Assessing potential of nanofiltration, reverse osmosis and membrane distillation drinking water treatment for pharmaceutically active compounds (PhACs) removal

Abstract

This study investigates the rejection of pharmaceutically active compounds (PhACs) by nanofiltration (NF), reverse osmosis (RO), and membrane distillation (MD). The Doce river located in Minas Gerais (Brazil - geographical coordinates 18°51′50.45″S and 41°56′46.86″ W), which is used for drinking water catching and raw sewage disposal, was chosen as the background matrix for this study. Betamethasone and fluconazole, among the 28 assessed PhACs, were the most recurrent during monitoring. The results show that the PhACs rejection by NF and RO membranes decreases as the permeate recovery rate (RR) increases. The first PhAC occurrence in the permeate happened at 40% and 60% RR for NF and RO, respectively. MD showed a rejection > 99% for both fluconazole and betamethasone for up to 70% RR. NF and RO reject PhACs mainly through size exclusion and hydrophobic interactions, whereas, MD rejects PhACs due to their low volatility. All evaluated processes lead to a toxicological risk reduction. MD did not show any tendency of fouling, while NF and RO show flux decline mainly due to membrane fouling, which was more evident in RO. The membrane fouling occurred due to deposition and/or pore blocking by natural organic matter since the water salts concentration is low. Opex was estimated at 0.50, 0.43, and 1.96 US$/m3 for NF, RO and MD respectively. Although the MD process is more robust, the practical application is restricted by the high cost. And, NF and RO are feasible alternatives to remove PhACs from drinking water.