TECHNOLOGY FOR FLUORIDE REMOVAL FROM UNDERGROUND WATER

Membrane technology has been established as a proven technology for desalination of seawater to provide drinking water in coastal areas. Yet little attention has been given to explore its potential for treatment of groundwater having some inorganic pollutants. In this study, various membranes were tested to select a suitable membrane for this purpose. Initially, experiments were done with nanofiltration membrane and was observed that all the monovalent ions are rejected less as compared to bivalent ions. But fluoride shows exceptional behavior. This may be due to low solubility product of calcium fluoride. Thus fluoride may precipitate out in hard water and so rejected better. But, the problem associated with nanofiltration membranes is the very low recovery.

So, to overcome this problem hyperfiltration membrane was used and experiments were done at varying range of operating pressure, feed flow rate, pH of feed water, temp. of feed water and concentration of feed water, because the membrane separation efficiency depends upon operating conditions and chemical composition of feed water. Thus, optimum conditions for maximum efficiency were selected and the water samples collected from rural areas of district Gurgaon were treated at the optimum operating conditions. The results showed that at high pressure, hyperfiltration membrane rejects almost the all the ions upto 99%, thus leading to need of remineralization and cost is also high due to high pressure requirements. But at low pressure, rejection is in the range of 88% to 93%, which allows some essential minerals to remain in water and also the cost of process is reduced.