Pump-less forward osmosis and low-pressure membrane hybrid system for the removal of selected pharmaceuticals from water

The number of pharmaceutically active compounds (PhACs) has increased with the development of the pharmaceutical industry and is continuously detected in aquatic environments. This study demonstrates a pump-less forward osmosis low-pressure membrane (FO-LPM) hybrid system for the effective removal of selected PhACs (i.e., propranolol (PRP), naproxen (NPX), and antipyrine (AP)), enabling sustainable and safe wastewater reuse. The optimal operating condition of the FO-LPM hybrid system was identified as a draw solution of 1 M NaCl and a nanofiltration membrane, providing an excellent balance between water flux and reverse salt flux. Under optimized conditions, maximum retentions of 98.8 %, 97.7 %, and 95.5 % for PRP, NPX, and AP were achieved, respectively. Additionally, different water chemistry parameters (solution pH, natural organic matter (NOM), and divalent cations (Ca²⁺)) were evaluated to understand the governing factors influencing PhAC retention in the FO-LPM hybrid system. In‘ the presence of NOM and divalent ions, the retention of PhACs by the FO-LPM hybrid system remained at 99.8 %. These results suggest that the primary governing factor for the retention of the selected PhACs by the FO-LPM hybrid system is size exclusion.