHODS:1,The addition of CaCl2 to spent alkali regenerant to precipitate fluoride $ then mix the supernatant with acid regenerant

2,Simple mixing of spent alkali/acid regenerants.

ConclusionThe most obvious way of reducing exposure to water-

borne fluorides is to change the water supply to one containing acceptable level of fluoride.The fluoridated water supplies to reduce dental caries is balanced by similar need to remove excessive amount of fluorides in naturally fluoridated water.

Thank you