MidAtlantic Biosolids Association

Microplastics and Biosolids

I have many years under my belt, and during the pandemic I started my eighth decade. Through each of those decades I have retained only vague memories of the mega-forces changing life on Earth, such as toxic chemical releases.  Do not ask me about when I first learned of persistent organic chemicals, as that is a vague memory. While Rachel Carson’s 1962 Silent Spring was in the background of my early response to the environmental movement, not until a flood of DDT appeared in Philadelphia biosolids in 1995 was DDT an issue of salience to me. I had no idea about flame retardants, even though they were ubiquitous, until a fateful moment at the 2004 meeting of the Chesapeake WEA in Ocean City, Maryland, when the first call from a news reporter came in about the flame retardant PBDE in biosolids. When requests occasionally came to me from national organizations looking for willing municipal participants in voluntary analytical surveys of new compounds of concern, as in radioactivity, dioxin and unregulated organics (targeted national sewage sludge surveys), I would raise Philadelphia’s hand each time. I figured that if I were vague about the risks of these things, I was not alone.

Plastics is one of those “things” today about which we in the biosolids profession are vague. Do not ask me about life on Earth before plastic, even though the year of my birth, 1950, is roughly tagged as the turning point for the introduction of plastics to our global consumer culture. I do not recall the first time I wrapped my lunches in plastic wrap, rather than in wax paper bags (about 1968). Neither do I recall as momentous the spotting of my first plastic soda bottle (about 1973).  When did plastic fibers so thoroughly replace natural fibers in the global clothing scene, and did I ever own a polyester leisure suit (the 1970s)? If I am so vague, I believe by and large we are all vague, particularly about the newest plastic issue - microplastics.

Perhaps we are vague because the term “microplastics” is so new.  According to Merriam-Webster the “first known” use of the term “microplastic” was in 1990.  If you check Google NGram Viewer (by the way, this is a super-cool feature), the number of its catalogued publications in which the word “microplastics” is used has shown a straight-line doubling since about 2012.  Microplastics is a term that is highly likely to be soon on everyone’s lips, just as PFAS, the “forever chemical,” is there now. Today’s worry about PFAS in our waters and foods may be tomorrow’s worry about microplastics in our waters and foods.

My vague understanding of pathways of microplastic movement in water and food was underscored by a recent journal article on microplastics in soil protists. I was even vague about what is a “protist.” For those of you who have not been following “systematics,” the arcane discipline of crafting the evolutionary “tree-of-life,” protists are the kingdom of life of non-plant and non-animal organisms that are eukaryotes (with cell nuclei) and mostly unicellular. Soil protists are those amoeba-like organisms living in the soil as opposed to fresh and ocean waters or inside animals. I had been only vaguely aware of this newly classified kingdom of life, but now I understand, through “Soil protists: a fertile frontier in soil biology research,” that protists constitute the first rung of the ladder in the food web and cycle of nutrients and carbon and “protists are the key trophic link facilitating nitrogen-uptake of arbuscular mycorrhizal fungi.”  In Phagotrophic Protists: Central Roles in Microbial Food Webs we learn “phagotrophic protists regenerate a large part of the organic nitrogen and phosphorus in bacterial and algal biomass.”

It cannot be good news that scientists have found microplastics in soil protists, as you do not want to gum up the first loop in the food chain. This could mean that everything above soil protists in the food chain is also accumulating microplastics. In Microplastics and phagotrophic soil protists: evidence of ingestion the authors explain “that most soil protists (>75% individuals) can readily ingest and keep MP within their food vacuoles, even at relatively small MP concentrations (0.1% w/w).…  This is the first report indicating that soil protists can play an important role in the transport and uptake of MPs in the soil food web.”

What does this have to do with biosolids? Very few articles today about microplastics and soil miss the opportunity to cast an eye toward biosolids as a potent source of microplastic, which hints at biosolids harming soil protists. As examples, Microplastics as pollutants in agricultural soils asserts “major causes of MPs pollution include application of biosolids and compost, wastewater irrigation…,” and Evidence of microplastic accumulation in agricultural soils from sewage sludge disposal claims “Sludge is proposed as a primal driver of soil microplastic pollution.”

