Pharmaceutically active compounds removal from surface water by membrane processes

Abstract

Pharmaceutically active compounds (PhACs) are a real threat all around the world as well as in Brazil. Conventional water and wastewater treatment are not efficient in the complete removal of these kinds of organic micropollutants of emerging concern ending up in the release of these compounds in the environment. This work aims to investigate the PhACs removal from surface water by membrane processes. Betamethasone and fluconazole, among the 28 assessed PhACs, were the most recurrent during monitoring of the Doce river located in Minas Gerais, which is used for drinking water catching and raw sewage disposal. The results show that the PhACs rejection by nanofiltration (NF) and reverse osmosis (RO) membranes is dependent of permeate recovery rate (RR) adopted The PhAC is completely retained at low RR, but increasing the RR above 40% and 60% for NF and RO respectively resulted in the membrane retention loss. The mechanism of NF and RO PhACs rejection involves size exclusion and hydrophobic interactions. Direct contact membrane distillation (DCMD)showed a rejection >99% for both fluconazole and betamethasone even at high RR (70% RR). The retention of PhACs by MD membrane occurs predominantly by membrane rejection which is mainly governed by volatility and, to a lesser extent, by hydrophobia. DCMD 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. Operational cost was estimated at 0.50, 0.43, and 1.96 US$/m3 for NF, RO and MD respectively. A factorial design 23 was used to assess the influence of natural organic matter and Ca and Fe ions on DCMD in order to achieve rejection of 25 PhACs in water. DCMD provided safe water with high PhACs removal (>98%) in all studied cases. The PhAC retention was not affected by HA, Ca and Fe ions in the concentration range evaluated (20-80 for HA, 12-200 for Ca and 12-200 for Fe), except for betamethasone. Permeate flux was not significantly influenced by HA concentrations and was associated to the presence of Fe and Ca. The mathematical model proposed here explained 63,7% of the total response variation, indicating a reasonable adjustment to the DCMD. Thus, in general, MD is less influenced by the feed composition than NF or RO, implicating in higher PhACs rejections, and although the cost was much higher than RO or NF, the possibility of utilization of renewable energy turns this process very promising for producing drinking water with much smaller concentrate production