Dissolved Oxygen and Survival of Coliform Organisms and Enterococci

Abstract

This paper presents the results of a laboratory study to measure and compare the survival of the coliform and enterococcus groups in waters containing different concentrations of dissolved oxygen (DO). Three separate experiments were performed. Nine 4‐liter flasks were used in each. Each flask contained a 1 per cent dilution of sewage in BOD dilution water. Three replicate flasks had a low DO level, obtained by stripping the oxygen with nitrogen gas at the time of each sampling. Three other replicate flasks had a high DO level, obtained by diffusing oxygen through the contents at the time of each sampling. The last three replicate flasks had a normal DO (near saturation). The temperature of the contents of all the flasks was controlled at 20°C. The contents of each flask were mixed uniformly at the time of each sampling. All flasks were kept dark at all times, thereby removing light as a variable. Determination of the number of coliform organisms and enterococci was made daily on the contents of each flask, using the membrane filter technique.