title: Isolating the impact of septic systems on fecal pollution in streams of suburban watersheds in Georgia, United States.
abstract: The presence of multiple sources of fecal pollution at the watershed level presents challenges to efforts aimed at identifying the influence of septic systems. In this study multiple approaches including targeted sampling and monitoring of host-specific Bacteroidales markers were used to identify the impact of septic systems on microbial water quality. Twenty four watersheds with septic density ranging from 8 to 373 septic units/km2were monitored for water quality under baseflow conditions over a 3-year period. The levels of the human-associated HF183 marker, as well as total and ruminant Bacteroidales, were quantified using quantitative polymerase chain reaction. Human-associated Bacteroidales yield was significantly higher in high density watersheds compared to low density areas and was negatively correlated (r = -0.64) with the average distance of septic systems to streams in the spring season. The human marker was also positively correlated with the total Bacteroidales marker, suggesting that the human source input was a significant contributor to total fecal pollution in the study area. Multivariable regression analysis indicates that septic systems, along with forest cover, impervious area and specific conductance could explain up to 74% of the variation in human fecal pollution in the spring season. The results suggest septic system impact through contributions to groundwater recharge during baseflow or failing septic system input, especially in areas with >87 septic units/km2. This study supports the use of microbial source tracking approaches along with traditional fecal indicator bacteria monitoring and land use characterization in a tiered approach to isolate the influence of septic systems on water quality in mixed-use watersheds.
authors.affiliation: Crop and Soil Sciences, The University of Georgia Griffin Campus, 1109 Experiment St, Griffin, GA, 30223, USA. Electronic address: robsowah@uga.edu.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Sowah
authors.affiliation: Crop and Soil Sciences, The University of Georgia Griffin Campus, 1109 Experiment St, Griffin, GA, 30223, USA.
authors.forename: Mussie Y
authors.initials: MY
authors.lastname: Habteselassie
authors.affiliation: Crop and Soil Sciences, The University of Georgia, 3111 Carlton St, Athens, GA, 30602, USA.
authors.forename: David E
authors.initials: DE
authors.lastname: Radcliffe
authors.affiliation: Center for Urban Agriculture, The University of Georgia Griffin Campus, 1109 Experiment St, Griffin, GA, 30223, USA.
authors.forename: Ellen
authors.initials: E
authors.lastname: Bauske
authors.affiliation: The University of Georgia, Marine Extension and Georgia Sea Grant, 1030 Chicopee Building, Athens, GA, 30602, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Risse
mesh_terms: D041963:Bacteroidetes / Q000302:isolation & purification; D004784:Environmental Monitoring; D005243:Feces / Q000382:microbiology*; D005845:Georgia; D006801:Humans; D045483:Rivers / Q000382:microbiology*; D014871:Water Microbiology; D014876:Water Pollution; D060753:Water Quality
keywords: Bacteroidales markers; Baseflow; Fecal pollution; HF183; Septic density; Water quality