Clean Water Advocacy - Newsroom - AMSA in the News
Clearing The Air
By Ray Pelosi
American City & County, Oct 1, 2003
Cutting-edge technology, and regulatory and industry safeguards have ensured
safe methods of treating wastewater and producing biosolids — the solid organic
materials recovered from treatment plants for land use. Although numerous
studies have shown that biosolids are safe to use as fertilizer, the materials
still can have a foul odor, so many people recoil at the thought of having the
treatment plants or biosolids-fertilized land anywhere near their homes. That
visceral response can block efforts to build or expand wastewater treatment
facilities, and to burn, bury or fertilize with biosolids.
“Public perception revolves around this issue,” says Adam Krantz, managing
director of government and public affairs for the Washington, D.C.-based
Association of Metropolitan Sewerage Agencies (AMSA). “[We need to] move the
public away from fear to knowledge. The [disgust] factor needs to be reduced.”
Educating people, especially about the benefits of using biosolids to grow crops
and restore lands, is the way to do that, Krantz says.
Government and industry need to do a better job of telling and showing people
why treatment operations and biosolids are safe and what has been done to
control odors. It is just as important for them to talk about current and
planned research and development to lessen odors further. People disgusted by
the smell and/or fearful that biosolids cause illness need reassurance on that
score. Addressing residents' complaints in that way can help clear the air
around the volatile subject.
No piece of cake
Residents' frustration with odor is tied to antipathy toward building treatment
centers or spreading biosolids near them — the not-in-my-backyard syndrome. It
can pit bedroom-community residents against utilities and farmers who use the
treated biosolids as fertilizer.
At the bottom of the odor problem are the biosolids cakes — the solids produced
after sewage sludge goes through treatment — particularly the cakes produced by
anaerobic digestion, in which bacteria that do not use oxygen degrade the
sludge. The cake is the biggest problem because anaerobic digestion stabilizes a
larger total volume of sludge than any other process.
A draft study on biosolids odors by the Alexandria, Va.-based Water Environment
Research Foundation (WERF) found that, in general, the more bioavailable protein
in the biosolids cake, the worse and longer-lasting the odors. The study also
found that incomplete digestion or high shear (friction) on biosolids during
dewatering could leave more bioavailable protein in the cake.
High shear can be reduced by using lower-energy methods for dewatering, such as
belt filtration. However, the WERF draft study cautioned that attaining more
complete anaerobic digestion, or dewatering with lower shear, cannot cut down on
odors independent of upstream conditions or the nature of downstream processing
equipment or storage conditions. Alternatively, proteins can be destroyed by
methods including pre-pasteurization, which ruptures bacterial cell walls, and
sonication, which breaks down cell walls with high-frequency sound waves.
“Certainly, there have been a lot of advances in odor control technology that
allow for decreasing — to a great degree — the odor generated by a treatment
plant,” says Mike Sullivan, supervising engineer for the Los Angeles County
Sanitation District. For example, plants can cover a primary sedimentation tank
“and pull the air out from underneath to treat it,” Sullivan explains. Or, if
biosolids are processed outdoors (e.g., through composting), they can be put in
enclosed storage.
Biofiltration, he says, is a popular treatment that uses porous organic material
“so that the air you're treating moves through at a fairly low speed, giving you
a natural breakdown of odor compounds.” Chemical and carbon treatments — two
other frequently used options — remove specific odor compounds.
However, there's no such thing as a completely odor-free plant. For instance,
biofilter material itself is an odor source. “If it's wood chips, the air is
going to smell like wood chips,” Sullivan says.
Respecting, responding to objections
Because plants cannot completely remove odors from biosolids, local governments
must contend with residents who suspect that plant odors cause illness. While
the Washington, D.C.-based National Academy of Sciences' National Research
Council (NRC) has found no documented cause-effect link between exposure to
biosolids and people becoming ill, the group is calling for new and extensive
research to clarify the potential negative health effects of biosolids.
Odor researcher William Cain, of the Chemosensory Perception Laboratory at the
University of California, San Diego, also emphasizes the lack of a cause-effect
link. “The evidence is, at most, so scant that it's essentially zero,” he says.
“You can have symptoms from odors you don't like, but this is not illness. Most
of these are non-specific symptoms that can have any number of origins.”
Cain notes that some of the most odorous compounds in biosolids — amines,
carboxylic acids and mercaptans — create the characteristic taste and smell of
fish (amines) and the taste of most cheeses (carboxylic acids) and beers (mercaptans).
“If odors [affect health], then which odors, and at what concentration?” he
asks. “No one has made any attempt to specify this any more or apply
quantification. You've got to start dealing with it one odor at a time.”
However, there is a distinction between odor and toxicity. “[Treatment plants
can] put out things that are at a toxic concentration, [or] pollute so badly
that their emissions could cause health effects,” Cain says. “If things are in
this toxic range, beyond the limits imposed by regulations, then we're not
talking about odor. We're talking about toxicity, so we have to stay below the
level where people would become ill.”
Normal emission levels, Cain asserts, are well below the toxicity range.
“California, in particular, has been extremely conservative in setting these
reference levels, to the point that industry complains that it's over-regulated.
There's a large margin for error,” he says.
