Defluoridation of Ethiopian Rift Valley Region water using reverse osmosis membranes

Abstract

Defluoridation of Ethiopian Rift Valley Region (ERVR) raw ground water using reverse osmosis (RO) membranes was studied. Four RO membranes CA995PlE, HR98PP, LFC and ESPA delivered by DSS and Hydranautics were investigated for the retention of fluoride in fluoride water. All four membranes were observed to effectively retain fluoride. The fluoride retention of the membranes were in the ranges from 94 to 99% and larger than those of chloride. The LFC membrane was tested for Ethiopian Rift Valley Region raw ground water. For the same range of feed concentration, the retention and permeate fluoride concentration is comparable for raw ground water and artificially constituted fluoride water. However, the membrane fouling was serious. About 85% of the flux loss was recovered by treating the membrane with HNO₃ solution with pH 2 at 50 °C. The true causes of the fouling and the best treatment for the fouled membranes requires further investigation.