Treating complex industrial wastewater in a new membrane-integrated closed loop system for recovery and reuse

AbstractA membrane-integrated continuous system was designed with new orientation of the membrane modules and investigated for treatment of industrial wastewater using forward osmosis (FO) in the upstream and nanofiltration in the recovery stage. Effects of applied pressure, cross-flow rate of feed water, variations of draw solution concentration and the run time on effectiveness of the system in separation and yield of pure water flux were studied in a continuous scheme in the context of pharmaceutical wastewater being a very complex system. Polyamide composite membranes out of a given lot were screened for application in FO and draw solute recovery stages. Two draw solutions in different concentrations (made of NaCl and MgSO4) were examined, where 0.5 M NaCl was found to be the best one for the FO stage. During investigation with pharmaceutical wastewater, more than 97 % purification could be achieved in terms of chemical oxygen demand while analysis of specific compounds such as Nebivolol and Paracetamol indicated almost 100 % removal. The study revealed that the new design could significantly reduce concentration polarization and reverse salt diffusion resulting in a sustained yield of pure water flux of around 52 L/m2h using NaCl as draw solute. Downstream nanofiltration module operated at only 12 bar trans-membrane pressure ensured continuous recovery and recycle of 99 % of the draw solute while producing safe reusable water at the rate of 58–60 L/m2h. The study culminates not only in a new design for a clean water environment but also in definite policy suggestions.