Sunday, March 5, 2017
I am a science nerd and always have been. Just this week I got real excited by ”Harvesting therapeutic proteins from animal slobber” in this week’s (2/22/2017) Chemical & Engineering News, just as I was about “Slow-release nitrogen fertilizer could increase crop yields: A new nanoparticle-based fertilizer…” in the same issue. I spend several hours a week updating my EndNote database, where I have catalogued over 3,000 science journal articles. I received my tee-shirt this week: March for Science – Earth Day 2017. I occasionally, for fun, visit the National Center for Emerging and Zoonotic Infectious Diseases (NCEZID) just to catch up. I jump at the chance to encourage people to listen to The Great Courses audio lecture series Earth's Changing Climate.
I take science seriously, which explains my annoyance at seeing the negative news clipping below and receiving word that David L Lewis is again pretending to be an honest whistleblower scientist fired by the US EPA over his opposition to Part 503 regulations. Apparently a new documentary is in the works featuring Lewis as a hero: How EPA Faked the Entire Science of Sewage Sludge Safety: A Whistleblower’s Story. It was just in January that I started out a newsletter noting that "David Lewis, long-retired from EPA but not from anti-biosolids activism, has posted to the United Sludge Free Alliance his 'recommendation for a new EPA Clean Soil Standard'.” And this week I learned that Caroline Snyder has been stirring up folks in eastern Pennsylvania that there are no science articles showing biosolids is safe. THIS IS NOT TRUE!
Lewis’s argument of biosolids risk is absurd on its face. Virtually every state and federal regulatory system accommodates and supports biosolids recycling; that is hundreds of environmental regulators. Virtually every scientific article finds positive attributes of biosolids use in soils; I have 600 such references, authored by probably more than 1,500 scientists. The wastewater profession backs this practice; WEF counts itself having 33,000 members. For DL Lewis to be on the right side of this issue, these scientists, engineers, and regulators would need to be in some sort of mass conspiracy. How can rational media reporters be so blind to this absurdity?
The “fake news” story that is told around biosolids follows common themes of mythology. A number of years ago, Pulitzer Prize winning science writer Jon Franklin explored this theme in “Biosolids Hits the Fan” presentation to the opening general session the last time the national biosolids conference was held in the Seattle vicinity.
This argument has also been provided a veneer of respectability by several journal articles, now over a decade ago. Lewis made that case in Interactions of pathogens and irritant chemicals in land-applied sewage sludges (biosolids). He speculated that “an increased risk of infection may occur when allergic and non-allergic reactions to endotoxins and other chemical components irritate skin and mucus membranes and thereby compromise normal barriers to infection.”
Works by other familiar anti-biosolids activists have appeared in technical journals. Today’s most active activist, Carolyn Snyder, authored in 2005 for the International Journal of Environmental and Occupational Health the article The Dirty Work of Promoting “Recycling” of America's Sewage Sludge. Helane Shields authored in 2003 for an online publication, NEW SOLUTIONS: A Journal of Environmental and Occupational Health Policy, an ominously titled article Sludge Victims: Voices from the Field. And in that same year and in the same publication, a more extensive treatment of the claims of biosolids-related illness was set forth by Cornell Waste Management Institute’s Ellen Z Harrison, Investigation of Alleged Health Incidents Associated with Land Application of Sewage Sludges: “Residents near land application sites report illness. Symptoms of more than 328 people involved in 39 incidents in 15 states are described.” A journal article with a theme linking biosolids use to environmental justice is Public Officials’ Perspectives on Tracking and Investigating Symptoms Reported Near Sewage Sludge Land Application Sites. The authors of this paper observed: “Residents living close to treated farmland have reported becoming ill following land application of sludge. No systematic tracking or investigation of these reports or of land application practices that could affect off-site migration of chemical and biological constituents of the sludge has occurred, however.”
These “science” articles share the specific feature that neighbors to land application sites are self-reporting symptoms of ill health. This is not medical science. Medical science is founded on objective measurements and on plausible mechanisms linking pathogens or toxins to health effects. These standards of medical science are not met with self-reported illnesses.
