The Occurrence of Enteric Viruses in Polluted Water, Correlation to Indicator Organisms and Factors Influencing their Numbers

Abstract

Samples from a stream polluted with treated domestic effluent were examined for the presence of enteric viruses and indicator organisms viz. total and faecal coliforms, faecal streptococci and coliphages. Strong seasonal patterns in both the occurrence and number of enteric viruses, coliphages, and to a lesser extent faecal streptococci, were observed. The incidence of the highest and lowest number of enteric viruses and coliphages plotted on a time scale followed a sine curve as opposed to the variations of temperature which followed an inverted sine curve. Indications are that the survival of these organisms is inversely proportional to temperature with lower temperatures (below 13°C) being conducive to a slower die-off rate. The square of the correlation coefficient between the viral numbers and temperature was calculated at R2 = 0.4. This coefficient of determination only improved to R2 = 0.46 by combining data from other physical and physico-chemical and biological determinations. Temperature may be considered a useful aid in predicting the possible presence or absence of enteric viruses in raw water. Of all the indicator organisms examined only results on coliphages behaved similar to that of enteric viruses and should therefore be considered the best biological indicator for viral behaviour under these circumstances.