Background and purpose: Fluoride is a major mineral pollutant in groundwater. Long-term exposure to high concentration of fluoride in drinking water causes dental fluorosis, skeletal and non-skeletal fluorosis. Therefore, highly efficient water treatment that could lower the concentration of fluoride in groundwater is a challenge. This study aimed at evaluating the efficiency of Nanofiltration and the effects of pressure and temperature on the removal of fluoride from groundwater.
Materials and methods: The study was conducted in laboratory scale by pilot plant using Nanofiltration membrane (FILMTEC-NF90-4040). Raw water fluoride concentration was between 1.50 and 2.17 mg/L and pressures and temperatures were 4 to 12 bars and 10 to 30°C, respectively. Fluoride ion concentration was measured by spectrophotometry using a standard SPADNS method.
Results: The lowest and highest efficiency rates in removal of fluoride were 30% and 70%, respectively. We also observed that increase in pressure and temperature increased efficiency and the membrane permeate flow rate. Fluoride concentrations in all water samples were less than standard levels.
Conclusion: Nanofiltration was found with favorable efficiency in removal of fluoride from groundwater. Operating pressure and temperature are amongst the parameters that affect the performance of the process and increase the efficiency of fluoride removal by Nanofiltration.