Agricultural waste and private septic systems were major sources of pollutants
Major hurricanes Florence and Michael, which hit the Southeastern United States in 2018, not only killed approximately 70 people and caused an estimated $25 billion in property damage, but they also caused widespread bacterial contamination in water wells across the region.
Michael hit the Florida panhandle as the fourth largest hurricane in the nation’s history, damaging Georgia the most, but continuing on to leave a path of flooding all the way to Virginia. Other affected states were Alabama, North Carolina, and South Carolina.
Hurricane Florence dropped more than 10 trillion gallons of rain over the Carolinas and Virginia — almost 3 feet in some spots.
The drenching storms may have compromised the safety of an estimated 731,000 private wells across the region. Pathogens likely found in floodwater are E. coli, Salmonella, and Campylobacter, while bacteria in the Vibrio genus may be washed inland during storm events. Norovirus and adenovirus are also possible contaminants, given the presence of sewer system damage and spills. Bacteria typically enter private wells through cracks or gaps, which are common in older wells, or by seepage into groundwater. Wellheads often are damaged by debris floating in floodwater.
Exposure, by ingestion or through broken skin, can cause contagious diarrhea, vomiting, and nausea. The severity of symptoms ranges from asymptomatic cases, to mild gastrointestinal distress (rarely identified as water-related), to cases requiring hospitalization.
Health departments in the affected states have provided water testing, often free, and have found contamination is common in samples provided by well owners.
After Florence, an estimated 332,798 privately owned wells in North Carolina may have been compromised. As of late October, about 15% of the nearly 650 samples submitted contained fecal coliform and E. coli bacteria, up from 2% before the storm.
The state has the fifth highest concentration of residential water wells in the nation, with approximately 2.4 million residents primarily drinking water pumped from beneath their own yards. Many residents avoid testing for fear their wells might be condemned. Although testing may be free, replacement of wells is not.
Common sources of contamination in North Carolina are pig farm waste lagoons, some of which were damaged in the storm; 33 of them overflowed. Conventional wastewater treatment plants also overflowed and spilled sewage into rivers. Thousands of private septic tank systems may have released human waste during flooding.
Florida and Georgia
After Hurricane Michael hit the Florida panhandle and entered Georgia, 24 Georgia counties tested wells, with 19 of 50 samples testing positive for fecal coliform and E. coli. Thirty-five Florida counties also provided free testing; however, only one of the Florida samples out of the 82 collected showed dangerous levels of contamination.
Preparing for Future Storms
In agricultural areas with animal waste lagoons, waste-to-energy treatment with anaerobic digestion could lessen the chance of contamination due to overflow during heavy rains. The processis used to extract biogas from organic wastes. Digestate, a byproduct of the anaerobic digestion process, is a stable, fermented waste that can be reused as a fertilizer. The biogas can be used to co-generate electricity to power operations.
In anticipation of future storms, researchers now use experience from hurricanes as a learning tool, and have recognized that establishing relationships with the well owners in a region well before a storm hits creates more durable networks to respond to such disasters.