Nevertheless, WERF (now WE&RF) actively responded to these wide-spread and persistent public concerns. It sponsored research leading to the 2005 report. Health Effects of Biosolids Odors: A Literature Review and Analysis. This review was followed by WERF’s more proactive Epidemiologic Surveillance and Investigation of Illness Reported by Neighbors of Biosolids Land Application Sites, Phase 1, “a draft protocol designed to be used by local, state, and federal health and environmental officials,” and by Pilot Testing: Surveillance and Investigation of the Illness Reported by Neighbors of Biosolids Land Application and Other Soil Amendments, which tested the protocol. This project had its bumps in the road, in part because the Phase 1 authors were in disagreement with the focus and findings as they were shaped by the project review team. One underlying issue is this: are people who believe they have been sickened by biosolids exposure in fact experiencing ill health?
I took a shot at the issue of whether, in the absence of pathogen and toxicant exposures, can biosolids make people sick? I had been put on to this topic by Dr. William Cain, the principal investigator of WERF”s first report on health effects, in a visit to his odor lab shortly after his WERF report was complete. He explained that the chemical sensing system, particularly the trigeminal nerves in the nose, could be triggered by biosolids odors and that odor triggers could cause physical reactions, even subconscious ones. After a long, circuitous path of journal reading, I set this argument down in 2007 in Biosolids Odorant Emissions as a Cause of Somatic Disease: What Ought to be Our Profession’s Response? I convinced myself that we, as environmental professionals, ignore odor complaints at our peril. My basic argument is that we can reasonably predict that someone in a community affected by biosolids odors may become fearful and experience physical manifestations of panic arising from odors, not pathogens.
Over the past ten years, scientific tools for investigating pathogens and exposures are increasingly sensitive and affordable. Has science raised the level of concerns with biosolids-borne toxicants and pathogens? The short answer is no.
But we do now know a lot more about biosolids-borne microbes. A series of reports were issued by Dr. Jordan Peccia’s lab at Yale University. He and his grad students looked far beyond our traditional, regulation-inspired indicator organisms. In Toward a consensus view on the infectious risks associated with land application of sewage sludge he concluded “such analysis demonstrates that the tradition of monitoring pathogen quality by Salmonella spp. and enterovirus content underestimates the infectious risk to the public…” In Source tracking aerosols released from land-applied class B biosolids during high-wind events, Peccia’s team concluded that “[T]he application of DNA-based source tracking to aerosol samples has confirmed that wind is a possible mechanism for the aerosolization and off-site transport of land-applied biosolids." Further, in Prevalence of Respiratory Adenovirus Species B and C in Sewage Sludge, the researchers asserted “[T]hese findings reinforce the necessity to consider aerosol exposure to sewage-derived pathogens." But, in terms of actual risk, the evidence seemed to point to exposures not being of great health concern. In Respiratory Toxicity and Inflammatory Response in Human Bronchial Epithelial Cells Exposed to Biosolids, Animal Manure, and Agricultural Soil Particulate Matter the article “…suggests that an inflammatory aerosol exposure in the TB region could only occur under worst case scenarios…,” which seems relatively benign.
The other major team looking at the microbial content of biosolids and its implication for worker and community health is at the University of Arizona, that of Drs. Ian Pepper and Chuck Gerba. This team put out the report Pathogens and Indicators in United States Class B Biosolids: National and Historic Distributions, a “major study of the incidence of indicator organisms and pathogens found within Class B biosolids within 21 samplings from 18 wastewater treatment plants across the United States….illustrating that the Part 503 Rule has been effective in reducing public exposure to pathogens relative to 17 yr ago.” As with the Yale work, this team’s graduate students studied Bioaerosol transport modeling and risk assessment in relation to biosolid placement, concluding that for nearby residents “little risk of infection from aerosolized bacteria and at no risk from aerosolized viruses.” This works was also reported and confirmed in Estimation of bioaerosol risk of infection to residents adjacent to a land applied biosolids site using an empirically derived transport model. When the new assessment tool, QMRA, or quantitative microbial risk assessment, was applied to manures and biosolids, in Land Application of Manure and Class B Biosolids: An Occupational and Public Quantitative Microbial Risk Assessment, the researchers showed that “decreases in risk were typically over six orders of magnitude beyond 30 d. Nearly all risks were reduced to below 10−4 when using a 4-mo harvest delay for crop consumption.” These confirmed the effectiveness of Part 503 management regulations.
