Persistence of Escherichia Coli in Recreational Coastal Water and Sediment

A laboratory based microcosm study was undertaken to determine the persistence of the faecal indicator organism Escherichia coli in coastal recreational water and sediment under varying environmental conditions. Intact sediment cores were taken from three distinct coastal sites in the Adelaide metropolitan area and the overlying water was inoculated with known concentrations of E. coli. The concentration of E. coli in water and sediment was determined by the membrane filtration method on days 0, 1, 2, 7, 14, and 28 following inoculation. It was demonstrated that E. coli could persist in coastal sediment for greater than 28 days when incubated at 10°C. Temperature was found to have an inverse relationship with E. coli survival in both water and sediment. In general the decay rate for E. coli was greater in water than in sediment. Small particle size and high organic carbon content were also found to enhance E. coli survival in coastal sediments.