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<p>Contaminants of emerging concern (CECs) can threaten aquatic ecosystems and human health. Both rural and urban areas are main sources of CECs to the environment. In rural areas, veterinary pharmaceuticals (VPs) are used to prevent diseases and protect the health of farm animals. The excrements of medicated animals are spread as manure to agricultural lands, where, after rainfall, VPs can be mobilized and reach surface waters through runoff. In urban areas, pharmaceuticals excreted by humans are collected in sewage systems and are only partially removed in wastewater treatment plants (WWTPs). Eventually, pharmaceuticals can reach surface waters through discharge of WWTP effluent. Currently, most of the predictive models only consider one source type, e.g. WWTPs or agricultural land. This limits their prediction performance since many CECs are being emitted by multiple source types. Therefore, the aim of this study is to integrate urban and rural sources of CECs in one regional water quality assessment.</p><p>Here, we predicted the concentration of CECs in the Eem river basin, the Netherlands, given land-use data combined with hydrological modeling. This allows for integrated evaluation of rural and urban emissions. These emissions were predicted with models developed within the context of the SUSPECt project (https://cec-partnership.nl/web/index.php/projects/suspect). CECs exposures were predicted with the Dutch National Water Quality Model where WWTPs emissions were included as point sources and rural emissions as diffuse sources. The temporal resolution of the model hydrology is seasonal. This is key to analyze the temporal variation of concentration due to manuring of agricultural lands which mainly occurs in Spring.</p><p>Predicted concentrations were successfully compared to measured concentrations taken in the SUSPECt project and from the database of the KIWK project (www.kennisimpulswaterkwaliteit.nl) for 6 compounds: carbamazepine and fipronil (only urban sources) and trimethoprim, sulfamethoxazole, permethrin and dexamethasone (urban and rural sources).</p>

The use of chemicals by society has resulted in calls for more effective control of their emissions. Many of these chemicals are poorly characterized because of lacking data on their use, environmental fate and toxicity, as well as lacking detection techniques. These compounds are sometimes referred to as contaminants of emerging concern (CECs). Urban areas are an important source of CECs, where these are typically first collected in sewer systems and then discharged into the environment after being treated in a wastewater treatment plant. A combination of emission estimation techniques and environmental fate models can support the early identification and management of CEC-related environmental problems. However, scientific insight in the processes driving the fate of CECs in sewer systems is limited and scattered. Biotransformation, sorption and ion-trapping can decrease CEC loads, whereas enzymatic deconjugation of conjugated metabolites can increase CEC loads as metabolites are back-transformed into their parent respective compounds. These fate processes need to be considered when estimating CEC emissions. This literature review collates the fragmented knowledge and data on in-sewer fate of CECs to develop practical guidelines for water managers on how to deal with in-sewer fate of CECs and highlights future research needs. It was assessed to what extent empirical data is in-line with text-book knowledge and integrated sewer modelling approaches. Experimental half-lives (n = 277) of 96 organic CECs were collected from literature. The findings of this literature review can be used to support environmental modelling efforts and to optimize monitoring campaigns, including field studies in the context of wastewater-based epidemiology. Graphical abstract