More study needed
The Washington, D.C.-based Environmental Protection Agency (EPA) established
rules in 1993 to regulate the use of biosolids in the United States, but the
science of assessing risks has changed significantly since then. NRC has called
for more scientific work “to reduce persistent uncertainty about the potential
for adverse health effects.” NRC primarily wants: improved risk-assessment
methods to set better standards for chemical limits and pathogen-reduction; a
framework to examine the effect of biosolids exposure on health — including a
way to document successes in preventing or lessening exposures to pathogens and
toxic elements — and more staff and funding for EPA's biosolids program.
EPA's response to the NRC recommendations is a strategy that would conduct
priority research to update scientific support for its rules governing
biosolids, combine results of intra- and extra-EPA research to strengthen the
sewage sludge program, and continue to increase partnerships and communication
with the public and other interested parties. In the next two fiscal years, EPA
hopes to implement the strategy in several ways, including determining if any
additional pollutants should be regulated, surveying the published evidence of
pollution occurrence and its effects, and creating a dialogue with other
health-related federal agencies to consider tracking incident reports and
investigating whether exposure to biosolids can be linked to health problems.
Meanwhile, stakeholders in the biosolids debate are trying to resolve their
differences. For example, EPA and WERF met with representatives of organizations
concerned about land application of biosolids to discuss issues and find some
common ground at a Biosolids Research Summit in July. EPA also is thinking of
conducting research and tracking field studies by other parties to learn more
about what happens to pathogens in the soil and air after sewage sludge has been
land-applied. From that, EPA could determine if changes to its biosolids
regulations are necessary to safeguard public health.
On a parallel track, EPA, the U.S. Department of Agriculture and Pennsylvania
are collaborating on studies to measure the exposure levels for pathogens,
odors, particulates and endotoxins in and around the sites where biosolids are
land-applied. The trio also combined to form an Information Sharing Group, which
includes individuals who discuss their environmental concerns with researchers
to help shape how research studies are conducted.
Conflict resolution
While studies about biosolids safety are ongoing, some local governments are
wrestling with the idea of land application bans. In some states — notably
Virginia, California and Florida — some local governments have banned or are
considering a ban on Class B biosolids because they contain some pathogens.
(Class A biosolids are pathogen-free, but most farmers prefer nutrient-rich and
inexpensive Class B biosolids.)
But Class B land application is controlled by techniques that further reduce
pathogen levels before crops are harvested or people are exposed to the
biosolids. Additionally, biosolids, which are regulated, are applied to only 1
percent of all agricultural land in the U.S., “whereas the majority of soil
amendments, like manure and commercial fertilizers, are unregulated,” says Sam
Hadeed, technical and communications director for the Alexandria, Va.-based
National Biosolids Partnership, an alliance between EPA, AMSA and the Water
Environment Federation that helps local governments improve biosolids
management.
Conversely, the Denver Metro Wastewater Reclamation District has been building
public trust in the land application of biosolids at its Deer Trail, Colo.,
farm. While buying the land, Metro faced opposition from neighbors who
complained about land application practices, truck traffic to and from the site,
and soil erosion. By 1997, when Metro announced that it would accept treated
groundwater from a Superfund site, it was hit with a barrage of angry criticism,
culminating in a cease-and-desist order from Elbert County — where 60 percent of
Metro land lies — that stopped biosolid application.
“The choice was, ‘Do we want to go to court and fight these guys or do we want
to live with them?’ and we decided on the second course,” says Steve Frank,
Metro's public information officer. Metro began a dialogue with opponents and
ultimately joined Elbert and Arapahoe counties in contracting with the U.S.
Geological Survey (USGS), in Reston, Va., to conduct a monitoring program that
analyzed the biosolids and the soil at the farm to determine whether surrounding
property, groundwater or surface waters had been contaminated. Each year, USGS
meets with the community to report on the program.
The change in public opinion has been slow but steady. In 2000, the year after
the program began, Metro surveyed the farm's neighbors, elected officials,
residents and community leaders to determine their level of satisfaction with
its efforts. Metro received a “D” grade from the still-skeptical populace in
2000, but, three years later, it received a “B” grade.
“There are probably a few people who will go to their graves saying, ‘I just
want you guys to leave’, but, by and large, there has been greater acceptance
because of our consultations with everyone,” Frank says. “We're getting there.”
Like Metro, other local government agencies are allaying residents' fears by
going beyond the regulatory minimums to achieve credibility. The National
Biosolids Partnership's Environmental Management System (EMS), a voluntary
demonstration program, is helping public utilities gain acceptance for biosolids
use. “We knew that to gain and maintain public acceptance for biosolids
programs, [we] had to have good performances in environmental protection,
regulatory compliance, public participation and quality environmental
practices,” says Peter Machno, EMS manager.
Orange County, Calif., became the first of 53 participating agencies to meet the
five requirements for gaining certification as an EMS program in August. It
documented its responsibilities from biosolids pre-treatment to final treatment;
adopted the Partnership's Code of Good Practice, which specifies goals and
commitments for system practice and management; and operated its program
according to 17 principles concerned with critical control points. It also
conducted a third-party audit of its performance, and it pledged continual
system improvements on regulatory compliance, public participation, quality
management practices and environmental protection.
Los Angeles also has received its certification, and NBP expects that another 20
agencies will complete audits by mid-2004. But the Partnership emphasizes that
EMS certification signifies the beginning, not the end, of a continuous
commitment to quality.
Agencies must be proactive, Frank concludes. “You need to get involved as early
as you can with people who believe they have a stake in what you're about to
do,” he says. “They want to be involved. They want to have some control over it
instead of just sitting there waiting for something to happen.”
Ray Pelosi is an Atlanta-based freelance writer.