Development of Pathogen Risk Assessment Models for the Evaluation of Sludge Management Alternatives

摘要

A need exists to understand the risks to human health posed by the various methods of disposal and utilization of wastewater sludge. Our purpose is to clarify why this need exists and suggest an approach that could be used to help make rational decisions concerning sludge management. Limitations placed on the disposal of sludge make the utilization of sludge as a resource appear not only desirable, but also necessary. There are several types of pathogens found in sludge. These include some bacteria, viruses, parasites, and fungi. This modeling study will primarily involve methods of sludge utilization. The initial emphasis will be to determine the risk due to pathogens that result from sludge applied to land as a fertilizer or soil conditioner and from sludge fed to animals. It is recognized that there are many methods of sludge treatment that reduce pathogens, many ways to utilize sludge, and many routes of pathogens from sludge to man. However, for any particular application, the number of cost-effective treatments that can be used to reduce the pathogen load of sludge and the number of pathways of these pathogens to man is limited. The ultimate goal of this type of study will be to determine the amount of treatment needed to reduce the pathogens at any given point in the environment to a level where the risk to human health is greatly reduced or eliminated. Some of the desired attributes of a predictive model that accurately depicts pathogen survival and movement in the environment are listed. A summary of the benefits to be realized from a modeling approach to the determination of pathogen risk resulting from sewage sludge utilization is given. (ERA citation 04:024628)