AN IMPROVED METHOD OF FLUORIDE TREATMENT 
IN AQUEOUS EFFLUENT

INTRODUCTION 

For human consumption, fluoride concentration in water should be between 0.8 ppm to 1.5 ppm. Potable water having fluoride less than 0.8 ppm is not good for tooth, bone etc. Again, if the fluoride concentration is more than 1.5 ppm, it causes a disease called "fluorosis", which is a major problem in many villages of our country.

In industrial effluents, fluoride concentration can be as high as 5%. This industrial fluoride effluent can be of both acidic and alkaline nature. If this high concentration of F- ion is not treated properly before its disposal, it may lead to serious environmental and public health hazard. So, the fluoride waste is generally treated by the conventional method of lime treatment before its final disposal. By this method, though the fluoride concentration of the effluent can be reduced, it can not be lowered to less than 10-15 ppm. Further, solubility of CaO specially in alkaline medium or in plain water is poor as a result of which the whole process becomes very slow. 

PROCESS 

As per the improved patented method developed in Bhabha Atomic Research Centre, the process consists of Calcium (Ca⁺²) treatment of effluent followed by complexing the fluoride ion and pH control. This method has been very effective to reduce the fluoride concentration in both acidic and alkaline effluents, down to 1.5 ppm. The process as such is relatively faster also. The solid waste, primarily CaF₂ generated out of this process, can either be dried and used/sold or disposed off as solid waste depending upon the specific industrial activity.

EQUIPMENT 

The standard chemical processing equipments such as treatment tanks with agitator, settling tanks, pumps , filter presses, pH meter, flow meters and fluoride specific ion meter would be required.

INFRA-STRUCTURE REQUIREMENT