The scientific process depends on critical peer review and debate. Modern biosolids recycling policy and practice rests on a body of scientific research, review, and debate conducted for over 40 years. A large proportion of government and university scientists working with biosolids have come to believe that biosolids recycling in accordance with current laws and best management practices represents "negligible risk" (this is the finding of the 1996 National Research Council review of the federal biosolids program; see below).

Still, there continues some discussion regarding new angles in the practice of recycling biosolids and other residuals. We at NEBRA believe that this robust scientific analysis and debate will lead to even better practice and policy.

Below are the key documents that provide an overview of the scientific basis for biosolids management, including biosolids application to soils. These documents, including U. S. EPA risk assessment and two reviews by expert panels of the National Research Council of the U. S. National Academies of Science, represent the scientific consensus on this topic.

Today, some research continues on the traditional research topics in this field: trace elements of concern (heavy metals), priority organic chemicals, and bioaerosols. Those topics have, by now, been quite thoroughly addressed in the scientific literature. But there are other topics of current interest:

• What are the impacts of traces of chemicals in wastewater and biosolids that come from pharmaceuticals and personal care products (PPCPs), also known as "microconstituents"?
• What are the impacts of particular treatment technologies, including possible triggering of bacteria reactivation and regrowth in some Class B biosolids?
• How do biosolids generate malodors and what process controls can be adopted to stop this from happening?
• How can energy production from biosolids be optimized, for example, with anaerobic digestion?
• What are the carbon emissions from various biosolids management processes, and how can biosolids management programs minimize those emissions and maximize efficiency and sustainability?

NEBRA continues to track progress on these and related research topics and reports them here and in NEBRAMail.

Federal EPA Risk Assessment & Reviews of Biosolids Recycling

The Part 503 Regulations

The U.S. Environmental Protection Agency (EPA) published regulations for biosolids at 40 CFR Part 503 in accordance with the Clean Water Act. Details about the 503 rule are available in A Plain English Guide to the EPA Part 503 Rule. The full risk assessment process that led to the final standards found in the 503 regulations can be accessed here: A Guide to the Biosolids Risk Assessments for the EPA Part 503 Rule.

For a copy of the formal February 19, 1993 Federal Register publication of the Part 503 rule, with the full rationale and responses to comments, in a searchable PDF format (it is a large file), contact NEBRA.

Additional EPA information on biosolids is available here.  

Use of Reclaimed Water and Sludge in Food Crop Production (1996)

This is the first of two National Academy of Sciences expert panel reviews of the federal biosolids Part 503 regulatory program. It concluded…

"In summary, society produces large volumes of treated municipal wastewater and sewage sludge that must be either disposed of or reused. While no disposal or reuse option can guarantee complete safety, the use of these materials in the production of crops for human consumption, when practiced in accordance with existing federal guidelines and regulations, present negligible risk to the consumer, to crop production, and to the environment." (National Research Council: The Use of Reclaimed Water and Sludge in Food Crop Production," National Academy of Sciences, 1996, p.13.)

Biosolids Applied to Land: Advancing Standards and Practices (2002)

In 2000, the U.S. Environmental Protection Agency (EPA) asked the National Academy of Sciences to "review information on the land application of sludge and evaluate the methods used by the U.S. EPA to assess risks from chemical pollutants and pathogens in sludge." The Academy convened another National Research Council (NRC) panel that released its final report, Biosolids Applied to Land: Advancing Standards and Practices, in July, 2002. This report found:

"There is no documented scientific evidence that the Part 503 rule has failed to protect public health. However, additional scientific work is needed to reduce persistent uncertainty about the potential for adverse human health effects from exposure to biosolids. There have been anecdotal allegations of disease, and many scientific advances have occurred since the Part 503 rule was promulgated. To assure the public and to protect public health, there is a critical need to update the scientific basis of the rule to (1) ensure that the chemical and pathogen standards are supported by current scientific data and risk-assessment methods, (2) demonstrate effective enforcement of the Part 503 rule, and (3) validate the effectiveness of biosolids management practices" (from Summary, page 3, prepublication copy).

