Sewage Backup – Why Test?

Damage from flood water containing sewage and feces is a very common problem encountered by home owners and building managers. Environmental professionals are often called to address the problems. Sewage wastewater, if it contains fecal waste, may be contaminated with a wide variety of microbes, including viruses, parasites, bacteria, and yeasts. Many of these are pathogenic to humans. These microbes must be removed with sewage wastewater and the environment must be disinfected with appropriate biocides. In the event of sewage water contamination, cleanup, disinfection and testing are necessary to ensure that the cleanup and disinfection are successful and the living environment is free of contamination from sewage associated microbes.

Sewage backup could lead to sewage contamination of the occupied spaces. Exposure to sewage contamination increases the risk of contracting diseases of the digestive system and other related illnesses. Potential disease causing organisms in sewage contamination include Escherichia coli, Salmonella, and Shigella.

Sources of sewage contamination may include raw sewage backup, severe flooding and leaking sewer lines or septic tanks. To determine the potential health risks from sewage contamination swab samples could be collected and tested for total coliforms, fecal coliforms and Enterococcus.

Sampling for indicator organisms can be performed before and after clean up. Sampling after cleanup is recommended to determine if the cleanup was successful.

Fecal Coliforms

The term “fecal coliform” is rather misleading since not all bacteria found in this group are of fecal origin. Fecal coliforms include bacteria such as E. coli, Klebsiella, Enterobacter, and Citrobacter. With the exception of E. coli, these bacteria could also be associated with plants.

e coli

Escherichia coli (E. coli)

As mentioned above the E. coli belong to the fecal coliform group. Presence of E. coli is a reliable indication of fecal or sewage contamination. However, E. coli has also been isolated from soil suggesting that it may not be 100% reliable indicator of fecal or sewage contamination.


Enterococci are a subgroup within the fecal streptococcus group. Enterococci are typically more human-specific than the larger fecal streptococcus group. EPA recommends enterococci as the best indicator of health risk. They are rarer than the coliforms in the environment and are always present in the feces of warm-blooded animals.

Site assessments to determine bacteria contamination on structural compounds, in water, or for remediation clearance purposes.