Scientifically proven effects of microplastics on soil health are vague, and the connection to biosolids even vaguer.  One comprehensive review paper sifted through the science journal articles to date: Source, migration and toxicology of microplastics in soil.  As with other reports, “land application of sewage sludge” and “compost and organic fertilizers” are suspected sources of microplastics in soils.  From a high-altitude viewpoint, the authors assert “The presence of microplastics severely reduces soil quality… the migration and trophic transfer of microplastics in heavily contaminated soils, particularly those in wastewater-irrigated and plastic-film covered areas, pose substantial risks to the ecosystem… Microplastic-induced changes affect soil function and soil microbial communities.”  But the authors admit that few scientific studies have been done. They explain the expected effects in such couched phrases as “the bioaccumulation and biomagnification of microplastics may adversely affect terrestrial food webs,” “uptake of microplastics by organisms can damage important ecophysiological functions that control health and biodiversity,” and “much more researches need to be conducted to address knowledge gaps of influences of microplastics on plants and future studies will be of great interest.” The message is: send more money for research if you want scientifically valid results.

The urgency for research into effects of biosolids-borne microplastics on soil health is rising fast. A barometer of the brewing storm of interest in this topic can be found in Google Scholar. The number of science journal articles that are captured by the search terms “microplastics, sewage sludge” in the year 2010 was eleven. In 2015 the number was 114. By 2019, the number was 730; in 2020 the number is 1,510; and by mid-2021 the number is already 1,410. That is explosive growth in research interest. Note, too, that these numbers are about a factor of 5 higher than the number of citations returned from the search term “PFAS, sewage sludge.” Interestingly, the total Google results for “PFAS” are nearly 50 million, but for “microplastics” less than 5 million. This leads me to presume that the public imagination around the health and environmental effects of PFAS leads by a wide margin the public’s imagination around microplastics, while scientists are far ahead of the public in their imagination of adverse effects microplastics. Scientists seem to be lining up behind microplastics as a significant health and environmental risk.

Even a disinterested spectator might presume that future releases of microplastics is heading upward, not downward. The big trend is an unabated upward production rate for plastics, fostered in part by fracking (Annual production of plastics worldwide from 1950 to 2020: “Global plastics production totaled 368 million metric tons in 2019”). New NGOs, such as Beyond Plastics, are calling attention to the global risk of rising plastic use: “One million plastic bottles are bought around the world every minute.”

For wastewater and biosolids, a principal source of increasing plastic is microfibers released during clothes washing.  Microfiber release from different fabrics during washing reports “Our data suggested that microfibers released during washing of synthetic fabrics may be an important source of microfibers in aquatic environment…Thus, more efficient filtering bags or other technologies in household washing machines should be developed to prevent and reduce the release of microfibers from domestic washing.” Also at play is the overwhelming shift in global fashion, as explored in the documentary The True Cost. The article The global environmental injustice of fast fashion, reports “globally, 80 billion pieces of new clothing are purchased each year.” That is more than 10 items annually for all Earth’s people. Microfiber Masses Recovered from Conventional Machine Washing of New or Aged Garment found “washing synthetic jackets or sweaters as per this study would account for most microfibers entering the environment.” Where does the plastic in jackets come from? Ironically, the principal outlet for recovered plastic bottles is as synthetic fleece, the biggest source of microfibers in wastewater and biosolids.  According to a National Geographic website, “Polartec … has diverted about 1.5 billion PET bottles from landfills and continues to lead the outdoor industry in both performance fabrics and sustainable innovation.” This recycling success does not help the wastewater industry.

To its credit, the clothing industry is worried about environmental releases of microplastics and is in pursuit of “sustainable” options.  A recent positive development is offered by Intrinsic Advanced Materials through its  “CiCLO technology.” This is an “additive that is combined with polyester and nylon [which] creates millions of biodegradable spots in the matrix of the plastic” and thereby “allows plastic-based fibers like polyester to degrade similarly to a natural fiber in marine environments, wastewater treatment plants and landfill conditions.” Polartec will be among the first to use it. We can hope it works.

The wastewater profession seems vague whether microplastics are a problem and whether research ought to be a priority. In June 2019, I attended the IWA Leading Edge Conference in Edinburgh, which featured a full session on microplastics, a global first for this topic, including Are microplastics a challenge for wastewater treatment? The session seemed a plea for research money for the very basics, to figure out how to measure and characterize microplastics in effluent and biosolids. With the overwhelming flood of plastics accumulating on Earth every day, this scope seemed an inadequate response to the global risks from plastics. But, in truth wastewater engineers and operators do not consider in any meaningful way the capture of plastics and microfibers as an objective in their treatment processes, and in truth biosolids managers do not consider in any meaningful way the potential effects of biosolids-borne plastics on soils and crops. Is this beginning to change?

