Treatment of Nanofiltration and Reverse Osmosis Concentrates: systematic study of coagulation, precipitation, and ion exchange

This paper discusses the treatment of membrane concentrate from nanofiltration (NF) and reverse osmosis (RO) between primary and secondary membrane stages, in an effort to increase membrane recovery rates and decrease the concentrate volume. The paper evaluates lime softening, ferric sulfate coagulation, and ion exchange as individual, intermediate treatment processes for membrane concentrate. The objectives of this paper was to determine the effect of the chemistry of membrane concentrate on treatability, compare coagulation, softening, and anion exchange in terms of removal efficiency of DOM and inorganic ions, and to evaluate combined ion exchange as a treatment process that targets both DOM and inorganic ions.