Micropollutant fluxes in urban environment – A catchment perspective

[Display omitted] •Holistic understanding of the sources and fate of 142 CECs in a river catchment.•169 kg d−1 of CECs enter WTWs: 168 kg d–1 in the liquid phase, 1.4 kg d–1 in the solid phase.•WTW treatment: 155 kg d−1 removed from the liquid phase across the catchment.•Population normalised loads show low variation in the catchment: 154 ± 12 mg d−1 inh−1.•Direct disposal of unused CECs via sewerage system contributes to localised CEC hotspots. This study provided a holistic understanding of the sources, fate and behaviour of 142 compounds of emerging concern (CECs) throughout a river catchment impacted by 5 major urban areas. Of the incoming 169.3 kg d−1 of CECs entering the WwTWs, 167.9 kg d−1 were present in the liquid phase of influent and 1.4 kg d−1 were present in the solid phase (solid particulate matter, SPM). Analysis of SPM was important to determine accurate loads of incoming antidepressants and antifungal compounds, which are primarily found in the solid phase. Furthermore, these classes and the plasticiser, bisphenol A (BPA) were the highest contributors to CEC load in digested solids. Population normalised loads showed little variation across the catchment at 154 ± 12 mg d−1 inhabitant–1 indicating that population size is the main driver of CECs in the studied catchment. Across the catchment 154.6 kg d−1 were removed from the liquid phase during treatment processes. CECs discharged into surface waters from individual WwTWs contributed between 0.19 kg d–1 at WwTW A to 7.3 kg d−1 at WwTW E, which correlated strongly with the respective contributing populations. Spatial and temporal variations of individual CECs and their respective classes were found in WwTW influent (both solid (influentSPM) and liquid phases (influentAQ)) throughout the catchment, showing that different urban areas impact the catchment in different ways, with key variables being lifestyle, use of over-the-counter pharmaceuticals and industrial activity. Understanding of both spatial and temporal variation of CECs at the catchment level helped to identify possible instances of direct disposal, as in the case of carbamazepine. Analysis of surface waters throughout the catchment showed increasing mass loads of CECs from upstream of WwTW A to downstream at WwTW D, showing clear individual contributions from WwTWs. Many CECs were ubiquitous throughout the river water in the catchment. Daily loads ranged from 0.005 g d-1 (ketamine, WwTW A) up to 1890.3 g d-1 (metformin, WwTW C) fo