Fertile ground

From flush to farm, the conversion of raw sewage sludge into treated biosolids used as fertilizer is a complex and heavily regulated process. Biosolids are the solid, semisolid or liquid untreated residue generated during the treatment of domestic sewage in municipal wastewater treatment plants. The U.S. Environmental Protection Agency (EPA) encourages the beneficial reuse of these nutrient-rich organic materials and has set strict standards under which wastewater residuals can and cannot be recycled as soil amendments.

Beneficial uses

Biosolids are basically a slow-release fertilizer with low concentrations of other plant nutrients. Besides having significant amounts of nitrogen, biosolids also contain potassium, phosphorous and essential micronutrients such as zinc and iron. The organic matter in biosolids can improve soil quality by improving water holding capacity, soil structure and air and water transport. Additionally, biosolids can decrease topsoil erosion.

Even though there has been a growing trend in the last decade to recycle biosolids, another trend has been an increasing number of ordinance bans on biosolids.

Besides their environmental benefits, biosolids can provide an economic benefit. Colorado State University agronomists have shown that continuous application of three-dry tons (per acre) every other year to dryland wheat produces comparable yields, higher protein content and larger economic returns compared with the use of 50 to 60 pounds (per acre) per year of commercial nitrogen fertilizer.

Severely disturbed soils can be reclaimed through the addition of biosolids as replacement for topsoil. Biosolids have been used successfully to reclaim surface strip mines, large construction sites, parks, wetlands and landfills. Biosolids also have proven valuable in horticultural and landscaping uses; they can be composted with yard clippings, wood chips, sawdust or crop residues. As well, the treated wastewater residuals can improve forest productivity, increasing the growth of hybrid poplars and enhancing the aesthetic value of Christmas trees. sludge

Communities benefit from the land application of biosolids because this disposal method frees up much needed room in municipal landfills. In many states, landfill space is already inadequate for solid waste needs and constructing new landfill sites can be politically challenging. The costs to the community are considerably less with land application than with other disposal methods, such as landfilling or incineration.

Regulating biosolids

In February 1993 in compliance with section 405 of the Clean Water Act, EPA published the standards for the use or disposal of sewage sludge, 40 Code of Federal Regulations 503, 58 Federal Register 9248, known as the Round One sewage sludge regulation. Commonly called the 503 rule, the standard is designed to protect human health and the environment. This regulation sets the limits for metals, pathogens and total hydrocarbons for land application, surface disposal and incineration of sewage sludge. It also governs the stability of the materials by reducing the attraction of vectors (such as flies), agricultural practices, site restrictions and crop harvesting restrictions.

This regulation establishes two main types of biosolids. Class A biosolids have been treated to remove all pathogens, among other contaminants. In more populated areas, it may be necessary to produce Class A or Exceptional Quality (EQ) biosolids. EQ biosolids refers to a type of biosolids that not only is Class A, but achieves vector attraction reduction and meets the highest quality criteria for pollutant concentrations as stated in the Part 503.13 rule.

Under the 503 rule, Class B biolids may have a minimal amount of pathogens. This type of biosolids have associated site restrictions for public access, animal grazing and types of crops. In rural areas where agricultural land is available, Class B biosolids are the product of choice among the agricultural community. Class B biosolids can be applied as a liquid or cake in a similar manner to fertilizers and manures.

New standard for dioxins

Section 405 of the Clean Water Act also requires a Round Two regulation for pollutants not previously regulated in Round One. As the result of the citizen's suit Gearhart vs. Browner, Civ. No. 89-6266-HO (D.Ore.), EPA was required to propose Round Two regulations by December 15, 1999, and to take final actions by December 15, 2001. In November 1995, EPA notified the court that, based on risk assessment results, the agency was considering further regulations only for dioxins.

The proposed dioxin standard was signed on December 15, 1999, and published in the Federal Register (Vol. 64, Number 246, Pages 72045 - 72062) for comment on December 23, 1999. The public comment period was extended to March 23, 2000. The Federal Register notice of the rule may be viewed on the Internet at www.epa.gov/fedrgstr/EPA-WATER/1999/December/Day-23/w33033.htm..

Chlorinated dioxins are unintentional byproducts of certain manufacturing processes and incomplete combustion of organic waste. Dioxins are biologically active organic compounds that cause a variety of adverse health impacts (both carcinogenic and non-carcinogenic) on mammalian species, including humans, at very low and chronic doses. Dioxins are not created in the sewage treatment process; rather dioxins that enter the sewage treatment works become concentrated during the wastewater treatment process.

