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Septic science key to cleaner water

There are an estimated 1.3 million septic systems in Michigan state and at least 10 percent of them are failing, leaking contaminants into Michigan’s ground and surface waters, according to a report from Michigan’s Department of Natural Resources.

Image of MattSchrenk in his lab
MSU geomicrobiologist Matt Schrenk will lead a Michigan Sea Grant to develop new tools that will sort sources of contamination into the Saginaw Bay Watershed and train future Earth science students. Credit: Harley J. Seeley

Michigan State University’s Matt Schrenk, associate professor with joint appointments in the Department of Earth and Environmental Sciences (EES) and the Department of Microbiology and Molecular Genetics (MMG), is lead investigator of a 2-year, $143,000 Michigan Sea Grant project that will combine high resolution microbiology and geochemical studies to pinpoint the toxic leaks.

“I noticed that many of the tools health departments use to track contamination are several years behind the state-of-the-art and not easily adaptable to emerging contaminants,” said Schrenk after attending the Michigan Septic Summit in Traverse City in 2019. “With this grant, we are going to conduct a detailed survey of septic systems to understand both their geochemistry and microbiology with the aim of developing novel and sensitive tracers to measure potential contamination of failing septic systems versus other sources.”

Michigan is the only remaining state in the United States without a statewide septic code. In other words, many septic systems fail to get regular diagnostic check-ups until it is too late to prevent them from leaking.

Contaminants from these failing systems overlap with environmental contamination from agriculture, industry, and municipal wastewater. Until Schrenk’s efforts, there has been no way to separate these converging sources of contamination, muddying the waters when it comes to regulations that would improve water quality.

“Waste from geese and other animals and outputs from industrial operations make it hard to tell what impact individual septic systems are having on the environment,” Schrenk explained. “My lab is heading up the metagenomic sequencing that takes DNA from all the microbes in groundwater to ‘see’ who’s there and detect the source of the contamination. The tests will go a long way toward curbing the source of the contamination.”

Image of septic microbes
Microorganisms in septic systems have developed unique responses to nutrients, pharmaceuticals and personal care products ubiquitous in septic systems, providing a unique fingerprint to locate their place of origin. Credit: Matt Schrenk

The Schrenk Lab will begin sampling both functioning and failing septic tanks in the Saginaw Bay watershed around Bay County Michigan this summer using the highly sensitive DNA sequencing tools to trace specific microorganisms. The tests will determine if distinctive blends of microbes and chemical compounds might serve as a unique “fingerprint” pointing back to their septic system of origin.

Contaminant runoff has caused enough environmental damage, harmful algal blooms and beach closures in the Saginaw Bay watershed, which contains the largest freshwater ecosystem in the United States, for it to be designated an Area of Concern by the U.S. Environmental Protection Agency for the past 30 years.

Being able to identify the source of these contaminants would be like accurately diagnosing a sickness—the first step on the journey towards health.

Their investigations are bolstered by the extensive mapping and community outreach efforts of Joel Kwiatowski from the Bay County Health Department. Over the past few years, Kwiatowski and colleagues have developed a detailed map of more than 12,000 septic tanks in Bay County and their relationship to water resources in the Saginaw Bay watershed.

Schrenk and his team will overlap their biological and chemical data with the mapping data, tracking contaminants to their source to better inform successful remediation approaches.

Leanne Hancock filtering groundwater samples
Leanne Hancock, co-investigator on the grant, filtering groundwater samples in the field to bring back to the lab for analysis. Credit: Matt Schrenk

“Coming up with a comprehensive system of microbial and geochemical tracers that detect septic leaks could be instrumental in helping local and state agencies restore the water quality and ecosystem health of Michigan’s Saginaw Bay watershed,” said Schrenk, who will work with co-investigators Sherry Martin and Leanne Hancock, both EES geochemists.

The grant will also provide valuable training for EES graduate and undergraduate students.

“Because it is local, this fieldwork is an excellent mechanism for engaging more diverse students in environmental sciences,” Schrenk said. “I’m elated about working with Michigan Sea Grant and their extensive network of education and outreach specialists to maximize the impact of our work.”

“I can’t wait until we can actually get out to begin sampling the septic fields and associated water resources,” Schrenk added.

Sea Grant was established in 1966 as a partnership between the National Oceanic and Atmospheric Administration and a national network of 34 university-based programs in every coastal and Great Lakes state. It supports a network of over 12,000 scientists and over 900 graduate students in cutting-edge research regarding climate change, energy sources, coastal processes and water management.

For more information about Michigan Sea Grant and Schrenk’s project, please visit: https://seagrant.noaa.gov/Program-Locations/MI.


Banner image: MSU scientists are developing tools that will trace sources of watershed contamination to specific septic systems at homes such as these along the Kawkawlin River, which flows into the Saginaw Bay of Lake Huron. Credit: Leanne Hancock