Environmental and human health risk assessment of pharmaceuticals in surface and drinking water treated by conventional and membrane separation processes

Abstract

The aim of the present study was to assess environmental and human toxicological risk of pharmaceutically active compounds (PhACs) in raw and treated water of four Brazilian water supply systems and to analyze the risk reduction capacity of nanofiltration (NF), reverse osmosis (RO) and membrane distillation (MD). In order to achieve this, 28 compounds were selected for evaluation. PhACs were quantified by high performance liquid chromatography (HPLC) coupled to mass spectrometer (MS). The hazard quotients (HQ) were calculated by the ratio between the highest measured environmental concentrations (MEC) in each water source and the predicted non-effect concentration (PNEC). The human margin of exposure (MOE) was calculated by the ratio between the safe exposure level, estimated by the tolerable daily intake (TDI), and the MEC. Pharmaceutical compounds residues were detected in all evaluated water supply systems, in concentrations in the order of ng/L. Betamethasone, prednisone and fluconazole were the most frequent and abundant compounds, both in surface and treated water. PhAC occurrence was susceptible to seasonality and to the socio-economic conditions of the region. Regarding toxicity potential, less than 1% of the evaluated PhACs were classified as non-toxic and approximately 60% were considered highly toxic. Both raw and treated water from the four water supply systems were subject to environmental risk at some level owing to at least one PhAC. The toxicological risk reduction capacity of conventional DWTPs was only partial, making potable water still a risk to the environment. Besides, atorvastatin presented MOE below 100, indicating a significant risk to public health. NF, RO and MD processes were applied for the treatment of one of the evaluated water supply systems and the results confirmed the high PhAC removal capacity of the membrane separation processes (MSP). PhAC rejection of NF and RO decreased with the increase of the permeate recovery rate (RR). It was possible to quantify the compounds in permeate stream at 40% and 60% of recovery rate, respectively. MD was able to reduce PhAC concentrations until below the quantification limit up to a RR of 70%. Owing to the high removal efficiency and, consequently, the low concentration of PhACs in the water treated by the MSP, no environmental or human health toxicological risk was observed. Besides presenting the highest PhAC removal, MD showed no tendency to fouling, which was the main cause of flux decline in RO and NF processes. On the other hand, MD presented the highest operating cost, which could be reduced, however, by using low-cost energy, such as solar or residual heat.