ANALYZING DAILY VARIABILITY IN E. COLI CONCENTRATIONS IN AN URBAN STREAM

E. coli contamination of urban streams is common in many older Great Lakes cities due to combined sewer overflow (CSO). E coli levels are found to be variable along a given stream reach moving away from their source. In order to understand this variability, levels of E. coli were measured to determine if photo degradation or dilution impacted abundance. Water samples were taken in five locations along a stream reach every two hours over a twenty-four hour period. The highest levels of E. coli were recorded at locations closest to the CSO, which represented shaded region of the stream, at 12pm and 6pm, with lower levels of E. coli measured downstream. Results show a diurnal signal at locations furthest away from the CSO. While downstream dilution may also have caused reduction in levels of E. coli, concentrations were constantly above acceptable health standards.