Is sewage sludge safe on crops?

Guest Column:
Published: Mar 16, 2011 02:00 AM
Modified: Mar 15, 2011 05:43 PM

Is sewage sludge safe on crops?

by Betty Cross

A recent article in The Cary News highlighted a new dewatering device at the Cary wastewater treatment plant. The new equipment will separate liquid from solids resulting in dewatered sewage sludge, which can then be labeled as "fertilizer." There is much more to know about the composition of sewage sludge than is revealed in the story. Wastewater treatment plants were never designed to produce fertilizer. Wastewater treatment plants were designed to clean the water discharged from the plant.

Though sewage sludge contains nitrogen and phosphorous beneficial to crops, it also contains myriad other chemicals, heavy metals and pathogens harmful to the environment and human health. The Environmental Protection Agency sets limits for only nine heavy metals (out of 28) and certain pathogenic bacteria. Only a few organic chemicals are measured out of thousands in use. Because our waste streams have been channeled into centralized wastewater treatment plants, everything sent down the drain from homes, hospitals and businesses, along with stormwater runoff and landfill leachate, winds up concentrated in sewage sludge.

Two examples of chemicals harmful to humans, and for which limits in sludge have not been set, are the antibacterials triclocarban and triclosan. These endocrine disruptors are found in many consumer products and concentrate in sewage sludge. A study at Johns Hopkins' Bloomberg School of Public Health determined that approximately 75 percent of the ingredients washed down the drain by consumers persist during wastewater treatment and accumulate in sewage sludge. In the EPA's Targeted National Sewage Sludge Survey, triclocarbon was found in 100 percent of the samples taken and triclosan was found in 94 percent. These two chemicals interfere with hormones needed for proper brain and reproductive system development in children. A recent study at Ohio State University shows that both chemicals can enter the food chain through sewage sludge used as fertilizer on agricultural fields. There is nothing in the dewatering process that removes triclocarban or triclosan from sewage sludge.

Another disturbing finding from the Water and Environment Research Foundation (WERF) is that dormant bacteria in dewatered sewage sludge can reactivate when exposed to air and water. The researchers suspect that anaerobic digestion and high centrifuge separation renders some bacteria viable but nonculturable, therefore non-measurable. Once the bacteria leave the treatment process, they can multiply exponentially. It seems there is no way to assure consumers that dewatered sewage sludge is free of pathogenic bacteria.

If shopping for compost or fertilizer this spring, whether in bags or in bulk, ask what's in it. If the answer is sewage sludge, please be aware, no one really knows what it contains or if it is safe to use. It hasn't been tested.

Cross is the co-chairwoman of the Sewage Sludge Action Network.

H.R.254 - The Sewage Sludge in Food Production Consumer Notification Act

Stop Toxic Sludge Dumping on Farmland and Pastures!

Toxic sewage sludge used to be dumped into the oceans, killing fish and marine life. After public pressure put an end to ocean-dumping, toxic sludge began to be spread on farmland, touted as natural "fertilizer." In 1998 the sludge industry tried to get the USDA to allow toxic sewage sludge to be used as a fertilizer on organic farms, but the OCA's Save Organic Standards campaign and an aroused organic community stopped this insidious effort. Today millions of pounds of sludge are dumped on Monsanto's crops, including cotton, corn, and soy grown for animal feed and fuel. This toxic sludge is, by law, allowed to contain dangerous levels of pathogens, viruses and bacteria. The sludge pathogens that survive sewage "treatment" are the hardiest superbugs, bacteria that have developed a resistance to antimicrobials and antibiotics.

Toxic sludge used on food crops must be processed to reduce pathogen contamination, but is still rife with heavy metals and all manner of industrial chemicals from flame retardants to metal plating compounds.

If it isn't safe to dump in the oceans, it isn't safe to spread on farmland and pasture land!

Stop toxic sewage sludge from being dumped on farmland! Ask your Member of Congress to cosponsor H.R.254 - The Sewage Sludge in Food Production Consumer Notification Act

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Sewage Sludge Action Network Reorganizes

The Sewage Sludge Action Network (SSAN) has announced that it has reorganized as a project of The Center for Community Alternatives, a 501(c)(3) non-profit organization headquartered in North Carolina.

SSAN is comprised of residents of Alamance, Orange and Chatham counties, and says it will continue to focus on educating the public about the risks to public health and the environment from the spreading of sewage sludge from wastewater treatment plants on farmlands.

Each year hundreds of thousands of gallons of sewage sludge are spread on farmlands in over 70 counties in North Carolina. Farmers are given sludge free of charge to be used as a fertilizer and are not informed about the vast amounts of unregulated, untested toxic chemicals that concentrate in sewage sludge.

Betty Cross, SSAN Co-Chair, said that antibacterials found in sewage sludge are a special concern. “Triclosan and triclocarban are endocrine disrupting chemicals that concentrate in sewage sludge. These two chemicals interfere with hormones needed for proper brain and reproductive system development in children. Studies show that both chemicals can enter the food chain through the use of sewage sludge used as fertilizer on agricultural fields.”

SSAN is working at a grassroots level on a number of projects that include:

  • Developing a farmer education program on the risks of using sewage sludge as a fertilizer;
  • Increasing buffers on sludge spreading near schools, day care centers and other public places;
  • Protecting drinking water supplies by removing sludge fields permitted in critical watersheds;
  • Advocating for stricter enforcement and regulation of sludge spreading;
  • Partnering with other organizations dedicated to protecting NC’s surface waters, drinking water supplies, farmlands, and public health; and,
  • Producing a local documentary that includes interviews with local residents about their opinions and experiences with sewage sludge.

