Continuous regeneration of the draw solution in textile wastewater treatment using a combination of simultaneous forward osmosis and reverse osmosis

• Textile wastewater was treated by simultaneous forward osmosis and reverse osmosis. • FO draw solution was continuously concentrated by RO. • Chemical oxygen demand and total organic carbon were rejected above 99%. • Simultaneously, clean water was obtained as the reverse osmosis permeate. The concerning and abundant textile wastewater can be treated by forward osmosis (FO) in order to reduce its volume and simultaneously recover clean water. However, the productivity of FO depends on the concentration of the draw solution that is used. In this work, a simultaneous application of FO and reverse osmosis (RO) is proposed. The HFFO14® FO membrane (Aquaporin, Denmark) was employed to concentrate a real textile wastewater, whereas the SW30-2540 (DuPont, USA) RO membrane was employed to simultaneously regenerate the draw solution, which consisted in a 0.7 M NaCl solution, and to obtain a clean water stream. The concentration of the textile wastewater increased until 90% water recovery was achieved. The rejection values obtained for the chemical oxygen demand and total organic carbon were in the range 99 – 100%. Afterwards, the previously concentrated textile wastewater was again processed until a volume concentration factor of 16.5 was reached. Stable values of permeate flux (around 4 L/h·m 2 ) were obtained in the FO process, whereas the reverse osmosis step permitted the maintenance of a stable conductivity in the draw solution and provided clean water as permeate.