Evaluating the treatment of synthetic secondary treated tannery effluent by forward osmosis: Effect of draw solution concentration

Forward Osmosis (FO) is a suitable pretreatment process to Reverse Osmosis (RO) for secondary treated sewage reuse and secondary treated industrial effluents. In this study, FO process employing aquaporin FO membrane is investigated for concentrating synthetic secondary treated tannery effluents using 20 g/L and 38 g/L of NaCl solution as draw solution (DS). Results showed that 38 g/L NaCl solution when used provided higher flux and lower flux decline ratio as compared to 20 g/L NaCl solution. The solute rejection by FO membrane was more in FO experiments using 38 g/L NaCl solution as DS as compared to 20 g/L NaCl solution. Contact angle, fourier transform infrared spectroscopy and scanning electronic microscopy tests on pristine and chemically cleaned membranes indicated change in membrane structure and presence of foulants on membrane surface indicating insufficient chemical cleaning. Findings signify implications on concentration of DS and cleaning method adopted for concentrating treated tannery effluent using FO process.