Variability and Decay Patterns of E. coli in Drainage Water

摘要

The objectives of this study were to document the temporal variability and decay in numbers of Escherichia coli within drainage systems by monitoring E. coli concentrations in the discharge from two tile drainage systems and within a surface water system throughout Nova Scotia, Canada. Both water systems have been impacted by agricultural tillage and cropping activities. Intensive hourly sampling occurred during sampling events that lasted between 24 and 96 h. A total of 695 samples over five sampling events were collected within the surface water system and 708 samples were collected over five sampling events within the tile drainage systems. Membrane filtration using the mColi-Blue medium was used for bacterial analysis. The results indicated thatE. coli concentrations of surface water frequently exceeded the Canadian bacterial guidelines for recreational waters (200 E. coli CPU 100 mL~(-1)). Significant temporal variability was observed in all water samples. Peak E. coli concentrations normallyoccurred during the onset of high flow and decreased throughout the flow event. Decay constants for the E. coli concentrations were determined relative to time and accumulated flow using an exponential decay function. The surface wafer system showed decay constants of 0.28 and 0.35 relative to time and 0.013 relative to accumulated flow. The subsurface drainage system showed decay constants of 0.073 and 0.10 relative to time and 0.69 and 0.83 relative to accumulated flow.