Sustainability of land-application of class B liquid biosolids

Authors: PEPPER, I - UNIVERSITY OF ARIZONA; ZERZGHI, HURUY - UNIVERSITY OF ARIZONA; Brooks, John; GERBA, CHARLES - UNIVERSITY OF ARIZONA

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2008
Publication Date: 7/1/2008
Citation: Pepper, I.L., Zerzghi, H., Brooks, J.P., Gerba, C.P. 2008. Sustainability of land application of class B liquid biosolids. Journal of Environmental Quality. 37:S-58-S-67.

Interpretive Summary: Biosolids land application has been a contentious subject throughout the United States. The Environmental Protection Agency has enacted rules to protect the population; however sustainability of the practice is in question. To properly sustain biosolids application, one must demonstrate that biosolids land application is not only beneficial to the land in question, but also not harmful to beneficiaries of the land (i.e. direct consumers, indirect consumers, and neighboring populations). In short, over a 20 year period of studies conducted in the desert southwest portion of the country, it has been demonstrated that biosolids land application can be sustainable. The most common concerns have been with regard to biological (pathogenic microorganisms) and chemical (heavy metals, nutrients) constituents. These studies have demonstrated that biological and chemical risks were minimal, and pose only minor concerns given that EPA rules were followed. It is important to note that despite these studies having been conducted under field conditions; there are specific environmental, biological, chemical, and physical properties associated with these sites and as such sustainability may only be local and not applicable to all environments. As such, studies of this breadth and scope should be conducted elsewhere to ascertain true biosolids sustainability.

Technical Abstract: The sustainability of land-application of Class B liquid biosolids can be evaluated based on a review of the literature with respect to: a) long term field plot studies; and b) more recent studies on the fate and transport of potential biological and chemical hazards resulting from land-application. The conclusion we have reached based on these two criteria is that land-application of Class B biosolids is sustainable. This conclusion is based on the following factors: 1) The risks to human health and welfare posed by many microbiological entities within biosolids have been shown to be low. In addition, risks from indirect exposures such as aerosolized pathogens or contaminated groundwater are also low. Based on this review, current US EPA guidelines for land application in the U.S. appear not only to be adequate to protect human health but also sustainable using current agricultural practices. However, vigilance is always necessary since new contaminants continue to emerge and need to be assessed. 2) Long term land-application has been shown to enhance microbial numbers, activity and diversity. Overall these are beneficial effects, and there is no evidence of adverse toxicity effects on the soil microbial community. 3) There was no evidence of long term persistence of enteric pathogens in the soil or evidence to suggest possible movement to groundwater. 4) Long term land-application also increased soil macro-nutrients including C, N, and P. 5) In addition, increases in available metal concentrations were modest, and no increase in salinity was observed.