"The mission of SSAN is to educate the public about the practice of spreading toxic sewage sludge on farm and forest land. In addition to poisoning farmland, sewage sludge contaminates groundwater, surface waters, the air we breathe and the food we eat,” said Myra Dotson, Chair of SSAN. “For 30-years this practice, disguised as “free fertilizer,” has turned farmland into toxic waste dumps, and has been largely unknown to citizens. The public has a right to know.”

The next SSAN meeting will take place on Thursday, Feb. 17 at 7 p.m. at the Orange Grove Volunteer Fire Department, 6800 Orange Grove Rd., Hillsborough, NC 27278. Interested members of the public are invited and encouraged to attend.

For more information contact Myra Dotson, Chair, SSAN at (919)270-7534 or mdotson at

Crops Absorb Pharmaceuticals From Treated Sewage

Each year, U.S. farmers fertilize their fields with millions of tons of treated sewage and irrigate with billions of gallons of recycled water. Through this treated waste, an array of pharmaceutical and personal care products (PPCPs) make their way unregulated from consumers' homes into farm fields. Now researchers find that at least one crop, soybeans, can readily absorb these chemicals, which raises concerns about the possible effects on people and animals that consume the PPCP-containing plants (Environ. Sci. Technol., DOI: 10.1021/es1011115).

Researchers have previously shown that food crops take up veterinary medicines from manure fertilizer and some cabbage species absorb human pharmaceuticals when grown in hydroponic conditions. But environmental scientist Chenxi Wu and colleagues at the University of Toledo in Ohio wanted to determine if a major food crop could absorb common PPCPs under more realistic agricultural conditions, such as plants grown in soil. If the chemicals do find their way into the crops under real-life conditions, they could be toxic to the plants, Wu says. "Or they could accumulate through the food chain, and eventually end up in human consumers," he adds.

In a greenhouse experiment, the scientists focused on soybeans, the second most-widely grown crop in the U.S. Half the plants grew in PPCP-tainted soil, to simulate fertilization with treated solid waste, while the researchers irrigated the other half with chemical-spiked water, to replicate wastewater irrigation. They laced water and soil with three pharmaceuticals—carbamazepine, diphenhydramine, and fluoxetine—and two antimicrobial compounds found in personal care products—triclosan and triclocarban.

The scientists analyzed plant tissue samples by mass spectrometry at two life stages: just before the soybeans flowered and after they sprouted beans. Wu and colleagues found that carbamazepine, triclosan, and triclocarban concentrated in root tissues, eventually moving into the stems and leaves. The antimicrobial compounds triclosan and triclocarban also accumulated in the beans themselves. But the soybean plants barely absorbed diphenhydramine and fluoxetine—the chemicals only appeared at low concentrations in the roots. Overall, the plants absorbed the chemicals more efficiently by irrigation than through the soil. The researchers are still trying to determine why.

Environmental chemist Chad Kinney of Colorado State University, Pueblo, says the study underscores the need for further research into how PPCPs behave in agricultural settings. "The first thing you have to consider with human exposure through agriculture is whether it's even possible," Kinney says. "That's what was answered by this study."

Wu thinks that more toxicology studies should come next: "If you find those compounds in the plant, what are they going to do to the plants or to animals that eat the plants?"

Long-Lasting Chemicals Threaten the Environment and Human Health

ScienceDaily (Dec. 21, 2010) — Every hour, an enormous quantity and variety of human-made chemicals, having reached the end of their useful lifespan, flood into wastewater treatment plants. These large-scale processing facilities, however, are designed only to remove nutrients, turbidity and oxygen-depleting human waste, and not the multitude of chemicals put to residential, institutional, commercial and industrial use.

So what happens to these chemicals, some of which may be toxic to humans and the environment? Do they get destroyed during wastewater treatment or do they wind up in the environment with unknown consequences?

New research by Rolf Halden and colleagues at the Biodesign Institute at Arizona State University seeks to address such questions. The group's results, reported recently in the Journal of Environmental Monitoring, suggest that a number of high production volume (HPV) chemicals -- that is, those used in the U.S. at rates exceeding 1 million pounds per year, are likely to become sequestered in post-treatment sludge and from there, enter the environment when these so-called biosolids are deposited on land.

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When Research Turns to Sludge

It’s not just corporate funding that creates conflicts of interest. Even government and nonprofit funding can have strings attached.

By Steve Wing

Environmental epidemiologists sometimes hear from people dealing with pollutants and sickness. So I wasn’t surprised when Nancy Holt contacted me about the millions of gallons of municipal sewage sludge being spread on fields near her home in Orange County, North Carolina. Sometimes, she said, the stench was so awful that she and her husband had to cover their faces when they went outside. They had trouble breathing. Sores broke out on her grandchildren’s bodies after they played in a nearby creek. She had her well tested. It was contaminated with bacteria and chemicals. Droplets of wet sludge covered her mailbox.

By the time she called me at my office at the University of North Carolina at Chapel Hill, Nancy was fed up with the runaround from local, state, and federal agencies. Government employees had tried to reassure her that sewage sludge is safe, that existing rules protect public health, and that there is no evidence sludge ever harmed anyone. When she learned that our research group had been studying the effects of industrial hog operations on neighbors’ health and quality of life, she thought we might be able to evaluate the impacts of sewage sludge.

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