Removal of Fecal Indicator Bacteria by River Networks

Tao Huang,Stephen H Jones,Wilfred M Wollheim

doi:10.3390/w14040617

Abstract

Fecal contamination is a significant source of water quality impairment globally. Aquatic ecosystems can provide an important ecosystem service of fecal contamination removal. Understanding the processes that regulate the removal of fecal contamination among river networks across flow conditions is critical. We applied a river network model, the Framework for Aquatic Modeling in the Earth System (FrAMES-Ecoli), to quantify removal of fecal indicator bacteria by river networks across flow conditions during summers in a series of New England watersheds of different characteristics. FrAMES-Ecoli simulates sources, transport, and riverine removal of Escherichia coli (E. coli). Aquatic E. coli removal was simulated in both the water column and the hyporheic zone, and is a function of hydraulic conditions, flow exchange rates with the hyporheic zone, and die-off in each compartment. We found that, at the river network scale during summers, removal by river networks can be high (19–99%) with variability controlled by hydrologic conditions, watershed size, and distribution of sources in the watershed. Hydrology controls much of the variability, with 68–99% of network scale inputs removed under base flow conditions and 19–85% removed during storm events. Removal by the water column alone could not explain the observed pattern in E. coli, suggesting that processes such as hyporheic removal must be considered. These results suggest that river network removal of fecal indicator bacteria should be taken into consideration in managing fecal contamination at critical downstream receiving waters.

Highlights

Fecal contamination of surface waters is a worldwide concern due to its potential to contain pathogens that cause illness [1,2]
Hydrology controls much of the variability, with 68–99% of network scale inputs removed under base flow conditions and 19–85% removed during storm events
Removal by the water column alone could not explain the observed pattern in E. coli, suggesting that processes such as hyporheic removal must be considered. These results suggest that river network removal of fecal indicator bacteria should be taken into consideration in managing fecal contamination at critical downstream receiving waters

Summary

Introduction

Fecal contamination of surface waters is a worldwide concern due to its potential to contain pathogens that cause illness [1,2]. Pathogens are the most common pollutant leading to water quality impairments throughout the United States, and Escherichia coli (E. coli) is the most frequent cause of impairments [5,6]. Fecal indicator bacteria such as E. coli are used as a proxy for detecting the presence of pathogens and identifying potential health risks [7] since monitoring pathogens is expensive and time-consuming [8]. A river network perspective is essential to improve management of fecal pollution sources

Methods

Results

Conclusion