BioCycle March 2008, Vol. 49, No. 3, p. 48
Reported wastewater solids generated in 2004 totaled 7.2 million dry tons. About 3.5 million were managed via beneficial use and 3.3 million were disposed.
Ned Beecher, Kristy Crawford and Nora Goldstein

BIOSOLIDS – treated sewage sludges – have been “beneficially used” as soil amendments and fertilizers for decades. In 1993, the U.S. Environmental Protection Agency (USEPA) finalized national regulations for “the use and disposal of sewage sludge,” the so-called “Part 503” rules. Based on an extensive risk assessment, Part 503 provided a clear regulatory structure on which stable biosolids recycling programs have been built around the nation. While a few states, like Connecticut, had invested extensively in incineration technologies and have continued to burn most of their wastewater solids, a majority of other states, like Colorado, Maine and Washington, have steadily increased the recycling of biosolids to soils.
The USEPA calculated that in 1998 the total wastewater solids production in the U.S. (based on assumed wastewater flow) was estimated to be 6.9 million dry U.S. tons, “of which about 60 percent were used beneficially (e.g. land applied, composted, used as landfill cover) and 40 percent disposed of (i.e., discarded with no attempt to recover nutrients or other valuable properties).” BioCycle surveys of state biosolids coordinators, the last of which was published in December 2000, found that programs recycling biosolids to soils were “holding their own: … almost half of the states reporting recycled more than half of the biosolids generated. Eight states … beneficially use over 90 percent.”
In 2006, the North East Biosolids and Residuals Association (NEBRA) received a contract from the USEPA to conduct a national survey on biosolids regulation, quality, end use and disposal in the U.S. BioCycle worked on this survey project with NEBRA, as did the Northwest Biosolids Management Association, the Wisconsin Department of Environmental Services and other stakeholders. The final report and data-rich appendices are available for free download at www.nebiosolids.org. Highlights of the findings were presented in a May 2007 article in BioCycle (“Biosolids Management Trends in the U.S.”). This article provides further details regarding the project’s findings.
In the U.S., the infrastructure that leads to production of wastewater solids includes an estimated 16,583 Treatment Works Treating Domestic Sewage (TWTDS). The vast majority of these treatment facilities are small: 13,261 treat wastewater flows equal to or less than 1 million gallons per day (MGD). That leaves 3,322 that treat flows greater than 1 MGD, of which only 551 treat flows greater than 10 MGD. Biosolids recycling by a large percentage of these larger facilities accounts for the predominance of biosolids recycled to soils.
The 13,261 smallest TWTDS – considered “minors” by USEPA – are in relatively small communities. And as Elliott et al. (2005) discovered in their detailed survey work in Pennsylvania, these small TWTDS manage their wastewater solids in ways that are not necessarily represented by how larger TWTDS manage them. For example, minor (< 1 MGD) facilities will often: Store solids in wastewater or sludge lagoons that are only cleaned out every 5 to 20 years; Utilize the lowest cost and least hassle method for managing solids, such as landfilling; and/or Transport untreated solids to larger TWTDS for treatment.
The 2006 national survey collected data from 2004. Estimates were generated for every state, giving the first-ever comprehensive picture for the nation as a whole (Table 1). USEPA estimates that in 2004 there was an average of 34,201 MGD of wastewater treated in the U.S. (USEPA, 2006). Reported wastewater solids used and disposed in 2004 (all reported in dry U.S. tons) were 7,180,000 tons, 55 percent of which were beneficially used as fertilizers and soil amendments. As shown in Table 2, the number of states that reported recycling more than half of their biosolids in 2004 jumped to 30 (when compared to BioCycle’s 2000 data). Seven states reported beneficially using more than 90 percent. Tennessee and Indiana had the largest decreases in beneficial use, and Nebraska and New Hampshire had the largest increases. Twenty-one of the forty states that provided data in both surveys experienced little if any change (< 10 percent) in the percent of biosolids beneficially used.
While biosolids recycling programs appear to have been “holding their own” in the first half of this decade, there has not been the steady increase to 66 percent beneficial use, as USEPA had predicted for 2005 (USEPA, 1999). When asked, “Is beneficial use of biosolids increasing in your state?” a higher percentage of states answered “no” than in the BioCycle survey report of 2000. What appears to have emerged in this decade, however, are categories of beneficial use – other than application of biosolids to soils – that were not measured by the survey (these are expanded definitions of beneficial use that industry has started to use). Included are utilizing methane from digesters to produce energy; recovering heat from incinerators; using biosolids incinerator ash as clean daily cover at landfills, as a soil conditioner, in cement and asphalt and as clean fill material at a variety of locations; and piloting recovery of energy from landfilled biosolids (“bioreactor landfills”). If these uses had been included in the recent survey’s definition of beneficial uses, the 2004 data would likely show that close to two-thirds of U.S. biosolids are being utilized as resources – closer to the EPA prediction.
