Dual-stage nanofiltration seawater desalination: water quality, scaling and energy consumption

A dual-stage nanofiltration (NF) seawater desalination process was investigated as a novel seawater desalination technology, focusing not only on the permeate water quality, but also on the scaling possibility and energy consumption. Dow Filmtec(TM) NF90 was used in the experiment for its high rejection of total dissolved solids (TDS). The results show that the permeate TDS from the second stage could be as low as 200mg/L under an optimized condition. The operating pressures were only 3.5MPa in the first stage and 2.0MPa in the second stage. Operation pressure had the most significant effects on water permeate flux and TDS. Several indices were calculated to investigate scaling probability. The results indicate that scaling could occur in the first stage. Thus, a prevention method would be needed. The effects of the operating parameters on the energy consumption were also examined. The results indicate that dual-stage NF seawater desalination is a feasible technology in the view of water quality and energy consumption.