Selective elimination of bacterial faecal indicators in the Schmutzdecke of slow sand filtration columns.
Slow sand filtration (SSF) is an effective low-tech water treatment method for pathogen and particle removal. Yet despite its application for centuries, it has been uncertain to which extent pathogenic microbes are removed by mechanical filtration or due to ecological interactions such as grazing and competition for nutrients. In this study, we quantified the removal of bacterial faecal indicators, Escherichia coli and Enterococcus faecalis, from secondary effluent of a wastewater treatment plant and analysed the microbial community composition in compartments of laboratory model SSF columns. The columns were packed with different sand grain sizes and eliminated 1.6-2.3 log units of faecal indicators, which translated into effluents of bathing water quality according to the EU directive (<500 colony forming units of E. coli per 100 ml) for columns with small grain size. Most of that removal occurred in the upper filter area, the Schmutzdecke. Within that same zone, total bacterial numbers increased however, thus suggesting a specific elimination of the faecal indicators. The analysis of the microbial communities also revealed that some taxa were removed more from the wastewater than others. These results accentuate the contribution of biological mechanisms to water purification in SSF.
Helmholtz Zentrum München-German Research Center for Environmental Health, Institute of Groundwater Ecology, Ingolstädter Landstr. 1, Neuherberg, Germany.
Kristina R
KR
Pfannes
Department of Environmental Biotechnology, Helmholtz Centre for Environmental Research-UFZ, Permoserstr. 15, 04318, Leipzig, Germany.
Kilian M W
KM
Langenbach
Helmholtz Zentrum München-German Research Center for Environmental Health, Institute of Groundwater Ecology, Ingolstädter Landstr. 1, Neuherberg, Germany.|ExxonMobil Research and Engineering, 1545 Route 22 East, Annandale, NJ, 08801, USA.
Giovanni
G
Pilloni
Helmholtz Zentrum München-German Research Center for Environmental Health, Institute of Groundwater Ecology, Ingolstädter Landstr. 1, Neuherberg, Germany.
Torben
T
Stührmann
Helmholtz Zentrum München-German Research Center for Environmental Health, Institute of Groundwater Ecology, Ingolstädter Landstr. 1, Neuherberg, Germany.
Kathrin
K
Euringer
Helmholtz Zentrum München-German Research Center for Environmental Health, Institute of Groundwater Ecology, Ingolstädter Landstr. 1, Neuherberg, Germany.
Tillmann
T
Lueders
Department of River Ecology, Helmholtz Centre for Environmental Research-UFZ, Brückstr 3A, 39114, Magdeburg, Germany.
Thomas R
TR
Neu
Department of Environmental Biotechnology, Helmholtz Centre for Environmental Research-UFZ, Permoserstr. 15, 04318, Leipzig, Germany. jochen.mueller@ufz.de.
Jochen A
JA
Müller
Department of Environmental Biotechnology, Helmholtz Centre for Environmental Research-UFZ, Permoserstr. 15, 04318, Leipzig, Germany.
Matthias
M
Kästner
Helmholtz Zentrum München-German Research Center for Environmental Health, Institute of Groundwater Ecology, Ingolstädter Landstr. 1, Neuherberg, Germany.|Universität Duisburg-Essen, Campus Essen-Biofilm Centre-Universitätsstr. 5, 45141, Essen, Germany.
Rainer U
RU
Meckenstock
D058491:Bacterial Load; D058448:Biota; D013293:Enterococcus faecalis / Q000302:isolation & purification*; D004926:Escherichia coli / Q000302:isolation & purification*; D005374:Filtration / Q000379:methods*; D014871:Water Microbiology; D014873:Water Pollutants; D018508:Water Purification / Q000379:methods*
D014873:Water Pollutants
Bacteria removal; Ecology of slow sand filtration; Schmutzdecke; Wastewater reuse