Some Environmental Factors Affecting Survival of Fecal Pathogens and Indicator Organisms in Seawater

This study was conducted to determine the effects of certain environmental factors, such as temperature, salinity, and light, on the die-off of Salmonellatyphi, Salmonellavein, Shigellaflexneri, and Escherichiacoli, examples of fecal pathogens and indicator organisms in water. The survival of these organisms was investigated in different types of water: seawater, filter sterilized seawater, tap water, and normal saline. The organisms were counted every two hours for 8 hours, then daily for up to 7 days. It was found that there was no great difference in the survival times of the organisms tested at temperatures of 25 - 35°C, but at 40°C they died off more rapidly. The salinity of the seawater did not affect the survival time of the Salmonella bacteria. However, Sh.flexneri and E.coli appeared to survive for longer in freshwater than in seawater at temperatures of 30 - 35°C. Daylight, i.e., sunlight, had a deleterious effect on all test organisms, Survival times were shorter when exposed to daylight than in the dark in the different types of water, being from several hours to 24 h compared to several days in the dark. Artificial light had less effect than natural daylight. It was concluded that exposure to sunlight is the most important factor in the self-purification of water polluted due to sewage outfalls.