HOW BIOSOLIDS ARE USED OR DISPOSED
Biosolids Use And Disposal: Of the 7,180,000 tons reported used or disposed, 3,507,000 (49 percent) were managed via beneficial use (applied to land for agronomic, silvicultural or land restoration purposes); 3,252,000 (45 percent) were disposed; and 421,000 (6 percent) were stored, or their final use or disposal was not reported. It is likely that most of that 6 percent was destined for beneficial uses.
Beneficial Use Practices: Of the 3.5 million tons of biosolids beneficially used in 2004, applications of bulk biosolids to agricultural land dominate (74 percent of all biosolids going to beneficial use). Most of this is traditional Class B land application, but a good portion (at least 613,000 tons) is Class A. Distribution of Class A “Exceptional Quality” biosolids makes up 22 percent of the U.S. total of beneficially-used biosolids and includes significant amounts of biosolids compost and heat-dried pellet fertilizer. Reclamation (3 percent) and forestland application (1 percent) comprise the other beneficial uses.
Disposal Practices: Of the 3.2 million tons disposed in 2004, 63 percent go to municipal solid waste landfills. Thirty-three percent is incinerated (thermally processed). Data collected by the National Association of Clean Water Agency’s Biosolids Committee indicates that in 2004 there were 234 operating incinerators in the U.S. Four percent of the disposed biosolids goes to dedicated surface disposal units.
Biosolids Quality: For a large percentage of wastewater solids (2,903,000 tons or 43 percent), there is no data (or no data was obtained) regarding whether or not it met Class A or Class B standards. This lack of data is mostly due to the fact that wastewater solids that are landfilled or incinerated are not generally subjected to the same stabilization, testing and reporting requirements.
Of the remaining 57 percent of biosolids for which quality data were available for 2004, 60 percent (2,273,000 tons) were Class B and 40 percent (1,532,000 tons) were Class A. Almost all of the Class A biosolids met the low metals Exceptional Quality (EQ) criteria of the federal Part 503 regulations.
Biosolids Treatment Technologies: Part of the recent national survey asked each state biosolids coordinator to estimate the numbers of treatment facilities in their state that use each kind of biosolids treatment technology (e.g., digestion, lime/alkaline stabilization, belt filter press, etc.). While this data collection effort only obtained responses from half of the states, it proved useful in providing a sense of what technologies are most common (Table 3). It is important to note that these are minimum estimates from incomplete data from states and other sources. They serve only to provide a rough sense of the relative importance of various technologies.
WHAT IS DRIVING TRENDS IN THE U.S.?
Over the past dozen years, biosolids programs have experienced increased scrutiny from the media and the general public. Concerns have been raised about possible long-term environmental impacts, and impacts to the health of neighbors around biosolids processing and land application sites. Increasingly, organized opposition to the use of biosolids on soils has led to pressures on USEPA and state regulatory agencies. There have been several high-profile legal challenges, including a voter referendum ban on the importation of biosolids into Kern County, California. Although courts are rejecting that county ban and other challenges, the publicity around them have led some biosolids managers to avoid the hassle of beneficial use.
Many agencies – especially small ones – appear to have chosen easier options and are transporting wastewater solids to landfills or incinerators (Elliott et al., 2007). While the recent national survey cannot definitively corroborate this trend, it appears that it is mostly larger wastewater treatment agencies that choose to develop or contract for biosolids recycling programs.
As BioCycle has done in the past, the recent national survey asked state biosolids coordinators and others to identify the three most important pressures on biosolids recycling. In 2000, most biosolids coordinators identified malodors as the number one pressure. “Concern about pathogens was cited as the number two pressure … Suburban sprawl – both in terms of encroaching neighbors and decreasing availability of sites for land application – took third place on the list of pressures.” Negative media coverage, public perceptions, groundwater concerns, strict regulations, costs and other pressures were also mentioned.
In 2006, state biosolids coordinators and a self-selected sample of wastewater biosolids program managers were asked the same question. This time, six years later, state coordinators identified public perceptions and concerns as the number one pressure on biosolids recycling. Agricultural issues were second, and cost was third. One of the leading agricultural concerns mentioned has to do with competition with manures for nutrient applications on farmlands: “Large factory farms have given ‘nutrient application’ a bad name.” Sprawl and its impacts on reducing available suitable farmland remained a relatively high concern, but nuisance concerns, including malodors, were tied for fifth place. Pathogens were mentioned only indirectly as part of public health concerns.
