ARS | Publication request: Comparative microbial risks of land applied biosolids and animal manure

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: December 20, 2009
Publication Date: May 4, 2009
Citation: Brooks, J.P., Gerba, C.P., Pepper, I.L. 2009. Comparative microbial risks of land applied biosolids and animal manure [Abstract]. Water Environment Federation Residuals and Biosolids Conference. CD-Rom. p. 53.

Technical Abstract: The transmission of pathogens by land application of untreated human and animal wastes has been known for more than 100 years. In the United States there are more than 450,000 (EPA) animal feeding operations producing more than 100 million tons of animal manure per year. In addition, grazing animals also deposit large quantities of manure on range land. This study attempts to look at the relative risks of pathogens in biosolids vs. animal manure applied to land using a quantitative microbial risk assessment approach. This process involves four basic steps: pathogen identification, exposure assessment, dose-response and risk characterization. Several examples which were evaluated included risk to workers, produce crops, and children playing in a field. While some of these exposures may be considered worst case for biosolids because of site and application restrictions, they can commonly occur in areas where manure is applied. The risks are largely determined by the degree of treatment that the manure receives before land application, but risks compared to biosolids can be comparable, depending upon assumptions used in the risk model. Generally, annual risks of infection were greater than the accepted 1:10000 chance of infection for bacteria (applied manures) and viruses (biosolids) when land applied and only allowed an 1-month decay time period. Using more appropriate conditions of soil decay (> 6 months), land application of either residual resulted in risks below the accepted risk. This analysis can provide insight on the relative risks of animal waste and biosolid land application that will allow for a better grasp of the risks to the public and industry.