Fluoride mainly enters the human body through drinking water; 96-99% of it combines with bones, as fluoride has affinity for calcium phosphate in the bones. Excess intake of fluoride can lead to dental fluorosis, skeletal fluorosis, or non-skeletal fluorosis. According to WHO, the prevalence of Dental Fluorosis is correlated to drinking water fluoride in the following manner.
Fluoride in water has been proven to prevent tooth decay among children and to prevent root tip rot. The chemical acts by strengthening the tooth enamel and by making the enamel more resistant to decay. Although fluoride is safe at the concentrations less than 1.5 mg/L, an excess amount of fluoride in water can result in mottled brown stains on teeth. These stains is called dental fluorosis, which results from fluoride concentrations of 1.5 mg/L in drinking water.Dental Fluorosis is characterized, by discolored, blackened, mottled or chalky-white teeth. Extreme concentrations of fluoride can cause skeletal Fluorosis. Skeletal Fluorosis leads to severe and permanent bone and joint deformations. Fluorosis is an irreversible disease and there is no cure. Fluorosis is a disease that neither allows a person to live nor to die. Non-skeletal Fluorosis leads to gastrointestinal problems and neurological disorders. Fluoride can damage a fetus, and adversely affect the IQ of children.
Fluorosis can be detected in the neck, spine, knee, pelvis, shoulder and small joint of hands and feet. Castro-intestinal symptoms include abdominal pain, diarrhea, and constipation. Some neurological manifestations are nervousness, excessive thirst and tendency to urinate frequently. In spite of all these symptoms, it is common Fluorosis to remain un-diagnosed for a long time. In India fluorosis has spread across states, and across a variety of ecological regions.
Removal of fluoride from water is known as water treatment defluoridation. Once excess fluoride is detected in water, the obvious step is to defluoridate water. The technology to be adopted depends upon the fluoride levels in water and the volume of water to be defluoridated.
Fluoride removal plants installed in USA use beds of tri calcium phosphate as a base ~exchange material. These beds are regenerated by flushing with 1 to 1.5% sodium hydroxide solution followed by a dilute hydrochloric acid wash, or by use of CO2 to neutralize the excessive alkalinity resulting from the initial wash. There are two processes available for the treatment fluoride contaminated water. They are;
In the Activated Alumina Technology, if local alumina is used it has to be regenerated using acid and alkali whereas imported alumina does not require any regeneration. However the operation of the plant which is depending upon the import of alumina is not possible for long run. The disposal of solid alumina waste may lead to leaching out of aluminum and fluoride which may cause health hazards and pollute the nearby ground water sources.
The Reverse osmosis water treatment process can be used for places where the quality of water is affected either by single parameter or multiple parameter such as fluoride, Total dissolved solids, Total hardness, etc. For operating the plant high technical skill is required which may not be available in the rural areas. Further, this process involves prohibitive cost of operation and maintenance.
In India various technologies have been tested. “Ion exchange and chemical treatments are cost intensive, while physical methods suffer limitations, like frequent change in fluoridation beds and the inability to reduce fluoride to non-toxic levels. The clean-up schemes – both large and small have failed because of improper management.