Fate Evaluation of CSO-derived PPCPs and <i>Escherichia coli</i> in Tokyo Coastal Area after Rainfall Events by a Three-dimensional Water Quality Model

Abstract

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.

Prediction of Sunlight- and Salinity-Driven Inactivation Kinetics of Microbial Indicators with Validation in a 3D Water Quality Model

“…Their faster decay can be explained with the abundance of longer solar wavelengths presented in high-saline water since the shorter wavelengths were attenuated more in high-saline water. In addition, a previous study that monitored the concentration of bacteriophages in surface water in the area also mentioned the absence of F-phage, showing no long-term survival under high salinity [15].…”

“…Detailed information of the model was described previously [15] with modifications. In brief, the simulation program was written in FORTRAN.…”

“…In brief, the simulation program was written in FORTRAN. Model validation was previously conducted through a comparison of simulation results with observation results of salinity, temperature, and E. coli concentration [15,38]. The hydrodynamic model consists of two nested computational models, including the Tokyo Bay model and the Odaiba model.…”

“…Despite an aged sewer system, the various impacts of CSO contamination are still not fully understood, thus being frequently studied in recent years [11][12][13]. The estuary of Tokyo, Japan, is one such region that is often heavily contaminated by pollutants sourced from CSO [14][15][16]. A substantial number of CSO discharge points renders it a fundamental diffuse source of pollution, thereby introducing complexities in its management and control.…”

“…Nevertheless, the discrepancies in the effects of inactivation may arise due to variations in solar radiation intensity and the specific strains of E. coli engaged across different research investigations. On the other hand, water quality models are proven to be a useful and powerful tool to understand the behavior of pollutants and to support the decision making in water safety management [15]. They can be used to describe the temporal and spatial variability in microbial concentrations without labor-intensive workloads and limitations due to detection methods.…”