A membrane-integrated closed loop system for treatment of pharmaceutical wastewater

Experimental investigations were carried out in amembrane-integrated continuous FO-NF(Forward Osmosis-Nanofiltration) system for effective treatment of pharmaceutical wastewater. Effects of applied pressure, cross flow rate of feed water, variations of draw solution (DS) concentration and the run time on efficiency of treatmentof pharmaceutical wastewater were studied. Polyamide composite membranes were screened for application in forward osmosis and draw solute recovery stages. Draw solutions in different concentrations (NaCl and MgSO4) were examined for selection of the best type(0.5M NaCl) for the forward osmosis (FO) stage. Above 97% purification could be achieved in terms of chemical oxygen demand while analysis of specificcompounds such as Nebivolol and Paracetamol indicated almost 100% removal. The new design significantly reduced concentration polarization and reverse salt diffusion resulting in a sustained yield of pure water flux of around 52 L/m
²
h with NaCl as draw solute. By operating the downstream nanofiltration module at only 12 bar transmembrane pressure, continuous recovery and recycle of 99% of the draw solute could be done while producing safe reusable water (as per WHO standard)at the rate of 58-60 L/(m
²
h).