With many years under my belt (a belt most likely made of plastic), I will make a prediction that the future older me will look back some day and only vaguely recall a time when we all were NOT considering Microplastics in Biosolids.


Biosolids News 

Centrisys to Provide Decanter Centrifuge for Anaerobic Digestion Facility 
Colombia, MD (7/1/21) - Centrisys has secured an order from Bioenergy Devco for a decanter centrifuge for the Maryland Food Center Anaerobic Digestion Facility which is targeting to be fully operational before year’s end. The facility will be one of the largest organics recycling facilities on the East Coast and will manage 70,000 to 100,000 tons per year of food and agricultural waste to be sustainably processed into natural gas.

Why Others Praise the Merrell Families
Kokomo, IN (6/26/21) - Merrell Bros is a company that specializes in making municipal biosolids more friendly and applying them as fertilizer on farmland. The brothers that run the company were named honorary master farmers.
Forward Thinking Pays for Merrell Brothers  

Federal EPA Investigation Opened On Controversial Biowaste Facility in Fairborn
Fairborn, OH (6/24/21) - The Environmental Protection Agency office based in Chicago has opened an investigation into the Dovetail Energy Facility in Fairborn. The agency said they are focused on ensuring compliance with the Clean Water Act. Neighbors of the facility have complained of the odor and truck traffic that comes from the facility. Some have formed a group called Bath Township Concerned Citizens. A class-action lawsuit was also filed against the company by local residents in December of 2020.

Synagro Celebrates Milestone in Fort Worth Design-Build-and-Operate Drum Drying Facility Project
Fort Worth, TX (6/24/21) - Synagro celebrates the arrival of the 14ft diameter and 52ft long drum dryer that will be part of the new drying facility in Fort Worth that will process 100 percent of the biosolids produced by the city's Village Creek Water Reclamation Facility as Class A biosolids fertilizer.

Seaside Considers $3.1 Million Wastewater Infrastructure Investment
Seaside, OR (7/1/21) - Seaside’s public works director and a treatment plant operator presented a proposal to install a new press and drying system at the Seaside Wastewater Treatment Facility. If they move forward, the new process would likely produce a Class A biosolids product that they would look to sell for profit.

Brenda Renewables Clears the Air Regarding Facility Operations
Brenda Mines, BC, Canada (6/23/21) - Brenda Renewables company president and project manager, Matthew Malkin and Rolfe Philip, met with representatives of the Peachland's Watershed Protection Alliance (PWPA), a group that opposed the construction of the facility receiving biosolids and other organic wastes that will be anaerobically digested. During the conversation, Brenda Renewables' representatives clarified some misconceptions and addressed rumors.

Will You Drive A Hyundai Kona EV That's Powered By Human Waste?
Queensland, Australia (7/2/21) - A Hyundai Kona electric, named the S-Poo-V Number 2, is the second sewage-powered car from the company.

Complaints as Sewage Sludge Spread Over Fields Near Lathallan Roundabout
Scotland (6/22/21) - Community members are dissatisfied with Scottish Water's and the Scottish government’s responses to research suggesting spreading biosolids can be harmful to human and animal health. Scottish Water was given recommendations for improving the management practices, but changes were delayed because of the pandemic and Brexit.

Farmer Fined £2,000 for Spreading Sewage on Neighbours Land
Great Bavington, UK (6/21/21) - A farmer was fined and ordered to pay costs totaling more than £2,000 for mistakenly spreading sewage sludge on neighboring fields.


MABA Event Presentations

2021 Webinar - March 2021 on Enhanced Digestion

2021 Webinar - May 18 2021 on Solids Treatment

2020 November Phosphorus 101 Webinar

2020 Summer Webinar Series

2019 Summer Symposium

2018 Annual Meeting & Symposium

2018 Summer Symposium

2017 Annual Meeting & Symposium

2017 Summer Symposium

2017 NJWEA Workshop

2016 Annual Meeting & Symposium

2016 Summer Symposium

2016 NJWEA Workshop


Research Updates from Sally Brown, University of Washington

PFAS at Home

Last month’s research update was timed perfectly to coincide with the Sierra Club’s publication on toxic sludge and PFAS.  I was more than ready to move away from PFAS this month, to a topic like biosolids and soil health (likely pushed to August). Then I got this news alert from the Seattle Times that PFAS is in cosmetics.  I couldn’t let that one go.  So here you have yet another library on PFAS, one that includes the details on PFAS in your mascara.

