Distribution of pathogenic indicator bacteria in structural best management practices

Area of Science:

• Environmental Science
• Microbiology
• Water Quality

Background:

• Stormwater runoff can transport pathogenic indicator bacteria.
• Best Management Practices (BMPs) like Vortechs are used to treat stormwater.
• Understanding bacterial behavior within BMPs is crucial for water quality management.

Purpose of the Study:

• To evaluate bacterial distribution and survivability in relation to particle size within Vortech BMPs.
• To compare bacterial loads in sump water versus sediments.
• To assess bacterial dynamics following rainfall events.

Main Methods:

• Sampling of sump water and sediments from two Vortech BMPs over ten rain events.
• Analysis of five pathogenic indicator bacteria: E. coli, enterococci, fecal streptococci, total coliform, and fecal coliform.
• Quantification of bacteria associated with different particle size fractions.

Main Results:

• Most bacteria (80-95% in sump water, 60-80% in sediments) were associated with particles <50 µm and <106 µm, respectively.
• Bacterial concentrations in sump water surged one day after rainfall, especially for bacteria on smaller particles.
• Sediments showed higher bacterial concentrations than sump water and stable levels during dry periods, suggesting a favorable environment.

Conclusions:

• Smaller particle sizes play a significant role in bacterial transport and accumulation within BMPs.
• BMP sediments act as a reservoir for bacteria, potentially influencing downstream water quality.
• Differences between sampling sites suggest varying levels of external bacterial contamination, such as from highway runoff.