The removal of pharmaceutical compounds from water using membrane processes : performance, mechanisms, and the effect of salt.

Abstract

The occurrence of several categories of pharmaceutically active compounds (PhACs) has been reported in different water bodies all around the world. The risks of this issue are still not fully understood, however, the exposure to a plethora of PhACs creates a matrix effect that is bound to have repercussions on the environment and may constitute a “human health risk”. The properties of these contaminants and the bodies in which they exist are diverse, so their removal proves to be a challenge for conventional water and wastewater treatment technologies. Membrane processes, such as nanofiltration (NF) and reverse osmosis (RO), have gained popularity over recent years as an effective treatment technique for the removal of contaminants of emerging concern from water. This study aimed at evaluating the performance of a bench-scale membrane unit in removing PhACs from various water matrices. It investigated the removal of three common pharmaceuticals, individually and as a mixture: carbamazepine (CBZ), ibuprofen (IBF), and diclofenac (DCF). In addition, the influences of the PhACs properties, membrane types (NF, RO) and salt concentration on the removal process were studied. The effects of salt and the PhAC mixture were found to be more pronounced for NF membranes rather than RO, and for compounds with smaller molecular weights. These effects, when present, also varied based on the properties of the compounds such as the charge, size, and hydrophobicity, thus enhancing retention in some cases while reducing it in others. High rejection values (99percent) were reported for all PhACs in RO filtration at all salt concentrations. However, NF retention values varied for the different PhACs based on their properties as well as on the salt concentration. DCF rejection with NF was found to be high (90-99percent) as well as IBF rejection (85-96percent) and increased with increasing salt concentration. Moderate retention values were found for CBZ (65-77percent) and decreased with increasing salt concentration. All salt effects were buffe