The use of nanofiltration for desalination of the Black Sea water with concentrate utilization and harvesting

Results of a new desalination project development are presented. The project offers a new solution for Black Sea water desalination using the increase of recovery to achieve brine harvesting. The desalination technology consists of treatment of seawater by four steps of low pressure NF and RO membranes. The use of NF membranes ensures successful separation of concentrate into sodium chloride, magnesium chloride and magnesium sulphate concentrated solutions. The process requires a pressure value of 16 Bars at all membrane stages that provides low power consumption for the process of brine concentration. Concentrating of the brine uses the technology of the “osmotically assisted” RO. The successful calcium sulphate deposition and ion separation achieved is attributed entirely to the use of the “nanoNF” membranes developed and produced by “Membranium” Co (Rosnanotech, Vladimir, Russia). The efficient separation of monovalent and divalent ions achieved due to the large difference in their rejection by “nanoNF” membranes: 45-50 per cent for monovalent ions and 85-85 per cent for divalent ions.