Fecal indicator bacteria persistence under natural conditions in an ice-covered river.

摘要: Total coliform (TC), fecal (FC), and streptococcus (FS) survival characteristics, under natural conditions at 0 degrees C in an ice-covered river, were examined during February March 1975. The membrane filter (MF) technique was used throughout the study, multiple-tube (MPN) method parallel on three preselected days for comparative recovery of these bacteria. Survival studied seven sample stations downstream from all domestic pollution sources a 317-km reach river having 7.1 mean flow time (range 6.0 to 9.1 days). indicator bacteria densities decreased continuously successive this and, after adjustment dilution, most rapid die-off found occur first 1.9 days, followed by slower decrease. After relative TC less than FC FS, with 8.4%, 15.7%, 32.8% initial populations remaining viable, respectively. These rates are higher previously reported suggest that highest receiving streams can be expected degree ice cover. Additionally, FC-FS ratio greater 5 stations, indicating may useable determining source 7 low water temperatures. MPN MF methods gave comparable results FS both direct verified counts within 95% confidence limits respective MPNs samples, but generally lower index. Although filters near source. However, became more increasing time. study indicate heat shock is major factor suppression 44.5 C. Heat minimized extended incubation 35 before exposure temperature.