Water defluoridation using nanofiltration vs. reverse osmosis: the first world unit, Thiadiaye (Senegal)

The possibility of producing drinking water from brackish groundwater polluted with F- using nanofiltration (NF) process was previously studied at a pilot scale. Brackish groundwaters were taken from the south of Morocco (Tan Tan city) and from the center west of Senegal (Thiadiaye City). The performances of few commercialized NF spiral wound elements, low-pressure reverse osmosis (LPRO), and reverse osmosis (RO) were compared to a large-scale pilot experiments (membrane area, 7.6 m(2)). The following parameters were determined: hydraulic permeability, total salinity; and Cl-, F-, and SO42- removals were compared under the influence of various experimental parameters such as flow yield ratio, transmembrane pressure, energy consumption and water compositions before and after treatment. This study shows that NF provides specific advantages for fluoride removal as compared to LPRO and RO. Indeed, NF permits to reduce partially the total salinity and to reject selectively fluorides with a high flow yield ratio, at low pressure (lower than 20 bars) and therefore with a low energy consumption as compared to actual RO membranes. Furthermore, this paper presents the first NF plant in the world dedicated to water defluoridation by nanofiltration and built recently in Thiadiaye (Senegal) (fresh water production 33,000 L/h).