What can we say today with these new tools, new studies, new technologies, and new complaints? We still can confidently say that biosolids land application has not proved a significant source of pathogens that cause sickness in workers and communities. This is good, but not sufficient. Odors still provoke panic-related symptoms, so we need to continue our search for improved odor qualities. We should not be shy about offering to respond to claims of ill health effects of biosolids, because some of these reports arise from genuine fears. Class A pathogen treatment vastly reduces risks compared to Class B treatment, so our industry’s move to Class A is wise. Land management practices that prevent windblown dust, incidentally also reducing odorant releases, are always smart.
We know biosolids is safe, but our public does not. We need to go beyond our rational brain and toward our emotional nature, our heart, and follow our nose. Even the safest biosolids by any other name is Still Not a Rose.
Friday, February 24, 2017
We now have a word for it!
I read in the Washington Post (11/16/2016) that the Oxford Dictionaries recorded a 2000% increase in this word’s usage between 2015 and 2016, with the Brexit referendum in the UK and the Trump-Clinton campaign in the U.S. Oxford’s international word of the year for 2016 is: “post-truth.”
Oxford defines post-truth as: “relating to or denoting circumstances in which objective facts are less influential in shaping public opinion than appeals to emotion and personal belief.”
Oxford explains that “the ‘post-‘ prefix doesn't mean ‘after’ so much as it implies an atmosphere in which a notion is irrelevant.” It further notes that “post-truth” captures the “ethos, mood or preoccupations of .”
Facts are irrelevant? I don’t need to get into a political debate to explain to all of you biosolids practitioners what post-truth feels like. We experience post-truth frequently in debates over recovering resource value from our biosolids. I feel I will be using “post-truth” frequently going forward, perhaps more to myself than to our critics.
That is why the MABA annual symposium in Wilmington, Delaware, provided so great a respite from post-truth in its many manifestations, when we were treated to the truth-telling of 15 experts on a wide range of biosolids truth. I want to review half of these truth-telling presentations this week, and the rest in the subsequent News.
I don’t think anyone attending the symposium wasn’t blown away by the magic of Dr. Jeffrey Buyer’s presentation (The role of microbes on soil health and questions for biosolids research) on soil microbes. For me, one of the very astonishing slides, one that still has my head shaking, involved graphical representations of the microbial population diversity in human waste versus the microbial communities in the sewage in sewer pipe versus the communities in biosolids. The microbial profiles were entirely different! The biosolids truth: microbial populations we flush to the sewer bear almost no similarity to those in biosolids. Who knew?
Another point I took away from Dr. Buyer’s presentation was the resilience of soil microbial ecosystems. They preserve their characteristic microbial biome structure through drought, cultivation, fertilization and biosolids. There is one caveat, drawn from manure research, that repeated biosolids applications, over time, might be altering soil microbial communities. I find this a reassuring notion, for some reason, and one we can hope to support with future research. Check out Dr. Buyer’s presentation, and see for yourself this biosolids truth: biosolids constitutes a microbiome, the effects of which on soil is unexplored.
We experimented with teleconferencing speakers from remote locations. One prize presentation (Results of the National Sewage Sludge Repository at Arizona State University: Contaminant Prioritization, Human Health Implications and Opportunities for Resource Recovery) was from a newly minted PhD at Arizona State University, Dr. Venkatesan. He presented the work he has done over the past 5 years, along with Dr. Rolf Halden, on the National Sewage Sludge Repository. The repository is the collections of representative biosolids sample taken during the several rounds of testing by the US EPA some 15 years ago. Dr Venkatesan analyzed these for persistent organic pollutants. We celebrated with him the removal by the FDA of triclocan and triclocarban from consumer products this past year. We learned this biosolids truth: FDA’s ban of triclosan and triclocarban will eliminate 60 % of persistent pollutant loadings in biosolids.
Dr Venkatesan had a bold proposal for us. He asserts that biosolids is very much like the human being, in that it contains lipids that capture from daily exposure lipophilic contaminants in food, water and consumer products. Biosolids could be an early warning material for exposures to pollutants, one that is more immediate than a post mortem evaluation of you or me. The biosolids truth: biosolids contains a large array of chemicals that are markers of human exposure.