Biosolids managers also identified “public involvement, concerns of neighbors and others” as the top pressure, by a considerable margin. They, as a group, also chose agricultural issues as second most important, noting declining farmland due to sprawl, seasonal restrictions and competition with manures. These biosolids managers’ third choices were nuisance issues such as odors, dust and truck traffic.
STATE REGULATIONS
Over the past decade, even as public interest has increased, those regulating and managing wastewater and biosolids have generally remained positive about beneficial use on soils, cognizant of the extensive research and decades of experience that support the practice. However, public interest has pushed some states to increase regulatory oversight, including, most recently, Virginia.
The federal Part 503 rule established minimum standards for the use and disposal of wastewater solids (sewage sludge), but now most states have regulations that go significantly further. Nineteen states have updated their biosolids regulations since 2000. This trend has significant benefits, providing increased assurance to the interested public and helping improve the quality of biosolids management programs. Only ten states have no formal state biosolids regulations, and thus rely on the federal Part 503 rule.
One of the goals of the recent national survey was to assess the level of involvement of different states in the regulation of biosolids and the strictness of state regulations. Particular data collected by the survey were used as indicators. For example, if a state has a relatively high number of staff assigned to the biosolids regulatory program, it is assumed to be an indicator of a high level of state oversight and enforcement. Likewise, if a state has additional regulations that address newer issues, such as testing for organic chemical constituents, requiring nutrient management plans, or controlling the application of phosphorus in biosolids, then it can be considered to have a more robust, strict biosolids regulatory structure.
An analysis of these parameters allows a rough ordering of states regarding the level of attention they pay to biosolids management (Figure 1). In general, those states with higher population densities have stricter and more robust regulatory programs. Six Northeast states were ranked in the top 15: Vermont, Maine, Delaware, New Hampshire, New Jersey and New York. Other robust and strict state regulatory programs are found in Maryland, Virginia, Louisiana, Ohio, Kentucky, California and South Dakota. States found to have the least state regulatory activity are mostly located in the agriculture-rich middle of the country and/or have low population densities, including Missouri, Nevada, Alaska, Idaho, New Mexico, Wyoming, Kansas, Montana and North Dakota. In many of these states, regional EPA biosolids regulators take on significant permitting and enforcement responsibilities.
Since 1993, when the Part 503 rule was adopted, USEPA has offered states the option of becoming delegated to administer the biosolids program. Delegation requires that states have robust regulatory and enforcement programs that ensure that TWTDS’ compliance with Part 503 (at a minimum) is demonstrated. Delegation allows states some autonomy, and can streamline the regulatory process by avoiding involvement of, and reporting to, both state and federal authorities. So far, eight states are delegated: Arizona, Michigan, Ohio, Oklahoma, South Dakota, Texas, Utah and Wisconsin (twice as many as in 2000). Twenty-seven states are not interested in delegation; fifteen are in the process or are planning to seek delegation. South Dakota and Utah adopted all of Part 503 by reference. Michigan is delegated for land application only. Ohio and Wisconsin are delegated for land application, landfilling and surface disposal (not incineration and septage). Oklahoma and Texas reported only that they are delegated.
MANAGING SEPTAGE IN THE U.S.
In almost all states, the majority of the population is connected to centralized wastewater treatment facilities. In only a few states does the majority rely on on-site wastewater disposal – septic systems (Table 4). Nonetheless, septic systems play a role in wastewater management everywhere. These systems treat wastewater by separating solids and liquids and treating and returning the liquid into the ground through in-soil bacterial communities. The solids, called septage, are – or should be – pumped out of septic tanks every three to five years.
Obtaining data on septage management is more difficult than obtaining biosolids data because, in many states, septage is regulated and overseen at the county and/or local level (e.g. by health departments). At the state level, if septage is regulated and overseen, it tends to be a responsibility of the environmental agency, although health departments will sometimes take charge. While all but 10 states have formal state biosolids regulations, there are at least 15 that have no formal state regulations for septage and rely on the federal Part 503 rules (which apply to septage as well as biosolids). Only 14 of the states with septage regulations have updated them since 2000.
Looking at the number of full-time equivalents (FTEs) working in state agencies on septage, we see another indicator of the attention septage management receives. Only 18 states report that they devote one or more state FTEs to septage. Seventeen states report less than one FTE assigned to septage, and ten states report none. In short, at the state level, septage tends not to be given the same regulatory attention as biosolids.
