Posted: December 26th, 2011 - 10:04am
Source: 7th International Conference on Water Sensitive Urban Design

- Christelle Schang, Monash University, Department of Civil Engineering, Australia
- Dr Catherine Osborne, Monash University, Australia
- Dr David McCarthy, Monash University, Australia
- Mrs Ana Deletic, Monash University, Australia
If faecal microorganisms survive for extended periods in river bed sediments, then this might be a critical source of faecal microorganisms in the water column of contaminated streams that is difficult to remediate. To determine the ability of bacteria to survive in a historically-contaminated urban stream, we conducted viable counts of bacteria that are indicators of faecal pollution and pathogens in the bed and bank sediments of the Yarra River estuary, Melbourne, Australia. In a first stage, core samples were collected at three locations along the Yarra River on a monthly basis and the viable counts of E.coli, the traditional faecal indicator bacteria, was monitored over time in the water column and the bed sediments. In a second stage, viable counts of E. coli and the bacterial pathogen, Campylobacter, were monitored over time at different depths within the cores. The results show that E. coli Campylobacter can survive in the bed sediments of the Yarra River estuary. However, the survival of Campylobacter outside of a mammalian host raises concern, because pathogenic strains of this microorganism could also be surviving in the bed sediments and could cause significant health risks to users of the estuary if resuspended. The growth dynamics of both indicator and pathogenic bacteria are complex and depend on a number of parameters, such as concentrations of O2 and CO2etc, so further work is required to determine what chemical and biological factors minimize this source of potentially pathogenic bacteria in historically-contaminated streams.