Phosphorus was a VERY BIG DEAL in the two-day symposium. Trudy Johnston had arranged participation by regulators from Pennsylvania, Delaware, Maryland and Virginia, each states with phosphorus contributions to the Chesapeake Bay and with programs to reduce flows of phosphorus to the Bay. Dr. Herschell Elliott of Penn State University provided in his presentation (Will phosphorus scuttle biosolids land application? ) the scientific basis for a nuanced approaches to the effects of soil phosphorus loadings. But to place the issue in the context of the politics of inter-state management, Synagro’s John Uzupis described (An agronomic review of phosphorus in biosolids and how it relates to the Chesapeake Bay States of Maryland, Pennsylvania and Virginia ) the likely regulatory path. The biosolids truth: regulation of phosphorus at wastewater plants continues to be the easier path for regulators than control of farmland losses.
For me the bottom line is the faster we embrace technologies to extract P from wastewater influent or from sludge solids, the better we will be from a biosolids application standpoint. This point circles back to Dr. Venkatesan’s presentation, when he tells this biosolids truth: biosolids is a valuable source of phosphorus and deserves recovery. Dr. Venkatesan reported on the work of his ASU colleague, Paul Westerhoff, on calculating the value of biosolids (Characterization, Recovery Opportunities, and Valuation of Metals in Municipal Sludges from U.S. Wastewater Treatment Plants Nationwide). This study give a high commodity value to P among a large array of other elements. Though the crisis is not yet upon us, at least not nearly as closely as climate change, the threat of future global P shortages genuinely warrant action today.
Yes, biosolids can be complicated, with a swirl of issues, such as persistent pollutants and phosphorus, yet science holds out, with hope and vigor, the possibility of TRUTH. This will be the only way we can get beyond biosolids post-truth, with relentless commitment to Biosolids Truth.
In this season of ghosts and goblins, slime seems always to be an appropriate prop. In my very first professional presentation to a biosolids forum, an IWA conference in Los Angeles in 1989, I used a literary device, as I am wont to do, for my speech. I used a silly children’s book I had for my boys that described the many uses of . I, of course, transmogrified this conversation to one about “sludge,” in a sort of Gilda Radner’s Emily Litella “never mind” riff popular several decades ago on Saturday Night Live (see my favorite on ). But, really, the connection between slugs and sludge is more than onomatopoetic and more than a “d.”
One thing slugs and sludge have in common is “slime.” And slime is a lot more complicated and engaging upon second reflection than upon first, and certainly deserving of deep study.
In the case of slugs, I learned in just how complex is the trail mucus of a terrestrial slug. If you have ever inadvertently stepped on one, “slime” takes on real meaning. But to it is a gel with a dilute polymer mixture that contains a specific glue protein that crosslinks with other polymers, providing the adhesive properties necessary for snail locomotion. This “trail mucus” slime may very well may hold the secrets of future strong, flexible adhesives. Who knew?
So, what do we NOT know about slime in biosolids? A whole lot less, I think, than we need to know. Slime may be the key to digestibility, dewaterability, energy recovery and odors, a sort of biosolids form of the (another Halloween allusion.)
The slime I am referring to is a part of the emerging science of EPS, or extracellular polymeric substances. (This is not a mystical, Halloween season nod to ESP, or extrasensory perception.) How EPS in biosolids changes with treatment before, during and after sludge digestion is key to the quality of the final product. By quality I mean, at the end of the treatment process, does the product look and smell like a lump of p__p, or does it look and smell like garden soil?
Scientists are doing some amazing work on the EPS in sludge. EPS is released by microbial cells during either anaerobic or aerobic treatment processes. EPSs come in several forms. In the paper , EPS is separated into “four fractions: (1) slime, (2) loosely bound extracellular polymeric substances (LB-EPS), (3) tightly bound EPS (TB-EPS), and (4) pellet.” EPSs are very complex and their role in creating stable flocs, their influence on dewaterability, and the impacts of different treatment on their characteristics have been difficult for scientist to tease apart. concluded: “the knowledge regarding EPS is far from complete and much work is still required to fully understand their precise roles in the biological treatment process.”
Slime is in many ways a positive component of EPS. The journal article concluded: “The slime EPS was better for bioflocculation….” Against this flocculation role, slime is a negative for dewatering, and a research focus is on how treatments alter the slime. In the , we are told that “During hydrolysis and acidification, PN [protein] was transferred from the pellet and TB-EPS [tightly bound-EPS] fractions to the slime fraction… Further investigation suggested that CST [capillary suction time] was affected by soluble PN…, “ which is not a positive attribute.
