Digesters on a Low-fat Diet

The maintenance manager at Landis Sewerage Authority was quite graphic in his description of the fibrous mess in his digester’s sampling port. Landis has been accepting FOG (fats, oil and grease) and liquid HSOW (high strength organic wastes) for about a year.  The operators believe rags are coming in with restaurant grease trap wastes. These are ground up at the liquid waste receiving station, and, once in the digester, the rag fibers have attracted grease and human hair. The maintenance team had seen these fibrous grease balls clogging the sampling port pipe, congealed into an indurated, hairy mess.  The pipe had to be cut out, and the manager intended to make a cross-sectional cut of the pipe for illustrative purposes. He hadn’t seen a mess quite like this before Landis had begun accepting the wonderful FOG and HSOW that had allowed its digester to nearly double biogas production.

Hmmm, this is a downside of co-digestion that I hadn’t heard articulated so graphically – raggy, hard grease balls.  I had for many years listened to operator stories of mysterious mop heads in digesters.  But the clog in the Landis digester pipes seemed a particularly nasty version of these.

I recalled a 2010 presentation by Virginia Tech professor, now emeritus, John Novak, about the complexity of oils and fats and their fate in mesophilic anaerobic digesters.  This was a presentation to the Mid Atlantic Biosolids Association specialty conference on co-digestion substrates in 2010. Dr. Novak made the point in his presentation, “Codigestion at WWTPs – Digester Operations,” that not all grease is good for biogas production in digesters. Specifically, certain heavy lipids (chains of 16 and 18 carbons of saturated and mono-unsaturated fats) resist digestion, are difficult to solubilize in digesters, and may exert toxicity. Meat-sourced oils (forming stearic acid) and favorite cooking oils such as palm and coconut (forming palmitic and myristic acids) are just such long-chain saturated fats. These oils degrade into fatty acids that agglomerate and form “micelles,” or what are more commonly known as grease balls. A fatty acid such as stearic acid can then saponify (form a soap) and, in the presence of calcium ions, become hard, greasy lumps, long before microbes can convert the fatty acids into biogas. 

The sources of saturated fats that clog our digesters are the same staples in the American diet that clog our arteries – pizza and burgers, garnished with cheese, bacon and sausage.  You can see this in a table of the sources of stearic acid.  

While the biochemistry of the different fats in wastewater operations is not well understood, the subject is now gaining research interest, as in “Anaerobic co-digestion of fat, oil, and grease (FOG): A review of gas production and process limitations.”  This work was done at a laboratory of Dr. Francis L. de los Reyes III,  at North Carolina State University, whose paper observed: “anaerobic digestion of high lipid wastes has been reported to cause inhibition of acetoclastic and methanogenic bacteria, substrate, and product transport limitation, sludge flotation, digester foaming, blockages of pipes and pumps, and clogging of gas collection and handling systems.”

Clogging…. This is an essential issue for Landis. For all of the trouble that grease balls and mop heads present to wastewater operations, I am curious that they receive very little scientific and engineering attention.  And the role of rags in the formation of grease balls and mop heads has been barely noticed in the technical literature.  A word search of the WEF Manual of Operations on solids treatment came up with not a single reference to rags.

To my delight, the same Dr. de los Reyes who is researching the digestion of lipids has done some works with rags.  He practically stands alone in this field of research, testimony perhaps to how hard it must be to find engineering graduate students with senses of humor sufficient to study the physiochemical behavior or rags and grease in wastewater. But they do have a recent landmark study of sewer collectors, in which rags play a big part: Evidence for Fat, Oil, and Grease (FOG) Deposit Formation Mechanisms in Sewer Lines.

Our treatment plant operators are experts on what typically happens when rags get to the plant in the influent stream.  If the way treatment plant operators manage rags is to trap as many as possible on headworks bar screens, then to catch the rags that get through the screens within the scum collectors, or then to unwrap the rags loose from bars and chains in the treatment tanks, what happens when the rags ultimately get into the digesters?  Not much, except to presume they reside in the digester, gathering together with hair and grease to form mop heads, until the next digester cleaning.

