Bacterial and molecular contamination of a small freshwater effluent used for drinking water

Sewage contamination of freshwater occurs in the form of raw waste or as effluent (at varying levels of treatment) from wastewater treatment plants. Global management of this contamination has focused on detection of live sewage-indicating bacteria in freshwater, drinking water, and irrigation systems. While raw waste (animal and human) and underfunctioning WWTPs can introduce live enteric bacteria to freshwater systems, most WWTPs, even when operating correctly, do not remove bacterial genetic material from treated waste, resulting in the addition of concentrated enteric bacterial DNA (molecular contamination), including antibiotic resistance genes, into water columns and sediment of freshwater systems. In freshwater systems with both raw and treated waste inputs, then, there will be increased interaction between live sewage-associated bacteria (untreated sewage) and molecular contamination (from both untreated and treated wastewater effluent), with the potential of increasing antibiotic resistance in the live bacterial populations. To evaluate this understudied interaction between molecular and bacterial contamination in the freshwater environment, we conducted a three-month field-based study of sewage-associated bacteria and genetic material in water and sediment in a freshwater tributary of the Hudson River (NY, USA) that supplies drinking water and receives treated and untreated wastewater discharges from several municipalities. Using both molecular and culture-based bacterial analyses, we demonstrate both treated and untreated sewage influences on water and sediment bacterial communities in this tributary, and water-sediment exchanges of enteric bacteria and associated genetic material with rain events. Furthermore, treated sewage effluent on this waterway serves as a concentrated source of int1 (antibiotic resistance) genes, which appear to collect in the sediments below the outfall along with fecal indicating bacteria, serving as a possible genetic exchange substrate and a source for future molecular and bacterial water contamination. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=144 SRC="FIGDIR/small/530486v1_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@1abdb61org.highwire.dtl.DTLVardef@1cfc550org.highwire.dtl.DTLVardef@1a33647org.highwire.dtl.DTLVardef@40829e_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIIn a model freshwater system used both as drinking water and wastewater disposal, C_LIO_LIBacterial and genetic material differ between water and sediment compartments C_LIO_LILive bacteria C_LI