Some creative research is in full swing to modify EPS. A bioengineer, S Kavitha, at Anna University in India, entered full force in 2014 the science literature with studies examining an array of biological and chemical approaches to altering the EPS of sludges to achieve improved processes. Her focus has been primarily on the digestibility and dewaterability of waste activated sludge (WAS). She has examined different additives for breaking up EPS-controlled flocs in WAS to expose them to biological decomposition:
But Kavitha is far from alone in studying ways of altering EPS. Researchers from other groups have recently given us these papers:
- found that “The sludge after STAD exhibited better flocculability and dewaterability than that after the prolonged aerobic digestion.
- found that “The results indicated that sludge dewaterability was improved by decreasing solution pH [with potassium ferrate] in terms of filtration rate and cake solids content.”
We even have two new terms of art describing biological approaches to biosolids processing -- bioleaching and biodrying.
The term “bioleaching” is applied to a biological approach to conditioning biosolids for dewatering. Bioleaching involves inoculating WAS with specialized bacterium, along with an effusion of iron, to chew up the EPS, and hence improving dewaterability. Researchers are looking at Acidithiobacillus ferrooxidans -- . This paper had four highlights: “Rapid flocculation of sewage sludge was achieved using iron-oxidizing bacteria; A. ferrooxidans biogenic flocculant significantly improved the sludge dewatering; a rapid reduction of EPS content was achieved during sludge flocculation; and, a positive correlation between EPS reduction and sludge dewaterability was observed.” This all sounds great.
Other researchers report on “biodrying.” In the paper the authors claim “62% of total water removal [in a ]thermophilic phase ... transforming bound water to free water and modify(ing) the sludge structure and improves dewaterability.” This approach has already leaped to the commercial side. It was presented as the reactor at the conference in August 2015 .
Uniting these approaches to altering biosolids properties is the deployment of biological, in contrast to mechanical, processes to reduce EPS in sludges and drive physical properties in favorable directions of digestibility and dewaterability.
This brings me back to one of the mysteries of my early days in biosolids, back to my “never mind” word play with slugs and sludge, and back to the day before “biosolids.” I wondered then why was the Chicago air-lagooned biosolids so pleasant and why was such a great product? Perhaps what we didn’t know then, and what we are learning today, is that those processes chewed up the EPS effectively, with a big payback. I asked back then why was Philadelphia’s biosolids compost so gummy and I ask today why is the thermally hydrolyzed biosolids surprisingly pungent? Perhaps what we still don’t know today is how to chew up the EPS effectively.
We are still very early on the learning curve with EPS, so when we do learn what we need to learn, I am betting that we will then be close to describing a “high quality biosolids” product. Then our EPS will be transmogrified into ESP, an Extra Special Product.
I have a tremendous idea for a new biosolids research project, but first….
It was no big surprise that one of my wife’s Christmas gifts to me was Gut: The Inside Story of our Body's Most Underrated Organ. I have displayed at home, as well as in my biosolids commentaries, an abnormally high interest in the human gut microbiome. To my delight, this book, translated from German and written by Giulia Enders, a young female, award-winning, Ted-talk-giving, science writer, is a breezy and comprehensive work. It is, as Amazon says, a “beguiling manifesto.”
Clearly, one of its main messages is that the health of the human gut microbiome effects the health and well-being of its host, that is you and me. I checked with Amazon, and Ender’s “gut” book shares the virtual bookshelves with a whole host of similar titles, also drawing on the connection between happy microbes and happy people: The Microbiome Cookbook: 150 Delicious Recipes to Nourish your Microbiome and Restore your Gut Health, The Mind-Gut Connection: How the Hidden Conversation Within Our Bodies Impacts Our Mood, Our Choices, and Our Overall Health, The Good Gut: Taking Control of Your Weight, Your Mood, and Your Long-term Health
This flurry of book is all very new, each book printed in 2016.
Then the news services on January 3rd reported that a new organ had been uncovered in the human body, one connected to the intestines, and called the “mesentery.” Another young female science writer with Live Science, Sarah G. Miller, wrote the article Gut Decision: Scientists Identify New Organ in Humans: “scientists can now focus on learning more about how the organ functions, Coffey said. In addition, they can also learn about diseases associated with the mesentery, he added.”
