Occurrence and fate of emerging contaminants in wastewater, groundwater and drinking water

The presence of organic micropollutants (OMPs) in the aquatic environment is believed to pose risk to human health and ecosystems. Humans with different demographic characteristics and anthropogenic activities are the main OMPs producers in the aquatic environment. These substances are entered into the sewage networks and raw wastewater in wide ranges. In many cases, WWTPs are not capable of effectively removing OMPs and therefore these OMPs residuals are discharged into the surface water with treated effluent. On the other hand, these compounds contaminate the groundwater by leakage from the sewage networks and septic tanks, and exchange between groundwater and surface water. A serious problem occurs when contaminated surface water and groundwater are used as a source of drinking water. Due to the fact that the conventional drinking water treatments like coagulation, flocculation, and disinfection, are not specifically designed to remove these organic micropollutants, the OMPs residues remain in the treated water and thus the development and implementation of additional (advanced) treatment steps, like activated carbon, ozonation, ultraviolet light, and membrane treatment, are strongly recommended although more expensive in operation and maintenance costs. On the other hand, reducing the amount of OMPs discharged in water resources could be more cost-effective to tackle the risk of emerging organic contaminants than the additional advanced treatments. These reasonings are also in line with the current policy strategies to manage OMPs residues which are turned from reactive to proactive to more efficiently tackle the issue of the OMPs environmental risk. To support this from reactive to proactive transitions some relevant improvements should be pursued in the available knowledge on the occurrence, fate, toxicity, human health and ecological risks of OMPs residues, in order to support the implementation of source-oriented and use-oriented policy approaches, aimed to prevent and reduce pollution and to implement end-of-pipe measures to safely dispose and remove OMPs residues in a cost-efficiency perspective. In this study, three different components of the OMPs environmental risk framework were investigated. The first component concerns the presence of OMPs residues in the effluents of wastewater treatment plants (WWTPs) that are significant polluting sources for surface waters. The second component is about the presence of OMPs residues in the groundwater which is also very frequently used as a drinking water supply source, and the last component is related to the OMPs residues in the effluent of drinking water treatment plants (DWTPs) and the robustness of different water treatments against OMPs in DWTPs. Since exchanges between the aquifers, rivers and sewage networks can cause the contamination of surface water and groundwater, our results revealed that implementation in a WWTP of additional processes to remove OMPs will help to reduce their presence in surface water and groundwater resulting in less concentration of these compounds in the influent of drinking water treatment plants. This assessment might provide new insight into the implementation of end-of-pipe” (EOP) policies. Moreover, any improvement of the understanding regarding the OMPs load in the water cycle might be essential for the environmental risk assessment. Decreasing the amount of OMPs in water resources can be more cost-effective to tackle the environmental risk of emerging organic contaminants than the additional advanced treatments in DWTPs.