Biosolids – understanding benefits and risks

August 16, 2016
By Georgine Yorgey
Biosolids being spread on agricultural fields. Photo: A. Bary.

Biosolids being spread on agricultural fields. Photo: A. Bary.

Biosolids?  Yes, that means sewage sludge.  Well, sort of.  But before you say YUCK and click off the page, let’s start with what they really are: biosolids are the materials produced from digestion of sewage at city wastewater treatment plants. They are rich in plant nutrients such as organic carbon, nitrogen, and phosphorus, and can be applied to wheat, alfalfa, and timber land for plant fertilization and soil conditioning. When biosolids are applied at rates that meet plant nutrient needs, farmers and researchers are seeing crop yields equal to or greater than those seen with synthetic fertilizer. Applying biosolids as fertilizer also allows them to be recycled for a useful purpose rather than disposed of in landfills or incinerated.

In addition to the benefits to plant growth and the waste stream, biosolids can serve another role.  Applying biosolids to the land can benefit the climate because they sequester carbon in the soil in the form of enhanced organic matter. Given current climate concerns, that could be one small but important piece of a wider mitigation strategy.

Biosolids covering agricultural soil prior to incorporation. Photo: A. Bary.

Biosolids covering agricultural soil prior to incorporation. Photo: A. Bary.

While the benefits of biosolids are many, there are also perceived risks.  A new WSU Extension fact sheet: Guide to Biosolids Quality by Shannon Mitchell, Chad Kruger, and me, digs into these risks and discusses major categories of contaminants and explains what is currently known about them. Concern about contaminants arises because municipal facilities treat wastewater from industrial and household sources that may contain small amounts of various contaminants including metals, pathogens, antibiotics, industrial and household chemicals, odorants, and aerosols. Some of these contaminants (often called “emerging contaminants”) may be compounds whose impacts are not well understood.

To date, research indicates that the major classes of contaminants in biosolids pose a minimal risk to human, animal, or environmental health. This is often because contaminants do not appear in sufficiently high concentrations to cause harm or because they are not taken up by crops even when present in soils. To further minimize risk, the application of biosolids is highly regulated by state environmental protection departments and by the EPA.

Notice that I said “to date.” Ongoing research on biosolids continues to investigate contaminants and potential impacts. New research findings are reviewed periodically and risk assessments conducted to reevaluate the effectiveness of existing biosolids land-application regulations.

For all the details, see the extension publication or visit the Washington State University Biosolids Management website.

Thank you to Amy Pendegraft for her contributions to earlier drafts of this post.

11 comments on “Biosolids – understanding benefits and risks”

  1. David Steinbrunner said on August 16, 2016:

    Yuck and yuck again. Disgusting
    There is no need to use bio solids in agriculture.

    • myra dotson said on August 17, 2016:

      you are so right David!!

  2. myra dotson said on August 17, 2016:

    It is stated: “They are rich in plant nutrients such as organic carbon, nitrogen, and phosphorus,”… Concentrated sewage sludge is also rich in heavy metals, pharmaceuticals, fire retardants, personal care products, and over 100,000++ other toxins and their derivatives…

  3. myra dotson said on August 17, 2016:

    It is stated: “Applying biosolids to the land can benefit the climate because they sequester carbon in the soil in the form of enhanced organic matter. ” DISPOSING of CONCENTRATED TOXIC SEWAGE SLUDGE [AKA BIOSOLIDS] to the land allows massive amounts of ‘offgassing’ of greenhouse gases… FOR YEARS !!!.. METHANE, HYDROGEN SULFIDE… MERCURY VAPOR… JUST TO NAME A FEW..

  4. Craig Monk said on August 17, 2016:

    Here is a piece of ongoing research Yorgey failed to bring up:

    Try reading a little know regulation 40 CFR 261.30(d) and 261.33 (4), every US industry connected to a sewer can discharge any amount of hazardous and acute hazardous waste into sewage treatment plants.

    When the sewage industry tells you “pre-treatment of these industrial chemical are strictly regulated”, read the EPA’s Office of Inspector General’s Report No.14-P-0363- 09/2014 where you will instantly see they are BALD FACE PREVARICATORS! (Just Google the Report number).

    Now tell me what happens to those persistent hazardous chemicals when you heat them up and mix ALL of them together in a digester and send them out to a farm, forest or even in consumer product bags only labeled made from “bio solid.”

    Chemicals that are persistent in the environment, bio-accumulate in people and/or wildlife, and are toxic are called PBTs. Because of these features, as long as they remain in commerce and may therefore be released into the environment, they will threaten the health of humans and wildlife.

    Farmers and Consumers are being badly used to dump municipal industrial, hospital, storm and household sewage on their farms to save cities money because of the cost to put it in a land fill. Go figure.