I can confidently assert that we will be hearing a lot about gut flora over the next decade, and we should take note of this for our work with biosolids, particularly for the positive connection between microbial communities and human health. A major research question was which gut microbes caused major gastrointestinal illnesses, such as Crohn’s Disease and ulcerative colitis, in hope of an easy path for medical control. But the nature of gut ecosystems was too complex for a simple answer. Instead researchers turned to the question how the gut ecosystem actively keeps us all healthy, particularly when so many species of gut microbes are known human pathogens.
Over the past several years, journal articles have addressed these questions:
· Does choice of foods affect the microbiome? Well, yes, at least in part (Long‐term monitoring of the human intestinal microbiota composition).
· Does use of antibiotics alter the gut flora? Well, yes, at least in part (Diversity, stability and resilience of the human gut microbiota).
· Does consuming daily doses of probiotics alter the gut flora? Well, yes, at least in part (Intestinal microbiota in human health and disease: the impact of probiotics).
· Is obesity influenced by gut flora? Yes, at least in part (Linking the gut microbiota to human health).
· Can gut flora really influence an individual’s emotional well-being? Well, yes, at least in part (Better living through microbial action: the benefits of the mammalian gastrointestinal microbiota on the host).
Wow! Who would have guessed that our health and well-being is really the result of our wonderful gut flora?
I realized in reading these reports that I had only a foggy idea of what comprised the human gut flora. We are all familiar with E coli as an important class of bacteria, but its distinction for us is not in its role in the human microbiome but its choice as an indicator of environmental contamination. And, as it turns out, it is not a particularly good indicator at that. Escherichia coli is just one species in a large class of protobacteriods, a group that together makes up perhaps a quarter of the 3 trillion microbes in the adult human gut. E coli’s role is relatively small in the gut, but its presence in activated sludge treatment works turns out to be very significant, which is one reason (along with its easy culturability in the laboratory) we know so much about it, why we track it, and why we regulate it.
But we are learning of far more important microbes. One particularly interesting microbial group in the gut is called Lachnospiraceae. Besides its very dominant role in the gut flora in a class of organisms called the Firmicutes, this group is interesting because it connects to my next topic, the sewerage system. One young, female professor in Wisconsin, Sandra L. McLellan, has emerged as a leader in researching the unique microbial ecosystem of sewers. She has identified the class of bacteria Lachnospiraceae as a robust indicator of human fecal waste, occurring in the human gut and in the sewer, and being distinct from microbes from other animal and environmental sources. Check out her paper, Sewage reflects the distribution of human faecal Lachnospiraceae, showing that public sewers fed with human-sourced food are the habitat for unique microbial communities, and this one microbe class that can be readily tracked, the Lachnopriracea. You heard it here first.
Just as we are on the early part of the learning curve of the microbial communities of sewers, the same is true with biosolids itself. This brings me to Kyle Bibby’s work while a PhD student at Yale University, where he characterized the biota of different biosolids products. In his paper, Pyrosequencing of the 16S rRNA gene to reveal bacterial pathogen diversity in biosolids, his intention is to clarify the potential array of pathogenic organisms, viruses as well as bacteria, that may be present in biosolids. But his work necessarily included a broader survey of microbial. He discovered that different processes, such as aerobic versus mesophilic anaerobic digestion vs composting, resulted in biosolids with microbial ecosystems common within processes but different between processes. Wastewater plants grow out of the influent food and microbes different biosolids-based microbial communities, each characteristic of treatment facility processes.
In his presentation to the MABA Annual Symposium, The role of microbes on soil health and questions for biosolids research, Dr. Jeffrey Buyer had covered Bibby’s work, but then extended the conversation to the effects of biosolids on soil microbial communities. He summarized soils research that showed many soil communities are stable, just as in the human gut, and that additions of various organic feedstocks, biosolids along with manures, help to push around, but not to fundamentally change, those soil microbial communities. Where we humans might eat a carton of Greek yogurt for our daily dose of probiotics, our annual application of biosolids may do the same for a healthy soil. Biosolids microbial communities make soils happy.
