This article is more than 5 years old. Information may no longer be current.
Freshwater fecal contamination increases with septic system prevalence
Click Here to Manage Email Alerts
Septic systems may be the leading source of river and lake fecal bacteria contamination in Michigan, according to recently published data.
“All along, we have presumed that onsite wastewater disposal systems, such as septic tanks, were working,” Joan B. Rose, PhD, of Michigan State University, said in a press release. “But in this study, sample after sample, bacterial concentrations were highest where there were higher numbers of septic systems in the watershed area.”
Rose and colleagues collected water samples from 64 watersheds within the state from Oct. 1-13, 2010. These were assayed for water chemistry and analyzed for the presence of Escherichia coli and the human-specific marker Bacteroides thetaiotaomicron, which has demonstrated higher sensitivity than other biomarkers when examining human-associated health outcomes, according to the researchers. These results were compared against landscape characteristics and septic system prevalence to evaluate water quality and the impact of human activity on watersheds.
“For years we have been seeing the effects of fecal pollution, but we haven’t known where it is coming from,” Rose said. “Pollution sources scattered in an area — called non-point — have historically been a significant challenge in managing water quality.”
Both E. coli and B. thetaiotaomicron were both routinely detected within sampled rivers, but no association was identified between the two. A relationship was identified between B. thetaiotaomicron and septic system prevalence, with higher concentrations of the biomarker detected within watersheds containing more than 1,621 septic systems (P = .002). This was not the case for wastewater treatment plants, which were not a driving factor of microbial water quality, the researchers wrote.
“Microbial source-tracking markers, such as the human-specific [B. thetaiotaomicron] marker, can provide a more refined tool to identify the impacts of nonpoint sources of human fecal pollution, which could help prioritize restoration activities,” the researchers wrote. “The influence of septic systems in riparian zones also indicates that additional localized control measures, including septic system maintenance and construction, should be implemented to protect water quality and human health.” – by Dave Muoio
Disclosure: The researchers report no relevant financial disclosures
Click Here to Manage Email Alerts