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The Science of Biosolids Recycling
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 30 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).
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), pathogens, and priority organic chemicals. But while those topics have, by now, been quite thoroughly addressed in the scientific literature, there are new topics of interest:
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.
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:
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. 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 in the early 1990s by the EPA risk assessment. Today, research and experience are fine-tuning the practices of biosolids recycling, which has become a mainstream way of managing the necessary byproducts of necessary wastewater treatment.
Biosolids Recycling to Soils – Online Scientific Resources
Since the 1970s, major land grant universities, government agencies, and others around the U. S. have studied use of biosolids in agriculture and for other applications to soils. Thousands of research papers have been published in peer-review research journals. Scores of university extension publications have addressed various aspects of biosolids use. Below is a sampling of research summaries available online regarding the safety and benefits of biosolids use on soils.
Note that, at the end of most of the following documents, there is a list of references that includes peer-reviewed published research. Such references to a body of scientific work is the hallmark of sound science. These documents are not based on one or two findings or the opinions of a few people; they are built on the developing understanding of many scientists.
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 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 blog on the importance of soil includes mentions of biosolids.
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.
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 conservative Cornell 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.)
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 NEBRA for 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.
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.
Microconstituents (trace organic chemicals) in Biosolids
What are the impacts of traces of chemicals in wastewater and biosolids that come from pharmaceuticals and personal care products (PPCPs) and other sources, sometimes collectively described as "microconstituents"?
Ned Beecher, Executive Director of NEBRA, summarized knowledge of PPCPs in wastewater and biosolids in the Fall 2008 edition of the New York Water Environment Association journal Clearwaters. Click here to download.
The Water Environment Association of Ontario (WEAO) published literature reviews on the fate and significance of microconstituents in biosolids in 2001 and 2010. See the WEAO website biosolids committee pages to learn more and download the reports.
Also in 2010, the Water Environment Research Foundation (WERF) completed a literature review on the state of the science regarding microconstituents in biosolids; see here.
At the January 2011 NEWEA Annual Conference, Ned Beecher, Executive Director of NEBRA, presented a summary of the state of the science on microconstituents in biosolids; download the presentation here.
And, in May 2011, NEBRA created an "Information Update" on the current state of knowledge regarding microconstituents in biosolids; download the document here.
Later in 2011, BioCycle published a review of trace organic chemicals (TOrCs) in biosolids by Hundal et al. Read it here.
An update of NEBRA's May 2011 summary of the literature on this topic is in production.
Pathogens and Class B Land Application
What about possible public exposure to pathogens from Class B biosolids applied to land?
Since the late 1990s, there has been concern and research regarding the possibility that pathogens and/or other emissions from Class B biosolids land application activities or biosolids composting facilities may cause health impacts to neighbors. (Note that there are few concerns about Class A biosolids, because they have been treated so levels of pathogens are similar to background soils or less.)
Research has found measurable health impacts in workers at confined feeding operations (e.g. hog farms) and compost facilities that process food waste, yard waste, and/or wastewater solids (sewage sludge). Apparently, exposure to high levels of organic dusts for extended periods of time - such as at composting facilities - can trigger measurable health impacts in some people.
The effects of exposure to unstabilized (raw) or Class B biosolids - which contain viable pathogens and may generate bioaerosols and dust - are not as clear. Research regarding the health of workers at wastewater treatment facilities, who are most highly exposed to unstabilized wastewater solids, has not found significant health impacts. Such workers are generally not considered to be in hazardous work conditions. Still, those managing large volumes of Class B biosolids or unstabilized wastewater solids (including workers at wastewater treatment facilities) are advised to use personal protective equipment, wash hands frequently, and avoid hand-to-mouth contact during work (see http://www.cdc.gov/NIOSH/docs/2002-149/2002-149.html). The same precautions are advised when working with animal manures, soils, etc.
There are reports in newspapers and on the internet of health impacts - mostly resipiratory and headaches - to neighbors of Class B land application sites. However, research showing a causal relationship between Class B biosolids and the health impacts is lacking (see, for example, this 2002 literature review from Québec: http://www.biosolids.org/docs/24902.pdf). Often, intense malodors are also present when impacts are reported, and there is evidence that odors cause physiological impacts (for example, see http://jeq.scijournals.org/cgi/content/full/34/1/129). This complicates the situation. Some biosolids have the potential to create malodors, and some people feel ill when exposed to bad odors, be they from biosolids or animal manures.
Researchers at the University of Arizona have collected air samples at Class B land application sites during actual land application activities around the country (http://wqc.arizona.edu/publications/index.htm). They conclude that risks to neighbors from bioaerosols from Class B land application are minimal. However, most of their work was conducted in the dry southwest, where conditions are not conducive to pathogen survival.
A health study of neighbors to permitted land application sites in Ohio published in 2008, appeared to find health impacts (see http://www.ohiowea.org/owea/residuals/HealthSurveyResidents08.pdf). However, the study's conclusions were subsequently challenged (see http://www.ohiowea.org/owea/residuals/FINALToledo%20Review08.pdf) and the authors released a clarification (http://www.biosolids.org/docs/University%20of%20Toledo%20Biosolids%20Fact%20Sheet%20on%20Health%20Survey%20Study_2008.pdf).
Research continues regarding this aspect of Class B biosolids land application. Given the hundreds of biosolids land application programs around the continent, many of which have been ongoing for a decade or more, and relatively few complaints of health impacts, this concern seems to be minimal and possibly localized. In the meantime, those managing Class B biosolids are required by all Northeast state and provincial regulations to maintain setbacks from neighbors for all Class B biosolids management activities, and public access to Class B land application sites is restricted. In recent years, there have been few complaints in this region.
Those managing biosolids land application programs strive to manage odors and take measures to reduce the potential for bioaerosol emissions or other exposures to pathogens. For example, biosolids that have been anaerobically digested tend to have low potential for odors, and injection of biosolids or incorporation in the soil immediately after application dramatically reduces any risk of pathogen exposure.
Similar measures are not required for the use of animal manures, of which there is a far greater amount being used on farms. And animal manures also contain trace elements (e.g. heavy metals), chemicals, including microconstituents (e.g. antibiotics), and pathogens.
Additional resources on pathogens in biosolids:
In 2005, BioCycle / JG Press published an excellent compilation of findings of a 2001 seminar of experts on biosolids and manure pathogen risks, titled Contemporary Perspectives on Infectious Disease Agents in Sewage Sludge and Manure (James E. Smith, Patricia D. Millner, Walter Jakubowski, Nora Goldstein, and Robert Rynk, editors, 2005). Contact BioCycle or NEBRA for details.
In 2011, U. S. EPA published Problem Formulation for Human Health Risk Assessments of Pathogens in Land-Applied Biosolids, which includes an excellent literature review. Download it here.
In 2011, the American Society for Microbiology published a summary of a workshop held in Washington, DC and chaired by Gary M. King, PhD of Louisiana State University. The workshop, involving expert research scientists from around the nation discussed the "microbiological concerns about land spreading, the appropriate disposal of biosolids, and the role of microbiology." Download the report here.