The survival of Escherichia coli in tropical estuarine water has been studied under controlled laboratory conditions using
microcosms. The survival has been assessed in terms of various self purifying factors of the natural waters such as biological,
chemical and physical factors. The biological factors considered included competition from other microorganisms, predation
by protozoa and coliphages. The suitability of the chemical composition of estuarine water has been studied under chemical
factors and negative impact of sunlight has been studied under physical factors. The results revealed that sunlight exerted
maximum negative impact, followed by biotic factors contained in the estuarine water. However, the chemical composition of
the estuarine water is found to be suitable for the growth and survival of E. coli. The injury exerted by each of the above
factors was also evaluated by using a selective and non-selective medium in conjunction. It was found that sunlight resulted in
100% injury of the cells as the cells failed to develop in a selective medium. While, sunlight resulted in the extinction of 90% of
the E. coli cells within the first two hours of exposure, biotic factors took nearly 24 hours to remove the same amount of
population.