Membrane Filtration of Groundwater for Removal of Fluoride and Arsenic in Gombe State

Elevated fluoride and arsenic concentrations in groundwater sources across Gombe State, North East Nigeria, have been associated with dental fluorosis and skin disorders in affected communities. This study evaluates nanofiltration and reverse osmosis membrane technologies for simultaneous removal of fluoride and arsenic from groundwater sourced from boreholes in Gombe and Dukku Local Government Areas. Groundwater samples containing fluoride concentrations of 4.8 to 7.6 mg/L and arsenic of 32 to 68 micrograms per litre were treated using flat-sheet nanofiltration and reverse osmosis membranes in a cross-flow bench-scale unit at transmembrane pressures of 5 to 15 bar. Permeate and concentrate samples were analysed for fluoride by the SPADNS colorimetric method and arsenic by atomic absorption spectrophotometry. Flux decline during filtration was monitored, and membrane fouling potential was assessed using modified fouling index measurements. The reverse osmosis membrane achieved fluoride rejection of 97.3% and arsenic rejection of 98.7% at 10 bar, producing permeate that met NSDWQ limits. The nanofiltration membrane achieved 84.1% and 81.2% rejection for fluoride and arsenic, respectively, at 12 bar with significantly higher permeate flux. Energy consumption for the reverse osmosis system was 0.48 kWh/m3 at 10 bar. A community-scale reverse osmosis unit sized at 5 m3/day would be economically feasible for communities of 200 to 300 people in Gombe State with appropriate subsidy support. Keywords: nanofiltration, reverse osmosis, fluoride removal, arsenic, Gombe State