Survival and viability of Escherichia coli in a thermally altered reservoir

Abstract

Escherichia coli survived and grew in a warm, monomictic reservoir receiving thermal effluent from a nuclear production reactor, which suggests that the presence of E. coli in these aquatic systems is not an indication of recent fecal contamination. Known populations of E. coli were placed in sterile diffusion chambers and suspended at various depths throughout the water column. Experiments were conducted during both ambient water conditions (reactor not operating) and thermally altered water conditions (reactor operating). E. coli populations were observed for changes in density by using optical density and direct and indirect counting methods. During both ambient water and thermally altered water conditions, E. coli survived and grew 2–3 weeks at each depth and at all stations. During thermal alteration, cell populations attained higher optical densities and maintained those densities for longer time periods than those during ambient water conditions. In addition, populations suspended in the hypolimnion generally maintained higher optical densities than those in the epilimnion. Data show that E. coli survives and grows for extended periods of time while it is in diffusion chambers in both aerobic and anaerobic portions of the water column.