Hurricane Florence’s floodwaters carried E. coli, other bacteria across Eastern NC
Scientists found several species of bacteria in floodwaters left behind by September 2018’s Hurricane Florence, according to a new study from researchers at N.C. State University and UNC-Chapel Hill.
Scientists took samples within two weeks of the storm, and again in mid-October, about a month after the storm. Every sample had E. coli in it, and scientists found Arcobacter butzleri — a relatively recently discovered bacteria that can cause diarrhea in humans — in 65 of the 88 samples.
“As we start to better characterize floodwater quality, it can provide insight on some of the risks related to exposure to floodwater,” Angela Harris, an N.C. State environmental engineering professor and the study’s lead author, told The News & Observer
Researchers also tried to determine where bacteria was coming from, with 21 samples tracing back to human waste and eight samples to hog waste. Of those, five samples had indicators of both human and hog waste, according to the study, which was published in the American Chemical Society’s journal ES&T Water.
“This suggests that there are certain sites that are experiencing this double burden. I think this is interesting — that when we think about risks, they’re not just spread out but some are kind of concentrated,” Harris said. Some of the sites that had both hog and human waste were around Bear Creek and Little Marsh River in Goldsboro.
Climate change means wetter storms
Hurricane Florence caused about 121 million gallons of untreated or partially treated sewage to spill in almost 600 incidents, The News & Observer has previously reported. During the 2018 storm, six lagoons full of hog waste breached, and water spilled over the tops of 33 more.
Harris and other scientists are concerned that climate change could lead to more heavy rains, increasing the threats from contaminated floodwaters. The N.C. Climate Science Report, released last September, said hurricanes are very likely to bring heavier rainfall in the coming years, while the frequency of severe thunderstorms is likely to increase.
By tracking the sources of contamination, Harris said, scientists can figure out how to prevent bacteria from contaminating floodwaters during future hurricanes and other strong storms. The study found, for instance, that higher levels of E. coli were associated with both hog and human waste, while listeria was associated with hog waste.
“In the management of animal feces, things like lagoon covers are kind of just a first step that can help prevent inundation and can help with dealing with extreme rainfall events that we are anticipating will become more frequent as we move into the future,” Harris said. She said helping municipalities move away from overflow pipes that combine stormwater and sewage could help keep human waste out of the environment.
The study did not find a link between either human or hog waste and levels of Arcobacter butzleri, meaning the source of that bacteria remains a mystery.
Like Campylobacter, Arcobacter butzleri is a bacteria that is found in feces and causes contamination when it is eaten or swallowed. Scientists have found the bacteria in a wide variety of foods, including fish, pork, poultry and vegetables.
Rachel Noble, a professor at UNC’s Institute of Marine Sciences who was not involved with the study, said that while A. butzleri can cause diarrhea and nausea, it likely won’t lead someone who’s been contaminated to seek care at an emergency room.
“It’s not something that I would completely ignore,” Noble said, “but it’s more one of these survey things that are out there.”
To become ill, Noble added, someone would need to swallow a substantial amount of the bacteria.
“This is very interesting and we should try to understand it better,” Noble said, “but at the same time, these are posing a really low risk as opposed to the four feet of standing water in someone’s home that’s about to electrocute their family.”
‘A cause for serious concern’
Noble said the study and others like it can provide better understanding of what bacteria floodwaters are carrying into municipal drinking water systems or across farm fields.
As part of a flood resilience study conducted by the N.C. Policy Collaboratory, Noble worked with Jill Stewart to measure microbial contaminants at a dozen sites after Florence. Stewart is a UNC environmental engineer who is also a co-author on the newly published study.
In the Collaboratory report, Noble and Stewart wrote that they had found contamination from both human and hog waste in floodwaters and called it “a cause for serious concern.”
“We have a lot more work to do to understand the risks microbial bacteria pose after hurricanes and other extreme events,” Noble said, likening the challenge to putting together a puzzle. “We’ve laid a couple of the corner pieces. We still have to get to some of the hard part in the middle.”
The N.C. Pork Council also is interested in tracking the source of more microbial contaminants, Roy Lee Lindsey, CEO of the pork industry trade group, said in a prepared statement. Lindsey said the findings of the newly released study are not surprising but are consistent with what was reported in 2018.
“All human activity — whether it is industry, agriculture, recreation, or just living — has an impact on our watersheds. Our farmers are always striving to be good stewards of our environment and support valid research into water quality issues,” Lindsey said in the statement.
Noble and Harris want to learn more about the ranges of microbial bacteria that are found in bodies of water during non-flood conditions, in order to better understand the impact that flooding has. Noble is part of a team taking routine water samples on the Newport River around Beaufort, a project that showed human waste was consistently contaminating water and led to the repair of a sewage line.
Harris is interested in how routine monitoring could show how the bacteria found in a body of water changes over time, as well as how contamination from previous floods might re-emerge.
With that monitoring, Harris said, “We can understand all of these dynamics that might be happening and try to tease out the complexity of these systems and how something that happens even months later might be impacting what we see and how a system responds to another event.”
This story was produced with financial support from 1Earth Fund, in partnership with Journalism Funding Partners, as part of an independent journalism fellowship program. The N&O maintains full editorial control of the work.
This story was originally published September 1, 2021 at 6:30 AM.