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Water sampling was conducted in the coastal area of Tokyo following two rainfall events in October and November 2016. The coastal area receives, through urban rivers, a considerable amount of combined sewer overflow (CSO) pollutants from overflow chambers and pumping stations. Five pharmaceutical and personal care products (PPCPs) including acetaminophen, theophylline, crotamiton, carbamazepine, and caffeine were analyzed and used as chemical sewage markers. In addition, two types of bacteriophage were counted as markers for viral contamination as well as the fecal bacterial indicators Escherichia coli and total coliform. High contamination by PPCPs and microbial fecal indicators was observed after the rainfall events. Five key markers were selected among nine target markers using correlation analysis and were used to express the spatial distribution and temporal change in CSO pollutants. Escherichia coli showed relatively fast die-off behavior and decreased sharply from one day after the rainfall events, while bacteriophages persisted for several days after the events. Somatic coliphage showed more persistent behavior than F-specific bacteriophage. Labile markers such as caffeine also showed high rates of disappearance. In addition, monitoring results suggested that combined analyses of PPCPs and microbial fecal indicators can provide a more informed discussion on the distribution and diffusion of sewage contaminants in coastal waters following rainfall events.

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This study developed a fate model of pharmaceuticals and personal care products (PPCPs), including acetaminophen, caffeine, and crotamiton, derived from combined sewer overflow (CSO) in the Tokyo coastal area. The target PPCPs were proposed as promising sewage markers having different persistency during treatment processes and in the environmental water. The PPCP model consists of hydrodynamic calculations and environmental kinetics by biodegradation and photodegradation. We considered inputs from pumping stations, sewage treatment plants, and urban rivers as CSO sources. We measured the PPCPs concentrations, Escherichia coli, and salinity in the collected surface water samples from several locations around Tokyo coastal area for consecutive days after rainfall events in October 2017 (113 mm), June 2018 (81 mm), and July 2018 (67 mm). We found high correspondence between simulation and monitoring results on E. coli and three PPCPs in the coastal locations for all events, suggesting that the model has the potential to quantitatively evaluate CSO-derived contaminants in the Odaiba Seaside Park and nearby locations. Simulation showed that acetaminophen concentration rapidly declined due to its susceptibility to sunlight and biodegradation. Caffeine and E. coli showed different attenuation rates, whereas crotamiton concentration did not change because of its comparable concentration level in CSO.