Submitted to: Journal of Environmental Quality
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/15/2010
Publication Date: 11/15/2010
Citation: Pepper, I.L., Brooks, J.P., Sinclair, R.G., Gurian, P.L., Gerba, C.P. 2010. Pathogens and indicators in United States Class B biosolids: national and historic distributions. Journal of Environmental Quality. 39:2185-2190. Interpretive Summary: The presence of bacterial, viral, and parasitic human pathogens in biosolids, or wastewater treatment solids, has proven to be a national public health concern. The use of these residuals on agricultural land has been a source of contention, though the process has been historically utilized, however in 1993, the USEPA created the Part 503 rule which limited the number of acceptable pathogens, crop use, and imposed time limits associated with land application and crop harvest. To date there have been no spatial or temporal (historic) studies which have documented the microbial quality of biosolids since this rule has been put into effect. This study found that biosolids have increased in quality with overall bacterial and viral indicators reduced, most likely as a result of more efficient wastewater treatment. Spatial investigations determined that biosolids are relatively similar in microbial quality from each corner of the United States. Some bacterial and viral pathogens were detected, though at low levels and reflected that for the most part, the Part 503 rule has been effectively utilized to increase biosolids microbial quality.
Technical Abstract: This paper reports on the first major study of the incidence of indicator organisms and pathogens found within Class B biosolids across the U.S. since the promulgation of the EPA Part 503 Rule in 1993. National distributions collected between 2005 and 2008, show that the incidence of bacterial and viral pathogens in Class B mesophilic, anaerobically digested biosolids were generally low with the exception of adenoviruses which were more prevalent than enteric viruses. No Ascaris ova were detected in any sample. In contrast, indicator organism concentrations were uniformly high, regardless of whether they were bacteria (fecal coliforms) or viruses (phage). Historic distributions were collected between 1988 and 2006, at one location in Tucson, Arizona. By comparing data collected prior to and after 1993, the influence of the EPA Part 503 Rule on indicator and pathogen levels within Class B biosolids can be inferred. In general, both bacterial indicator and pathogen loads (bacterial and viral) decreased from the 1980s to present. Presumably this is due to better and more consistent treatment of the wastewater, illustrating that the Part 503 Rule has been effective in reducing public exposure to pathogens relative to 25 years ago. The percent reduction of both indicators and pathogens during anaerobic mesophilic digestion was between 94 and 99% for all organisms illustrating that such treatment is effective in reducing pathogen loads.