Bacterial Indicator-species Survival on Impervious Surfaces

Fecal slurries of non-human origin were inoculated to impervious surfaces, and were subjected to varying levels of temperature, moisture, and UV exposure for extended periods. Net survival of E. coli and Enterococci under each treatment is separately modeled as a segmented log-linear regression with unknown breakpoints by maximum-likelihood methods. Factorial (between treatment) analysis of both breakpoint timing and intervening slopes is presented, providing information concerning relative influence of environmental factors on indicator-species survival at source areas. Additionally, initial slope of each model is compared to previously derived infeces survival studies (from the same source animals) to determine effects of rain-induced fecal dissolution on bacterial survival.This study is part of an ongoing effort to model the natural (non-sewage) background of such species in runoff. Integration of these results with a planned and similar pervious-surface study, analysis of the particle-size segregation of runoff bacteria, and source-area runoff/washoff studies will assist in separating the mechanisms by which indicator species enter, and are transported in, stormwater.