INSITU SURVIVAL OF INDICATOR BACTERIA, MS-2 PHAGE AND HUMAN PATHOGENIC VIRUSES IN RIVER WATER

Previous studies of microbial behaviour in situ have used dialysis sac s and diffusion chambers to permit contact of contained microorganisms with the external aqueous milieu. Their main limitation is a slow res ponse to changes in water quality, preventing adequate simulation of f ield conditions. This study used the ECODYNE system(TM), a new device responsive to real time changes in water quality. It consists of a hol low fibre membrane module and fluid reservoir which separates the test microorganisms from the external environment. Use of a mixture of Esc herichia coli, Enterococcus durans, MS-2 phage, poliovirus type 1 (Sab in) and hepatitis A virus (HM-175) allowed direct comparison of their survival in river water under identical conditions over a period of at least 24 hours. The results can be summarised as follows: a) survival patterns of E. coli in nutrient rich river water were highly variable , b) a ten-fold or greater increase in numbers of E. coli was sometime s observed in both laboratory and field tests, c) no regrowth was ever observed with E. durans, and its titre declined faster than that of E . coli, and d) over the first 24 hours, the phage survival was similar to that of the human pathogenic viruses. The observations regarding t he variable survival of E. coli and its potential for regrowth raise q uestions about its suitability as a water quality indicator. MS-2 phag e shows promise as an indicator of viral pollution, but requires furth er study. The ECODYNE system proved highly suitable in this study, and shows potential for other environmental interaction/environmental fat e studies including ecotoxicological investigations and monitoring.