The most common form of septage management regulatory oversight seems to be in the licensing and regulation of septage transport trucks. Thus, there are reasonably good data from most states on the number of septage transporters – they range from 35 in Nevada to about 50 in Delaware and Missouri, 350 in Indiana to 465 in Michigan, 723 in Illinois to 785 in California.
Data on what happens to the septage after it is transported is less available. Disposal at WWTFs appears to be the most common option for septage management around the country. Of the 34 states that provided this data, 11 said that more than 80 percent was hauled to WWTFs for treatment. Twenty states reported that 20 to 80 percent is hauled to WWTFs, while only three states said that less than 20 percent was hauled to WWTFs.
In 43 of 47 states reporting, septage can be land applied – and this appears to be the second most common choice for septage management. Twenty of these states only require that the septage land application process be in compliance with the federal Part 503 rule, while in 24 states there are additional state requirements. Massachusetts and Rhode Island do not allow any land application of septage. Twelve states report that up to 20 percent of their septage is land applied, thirteen report that 21 to 60 percent is land applied, and four states report that more than 60 percent is land applied.
A septage management option that has become less common in recent years is disposal in lagoons. Only 8 of the 34 states responding said that any septage was hauled to lagoons – and 7 of those said it was only a small percentage (1 to 20 percent). Composting of septage is even less common, apparently. Only 2 states (of 34 responding) said that any septage is composted.
Treatment at septage-only facilities is also uncommon, with only 4 of 34 states reporting that small amounts (less than 20 percent) of their septage is managed in this way. Landfilling and incineration manage small percentages (usually less than 20 percent) of septage in 5 of the 34 states responding.
SUMMARY/CONCLUSION
There are four essential findings of the national survey of biosolids use and disposal:
o In the U.S., centralized wastewater treatment continues to advance. Stricter standards for the quality of effluent released by wastewater treatment plants to receiving waters results in more solids (sewage sludge), as does increasing population. Thus, there will continue to be more wastewater solids to manage with every passing year.
o On the national level, the percentage of biosolids being beneficially used as soil amendments and fertilizers has remained essentially constant since the late 1990s. However, in close to half of states reporting, the percentage of biosolids beneficially used has changed by 10 percent or more (either up or down). Biosolids management is determined at the local level, as each wastewater treatment facility determines the best option for its particular situation. Increasingly, other beneficial uses – such as energy extraction – are being utilized.
o Beneficial uses of biosolids as soil amendments and fertilizers are still dominated by Class B land application to agricultural lands. However, the proportion and total mass of Class A biosolids being produced is increasing steadily.
o The regulatory playing field for biosolids has become more stable and predictable, with most state regulatory agencies involved with up-to-date protective regulations that allow for ongoing beneficial uses.
Putting these findings together, it is clear that the steady increase in the total mass of biosolids being applied to soils in the U.S. will continue. Biosolids composts, fertilizer pellets and other products will continue to be significant (albeit small, in comparison to manures) players in soil amendment and fertilizer markets.
Ned Beecher is Executive Director of the Northeast Biosolids & Residuals Association. Kristy Crawford worked on the national survey while at NEBRA.
REFERENCES
Elliott, H.A., R.C. Brandt, and J.S. Shortle, 2007. Biosolids Disposal in Pennsylvania: Cost Comparisons and Policy Considerations. Center for Rural Pennsylvania, Harrisburg, PA.
Goldstein, Nora, 2000. The state of biosolids in America: The BioCycle nationwide survey. BioCycle: Journal of Composting & Organics Recycling, 41: 12, December 2000.
National Association of Clean Water Agencies (NACWA), 2006. Biosolids Management: Options, Opportunities & Challenges. Washington, DC.
National Research Council, 2002. Biosolids Applied to Land: Advancing Standards and Practice. Washington, DC: National Academy Press.
U.S. EPA Office of Inspector General, 2000. Audit Report, Water, Biosolids Management and Enforcement (2000-P-10), March 20, 2000.
U.S. EPA Office of Inspector General, 2002. Status Report, Land Application of Biosolids (2002-S-000004), March 28, 2002.
U.S. EPA Office of Solid Waste and Emergency Response, 1999. Biosolids Generation, Use, and Disposal In The United States. EPA 530-R-99-009. September, 1999.
U.S. EPA Office of Wastewater Management. 2000. Summary of State Biosolids Programs, Draft Report. EPA 832-D-00-002. December, 2000.
U.S. EPA Office of Wastewater Management. 2004. A Plain English Guide to the EPA Part 503 Biosolids Rules. EPA 832-R-93-003. September, 2004.
U.S. EPA Office of Wastewater Management, 2006. Clean watersheds needs survey. http://www.epa.gov/owm/mtb/cwns/index.htm. Retrieved February 6, 2007.