Various types of Fluoride exist. The naturally occurring Calcium Fluoride exists in the earth's crust. The second is a man made byproduct of industry typically a combination of Hexafluorosilicic Acid and Sodium Silocofluoride. They are a waste byproduct from Phosphate Rock.

Fluoride in water occurs in two ways. Calcium Fluoride is naturally occurring in the earth’s crust and is often found in worlds water supplies accross the globe. Sodium Fluoride is the manufacturing byproduct of the Aluminum, steel and agricultural industries. It was initially disposed of in city cround water. The aluminum industry leaders successfully obtained approvals from regulatory agencies to dispose of in ground water. Once accepted, it became a new industry in and of itself for the primary manufacturers of the original waste byproduct. Today there are a variety of compounds that make up fluoridation products. Two widely used compunds are include sodium floride and sodium fluorosilicate.

Fluoride may or may not be beneficial in small quantities, though fluorosis can occur when consumed in excess amounts. Various technologies are being devoloped in both the developing and developed world as demand for defluoridation increases. Public awareness is in it's infancy on the topic as of now, and most people are either unaware of the fluorosis or assume their water suppliers are managing the matter.

It is estimated that less than 2% of Europe adds some type of fluoride to their drinking water. It is estimated that up to 64% of the United States municipalities purchase fluoride from the Fluoride industry and add it to drinking water. Long Island, NY's Nassau County water municipalities have discontinued fluoride's use. Suffolk County, LI, NY has never used fluoride in it's water supply. Portland, Oregon has never had fluoride added to their water supplies. Countries like France, Japan, Italy, Belgium Scotland, the Scandinavian countries, and others have never added fluoride, or else stopped adding it. Israel has banned fluoridation for 2014 – mandatory or voluntary. Today there is a lessening of municipalities adding fluoride to water supplies.

Fluoride typically occurs in the earths crusts as fluorspar(CaF2),cryolite (Na3AlF6), apatite(Ca5(PO4)3F), rock phosphate, mica, and hornblende. Rarely found outsid of it's iconic form (fluoride) Fluorine is the most electronegative element and is extremely reactive. Fluoride leaches off minerals and into groundwater. Worldwide the negative impact is increasing. As the population of the developing world continues to climb, people are forced to move into fluorotic areas.

Fluoride can contaminate water from man-made causes such as mining and the use of certain pesticides.

East Africa, mostly, the East African Rift Valley is affected severely by fluorosis likely because fluorotic minerals are often carried by water, evidenced by the fluoride rich soils in lowlands or valleys. Nearby highlands usually carry less fluorosis. The high fluoride volcanic rocks in the East African Rift result in significant amounts of fluoride in the Rift Valley. More than 61% of East African water sources having more than 1 mg of F /l (the recommended amount), 20% having more than 5 mg/l, and 12% having over 8mg/l.

Causes of Fluorosis

Developed nations often put fluoride intentionally into municipal water systems. Fluoride has been claimed by proponents to to give protection to tooth enamel. This has theory has been challenged by researchers after studies have shown it inconclusive. However fluoride in water is considered toxic when it reaches concentrations of 250 mg/l. Fluoride is retained by the body in large part when consumed. and will bioaccumulate over time and can result in fluorosis. The World Health Organization (WHO) recommends the ingestion not to exceed 4.0 mg of fluoride per person per day. Fluoride also comes from food, though the majority of fluorosis occurances come from the consumption of water with excessive amounts of fluoride. The WHO limits fluoride concentrations in drinking and cooking water to 1.5 mg though many suggest that 0.5-1.0 mg/L should be the limit. Because it is not so much the concentration of the fluoride that is of concern, but rather the total fluoride consumed. Fluoride limits should be used based on the average maximum temperature as well.

Defluoridation Process

Defluoridation of water reduces the concentration of fluoride in the water, to make it safe for human consumption. Various water treatments have the ability to reduce fluoride concentration including most other anions, and or cations in the water, are not considered to be defluoridation methods. General demineralising methods such as distillation, electrodialysis and resin de-anionisation reverse osmosis, which are able to remove fluoride are not , considered as defluoridation methods. A method that only remove's fluoride without any addition or reduction of other parameters is not yet discovered. The term “fluoride removal” is inprecise. Defluoridationis used to characterise methods that reduce the fluoride ion specifically, without major other changes to the quality of the treated water. The process of Defluoridation to reduce or remove floride is of singnificant importance to many nations, regions, and idividuals concerned with excess fluoride.

Defluoridation of water differs water treatments normally piped:

• Flluoride does not deteriorate the piped water quality technically or oganoleptically. It is usually only required for the portion of the water that is used for drinking and cooking.
• Defluoridation of large quantities of water, is environmentally unsound because of the accumulation of correspondingly large quantities of toxic sludge would create a more severe challenge to manage.
• Most large cities and towns are historically built in sites that use good water sources and do not need defluoridation..
• Industrialised countries easily prospect and transporting low fluoride water thereby reducing the need for defluoridation.

Defluoridation is most often required in rural areas in developing countries. Many defluoridation approaches have been launched, without unbiased field proof of success. The process or the technical set-up that may work in one context of socio-economic and environmental situation may be innefective in another. Local availability and acceptability of the required materials, fluoride contamination level and water quality are major factors to be considered when selecting the process and the design that minimises the capital and running costs.

Defluoridation technology can be simple, affordable, reliable and effective in various situations.

• Domestic: e.g. in the kitchen where piped water may likely or may not even be available.
• Community: e.g. a village or a market where the defluoridator is supplied with water through a pipe or a hand or power pump.
• Institutional: e.g. in schools/ working places where piped water may be available. The defluoridator should be protected from theft or misuse.
  

Defluoridation Process:

Sorption

A sorption process is normally designed in a plug flow filter column, including a medium that has a certain capacity of absorption, adsorption or ion exchange of the fluoride. This process requires recharge or regeneration of the medium upon saturation. Numerous media are known to have defluoridation properties, cf. Table.

Note: Bone char and activated alumina are worth mentioning (based on capacity, limitations and availabilty). Similar set-ups can be utilised in the activated alumina process which is preferred in strictly vegetarian societies that consider the use of (cow) bone char as unnaceptible.