Human Microbial Source Tracking Case Studies

Detect Human Fecal Load, Quantify % Human Contamination, Multiple Samples Recommended

Human MST Case Studies 2017-11-21T16:29:54+00:00

1. Human Fecal Contamination in Ecorse River Watershed

E. coli TMDL for Ecorse River Watershed

Water samples from the 42-mile Ecorse River Watershed in Wayne County, Michigan, which is home to approximately 160,000 people, were found to be “positive” of human fecal contamination through bacterial source tracking analyses conducted by Source Molecular Corporation in 2007.

The Water Bureau of the Michigan Department of Environmental Quality evaluated a subset of eleven sites monitored in the largely urbanized Ecorse River watershed for the presence of E. coli from human sources.  The Bureau sent water samples to Source Molecular, which then used the DNA-based Human Bacteroidetes ID™ method and Human Enterococcus ID™ method to screen for the presence of specific genes in samples suspected of containing human fecal matter.

All monitoring sites were sampled for E. coli for 23 weeks, from May 1, 2007, through October 2, 2007, when positive flow was present.  A total of 500 grab samples were collected in the watershed during the 23-week study.  Seven of the twenty-three monitoring events occurred during wet weather conditions.

The study found that there were frequent, almost consistent, exceedences of water quality standards on the Ecorse River during the 2007 study.  The human biomarker was present at almost all sites during dry conditions while fewer positive results were found in the watershed during wet conditions.  But the Bureau noted that it is likely that positive results would have been found at all sites if repeated sampling could have been performed during wet conditions.

Suspected point sources of human sources of E. coli included cross-connections between the sanitary and storm sewer systems, illicit discharges to storm sewers, failed on-site sewage disposal systems, and leaking sanitary sewers.  The Wayne County Department of Environment (WCDOE) conducted an illicit connection elimination project between 2002 and 2005, and identified 276 illicit connections to storm sewers and 4 illicit discharges of sanitary wastewater from 79 facilities.  While most of the illicit connections were corrected by June 2005, corrections at 15 remaining facilities were ongoing at the time of the study.  The Bureau suspects that existing illicit discharges from direct misconnections and poorly maintained sanitary sewers are the major source of the E. coli problems in the watershed.

2. Some Creeks in Florida Tested Positive of Human Fecal Contamination

Source Molecular MST analysis on Lower St. Johns River samples

Microbial source tracking analysis of water samples taken from certain points of Newcastle Creek, Miller Creek, Miramar Creek, Hogan Creek, and Big Fishweir Creek in Florida some years ago had confirmed human fecal contamination and, as a result, remediation programs are ongoing.

MST sampling performed in 2006 indicated that most of the bacteria sources in Newcastle Creek are human, supporting the possibility that Onsite Sewage Treatment and Disposal Systems (OSTDS) are contributing sources in this tributary.  At Miller Creek, a positive human marker was found.  Moreover, there were compliance issues with the private lift station and manhole at The Preserve at St. Nicholas Apartments, which caused multiple sanitary sewer overflows (SSOs) and led to high fecal coliform concentrations in the area. The City of Jacksonville took enforcement action and subsequently necessary repairs were made non-compliance fines were paid.  At Miramar Creek, consistent elevated fecal coliform loading within the Orlando Circle area was detected.  Septic tanks of older houses located less than 50 feet of the creek were suspected as the cause.  In 2009, the City of Jacksonville was also made aware of another potentially significant human source of fecal contamination based on evidence of homeless population within the vicinity of Miramar Creek.  Human markers were also positive at several sites of Hogan Creek.  Homeless populations and sewer infrastructure are suspected of contributing to the high counts.  Using MST data, there were also indications of a significant human source in some stations at Big Fishweir Creek due to septic tank failures and sewer collection system hiccups.

