Arsenic-contaminated groundwaters remediation by nanofiltration

Arsenic (As) is one of the most dangerous inorganic pollutants for the environment and human health that can be found in water streams. Membrane processes, like nanofiltration (NF) and reverse osmosis (RO), have successfully been applied for the removal of arsenic, but mainly from model solutions. Therefore, their efficiency in treating real contaminated sources, where also other species are present, still needs to be deeply investigated. In this direction, the present research deals with the application of NF for the remediation of natural As(V)-contaminated groundwaters. The sampling area was located in the Sila Massif (Calabria, Italy) where high values of arsenic in different environmental matrices, such as rocks, soils and waters, were detected. The geochemical analysis of three groundwaters showed As values exceeding the permitted content (10 ppb). These samples were treated by NF using two types of membranes commercialized by GE Osmonics, named HL and DK, both made of polyamide thin-film and with the same molecular weight cut-off (MWCO), but presenting different MgSO4 rejections and water fluxes. During the experiments, the water flux and the As rejection for each membrane at different operating pressures were evaluated. Both membranes led to an arsenic concentration in the permeate lower than 10 pbb for groundwaters with arsenic contents ranging from 59 to 118 pbb, while the highest water flux was obtained with the HL membrane.