A recent study indicates that human waste, whether treated or untreated, is contributing to the pollution of waterways in Delaware.
Delaware is home to many inland waterways that have significant microbial pollution from unidentified sources. A new study reveals that human waste, both treated and untreated, is likely responsible for the pollution affecting these Delaware watersheds. This research was published in Applied and Environmental Microbiology, a journal from the American Society for Microbiology.
As per the Clean Water Act, water bodies contaminated by pollutants that fail to meet clean water criteria are classified as impaired. In this new research, scientists collaborated with the state water quality monitoring team to gather water samples from various locations within three distinct inland watersheds in southern Delaware. They analyzed the DNA present in the water to identify the microbial communities. “The advantage of this study is that we collected samples monthly over two years, 2020 and 2021, allowing us to thoroughly examine various seasonal, tidal, and geographical differences,” explained study coauthor Jennifer Biddle, Ph.D., who is a professor at the University of Delaware’s School of Marine Science and Policy.
The researchers compared the DNA profiles from the water samples to a comprehensive library of DNA signatures from various organisms found in Delaware, including those from humans, domestic animals, and livestock. They discovered that a large portion of the microbial DNA in the sampled water was similar to human waste signatures, with little to no resemblance to animal waste signatures from either domestic or agricultural sources.
“The common assumption that living downstream from a cattle farm means your water is contaminated didn’t hold up in our findings. Instead, we mostly identified a human waste signature,” Biddle stated. The study implies that the microbial presence aligns more closely with that of human waste, both treated and untreated. “With a library containing over 10,000 microbial signatures, we determined that what we observed resembled human waste rather than that of geese or other animals. It appears there is not a significant issue related to animal waste in the waterway,” Biddle further explained. “While people may worry about waste from migratory geese or farm animals, our findings suggest those sources are not a significant concern.”
The research points towards infrastructure-related issues as likely culprits for the water pollution. “We detected a signature indicating septic system discharge in the water,” Biddle noted. “This highlights the necessity to investigate infrastructure issues and possibly outdated systems.” In Delaware, septic systems are only mandated to be replaced upon property sales; however, the study indicates that property owners should regularly verify that their septic systems comply with current standards.
“Our current capability to analyze the microbiology of an environment using extensive sequencing techniques has proven invaluable and has expanded its relevance beyond the usual EPA regulatory requirements,” Biddle concluded.
