title: Persistence of fecal indicator bacteria in sediment of an oligotrophic river: comparing large and lab-scale flume systems.
abstract: In this study, both a lab and a large-scale flume system were used to investigate the survival of fecal indicator bacteria (FIB) in bed sediments of an alpine oligotrophic river. To determine the influence of substratum on persistence, survival within 3-cm-deep substratum cages versus on thin, biofilm-covered ceramic tiles was tested. Moreover, the impact of bed shear stress on survival in bed sediments was explored. It was seen that in the lab-scale flume having a very low bed shear stress (0.3 N m(-2)), E. coli and enterococci survival in 3-cm-deep substratum cages was nearly the same as in a thin biofilm (200 μm). However, in the large-scale flume system characterized by a bed shear stress of 9 N m(-2), the added protection of the deeper substratum cages promoted considerably longer survival of E. coli and enterococci than the thin biofilm. Additionally, the FIB removal mechanisms in the two flume systems varied. At the lab-scale, enterococci was seen to persist twice as long as E. coli, while in the large-scale flume the two FIB were removed at the same rate. A comparison of qPCR analyses performed in both flumes suggests that bed sediment erosion and the influence of grazers/predators were responsible for FIB removal from the sediments in the large-scale flume, whereas in the lab flume FIB inactivation caused removal. These results indicate that hydraulic parameters such as bed shear stress as well as the presence of macroinvertebrates in a system are both important factors to consider when designing flumes as they can significantly impact FIB persistence in sediments of fast-flowing, alpine streams.
authors: Technische Universität München, Chair of Urban Water Systems Engineering, Am Coulombwall, D-85748 Garching, Germany; Temple University, Department of Civil and Environmental Engineering Office, EA 912, 1947 North 12th Street, Philadelphia, PA 19122, USA. Electronic address: e.walters@temple.edu.
authors: Evelyn
authors: E
authors: Walters
authors: Technische Universität München, Chair of Urban Water Systems Engineering, Am Coulombwall, D-85748 Garching, Germany.
authors: Korbinian
authors: K
authors: Kätzl
authors: Technische Universität München, Chair for Hydraulic and Water Resources Engineering, Arcisstr. 21, D-80333 München, Germany.
authors: Kordula
authors: K
authors: Schwarzwälder
authors: Technische Universität München, Chair for Hydraulic and Water Resources Engineering, Arcisstr. 21, D-80333 München, Germany.
authors: Peter
authors: P
authors: Rutschmann
authors: Technische Universität München, Chair of Urban Water Systems Engineering, Am Coulombwall, D-85748 Garching, Germany.
authors: Elisabeth
authors: E
authors: Müller
authors: Karlsruhe Institute of Technology, Engler-Bunte-Institut, Chair of Water Chemistry and Water Technology, Engler-Bunte-Ring 1, D-76131 Karlsruhe, Germany.
authors: Harald
authors: H
authors: Horn
mesh_terms: D016983:Enterococcus / Q000302:isolation & purification*; D004926:Escherichia coli / Q000302:isolation & purification*; D005243:Feces / Q000382:microbiology; D005858:Germany; D045483:Rivers / Q000382:microbiology*
keywords: Bed shear stress; Biofilm; E. coli; Enterococci; Flow channel; Reservoir of pathogens