EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Transport and removal of spores of Bacillus subtilis in an alluvial gravel aquifer at varying flow rates and implications for setback distances

Thomas James Oudega1,5, Gerhard Lindner1,3,5, Regina Sommer3,5, Andreas Farnleitner2,4,5, Georg Kerber6, Julia Derx1,5, Margaret E. Stevenson1,5, and Alfred Paul Blaschke1,5
Thomas James Oudega et al.
  • 1Institut für Wasserbau und Ingenieurhydrologie, TU Wien, Vienna, Austria (
  • 2Research Group Environmental Microbiology and Molecular Diagnostics 166/5/3, Institute of Chemical, Environmental and Bioscience Engineering, TU Wien, Vienna, Austria
  • 3Institute for Hygiene and Applied Immunology, Water Hygiene, Medical University of Vienna, Kinderspitalgasse 15, A-1090 Vienna, Austria
  • 4Research Division Water & Health, Karl Landsteiner University for Health Sciences, Krems, Austria
  • 5Interuniversity Cooperation Centre (ICC) Water & Health,, Austria
  • 6Gruppe Wasser – Ziviltechnikergesellschaft für Wasserwirtschaft GmbH, Braunhirschengasse 28, 1150 Vienna, Austria

To minimize the risk of waterborne disease outbreaks, drinking water wells should have a sufficiently large setback distance from potential sources of contamination, e.g. a nearby river. The aim of this study was to provide insight in regards to microbial contamination of groundwater under different hydraulic gradients, which can vary over time due to changes in river stage, season or pumping rate. The effects of these changes, and how they affect removal parameters, are not completely understood. In this study, field tracer tests were carried out in Vienna, Austria to evaluate the ability of subsurface media to attenuate Bacillus subtilis spores, used as a surrogate for Cryptosporidium and Campylobacter. The hydraulic gradient between injection and extraction was controlled by changing the pumping rate (1, 5 or 10 l/s) of a pumping well at the test site.  Attachment and detachment rates were determined using a HYDRUS-3D model and setback distances were calculated based on the 60-day travel time, as well as a quantitative microbial risk assessment (QMRA) approach. It was shown that scale must be taken into consideration when determining removal rate (λ), which is crucial for the calculation of setback distances, and that the effect of flow rate becomes more important at lower removal rates.

How to cite: Oudega, T. J., Lindner, G., Sommer, R., Farnleitner, A., Kerber, G., Derx, J., Stevenson, M. E., and Blaschke, A. P.: Transport and removal of spores of Bacillus subtilis in an alluvial gravel aquifer at varying flow rates and implications for setback distances, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1264,, 2022.