The findings are part of the Basin Management Action Plan (BMAP) for the Implementation of Total Daily Maximum Loads (TMDL) for Fecal Coliform adopted by the Florida Department of Environmental Protection in the Lower St. Johns River (LSJR) Basin Tributaries and developed by the Lower St. Johns River Tributaries Basin Working Group in cooperation with the FDEP in December 2009; and its corresponding 2010 and 2011 Progress Reports.

The BMAP focused on 10 tributaries — Newcastle Creek, Hogan Creek, Butcher Pen Creek, Miller Creek, Miramar Creek, Big Fishweir Creek, Deer Creek, Terrapin Creek, Goodbys Creek, Open Creek — which occupy approximately 6% or more than 166 square miles of the Lower St. Johns River Basin and which were identified as the worst-case waterbody identification numbers (WBIDs).  Currently, most surface waters in Florida, including those in the Lower St. Johns River Basin, are categorized as Class III waters, which mean they must be suitable for recreation and must support the propagation and maintenance of a healthy, well-balanced population of fish and wildlife.

Under Section 303(d) of the federal Clean Water Act, every two years each state must identify its “impaired” waters, including estuaries, lakes, rivers, and streams, that do not meet their designated uses and are not expected to improve within the subsequent two years. The Florida Department of Environmental Protection (FDEP) is responsible for developing this “303(d) list” of impaired waters.

The BMAP outlined projects and activities to address all of the identified sources of contamination and the 10 WBIDs are expected to meet the TMDL requirements following full implementation of the BMAP.  In the 2011 Progress Report, it was observed that fecal coliform concentrations declined at some creeks but slightly increased in others.  Ongoing remediation programs include the maintenance and repair of infrastructure, which helps to reduce fecal coliform loading that can occur with faulty systems. Drainage system rehabilitation projects were also completed in some areas.  The City of Jacksonville remains vigilant as to potential illicit connection (PIC) cases.

3. Study Confirms Need for New Markers in Marine Water Safety Analysis

Fecal indicator bacteria currently used in microbial source tracking analysis to determine if tropical marine waters are safe for bathing may not be enough to prevent human illness, according to a 2009 study supported by Source Molecular Corporation.

The study, which was a collaboration among the National Oceanic and Atmospheric Administration, University of Miami, Nova Southeastern University, Source Molecular Corporation, and the National Center for Environmental Health, Centers for Disease Control and Prevention, intended to evaluate the health risks to humans who were exposed to subtropical recreational marine waters with no known point source of contamination.

The study noted that the use of enterococci as the primary fecal indicator bacteria (FIB) for the determination of recreational water safety has been questioned, particularly in sub/tropical marine waters without known point sources of sewage.  Proposals, including alternative FIB (such as the Bacteroidales group) and alternative measurement methods (such as rapid molecular testing) to supplement or replace current marine water quality testing methods, which require culturing enterococci, have been made.

“The study reported symptoms between one set of human subjects randomly assigned to marine water exposure with intensive environmental monitoring compared with other subjects who did not have exposure. In addition, illness outcomes among the exposed bathers were compared to levels of traditional and alternative FIB (as measured by culture-based and molecular-based methods), and compared to easily measured environmental parameters. Results demonstrated an increase in self-reported gastrointestinal, respiratory and skin illnesses among bathers vs. non-bathers,” Christopher D. Sinigalliano of NOAA, one of the authors of the study, wrote.

Therefore, the researchers concluded that for non-point source subtropical recreational marine waters, their study suggests that humans may be at increased risk of reported illness, and that the currently recommended and investigational FIB may not track gastrointestinal illness under these conditions.  The researchers note that further epidemiologic studies are needed to confirm these results.

The study was the first prospective randomized exposure study in the U.S. and the first randomized exposure study in sub/tropical non-point source recreational marine waters globally.  Local adult residents who reported regularly bathing in recreational waters were recruited to participate.  Data was collected over 15 individual study days beginning December 15, 2007 and ending June 21, 2008.