 This one starts with the Sierra Club’s diatribe (Sludge in the garden Toxic PFAS in home fertilizers made from sewage sludge). Here is their big graphic:


There is a lot of text about how biosolids in your gardens is poison.  They do say that the answer is to stop using these chemicals, but that does not seem to be on the top of their list for actionable items. Just note the title of the publication.  Also, note in the graphic that the belching factory and the leaching landfill are more prominent sources than the home.  The home is the predominant source for most treatment plants across the US.

 They have data on a number of biosolids based soil products:


A high concentration of about 230 ppb is in one of the materials, but most products are under 100 ppb.  They also have a table of PFOS and PFOA concentrations in these “toxic” biosolids, using the Maine standards as a point of reference.  Maine has a limit of 2.5 ppb for PFOA and 5.2 ppb for PFOS.  All but one of the biosolids tested exceeded those limits for one or both of those compounds.  The highest values were from the BLOOM product tested (23.8 ppb for PFOA and 22.1 ppb for PFOS).  How you can come up with significant decimal places when you are talking about 23.8 in 1 000 000 000 is beyond me.  A friend of mine got BLOOM delivered last year.  She was eating tomatoes for months from her garden.  I think the Sierra Club is referring to a very subtle type of poison here.

Article number two takes us a step back from the trash talking and the sky is falling (Per‐ and Polyfluoroalkyl substance toxicity and human health review: Current state of knowledge and strategies for informing future research).  There's so much terror about these compounds.  How can they hurt us, and is there solid evidence of this harm?  This paper is a review of the state of knowledge on human impacts from PFAS exposure.  Here is the low down.  The VAST majority of the data is from PFAS and PFOA, referred to here as Legacy Compounds. 

Here is what has been documented with exposure to these compounds:

The authors note that some of these have been confirmed in animal studies.  They also have a great figure showing potential effects and strength of evidence.

They go through different potential adverse health effects and present the evidence. 

The critical thing here is that the impacts have been noted for the LEGACY compounds with the health implications of the hundreds of new varieties flooding the marketplace as yet unknown. 
That brings us to the third article, the one that got my attention (Fluorinated compounds in North American cosmetics).  Turns out that this stuff is in your cosmetics. At a mean and median concentration of 264 and 1050 ppb.  I got the conversions right this time.  Sierra Club is having a cow and, in the meantime, the stuff is in lipstick and mascara at concentrations higher than (a lot for most) than biosolids.  You do not see Revlon or Maybelline pulling products from the shelves.


Obviously, exposure potential is much higher if you put stuff on your lips and eyes instead of in your soil. 

Let us look at the behavior of these compounds in terrestrial systems.  That would be paper #4, (Sources, fate, and plant uptake in agricultural systems of per- and polyfluoroalkyl substances).  This review comes from Linda Lee and the team at Purdue, perhaps the world experts on the behavior of these compounds in the environment, and a speaker at the Northwest Biosolids September online Biofest.  A critical thing to note in this paper is that soils in North America with no known PFAS sources are found to contain PFOS and PFOA concentrations ranging from 0.02- 2.55 ppb.  A global study with solids collected from 62 locations with little to no human exposure found PFAS in all of them.  It is not the biosolids folks.  More people, by orders of magnitude, are exposed to lipstick than to biosolids.  Most of the studies the authors found were focused on biosolids-amended and irrigated soils, but perhaps future studies should focus on makeup counters. 

For an idea of what is in biosolids, and other residuals-based composts look to paper #5 (Removal of PFASs from biosolids using a semi- pilot scale pyrolysis reactor and the application of biosolids derived biochar for the removal of PFASs from contaminated water).  The numbers generally agree with the Sierra Club report, but the source is trusted, and the conclusions are more grounded in reality and not fear-mongering.  This paper is also from Linda Lee, with Rooney Kim Lazcano as the first author. 

Few food scrap composts were included here.  If more had been, this (from #4) is what they would have found: “Total PFAAs in organic waste composts ranged from 31 to 75 ng/g for those containing food packaging with PFAS concentrations being lower in composts of only food and yard wastes (≤ 18.89 ng/g).”

So, take that, soiled paper!

I would love for this hysteria to go away and for us to be able to focus on the amazing things biosolids do for our soils.  I, for one, haven’t worn makeup in decades (hard to scratch your eyes when you are wearing mascara).  Maybe it is time to expose the Sierra Club to the cosmetics counter.