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A risk assessment approach for setting criteria for pathogens in biosolids

Gibbs, R.A., Ho, G.E. and Unkovich, I. (1997) A risk assessment approach for setting criteria for pathogens in biosolids. In: AWWA 17th Federal Convention, 16 - 21 March, Melbourne, Australia pp. 120-127.

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Risks associated with pathogens in biosolids are uncertain and are potentially of major concern in the marketing of biosolids products. At present there are no formal National biosolids guidelines in Australia. US EPA regulations require the monitoring of biosolids for pathogens or indicator bacteria but criteria have been based on detectable limits for pathogens. Two problems with this approach are firstly that detection limits in microbiology are constantly changing, and secondly that in some cases criteria based on detection limits may result in unacceptable risk. For this reason a risk assessment approach has been developed and is described here. This risk assessment approach has been applied to setting criteria for pathogens in biosolids. This involved the steps of hazard identification, development of acceptable risk criteria, dose-response assessment, exposure assessment and calculation of limits. Based on this risk assessment procedure a limit of less than 1 Salmonella in 50 g of biosolids product is proposed for biosolids which are to have unrestricted distribution. It is recommended that limits for Giardia and enteric viruses should not be included in guidelines until methods for their detection in bisolids are more developed.

Publication Type: Conference Paper
Murdoch Affiliation: School of Environmental Science
Publisher: Australian Water & Wastewater Association
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