In September, 2002, Dr. Thomas Burke, Chair of the panel that wrote the report, issued a statement clarifying the panel's findings. "First, we found no evidence of an urgent public health risk from exposure to land-applied biosolids, based on our review of the scientific literature. Currently, there are no studies documenting adverse health effects from land application of biosolids, even though land application has been practiced for years. But this finding was tempered by the fact that few studies are available on human exposure to biosolids, and that, even when they are investigated locally, there are no means of tracking health allegations nationally."

In 2003, EPA responded to a petition that urged a moratorium on the use of biosolids on soils.  The petition cited several cases that they claimed indicated harm from biosolids.  In its response, EPA refuted the claims of the petitioners, undermining their allegations with contrary evidence from each case they cited.  EPA's response is available here.

In the years since the 2002 National Academy study, research scientists and U. S. EPA have continued to evaluate the potential risks to human health and the environment from use of biosolids on soils.  There continue to be no findings of significant harm from biosolids recycled in accordance with regulations and best practices.  The potential risks being evaluated by that research - such as microconstituents in biosolids - are very much smaller potential risks than those that were addressed by the original EPA risk assessment for elements and chemicals and by the later dioxin risk assessment. 

Today, research and experience are fine-tuning the practices of biosolids recycling, further advancing best practices.  For example, further improving understanding of the environmental relevancy of various forms of phosphorus in soils. 

Because of more than 40 years of research and experience, biosolids recycling to soils has become a mainstream way of managing the necessary byproducts of necessary wastewater treatment.

Pennsylvania State University....  a series of fact sheets summarizing their research: biosolids effects, biosolids use, biosolids quality,

Colorado State University....   Biosolids research (Dr. Ken Barbarick, Professor of Soil Science, Dept. of Soil and Crop Sciences, and others)

University of Florida....   George O'Connor, PhD, Professor of Soil and Water Science, with over 130 peer-reviewed publications, much on biosolids research.    Dr. O'Connor summarizes some of that research in this video lecture on "Organic Contaminants in Biosolids."   

See also IFAS Extension: "Food Safety on the Farm: Good Agrcultural Practices...Manure and Municipal Biosolids"

University of Washington....  Biosolids information compiled by Sally Brown, PhD, Research Associate Professor, School of Forest Resources

Virginia Tech....  Cooperative Extension discussion of biosolids concerns by Greg Evanylo, PhD, Professor, Dept. of Crop & Soil Environmental Sciences.

University of Arizona....  Charles Gerba, PhD, Professor of Microbiology...  and Ian Pepper, PhD,  Professor of    have conducted extensive researchon pathogens in biosolids.  Here is a summary of one project on pathogens and bioaerosols and nother evaluation of 20 years of land application of biosolids.

University of Missouri....  Extension publication on "Safety and Benefits of Biosolids"

Washington State University....  Webpage and resources on "Biosolids Management"

Soil Science Society of America....  A news release about use of soil amendments for urban gardening.

North Carolina State University....  the "waste management" program in the Soil Science Department continues biosolids research

Michigan State University....  Extension publication on "Utilizing Biosolids on Agricultural Land" by Lee Jacobs, PhD, Professor Emeritus, Dept. of Plant and Soil Sciences (began biosolids research in 1974).

New Mexico State University....   Extension publication on "A Sustainable Approach to Recycling Urban and Agricultural Organic Waste"

Water Environment Research Foundation....  sponsors research by independent university and other researchers on biosolids and wastewater topics.....  See here.  A list of WERF's biosolids research from 1992 - 2015 is here.

U. S. Dept. of Agriculture....  Rufus Chaney, PhD has published hundreds of papers and book chapters on biosolids since the 1970s.  See this video of lecture by Dr. Chaney regarding heavy metals in biosolids.

