Written by Courtnee Davenport

Every year, from Memorial Day to Labor Day, CRBI sends out dedicated field techs to collect water samples from 30 boat ramps, public beaches, and rivers from Weiss Lake to Allatoona Lake for Swim Guide. The goal for collecting these samples is to find out how much E. coli is present in these popular recreational areas. In order to help our community better understand what E. coli is, where it comes from, and why it matters that it could be in our waterways, CRBI has gathered information about this bacterium to help you make informed decisions about your summertime adventures. 

What is E.coli?

E. coli (Escherichia coli) is a fundamental bacterium that lives in the lower intestinal tract of humans and warm-blooded animals. It is predominantly found in the intestines, but it can also be present in various other sources, including soil, water, on plants, and on surfaces such as sidewalks and roads. This adaptable bacterium is capable of thriving in environments with or without oxygen and shows resistance to antibiotics and acidic environments. It thrives best at temperatures around 37℃ (98.6℉), which coincides with the typical internal temperature of the human body. 

Pathogenic vs Non-Pathogenic

A large number of E. coli strains coexist in the lower intestine, many of which offer benefits to their hosts. These beneficial strains provide essential nutrients such as energy-giving vitamin B₁₂ and bone-building, blood-supporting vitamin K. They also help create an oxygen-deprived environment that supports the majority of the gut’s microbial community. However, despite its typically beneficial nature, certain pathogenic forms of E. coli pose significant health risks leading to diarrheal diseases, colitis, or urinary tract infections. One well-known example of a pathogenic strain is Shiga toxin-producing E. coli O157:H7 (STEC). The primary habitat for STEC is found in ruminant animals, most notably, cattle. One concerning fact of STEC is its ability to survive in sediment and soil for several months. 

Common Sources

When in the intestinal tract of warm-blooded animals, E. coli remains contained and harmless, but it becomes a concern when introduced into the environment. The most common secondary sources of E. coli contamination are fecal matter, wastewater discharge, and stormwater runoff. 

Fecal Matter

It’s no secret: everybody poops. Because fecal matter originates from the intestinal tract, it naturally carries E. coli. Once fecal matter enters the environment (be it from livestock, wildlife, pets, humans..), it can contaminate soil, water sources, and surfaces. Rainfall or irrigation can wash the contaminated soil into rivers, lakes, and other water bodies. This is particularly concerning for water bodies used for recreational purposes as it can pose a risk to human health. 

Wastewater Discharge

Wastewater refers to water that has become contaminated or altered after being used in various domestic, commercial, industrial, or agricultural activities. It often contains human and animal waste, posing a risk to public health if not treated properly before reintroduction into the environment. For instance, in July 2023, a malfunction at Big Creek Wastewater Treatment Plant led to the release of partially treated wastewater into a 15-mile stretch of the Chattahoochee River near Roswell, GA. As a result, E. coli levels in the river exceeded 120,980 MPN (most probable number), significantly surpassing the EPA’s water quality standard of 235 MPN. This incident highlights the importance of effective wastewater treatment and facilities to protect both public health and the environment. 

Stormwater Runoff

Given that we know about E. coli’s ability to persist on soil, plants, sidewalks, and roads, it makes sense why stormwater runoff is one of the three most common secondary sources for E. coli contamination. When it rains, stormwater collects and transports fecal matter, localized wastewater spills, and other pollutants from the environment into water bodies. Additionally, storms have the potential to resuspend sediment-bound E. coli back into the water column leading to elevated E. coli levels. Proper stormwater management is another essential practice needed to protect public health and the environment. 

Safety Tips

💩 Do not swim after a rainstorm

💩 Do not swim if you smell sewage

💩 Do not swim if you have any open wounds

💩 Do not ingest water or open your eyes underwater

💩 Do practice good hygiene after swimming in a river or lake

💩 Do check the weekly E. coli levels on our Swim Guide (from Memorial Day to Labor Day)