Pergamon Wat. Res. Vol. 30, No. 9, 2045-2054, 1996 pp. Copyright 0 1996 Elsevier ScienceLtd PII: SOW-1354(!%)00@7!%6 Printed in Great Britain. All rights reserved 0043-1354/96 $15.00 + 0.00 RELATIONSHIPS BETWEEN INDICATORS, PATHOGENS AND WATER QUALITY IN AN ESTUARINE SYSTEM CHRISTOBEL M. FERGUSON’*, BRIAN G. COOTE’, NICHOLAS J. ASHBOLT*@ and IAIN M. STEVENSON’ ‘AWT EnSight, PO Box 73, West Ryde, Sydney, Australia 2114, *School of Civil Engineering, University of New South Wales, Sydney, Australia 2052 and ‘Faculty of Science, University of Technology, Sydney, Gore Hill, Australia 2065 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQ (First received August 1995; accepted in revised form February 1996) Abstract-This study examined water and sediment samples for a range of indicator and pathogenic microorganisms from six sites in an urban estuary, Sydney, Australia. Water quality was affected by rainfall and sewage overflows which were associated with significant increases in the concentration of faecal coliforms, faecal streptococci, Clostridium perfringens spores, F-RNA bacteriophage, Aeromonas spp., Giardia and Cryprosporidium spp. However, in sediments, only faecal coliform concentrations were significantly increased by rainfall, although sewage overflow again resulted in increased concentrations of faecal coliforms, faecal streptococci, C. perfringens spores and Aeromonus. Isolation of Salmonella appeared to coincide with wet weather events and occasionally identical serotypes were detected in sediments at several locations within the estuary. However, isolations of enteric virus were sporadic and did not appear to be exclusively related to wet weather events. C. perfringens was identified as the most useful indicator of faecal pollution and was the only indicator significantly correlated to the presence of pathogenic Giurdiu (r = 0.41, p i 0.05) and the opportunistic bacterial genus Aeromonas (r = 0.39, p < 0.05). F-RNA bacteriophage was not significantly correlated with any of the pathogens examined. Copyright 0 1996 Elsevier Science Ltd Key words-indicators, pathogen, water quality, sediment, enteric virus, Giardia, Cryptosporidium NOMENCLATURE ct = intercept /I, = regression coefficients lot = location I = locations, 1-6 j = dates, l-10 k = type, either top or bottom sediment fraction Iriver = the linear polynomial for distance of location, from the sewage overtlow point qriver = the quadratic polynomial for distance of location, from the sewage overflow point criver = the cubic polynomial for distance of location, from the sewage overflow point qtriver = the quartic polynomial for distance of location, from the sewage overflow point rvlkb = contrast between the location in Lime Kiln Bay and those in the Georges River INTRODUCTION Assessment of water quality has traditionally relied on the detection of faecal indicator organisms, *Author to whom all correspondence should be addressed: c/o Burns Philp R&D Division, PO Box 219, North Ryde, Sydney, Australia 2113 [Tel.: (2) 887 191I; Fax: (2) 888 31781. particularly total coliforms, faecal coliforms and faecal streptococci. However, these groups of microorganisms do not necessarily correlate well with the presence of pathogenic organisms. Davis et al. (1977) suggested that the total coliform group did not constitute a reliable source of information as to the pollutant content or condition of a water source, while Sayler et al. (1975) concluded that reliance on the coliform group created serious problems both in measuring environmental quality and in calculating risks to public health. The lack of significant correlations between the presence of traditional indicators and pathogens (Grabow et al., 1989; Araujo et al., 1990) and the ability of pathogens to assume a viable but non-culturable state (Grimes et al., 1986) has highlighted the inadequacy of indicator systems in predicting water quality and associated health risks. In addition, several studies have highlighted the importance of sediments as potential reservoirs for microorganisms in the aquatic environment (Hen- dricks, 1971; Grimes, 1975; Erkenbrecher, 1981). The prolonged survival of coliforms and possibly other faecal bacteria in sediments and the likelihood of 2045