Removal of fluoride from aqueous solution: status and techniques

Presence of various hazardous contaminants like fluoride, arsenic, nitrate, sulfate, pesticides, heavy metals, and other elements in ground water or surface water make the water unsafe and dangerous for the drinking purpose. The presence of any of these elements in drinking water in excess to the permissible limit is harmful for the human life. Fluoride is one of the elements which is very important for health especially for the children during teeth formation as well as harmful for human health if present in water more than permissible limit. Absence or insufficient amount of fluoride in drinking water causes dental caries during teeth formation of children whereas the presence of excess fluoride in drinking water causes dental and skeletal fluorosis. Therefore, maintaining of fluoride concentration within the safe limits is very important. The presence of excess fluoride in drinking water is a global problem. Excessive fluoride concentrations have been reported in ground waters of more than 27 developed and developing countries including India. In India, about 19 states are facing acute fluorosis problem due to excess fluoride concentration. Fluoride is the major inorganic pollutant of natural origin found in ground water. The excessive fluoride from the drinking water should be reduced to the permissible limit. Various technologies such as coagulation-precipitation, ion exchange, electrocoagulation/electrochemical treatment, membrane processes, nanotechnology, and adsorption are being used to remove fluoride from water. Every method of fluoride removal has its advantages and limitations of operations. The selection of treatment process should be site specific as per local needs and prevailing conditions as each technology has some limitations. The present paper deals with the short review on sources of fluoride, its effects on human health, and the techniques available for removal of fluoride from drinking water.