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How to Remove Floride From Water

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It's possible to remove fluoride from drinking water, but not every type of water filter will work.

AKASH MANDAL ( 99999-2-4321 )

::: Nalgonda Technique :::

The Nalgonda technique is a means of fluoride removal

that depends on the flocculation, sedimentation, and filtration of fluoride with the addition of aluminum sulfate and lime.This technique was developed by the National Environmental Engineering Research Institute in India in 1975 in response to fluorosis concerns. Aluminum sulfate (Al2(SO4)318H2O) is added to the water to acts as a flocculent. Though aluminum sulfate is commonly used in general water treatment as a flocculent, the amounts used in defluoridatoin are much higher (150 mg/mgF or 1000mg/L or 20 times.

the reaction results in an excess of H+ ions, Lime

(Ca(OH)2) is added to the water during the process to help maintain a neutral pH and hasten the settling of the sediment.The amount of lime added is typically 5% (by mass) of the aluminum sulfate added though some sources say significantly more (20-50% of alum by mass) should be added.The chemical processes, though admittedly are not fully understood , can be seen below:

Al2(SO4)318H2O => 2Al + 3 SO4 + 18H2O

2AL + 6H2O => 2Al(OH)3 + 6H+ F- + Al(OH)3 => Al-F Complex +undefined product 6Ca(OH)2 + 12H+ => 6Ca2+ + 12H2O

Additionally, some of the fluoride is able to form

precipitate with calcium. Ca(OH)2 + 2F- => CaF2 +2OH-

Most people are aware that there is a controversy

surrounding public fluoridation of drinking water. Here is a list of ways to obtain drinking water without fluoride.

Ways to Remove Fluoride from Water :: Reverse Osmosis Filtration - This is used to purify several

types of bottled water (not all), so some bottled waters are unfluoridated. Reverse osmosis systems are generally unaffordable for personal use. used in locales where fluorosis is prevalent. They are relatively expensive and require frequent replacement, but do offer an option for home water filtration. distillation filters that can be purchased to remove fluoride from water.

Activated Alumina Defluoridation Filter - These filters are

Distillation Filtration - There are commercially available

These Do NOT Remove Fluoride :: Brita, Pur, and most other filters - Some websites

about fluoride removal state otherwise, but I checked the product descriptions on the companies' websites to confirm that fluoride is left in the water. Boiling Water - This will concentrate the fluoride

rather than reduce it Freezing Water - Freezing water does not affect the

concentration of fluoride.

:: Steps to Reduce Fluoride Exposure :: Don't take fluoride supplements Read labels on bottled beverages - Unless they are made using distilled or reverseosmosis water, they are probably made with fluoridated public water Consider using unfluoridated toothpaste

Avoid drinking black or red tea - There are many health benefits associated with chemical compounds found in tea, but this may be a beverage to avoid if you need to reduce your fluorine intake. Black and red tea come from two different types of plants, but both leaves naturally contain high amounts of fluorine Be wary of tinned fish and canned food items - Fluoride may be used as a preservative

Avoid black or red rock salt or items containing black or red rock salt Avoid using chewing tobacco Void long term use of medication that contains fluorine.

A compilation of...

Fluoride Treatment Methods

The defluoridation methods are divided into three

basic types depending upon the mode of action :: Based on some kind of chemical reaction with fluoride: Nalgonda technique, Lime... Based on adsorption process: Bone charcoal, processed bone, tricalcium phosphate, activated carbons, activated magnesia, tamarind gel, serpentine, activated alumina, plant materials, burnt clay... Based on ion-exchange process: Anion/Cation exchange resins.

Filtration:: Reverse Osmosis Filtration Activated Alumina Defluoridation Filter Distillation Filtration.



:::::::: Process :::::::: The Nalogonda technique (named after the village in India

where the method was pioneered) employs flocculation principle 1. Nalgonda technique is a combination of several unit operations and the process invloves rapid mixing, chemical interaction, floculation, sedimentation, filtration, disinfection and sludge concentration to recover waters and aluminium salts. Alum (hydrated aluminium salts) - a coagulant commonly used for water treatment is used to flocculate fluoride ions in the water. Since the process is best carried out under alkaline conditions, lime is added. For the disinfection purpose bleaching powder is added. After thorough stirring, the chemical elements coagulate into flocs and settle down in the bottom.

