Evaluation of indicator microbe sampling and enumeration methods for Chicago area surface waters

Three main research objectives were investigated in the area of microbiological analyses and sampling of Chicago surface waters with special regards to the data quality objectives of a comprehensive epidemiological study referred to as "CHEERS" (Chicago Health, Environmental Exposure, and Recreation Study). Two indicator bacteria, E. coli and enterococci and two viral indicators male-specific and somatic coliphages were involved in the studies.;The first study adapted and validated EPA method 1602 (Male-specific (F+) and Somatic Coliphage in Water by Single Agar Layer (SAL) Procedure) to the surface water matrices of the CHEERS study. Previously, the EPA method was validated for drinking and ground waters only. The modified method performed well for male-specific coliphages, however slightly underperformed for somatic coliphages if compared to the criteria set for drinking/ground waters.;The second study explored the precision and accuracy of indicator bacteria E. coli and enterococci enumeration data for EPA methods 1600 and 1603. Spiked surface water samples were evaluated at five different processed volumes including all countable plates. The accuracy and precision of plate counts did not decline when colony counts exceeded the EPA-specified upper counting limits (60 colonies for enterococci and 80 colonies for E. coli). The highest processed sample volumes gave the most accurate and precise results for both, E. coli and enterococci bacteria.;The third study developed the proper sampling strategy for the characterization of exposure during secondary contact water recreation in the Chicago Area Waterways based on the spatial and temporal variability of indicator microorganisms. Two preliminary studies and three-month of field sampling with 1900 analytical results were included in the evaluations. Cross-sectional variability of microbe densities was not significant in the upper 10 cm surface of the Chicago waterways.