Dr. Buyer’s presentation this past November reminded me that Dr. Xunzhong Zhang at Virginia Tech, made a presentation to the 2013 MABA Annual Symposium, “Biostimulants Released from Biosolids have impact on Crop Stress Tolerance and Yield.” Dr. Zhang showed that biosolids release auxins and stimulate soil microbes to do the same, which together significantly increase crop growth. He shows that biosolids makes for happy soil microbes, in turn making plants happy.
So where have I gone with this? Our historical engagement with biosolids microbes has largely been in what goes wrong in controlling pathogen indicators in our treatment processes or where their presence in the environment is a marker for pollution. Instead, what we are learning, starting with the human microbiome, is how critical complex microbial communities are for health -- the health of our bodies, the health of transformative processes in sewers, the health of our activated sludge treatment systems, and in the health-giving properties of biosolids for plant growth.
The analytical tools are at hand and affordable, and only our imagination limits the questions we can ask. This is my research question. What attributes of biosolids microbial communities contribute most to a positive growth response in plants, and how can we design our treatment plant equipment to optimize those attributes? Instead of “high quality biosolids” research focusing mainly on attributes of odor, aesthetics, and handleability that influence human sensibilities, let’s look at biosolids from the viewpoint of the healthy plant. That would be a worthy research project. At least, that is what my gut tells me!
Research on POPs is really popping. We are learning at an accelerating rate of the fate of “persistent organic pollutants,” or the POPs, flushed down home drains and treated in systems where biosolids are destined for farm soils.
Our POP research rate may not be fast enough for some, as I learned very recently. David Lewis, long-retired from EPA but not from anti-biosolids activism, has posted to the United Sludge Free Alliance his recommendation for a new EPA Clean Soil Standard. I was reminded of just how “chemophobic” or “chemonoic” some people can be. Dr. Lewis’s report would have you believe the threat from POPs is significant and growing. It is neither, and accumulating research shows this to be true.
We are not only learning about POPs, we are reducing POPs. Back in the summer, the FDA issued a rule banning triclosan, triclocarban and other antibacterial POPs found in soaps and toothpaste. We learned from Dr. Arjun Venkatesan, Arizona State University, in his presentation to the MABA Annual Symposium, that this action will remove more than half of the POPs that find their way into biosolids.
Dr. Venkatesan has a unique vantage point to see POPs in biosolids. He is principal author of 7 science reports stemming from exhaustive analyses of the U.S. National Sewage Sludge Repository. The repository is a collection of representative biosolids samples, originating with three national surveys conducted by the US EPA two decades back, and now under the direction of Dr. Rolf Halden, Center for Environmental Security. Dr. Halden is “a noted expert in determining where in the environment mass-produced chemicals wind up…” and that expertise encompasses biosolids.
Dr. Halden has recently made the point that widespread use of industrial chemicals ensures that new questions about these chemicals will arise continually and science will be ongoingly playing catch-up to understand their potential effects on human and environmental health. Dr. Rolf Halden described the generation-long process well in Epistemology of contaminants of emerging concern and literature meta-analysis.
As environmental stewards, we biosolids practitioners necessarily need to support sound scholarship into POPs. The chemical and biological matrix in which POPs occur is highly complex and reactive, and the science will be deeply complicated.
The European Union seems to lead the way in addressing the fate of POPs. It has for two decades guided the testing for degradability of chemicals (OECD Degradability Testing) with a guidance document listing 7 types of tests. One test deploys a “301C sludge,” an “activated sludge precultured with synthetic sewage containing glucose and peptone.” Another is the 314 test which simulates transformations of chemicals in a sewer system.
In the US, the Water Environment & Research Foundation has led the way in POP research. Currently at work is Dr. Drew McAvoy, the principal investigator of the fate of flame retardants and two antibiotics in biosolids. His project on “Priority Trace Organics” appears right above “High Quality Biosolids from Wastewater” on WE&RF’s list of Recent Contract Awards.
Those of us with an eye on biosolids may not be fully aware that POP degradability is being studied in different portions of the wastewater system. These include the sewer system, the activated sludge process, nutrient removal processes and several kinds of digestion. Researchers are learning that unique microbial communities at work in each step can be important to the attenuation of POPs.
