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Factors Affecting the Concentration of Faecal Bacteria in Land-drainage Water
Abstract
Summary: The rate of discharge and the concentration of faecal bacteria in the water from a subsurface field drain were monitored, initially for one winter without application of animal excrement to the pasture, and, subsequently, for two winters when pig excrement was sprayed over the pasture. The concentrations of Escherichia coli and enterococci in the water were found to be affected by three main factors: the flow rate of the drain discharge; the number of bacteria in or on the soil and vegetation; and the application to the land of large volumes of semiliquid animal excrement over short periods of time. In the absence of excrement application, the concentration of faecal bacteria in the water was related to the flow rate and to time by an equation of the form: log bacterial concentration=a+b log flow rate-c days, where a, b and c are constants. The concentrations of bacteria in the water declined with time, the 90 % reduction times being 57 days for E. coli and 96 days for enterococci. The spraying of pig excrement over the pasture resulted in a 30- to 900-fold increase in the concentrations of faecal bacteria in the drain discharge within 2 h of the start of the spraying. The concentrations of faecal bacteria returned to their normal levels over a period of 2 to 3 days.
- Accepted:
- Published Online:
© Society for Gerenal Microbiology 1972