::::::: REACTIONS ::::: 2 Al2 (SO4)3 . 18H2 O + NaF +

9Na2CO3 [5Al(OH)3.Al(OH)2F] + 9Na2SO4+NaHCO3 + 8 CO2 + 45 H2O 3 Al2 (SO4)3 . 18H2 O + NaF +17NaHCO3 [5Al(OH)3.Al(OH)2F] + 9Na2SO4+ 17 CO2 + 18 H2O


:: Resources / Salient Features :: No regeneration of media No handling of caustic acids and alkalis Readily available chemicals used in conventional

municipal water treatment are only required Adaptable to domestic use Flexible up to several thousands m3 / d Applicable in batch as well as in continuous operation to suit needs simplicity of design, construction, operation and maintenance.

:: COTINUED :: Local skills could be readily employed Higly efficient removal of fluorides from 1.5 to 20 mg/L

to desirable levels Simultaneous removal of color, odor, turbidity, bacteria and organic contaminants Normally associated alkalinity ensures fluoride removal efficiency Sludge generated is convertible to alum for use elsewhere.

:: CONTINUED :: Little wastage of water and least disposal problem Needs minimum of mechanical and electrical

equipment No energy except muscle power for domestic equipment.

:: CONTINUED :: Economical - annual cost of defluoridation (1991 basis)

of water at 40 lpcd works out to Rs.20/- for domestic treatment and Rs.85/- for community treatment using fill and draw system based on 5000 population for water with 5 mg/L and 400 mg/L alkalinity which requires 600 mg/L alum dose. Provides defluoridated water of uniform acceptable quality.



:: Precipitation methods :: Method involving the addition in sequence, of an

alkali, chlorine and aluminium sulphate or aluminium chloride or both was developed. It is cheap and is used extensively in India. Though lime softening accomplishes fluoride removal, its high initial cost, large dosage and alkaline pH of the treated water renders it unsuitable for field application. Large dosage and alkaline pH of the treated water renders it unsuitable for field application.

:: Bone Char :: The uptake of fluoride onto the surface of bone was

one of the early methods suggested for defluoridation of water supplies. The process was reportedly one of the ion exchange in which carbonate radical of the apatite comprising bone, Ca(PO4)6.CaCO3, was replaced by fluoride to form an insoluble fluorapatite. Bone char produced by carbonizing bone at temperature of 1100-1600C had superior qualities than those of unprocessed bone and hence replaced bone as defluoridating agent.

The fluoride removal capacity of the product is 1000 mg/L ..

:: Contact Precipitation :: It is a technique by which fluoride is removed from the

water through the addition of calcium and phosphate compounds and then bringing the water in contact with an already saturated bone charcoal medium. YOU WOULD LOVE TOO WATCH THE PICTURES



Degreased and alkali treated bones Degreased and alkali treated bones are effective in the

removal of fluoride from initial fluoride concentration ranging from 3.5 mg fluoride/L to 10 mg fluoride/L to less than 0.2 mg fluoride/L Bone contain calcium phosphate and has a great affinity for fluoride. The bone is degreased, dried and powdered. The powder can be used as a contact bed for removal of fluoride in water. The exhausted bed is regenerated with sodium hydroxide solution.

Synthetic tri-calcium phosphate The product is prepared by reacting phosphoric acid

with lime(Bulusu). The medium is regenerated with 1% NaOH solution followed by a mild acid rinse

It has a capacity to remove 700 mg fluoride/L

:::::: Florex ::::: A mixture of tri-calcium phosphate and Hydroxy -

apatite, commercially called Florex, showed a fluoride removal capacity of 600 mg of fluoride per liter and is regenerated with 1.5% sodium hydroxide solution. Owing to high attritional losses, Florex was not successful and the pilot plants using this material were abandoned.

::::: Activated Carbon :::: Most of the carbons prepared from different carbonaceous

sources showed fluoride removal capacity after alum impregnation. High Fluoride removal capacities of various types of activated carbons had been reported. Alkali digested alum impregnated paddy husk carbon was an efficient defluoridating agent. Investigations have shown that carbonized saw dust when quenched in 2% alum solution forms an excellent defluoridating carbon. The defluoridating process is stoichiometric and equilibrium is established between carbon & fluoride. On exhaustion (after continued use) the carbon can be regener

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