    And one more item of interest. Phosphates are highest in sewage sludge because they come from laundry and dish washing detergents. Waste Water Treatment Plants can not control the concentrations so it is common for a field to be over burdened with phosphates. Look out at your algae blooms to figure out where excess phosphates ends up

    • myra dotson said on August 17, 2016:

      right on Craig…!!

  5. myra dotson said on August 17, 2016:

    It is stated: “This is often because contaminants do not appear in sufficiently high concentrations to cause harm or because they are not taken up by crops even when present in soils.” 3 points here… 1. More often than not, many contaminants are highly dangerous IN LOW CONCENTRATIONS… and 2. Many toxins ACCUMULATE.. OVER TIME… they never break down … so then end up being on the land in HIGH CONCENTRATIONS… after accumulating for years and years.. 3. No one knows the harm or even IF THEY ARE TAKEN UP BY PLANTS… not the CDC, not the EPA,.. not the state agencies..

  6. Caroline Snyder said on August 18, 2016:

    There is nothing “sustainable” about spreading biosolids on the land where we grow our food. This contaminated pollutant-rich mixture contains more than nutrients. As all the previous commentators have pointed out, it contains hundreds of persistent pollutants that accumulate in soil until the land is so polluted it can no longer grow most crops. This is not a potential scenario. It has already happened, e.g.in Augusta GA. For facts, rather than myths about the many risks linked to biosolids use, see
    http://www.biosolidsfacts.org

  7. Caroline Snyder Ph.D. said on August 19, 2016:

    This is a gross misuse of the word “sustainable”. Sustainable for whom? For sustainable agriculture and for protecting the nation’s soil for future generations? Or sustainable for industry and municipalities
    and sludge brokers who profit from this cheap method of sludge disposal. With scientific and anecdotal evidence mounting against land application, government agencies, industry funded scientists, sludge brokers, and cooperative extension services at land grant universities are frantically stepping up EPA’s Office of Water tax-funded Public Acceptance Campaign.
    They resort to narrowly scoped nutrient research, they ignore and discredit hundreds of reported and documented “incidents”
    linked to land application, they ignore the synergistic effects and interactions that occur in this complex pollutant-rich mixture, and they claim that low levels of priority pollutants are harmless. They concede that there might be a few pollutants that need further research, but overall, contrary to all evidence, they claim that the current regulations are completely adequate.They assume that application rate guidelines are known and enforced, which in many cases is not true. But even if the cumulative loading rate for lead,for example, were adhered to, does any sane person really believe that growing the nation’s vegetables and forage on soils containing 800 ppm of lead–the current permissible level–is safe?

  8. Ned Beecher said on August 28, 2016:

    The comments to date (1 – 7) are by long-term, dedicated biosolids opponents from around the continent whose arguments have been addressed and discredited (e.g. see recent Canadian scientists’ discussion: http://globenewswire.com/news-release/2016/08/10/863278/10164510/en/Biosolids-Wasting-a-valuable-resource-or-being-resourceful-with-a-valuable-waste.html).

    Caroline Snyder (a PhD in Germanic Languages and Literature) and the others are not trained scientists and have done no primary research on biosolids use. In her comments here, once again, Dr. Snyder assumes a conspiracy extending from EPA to all state environmental regulatory agencies, federal agencies (e.g. USDA, FDA), public wastewater treatment facilities, private companies, various scientists, and even university cooperative extensions – including WSU. What a conspiracy!

    What she describes is actually a growing consensus of scientists that biosolids recycling provides proven, measurable benefits and, according to 40+ years of research, does not appear to present significant risks to human health or the environment. Two reviews by the National Academy of Sciences, and several major “state-of-the-science” conferences of independent research experts, are part of this growing consensus.

    As this new WSU document reports, recycling nutrients, carbon, and energy through biosolids is an important part of improving the sustainability of our communities. About 60% of the wastewater solids produced in the U. S. are successfully recycled and have been for many years. More at http://www.nebiosolids.org/about-biosolids/.

  9. Caroline Snyder said on September 8, 2016:

    Mr Beecher never gets tired of attacking my credentials. I received my Ph.D from Harvard University in 1966 and am Professor Emeritus at the Rochester Institute of Technology, where I was one of the first faculty members nationwide to design and teach interdisciplinary Environmental Science courses. Before retiring I chaired RIT’s Department of Science, Technology,and Society.
    For the last 20 years I have researched and written about the politics and science of using contaminated waste, such as municipal sewage sludge as “fertilizer.” After co-chairing the NH Sludge Management Advisory Committee, I founded the non-profit, Citizens for Sludge-Free Land. Instead of responding to each of Mr.Beecher’s blatantly misleading claims, I refer readers to my August 29th written testimony before the PA Democratic Policy Committee:
    http://www.sludgefacts.org/testimony_to_Pa.pdf

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