The proposed rule would require facilities that prepare biosolids for application to test the biosolids for the presence of dioxins and also perform periodic monitoring to determine the level of dioxins. The proposed rule sets limits of 300 parts per trillion (ppt) of dioxins, above which biosolids may not be applied to the land because the agency has determined that sewage sludge with greater dioxins concentrations may present an unreasonable cancer risk to highly exposed individuals. All facilities would be required to test the level of dioxins present in their biosolids before land application, with two exceptions. Treatment plants treating less than one million gallons per day of wastewater and small businesses that prepare less that 290 metric tons of sewage sludge annually would be exempt from regulation.

The proposed rule would require facilities finding levels of dioxins between 30 and 300 ppt in their biosolids to monitor annually for dioxins, while facilities that find less than 30 ppt of dioxins would be required to monitor once every five years. Based on risk assessments, EPA is not proposing additional numeric standards or management practice requirements for dioxins in biosolids that are to be placed in surface disposal units or incinerated.

When asked in July by Environmental Protection about what date EPA would publish its final rule related to dioxins, Dr. Alan Rubin, a senior scientist with EPA, declined to give a specific date. "We will meet our deadline and promulgate the standard by December 15, 2001," Rubin said.

Environmental management systems

Formed in 1997, The National Biosolids Partnership (NPB) consists of the Association of Metropolitan Sewerage Agencies, EPA and the Water Environment Federation (WEF). In 1998, the U.S. Congress appropriated $900,000 for NPB and earmarked much of the funding for the development of an environmental management system (EMS) for biosolids.

Along the lines of the International Standard Organization's ISO 9000 and ISO 14000 EMS programs used by industry, the EMS for biosolids will be a voluntary program. One of its main functions is to help guarantee the responsible management of biosolids and to enhance the public's understanding of biosolids use or disposal practices, whether the option is land application, distribution and marketing, surface disposal, landfills or incineration. sludge

Unresolved issues

Even though there has been a growing trend in the last decade to recycle biosolids, another trend has been an increasing number of ordinance bans on biosolids, such as Johnson County, N.C.; Amelia County, Va.; and Kern County, Calif. In fact, there are currently more than 200 U.S. counties that ban or partially ban the use of biosolids. This backlash against land application of biosolids is being driven by urban sprawl that is turning farm lands into subdivisions at a rapidly growing pace. This issue of bans on biosolids will be addressed at a workshop at WEF's upcoming conference, WEFTEC 2000, in October in Anaheim, Calif.

Another area of controversy related to EPA's biosolids management is the agency's role is ensuring compliance with the Part 503 rule. On March 22, 2000, the inspector general (IG) for EPA released a report that was critical of EPA's administration of its biosolids program. To view the entire report, "Biosolids and Management," visit www.epa.gov/oigearth/postngs.htm and check out the latest postings, which list the report under "Selected Audit Reports (Oct. 1, 1999 through March 31, 2000)."

According to the report's executive summary, EPA does not "have an effective program" to ensure compliance with those requirements. The Part 503 Rule requires, among other things, that publicly owned treatment works (POTWs) that generate most U.S. sewage sludge to report annually to EPA on the presence of pathogens in the sludge and its ability to attract vectors. The IG report states that EPA has reviewed only 38 percent of those reports.

"EPA performs few biosolids related inspections of POTW operations, virtually no inspections of land application sites and few records inspections of POTWs or land appliers," the report said. "EPA does not have sufficient information to determine compliance levels with the Part 503 regulatory requirements. This may result in increased risks to the environment and human health, and cause a loss of public confidence in biosolids."

In response to a question in July from Environmental Protection about the Office of Water's response to the IG report, Eileen McMahon, a spokesperson for the IG Office said, "The final response has not yet been received by our office. We expect it sooner rather than later. I've been told that the Office of Water takes this issue very seriously."


For the biosolids programs to succeed, EPA must take a strong oversight role, which includes stringent risk assessment methods and better efforts to monitor compliance by POTWs and land appliers. In addition, POTWs and land appliers, need to implement EMSs in order to ensure biosolids projects meet strict safety and health standards. The public's confidence is crucial in aiding biosolids recycling to realize its full potential as a valuable resource.


U.S. Environmental Protection Agency Office of Wastewater Management — www.epa.gov/owm/bio.htm
National Biosolids Partnership — www.biosolids.org
Northwest Biosolids Management Association — www.nwbiosolids.org
Water Environment Federation — www.wef.org
Pennsylvania State University College of Agricultural Sciences' Department of Agronomy — www.agronomy.psu.edu/extension/ESI.html

This article appeared in Environmental Protection, Volume 11, Number 9, September 2000, Page 40.

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This article originally appeared in the 09/01/2000 issue of Environmental Protection.