Nanofiltration of textile wastewater for water reuse

Abstract

The textile industry produces a large amount of wastewater that is highly coloured with high loading of inorganic salt. Crossflow nanofiltration using thin film composite polysulfone membrane was used to recover the electrolyte solution and reject the colour. Using a synthetic textile effluent of reactive dye and NaCl solution, the study focused on the mechanism controlling flux and rejection by varying four main parameter; crossflow velocity, initial dye concentration, feed pressure, and electrolyte concentration. Results show that flux was dominated by the osmotic pressure created from the presence of NaCl, and that dye concentration did not significantly effect the flux or rejection. Working at low pressures of up to 500 kPa, relatively high fluxes were obtained, with an average dye rejection of 98% and NaCl rejections of less than 14%. Thus, a high quality of reuse water could be recovered. Even after a number of cycles, the membrane did not foul irreversibly, with an overall mean waterflux recovery of 99%.