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Given his 30 years' employment in the sewage treatment field, it is hardly surprising that Wayne Andersen has become inured to some of the nastier aspects of his occupation. A manager at the Blue Lake Wastewater Treatment Plant in Shakopee, Andersen doesn't even notice the stink anymore. "Do you smell anything?" he asks, and then shrugs at an affirmative response. "Olfactory fatigue, I guess."
Inside the Thickening and Dewatering Building--a cavernous, clean, and brightly lit industrial edifice filled with thick, acrid air-- Andersen pauses next to a covered conveyer belt. He plunges a bare hand into an opening and grabs a clump of brown substance that resembles worm bedding.
It is sewage sludge--the solid by-product of all that goes down the toilets and drains of some two dozen Minneapolis suburbs.
"When the sludge gets dewatered, it becomes a cake," Andersen explains. Then he makes a halfhearted vow to properly wash his hands before the next meal and cracks a smile: "But it's not the kind of cake your wife is going to make you."
That's not to say the sludge from the Blue Lake plant won't make its way back into the food chain. In fact, all the sludge generated at the plant--about 225 tons per week--is refined into pellets by a private outfit called the New England Fertilizer Company (NEFCO), which operates at Blue Lake under a contract with the Metropolitan Council. The final product is then trucked from Shakopee to western Minnesota, where it is applied to corn and soybean fields.
"We feel very good about what we do. This is the most ecologically friendly way [to deal with sludge], because we're recycling all the nutrients," asserts Bill Hansen, NEFCO's manager at Blue Lake. Hansen typically eschews the word "sludge" when referring to his company's product. Like many other people in the field, he prefers the term "biosolids."
That's what most industry and government officials have called it since the early 1990s, when the industry sponsored a naming competition as part of a public-relations move to foster acceptance of the agricultural use of sludge. Before settling on "biosolids," industry officials considered and then rejected a host of other candidates, including "the end product," "humanure," "bioresidue," "bioslurp," and "geoslime."
Feel-good nomenclature aside, the application of sludge to farmland--a practice that dramatically increased over the past decade thanks to aggressive promotion by the U.S. Environmental Protection Agency--has come under heavy attack of late. Critics say sludge poses threats to both human health and the environment because of the presence of toxic chemicals and disease-causing pathogens.
While there is no scientific consensus, critics point to a growing body of anecdotal evidence that people have been sickened--and in a handful of cases, killed--by exposure to sludge. Such allegations have caused a public reconsideration of the issue by the EPA.
The apparent shift in policy is in part due to a report issued in 2002 by the National Research Council, an arm of the National Academy of Sciences. Among other things, the report concluded that the risk assessment methodology used in the creation of the EPA's sludge regulations was outdated.
Then last summer, an Augusta, Georgia, jury blamed the deaths of some 300 dairy cows on the use of sewage sludge on nearby fields. That case was cited in a petition by a broad-based coalition of 73 labor, environmental, and farm groups that asked the EPA for an immediate ban on the land application of sludge.
On New Year's Eve, the EPA rejected that request. But at the same time, the agency did agree to sponsor a series of studies that would examine the human health and environmental effects of sludge. In addition, the EPA--which has long required testing for the presence of nine heavy metals--said it would consider more stringently regulating 15 other pollutants, including acetone and silver, that are commonly found in sludge.
Laura Orlando, a Boston-based civil engineer and adjunct professor of public health at Boston University who has long been active in the anti-sludge movement, is not impressed by the EPA's latest actions. "This means nothing in terms of protecting public health or the environment," Orlando says. "The only thing that will protect public health is an outright ban. More research, more testing, or adding 15 chemicals [to the regulations] will not protect public health."
Those opinions are echoed by David Lewis, a renowned EPA microbiologist whose criticism of the agency's handling of the sludge issue led to his firing last year. While Lewis is pleased by the agency's decision to take a closer look at the 15 pollutants, he says that doesn't go far enough. What's more, Lewis says, the EPA has revealed a bias in its selection of researchers for the public health studies, an important component of the new sludge initiative; those researchers--who were picked in a noncompetitive process--"have historically supported EPA's position that land application of sludge is safe," Lewis says.
Despite the EPA's acknowledgment of the need for more study, most industry and government officials still maintain that sludge is entirely safe when properly treated and applied. NEFCO's Hansen says that his company's product is rated EQ, or "exceptional quality," which means it is safer than most. That is because of a special heat-drying process that kills disease-causing pathogens such as salmonella, e. coli, and staphylococcus aureus.
But most of the 42,000 tons of sewage sludge spread across Minnesota farm fields last year is lower grade, Class B sludge, which typically contains measurable levels of pathogens. Jorja DuFresne, the biosolids coordinator with the Minnesota Pollution Control Agency, says Class B sludge is safe when properly applied. She points out that the state insists on certification and training for those who spread it.
In her 22 years working in the field, DuFresne says she has yet to come across a single documented case of a human health problem arising from the use of sludge in Minnesota.
At the Met Council and NEFCO, meanwhile, officials maintain that the levels of fecal coliform (an indicator of the presence of pathogens) and heavy metals remain well below EPA allowable limits. There is one main reason for that, according to Met Council spokesman Tim O'Donnell: an 85 percent decrease in the amount of heavy metals found in metro waste water, thanks to "pre-treatment" of sewage by industrial users.
None of that impresses sludge critics like Laura Orlando. "If you say the only thing we have to be concerned about is these nine heavy metals, many municipalities are doing a good job. I contend, along with thousands of other people, that sewage sludge toxicity goes well beyond the nine heavy metals," Orlando says.
In fact, she asserts, there are "tens of thousands of chemicals" that enter the sewage treatment plant and cannot be mitigated by conventional treatment. Those chemicals--most of which are never identified through existing testing protocols--wind up on farm fields and, eventually, dinner plates.
Concerns over one particularly ubiquitous group of chemicals--called PBDEs--have led the Swiss government to impose an outright ban on the use of municipal sludge as fertilizer, and other countries are poised to follow suit. But, Orlando adds, PBDEs "aren't even on the EPA's radar."
"There's no alchemy here," Orlando says of the treatment of sludge. "No magic that can make all this stuff just disappear."