Desalination of Groundwater from a Well in Puglia Region (Italy) by Al₂O₃-Doped Silica and Polymeric Nanofiltration Membranes

Some of the groundwater aquifers in the Puglia Region, Italy, suffer from high salinity and potential micropollutant contamination due to seawater infiltration and chemical discharge. The objective of this study is twofold: to evaluate the performance of the recently reported alumina-doped silica nanofiltration membranes for water potabilization, and to provide a possible solution to improve the groundwater quality in the Puglia Region while maintaining a low energy-footprint. Two lab-made alumina-doped silica membranes with different pore structures, namely S/O = 0.5 and S/O = 2, were tested with real groundwater samples and their performances were compared with those of a commercial polymeric membrane (Dow NF90). Moreover, groundwater samples were sparked with acetamiprid, imidacloprid, and thiacloprid to test the membrane performance in the presence of potential contamination by pesticides. At a trans-membrane pressure of 5 bar, NF90 could reduce the groundwater conductivity from 4.6 to around 1.3 mS·cm−1 and reject 56–85% of the model pesticides, with a permeate flux of 14.2 L·m−2·h−1. The two inorganic membranes S/O = 2 and S/O = 0.5 reduced the permeate conductivity to 3.8 and 2.4 mS·cm−1, respectively. The specific energy consumption for all three membranes was below 0.2 kWh·m−3 which indicates that the potabilization of this groundwater by nanofiltration is commercially feasible.