If we still believe the sewerage system is a mere collector, how wrong we are! One paper shows that “biodegradation in the sewer has a substantial impact on levels of surfactants and surfactant metabolites that ultimately reach wastewater treatment plants” (Biodegradation of nonionic and anionic surfactants in domestic wastewater under simulated sewer conditions). Another researcher, hoping to track illegal drug use, complained “in sewage epidemiology, it is essential to have relevant information of the sewer system” (Effects of sewer conditions on the degradation of selected illicit drug residues in wastewater) .
The fate of POPs within the treatment plant has proved enormously difficult to characterize. Classes of compounds degrade through different mechanisms, with water solubility being a key discriminator for biosolids-borne or effluent-borne POP discharges. Plant configurations vary, with the cycling of aeration, anoxic and anaerobic processes apparently having great influence on POP degradation. One article pointed out that “biotransformation parameters are impacted by in-situ carbon loading and redox conditions (Factors impacting biotransformation kinetics of trace organic compounds in lab-scale activated sludge systems performing nitrification and denitrification). An early review of this topic, Refinement of biodegradation tests methodologies and the proposed utility of new microbial ecology techniques, explained: “We were also able to compare various processes and pointed out activated sludge with nitrogen treatment and membrane bioreactor as the most efficient ones.” It seems we may one day learn how to design our treatment plants specifically to increase POP degradation. Hold that thought!
Our choice of biosolids stabilization technologies makes a big difference. I won’t get into the effects of digestion here, which are significant in their own right, but I will admit that, for POP reduction, composting is one of my favorite stabilization methods. A large body of research shows how robust composting is for POP degradation. The abundance of compost/POP research is in part because composting applies not only to biosolids but to the much vaster supply of animal manures, which like biosolids contain POPs. The good news is that fairly rudimentary composting techniques yield good results: “low-level manure management, such as stockpiling, after an initial adjustment of water content may be a practical and economical option for livestock producers in reducing antibiotic levels in manure before land application ( Antibiotic Degradation during Manure Composting).
Compost/POP research also stems from the concern that compost is a consumer product, with a direct exposure pathway to humans. But compost has consistently shown strong results in mitigating risks. For one paper (Organic Micropollutant Degradation in Sewage Sludge during Composting under Thermophilic Conditions) concluded “concentrations of all 12 micropollutants decreased during composting, and degradation was statistically significant for 7 of the 12 micropollutants.”
Much of our Biosolids/POP research has been with the pathway of biosolids to soil to micro/macro fauna (including humans). Understanding the gaps in the research record on these pathways was an early WE&RF concern. Trace Organic Chemicals in Biosolids-Amended Soils: State-of-the-Science Review provided the backdrop to the work that Dr. McAvoy now has underway.
For the most part, the research record for many types of biosolids-borne POPs re-affirms the capacity of the land treatment system, consisting of soil minerals, organic matter and in synergistic relationships with microbial communities, to trap and degrade a wide range of POPs. From among many dozens of recent journal articles in this domain, one review article, Plant uptake of pharmaceutical and personal care products from recycled water and biosolids: a review, concluded: “Field studies showed that the concentration levels of PPCPs in crops that were irrigated with treated wastewater or applied with biosolids were very low.” In another pertaining to potential human health risks, “our assessment indicates that the majority of individual PPCPs in the edible tissue of plants due to biosolids or manure amendment or wastewater irrigation represent a de minimis risk to human health” ( Human health risk assessment of pharmaceuticals and personal care products in plant tissue due to biosolids and manure amendments, and wastewater irrigation ). Nevertheless, in recognizing the enormous complexity of biological and chemical systems, “highlighting the significance of contaminant and soil properties in influencing risk assessment,” we must inevitably turn to risk modeling: A quantitative risk ranking model to evaluate emerging organic contaminants in biosolid amended land and potential transport to drinking water.
Modeling may seem to be the poor cousin to comprehensive analytical investigations, but it may be the great way forward. Imagine a future in which you “dial-in” options for source control, sewer maintenance, in-plant processes, biosolids stabilization methods and land treatment protocols, all of which, when taken together, accomplish nearly complete removal of POPs from pathways of human and environmental exposure. To accomplish so grand an endpoint, however, means making POP degradation an intentional and central goal of biosolids management, not an incidental consequence.How about we ”’POP’ the clutch” and accelerate our research into the fate of POPs through the entire treatment system and DRIVE THE POP OUT OF BIOSOLIDS.