Membrane process treatment for greywater recycling: investigations on direct tubular nanofiltration

On-site greywater recycling and reuse is one of the main ways to reduce potable water requirement in urban areas. Direct membrane filtration is a promising technology to recycle greywater on-site. This study aimed at selecting a tubular nanofiltration (NF) membrane and its operating conditions in order to treat and reuse greywater in buildings. To do so, a synthetic greywater (SGW) was reconstituted in order to conduct experiments on a reproducible effluent. Then, three PCI NF membranes (AFC30, AFC40 and AFC80) having distinct molecular weight cut-offs were tested to recycle this SGW with a constant concentration at 25°C at two different transmembrane pressures (20 and 35 bar). The best results were obtained with AFC80 at 35 bar: the flux was close to 50 L m⁻²  h⁻¹, retentions of 95% for chemical oxygen demand and anionic surfactants were observed, and no Enterococcus were detected in the permeate. The performances of AFC80 were also evaluated on a real greywater: fluxes and retentions were similar to those observed on SGW. These results demonstrate the effectiveness of direct nanofiltration to recycle and reuse greywater.