Environmental risk of pharmaceuticals in waters: Investigation on their occurrence and removal in conventional treatment plants

At present, approximately 15000 different pharmaceutical compounds are used in the European Union, including analgesics/anti-inflammatories. antibiotics, beta-blockers, lipid regulators, antidepressants and many more, for human consumptions (therapeutic or diagnostic purposes). One important emission source of pharmaceuticals in the water cycle is via human metabolism: in fact, once administered, these compounds are only partially metabolized by the human body, and therefore enter the water cycle either as parent (unchanged) compounds, or as a mixture of metabolites and/or conjugated compounds. Unfortunately, municipal wastewater treatment plants (WWTPs) are generally unable to effectively remove either unaltered or metabolized forms of pharmaceutical compounds (PhCs) from wastewaters, and as a results their occurrence in surface water has been documented. While the presence of pharmaceuticals in the environment is established, sources of these compounds in the environment, the pathways by which they reach sensitive receptors and their effects on these receptors are less characterized, moreover the latter must be determined before the effectiveness of risk mitigation measures can be assessed. Hospital wastewater (HWWs) represent an important source of PhCs, but has only slightly been investigated. In this work, an experimental investigation was conducted in the area of Ferrara, Italy, on the effluent of two different sized hospitals and the influent and effluent of the receiving municipal treatment plant of one of the examined hospitals. The aim was to investigate 73 selected pharmaceuticals, belonging to twelve different classes, comparing their occurrence in the effluent directly exiting the hospital with that, mixed with the local urban effluent, at the points of its entry and exit from the treatment plant. Consistent differences were found in the concentrations of some antibiotics, analgesics and lipid regulators in the two wastewaters, confirming that hospital effluents should not be considered as possessing the same pollutant nature as urban wastewater. Furthermore, analysis of percentage contributions of the hospital to the treatment plant influent evidences that hospitals represent one of the main sources of pollutants, in particular antibiotics, receptor antagonists and lipid regulators. Hence, an environmental risk assessment, performed on the effluent from the hospital and the influent and effluent from the treatment plant, revealed a high risk for 9 pharmaceuticals in hospital effluent and for 4 of the 9 substances in the treatment plant influent and effluent, with antibiotics being the most critical compounds in terms of contribution and potential environmental risk for the hospital. Moreover, the occurrence of 27 pharmaceutical compounds, belonging to different classes, in the effluent from two full-scale wastewater treatment plants (WWTPs) and their receiving water bodies in the sensitive area of the Po Valley (northern Italy) has been investigated. The receiving water bodies were monitored upstream and downstream of the effluent discharge points in order to evaluate the effluent impact on the quality of surface waters, commonly used for irrigation. Consequently, an environmental risk assessment was also conducted by calculating the risk quotient, i.e. the ratio between measured concentration and predicted no effect concentration. Collected data show that, although average values of the selected compounds were in general higher in the effluent than in the surface waters, some compounds not detected in the WWTP effluent were detected in the receiving water (upstream as well as downstream), indicating that sources other than treated effluents are present as contaminations during extraction and analysis have to be excluded. The most critical compounds for the environment were found to be the antibiotics sulfamethoxazole, clarithromycin and azithromycin. The study shows that the potential toxicological effects of persistent micropollutants can be mitigated to some extent by a high dilution capacity, i.e. a high average flow rate in the receiving water body with respect to the effluent. The results obtained from the conducted experimental investigations have been compared with those calculated by prediction models that represent the base for the environmental risk assessment. The results showed that there are differences between predicted and measured concentration, and these differences varied among the selected compounds and the sampling points investigated (influent, effluent and surface water), both predicted and measured concentrations are plagued by uncertainty and indicate that calculation models still need considerable refinement to increase model reliability and discriminative power. Finally, a tool to estimate the level of environmental risk posed by PhCs originated from HWWs at site specific catchment area to aid the authorities and decision makers in the management of HWWs and the reducing of PhCs discharged into the environment has been developed. The results suggest that due to the presence of PhCs, HWWs could pose a risk for the receiving environment and their risk is relevant to many factors. Erythromycin and sulfamethoxazole are potentially compounds of concern in the HWWs and they required a management, whilst other compounds may not required any management due to their low risk. The risk posed by HWWS due to the presence of PhCs could be reduced with various degree, and it is relevant to the characteristics of each catchment area where the hospital is situated. In some cases, the pathway of HWWs contribute significantly to the risk in the influent of a site-specific WWTP, and their contribution is correlated to the bed density. Nevertheless the limitations that the proposed tool experienced, it is provide a useful information about the management options that should be adopted to reduce the risk of HWWs.