Detecting and Distinguishing Sources of Sewage Pollution in Australian Inland and Coastal Waters and Sediments

Abstract

Sewage pollution often causes public concern, and, therefore, assessment of fecal pollution with the traditionally used indicator microorganisms has been a standard monitoring approach. Molecular markers such as fecal sterols, however, may overcome shortcomings of the classical bacterial indicators. The principal human fecal sterol is coprostanol (5β-cholestan-3β-ol), whilst herbivore feces are dominated by C29 sterols (24-ethylcoprostanol and 24-ethylcholesterol). In a pilot investigation, combined fecal sterol and bacterial indicator measurements were used to distinguish fecal pollution from human, herbivore, domestic pet and bird inputs in inland waters during a rain event. Native birds were found to be a major source of the fecal pollution. In a further application of the molecular marker technique in marine waters, Sydney's coastal environment was surveyed before (1989) and after (1992 and 1993) commissioning of deep ocean outfalls in 1991. Most sites showed large increases in the amount of coprostanol present after commissioning of the deep ocean outfalls. Compared to the distribution in 1989, areas of highest concentration of coprostanol were observed further off-shore in 1992 and 1993, adjacent to the diffusers. Minimal dispersion was apparent to regions further off-shore. A decrease in the concentration of coprostanol in sediments in 1993 relative to 1992 reflects a decreased discharge of sludge. These findings suggest the molecular marker approach will be useful to determine future temporal changes in Sydney's coastal environment, including effects due to changing effluent disposal practices.