The application of reverse osmosis and nanofiltration to the removal of nitrates from groundwater

The intensive development of agriculture and application of chemicals led t o the contamination of many natural water reservoirs and groundwaters with nitrates. This paper reviews an attempt at removal of nitrate ions from tap water by means of the combined processes of reverse osmosis and nanofiltra tion. In the first stage, the water was filtered on nanofiltration membrane s which resulted in the absence of bivalent ions in the obtained permeate. Then the filtrate was concentrated using reverse osmosis. Because the subst ances forming membrane scale (CaSO4, CaCO3) were removed from the filtrate, the efficiency of this process was limited mainly by the osmotic pressure of the retentate.