Die-off of pathogens and assessment of risks following biosolids application in pine forests

J. Levitan; J. Nair; G. Ho; N. Penney; I. Dumbrell

Timber is one of a few agricultural products that is not linked to the human food chain, and thus can be submitted to a number of practices not usually considered appropriate for other markets such as horticulture. Direct application of biosolids to plantation stands as a substitute for commercial fertilisers is one of these practices. However, there maybe significant health issues in regards to the potential for pathogens to be introduced to the environment through the use of the biosolids. Despite the treatment processes that wastewater sludge undergoes to be classified as biosolids prior to direct land application, some pathogens survive and therefore there is a potential for infection of the local human population. The research objective of this study is to establish the human health risk of using biosolids in a plantation stand. The die-off of indicator pathogens will be monitored to establish their ability to survive once the biosolids are applied to land. The health risks of airborne pathogens will be determined through studies into the ability of pathogens to be transported via the smoke from a burn off scenario. A literature review established that the indicator pathogens for this study would be Escherichia coli, Clostridium perfringens, Salmonella spp., and Coliphage. Preliminary results indicate that there are some colonies of the indicator pathogens present but at very low levels, however further results are needed to establish a firm conclusion. Preliminary results show there is potential for some pathogens to be transported via the smoke initiated from a burn off. Given the low pathogen numbers in the applied biosolids, spiked biosolids samples have also been used to provide a point of comparison. These preliminary results support the current literature, however further analysis is required in order to firmly establish the health risks of this potential occurrence. Further research to intensively monitor the pathogen die-off in the first year post-application is required and will be combined with the data from the multiple years’ post-application samples. Research into the ability of dust generated from the biosolids due to vehicle movement to transfer pathogens is also required to establish the health risk both to members of the general public and also the plantations workers. The effects that the pine trees themselves and specifically the addition of pine needles to the soil organic matter will also be researched to establish if this phenomenon has an effect of the die-off of pathogens. The results from this study can be transposed to agricultural systems and may aid in future decision making in regards to the use of biosolids particularly areas linked to the human food chain.

Die-off of pathogens and assessment of risks following biosolids application in pine forests

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