Laundry water recycling in ship by direct nanofiltration with tubular membranes

The present study deals with the feasibility to implement, on board ship, a direct nanofiltration process in order to treat laundry grey waters and recycle 80% to the inlets of the washing machines. At first, a specific methodology for real laundry grey water production was set up at the laboratory for the purpose. Characteristics of the lab-produced grey water are close to those observed on board (pH 7, 1300 mgCOD/L, 80 mgTSS/L). Then, a membrane screening in view of a selection was realised at the lab scale. A direct nanofiltration process (without pre-treatment) on tubular PCI-AFC80 membrane (35 bar, 25 °C, volumic-reduction-factor 5) allowed us to produce a permeate free of micro-organisms and suspended solids and with only 48 mgCOD/L and 7 mgTOC/L. Based on these satisfactory preliminary results, a techno-economic study was conducted (up-scaling) with the aim of producing daily 52 m3 of recyclable permeate from 65 m3 of polluted grey water. Finally, orders of magnitude, both for energetic consumption and processing costs, are proposed.