Study: Humans largest cause of watershed waste

While a study of three watersheds in Delaware – including two in Sussex County – concluded humans are the most significant contributors to fecal contamination, the levels are not cause for alarm, the lead researcher said. 

The study contradicted the results of an earlier report that had found wild and domesticated animals were the largest contributors, said professor Jennifer Biddle, who is based at the University of Delaware’s School of Marine Science and Policy in Lewes.

“Our study shows that wild and domestic animal waste had a minor impact on waters, overshadowed by the contributions of humans or natural systems [sediment] alone and unknown sources,” according to a summary of the study’s findings.

Biddle said 99.9% of microbes are not harmful to humans. She noted the study did not detect those that can sicken humans.

Tests for bacteria associated with feces from a wide variety of animals, including humans, were conducted on soil and surface water in the Love Creek and Broadkill watersheds in Sussex County, and the Murderkill watershed in Kent County.

The underground aquifer from which drinking water is drawn is too deep to be contaminated by surface water, Biddle noted. The study sampled soil and water for 158 possible sources of fecal matter, including 17 native fauna, three types of human-related waste and native sediment. That is far more potential sources than tested in the earlier study, Biddle noted

“The big message is that this isn’t anything concerning,” she said, noting the study results and any future work could monitor for problems and help prevent them.

The study demonstrates a need for people and governments to be conscious of how they affect the environment, Biddle said.

“Humans have a big impact on the environment, and we have to be mindful of that,” she said.

That includes a wide range of issues, from how much fertilizer homeowners use on their lawns to decisions that county governments make in approving housing developments, she said.

“We noted significant differences per watershed tested and hypothesized that these impacts are based on land use in and around the watersheds,” according to a report on the study results.

The testing did not pinpoint the exact geographic sources of contamination or identify many of the animals that produced the feces, Biddle said. The study may, however, serve as a baseline for additional research that could answer those questions, and provide guidance in how people and governments can reduce their negative effects on the environment, she said.

Biddle said she has no money at this time, but plans to pursue funds to continue her work.

She said she had hoped to test waste pumped from septic tanks and water near the beaches in the watershed, but logistical difficulties made it impossible.

The effects of rainfall, temperature and nutrients entering watersheds on fecal matter levels could also be studied in the future, she said. More testing may help determine if there is less fecal matter in watersheds after existing homes that have septic systems that filter waste on site are switched to sewers that move household and commercial waste to wastewater treatment plants that process the material before releasing it to the environment.

Wastewater treatment systems do a much better job than septic systems in keeping fecal matter out of watersheds, Biddle said. The study found treated water released from the Kent County wastewater treatment system did not significantly increase the amount of fecal matter in the Murderkill watershed, she said.

More than half of septic systems are typically found to be inadequate and require repair or replacement when homes are sold, Biddle noted.

The Murderkill watershed has 7,811 permitted septic systems, followed by the Broadkill with 7,182 and Love Creek with 2,328. The Murderkill and Broadkill watersheds are located in more densely populated areas.

More housing developments are being connected to sewer systems in Sussex County, Biddle said, although some areas remain on septic systems.

The state issues advisories when bacterial pollution is detected at concerning levels. There have been 138 beach closings in the past 20 years due to high bacterial loads, according to the study report. The sources of that contamination were unclear, Biddle said.

Delaware is the most polluted state in the nation, with 97% of rivers and streams, and all estuaries classified as impaired, according to the 2022 Environmental Integrity Report cited in the University of Delaware study.

The Delaware Department of Natural Resources and Environmental Control has been monitoring waterways, and results are available on its website, Biddle said. 

Delaware has major waterways that drain water from mixed land use and many are influenced through tidal interactions with Delaware Bay, according to the report.

Samples were collected bi-monthly in the Broadkill and Murderkill watersheds from January 2020 to November 2021 and monthly from the Love Creek watershed in summer 2021.

The water sampling areas include around wastewater treatment facilities and community septic systems throughout southern Delaware. Soil samples were also taken by the Delaware Department of Health and Human Services’ Division of Public Health as part of the wastewater monitoring program for COVID from 12 wastewater treatment plants across the state, including seven in Sussex County.

Study results were shared with DNREC’s water and watershed divisions, and the Delaware Environmental Monitoring Coordinating Council, a statewide working group dealing with environmental issues.

The Delaware River Basin Commission, a member of the council, declined to comment on specifics of the study, but emphasized the importance of protecting the watershed and drinking water.

“Despite the long-term nature of investments and study needed to achieve ‘swimmable’ waters by significantly reducing bacteria loadings, the Delaware River Basin Commission and its state and federal co-regulators have an aligned interest in making continued improvements in water quality in the Delaware River Estuary and providing additional opportunities for safe and equitable recreational uses,” Elizabeth Brown, director of external affairs and communications for the commission, said in an email.