If in accepting liquid wastes directly into the digesters your agency is thereby bypassing those several rag-trapping steps between the headworks and the digesters, how are you handling the rag challenge?  Aren’t you asking for a good deal more rags and fibers in the digesters than is typical in wastewater operations? Do we sufficiently understand how rags and fibers react with oils, grease and hair to know if we can take steps to avoid excessive grease ball formation and clogging?  

This is where real-world experience counts.  Derry Township, Pennsylvania, has been taken in high strength wastes for a decade. It’s not hard to get Executive Director Wayne Schutz to bottom-line his advice: “NEVER, EVER, EVER feed that FOG stuff directly to the digester!!!  Aerate, mix, chop, and bio-augment to break the long chains VFAs; do a pH adjust; screen, de-grit, settle, grind, macerate, chop and macerate again; then feed to digester!!”

Dr. Novak offered in his 2010 presentation several ideas about the grease balls.  He suggested that those agencies looking at trucking in HSWO containing long-chain oils consider deploying advanced digestion, such as acid-phase digestion and/or thermophilic digestion. He recommended vigorous digester mixing, to help break up the agglomeration of grease balls.  He believes that microbial communities will, over time, acclimate to the character of the feedstock to digesters, so plant managers ought to work toward lining up steady, consistent sources of HSOW. But, as Landis Sewerage Authority has discovered, this can be a difficult task in the dog-eat-dog world of waste haulers, for whom a fraction of a cent per gallon lower disposal price down the street has them drive past the reliable neighborhood treatment plant. 

If your digesters have gotten filled with grease balls and mop heads, what can you do?  I spoke to Dr. de los Reyes about the challenges of rags and oils in digesters. He noted the difficulty of projecting from lab-scale digesters the behavior of the full range of FOG in full-scale sludge digesters: “Once the structure is there, it is difficult for the bugs to get to the grease.” He has been examining approaches that include increased digester mixing, microbial community acclimation, bio-augmentation and biodegradable detergent supplementation to see if such tailored strategies might deal with the challenge of grease balls and mop heads.  But his most effective tool is old-school: “What I see is digester shut downs and companies coming in to pump it all out.” 

There you have it. If you take in an assortment of FOG and HSOW, be prepared for frequent digester cleaning.  For our anaerobic digesters, healthy co-digestion means Digesters on a Low Fiber Diet.

Closing the Circle with Biosolids

The “virtuous circle” is what I long ago termed the recovery of resource value from biosolids, so self-evident to me is the wisdom of our biosolids recycling enterprise. I bookmarked in my browser the Ellen McArthur Foundation’s Circular Economy website a decade ago, so immediately compelled I was to see a connection to our biosolids profession's mission of environmental stewardship. Two years back I wrote a piece on biosolids as part of the circle of life, starting out with a quotation from New-Age philosopher Deepak Chopra. I have a website launched to celebrate the “gospel” of biosolids recycling, The Resource Circle, and, even though I haven’t promoted it with a full-out effort, the site has already attracted a few detractors.  You see, I am “all in” with this "circle" concept.

You can imagine my instant interest, then, in the front cover feature of the June 27th issue of Chemical & Engineering News --”Closing the loop on material recycling: Big brands and regulators seek to jump-start the circular economy.”  While one article dealt with challenges faced by brand-name clothing manufacturers, the pertinent article for our profession is “Europe circles the circular economy,”  

While the U.K. and the European Union have a vigorous political dialogue underway with Brexit, between its chemists and environmentalists is a vigorous science debate on how to implement a Circular Economy.   The European Commission launched in January 2016 its “Circular Economy Strategy,” in a public summary report entitled Closing the loop: New circular economy package. 

