A hybrid method for the removal of fluoride from drinking water: Parametric study and cost estimation

A hybrid technique (electrocoagulation followed by microfiltration) was utilized for an efficient defluoridation of contaminated drinking water. Three samples of drinking water with an initial fluoride concentration of 7.89, 4.79 and 1.78 mg/L were collected from a hand tube well located in Karbi Anglong district of Assam, India. Effects of different operational parameters such as initial fluoride concentration, current density and pH on the removal of fluoride were extensively investigated in the electrocoagulation chamber. For a current density of 15 A/m(2) and an electrode distance of 0.005 m, an efficient removal of 0.0097, 0.335 and 0.656 mg/L was observed for initial fluoride concentration of 1.78, 4.79 and 7.89 mg/L, respectively. The uptake of fluoride was the highest at pH = 7.9 with a final fluoride concentration of 0.43 mg/L. Filtration studies were performed using indigenously prepared membrane. An increase in flux from 7.98 x 10(-5) to 19.19 x 10(-5) m(3)/m(2) s was observed with an increase in transmembrane from 196 to 509 kPa. Produced flocs were scraped from the membrane surface, dried and characterized to confirm the presence of fluoride. The proposed hybrid technique was able to lower the concentration of fluoride from contaminated drinking water within the permissible limit as per WHO of 1.5 mg/L.