Purdue University, Indiana....   Extension publication on "Land Application of Municipal and Industrial Biosolids" (1994)

Cornell University....   New York's land grant university provides important recommendations to farmers.  Because of the work of the Cornell Waste Management Institute (CWMI), which has argued for even greater safety margins in the regulation and management of biosolids, Cornell's recommendations to farmers for "sludge" use are some of the most stringent on the continent.  Yet pretty much all biosolids products in use today can meet these very conservativeCornell Extension recommendations.  Note that the NY Dept. of Environmental Conservation published a thorough rebuttal to the 1997 CWMI "Case for Caution" report, clearly demonstrating that CWMI's arguments for stricter regulation of trace elements (heavy metals) in biosolids were not supported by the preponderance of science.  (Contact NEBRA for copies of these documents.)

University of California, Riverside....  Albert L. Page, PhD, Professor Emeritus, Dept. of Environmental Sciences - decades of research, including on biosolids (examples here)

Canadian Council of Ministries of the Environment....   This Canadian government agency has sponsored recent biosolids research projects and offers useful publications that include extensive literature reviews and lists.

The Ohio State University....  Extension fact sheet on "Land Application of Waste..."     Nicholas Basta, PhD, Professor, School of Environment and Natural Resources, was lead author of the literature summary:  Basta, N.T., J.A. Ryan, and R. L. Chaney. 2005. Trace element chemistry in residual-treated soil: Key concepts and metal bioavailability. J. Environ. Qual. 34: 49-63 - an important review of key concepts derived from many studies from the last four decades on trace element chemistry and phytoavailability in biosolids-treated soil (contact NEBRAfor a copy).

American Society of Microbiology....   "Land Application of Organic Residuals: Public Health Threat or Environmental Benefit?"

Virginia state health department....   conducted a review of the potential public health impacts of biosolids use and found no reason for the practice to be discontinued.

State of the science conferences:   Every 10 years since the 1970s, U. S. EPA, USDA, and land grant universities have convened an international conference on the state of the science regarding application of biosolids and other organic residuals to soils:

--1973, University of Illinois–  resulting book of technical papers: Recycling Municipal Sludges and Effluents on Land

--1983, University of Colorado - resulting compilation of technical papers

--1993, University of Minnesota - resulting book of technical papers:  Sewage Sludge: Land Utilization and the Environment

--2004, University of Florida - proceedings/technical papers published in a special edition of the Journal of Environmental Quality, Vol. 34 / #1, Jan-Feb 2005.

 --July 2014, Soil in the City Conference, Chicago, IL - proceedings/technical papers published in a special edition of the Journal of Environmental Quality, Vol. 45, pp. 2 -8, January 2016.  Download summary paper here.

Long-term research and demonstration sites

Several biosolids land application sites have had ongoing applications of biosolids for 20 years or more, during which research has been conducted to determine any potential long-term impacts.  These sites include:

University of Minnesota....  Research conducted at the Rosemount watershed study area yielded many published papers. 

Chicago biosolids land reclamation and land application sites in Fulton County, IL....   Started in the 1970s, these sites and the biosolids applied have had regular monitoring ever since.  The results: many published papers.

Pennsylvania land reclamation sites....   William Sopper, PhD, former Professor at Penn State Univ., studied "sludge" (as it was known then) used for land reclamation at devasted coal mine sites.  His research, which was compiled in the 1993 book Municipal Sludge Use in Land Reclamation, evaluated impacts on soils, plants, small mammals, birds, and surface and ground waters for a period of 20 years (back to the early 1970s).  He found negligible negative impacts and demonstrated significant long-term improvements in restoring native ecosystems.  Today's biosolids are of higher quality and their management has improved further since Dr. Sopper's research.  Similar successes with land reclamation have been repeated around the U. S.,and many of those sites have also been evaluated for impacts on plants and animals, with similar findings.

Denver Metrogro Farm....   This farm in eastern Colorado, owned by the Denver Metro wastewater treatment utility, has had biosolids applications annually for years.  It has been the site of routine monitoring by U. S. Geological Society scientists; their reports on online (one example).

Biosolids applications to farmlands in eastern Washington....  Biosolids from the King County (Seattle area) wastewater treatment facilities have been land applied for decades.  Ongoing research is conducted by the Univ. of Washington, Washington State Univ., and Arizona State Univ.  King County research summary webpage.

The NEBRA office has additional information, references, and referrals.