This initiative has very ambitious goals for 2030. One of these, to my mind, has “biosolids” written all over it: “The action plan for the circular economy aims to 'close the loop'…. This production and consumption model is based on two complementary loops drawing inspiration from biological cycles: one for 'biological' materials (which can be decomposed by living organisms) and one for 'technical' materials (which cannot be decomposed by living organisms). In both cases, the aim is to limit the leakage of resources as much as possible.”

We, especially, don’t want biosolids leakage.

The tagline to the C&E News article was particularly provocative. It said: “Tempers flare over how to deal with hazardous chemicals in closed loop systems of the future.”  The “flared tempers” have direct parallels to biosolids issues.

The article reported:  “Environmental activists say the 169 substances of very high concern, which include some phthalate plasticizers used in flexible PVC, that are already controlled under the EU’s Registration, Evaluation & Authorisation of Chemicals (REACH) chemical management law, should be automatically excluded from recycling systems under any circular economy legislation.”

The person representing chemists at the Helsinki Chemicals Forum in Finland is Peter Smith, executive director of product stewardship for the European Chemical Industry Council.  He said: “The devil is in the details…”  The article points out that “one devilish detail is which chemicals would be included in closed-loop recycling systems and which would be excluded on grounds that they present an unacceptable hazard to society.”  In Helsinki, Smith argues “Inclusion or exclusion should be made on a case-by-case basis by looking at costs and benefits.” The environmentalists yelled back, literally.

Herein lies the dilemma. Can there be an a priori sorting of good versus bad chemicals in products present tin today’s marketplace which dictate which loops are closed and which are not? Is biosolids in or out of the loop-closing exercise when such a priori choices are made?

I say they are well within the loop based on sound science.  From a public policy and opinion basis, and perhaps even from a science basis, the answer is still an open  one.

Work still lies ahead to close the loop regarding the effect of chemicals on loop-closing projects.  Europe’s Commission says the loop-closing effort needs to meet three simultaneous conditions:

1. Manufactures and government need to show they can adequately “characterize the health and environmental effects of thousands of chemicals, with new molecules constantly being developed.
2. ”Regulators and policy makers need to “…create market signals and framework conditions that will encourage rapid adoption of new technologies and practices.”
3.  Government and business need to activate in the market place for “sustainable consumption on a large scale.”

The European community has jumped out ahead on this project of almost mind-numbing complexity. Where is the U.S. in all of this?

While environmental policies have not been so clearly framed in terms of loop closing, a few such compatible initiatives live in the U.S.   To advocate for the design of sustainable “green products,” the Product Stewardship Institute brings together manufacturers, the waste industry and government. One of PSI’s advocacies is for adoption in the U.S. of a 15-year-old European initiative called Extended Producer Responsibility (EPR) laws. PSI is thinking pharmaceutical take-back programs, for instance -- a good thing for those of us who see the consequence of drugs flushed to the sewer.  To promote use of sustainable products, the Sustainability Consortium, constituted by many trade associations, large manufacturers and a few “civil society” organizations, claims “Members play an essential role in helping us get closer to achieving our mission to improve sustainability of consumer goods at scale.” It would be great for our industry when, for example, flame retardants and anti-bacterial compounds are phased out of use.  To create a commercial marketplace, Sustainable Purchasing Leadership Council, supports procurement standards for green products.    

How can the biosolids profession get into the loop-closing game?

What if we biosolids practitioners were to join the “closing the loop” movement by demonstrating that biosolids are a part of the emerging “bioeconomy,” in contrast to the “fossil economy.” We, too, could help produce fun videos explaining how our biosolids-based products are good for communities and the environment, as the Brits did with the YouTube animation “The bioeconomy starts here!”  We, too, could get our biosolids-based materials classified as a “biobased products,” or perhaps even designated by the USDA as “biopreferred.”

What if we leaders of the nation’s wastewater systems were, with a coordinated voice, to take part in the “activation of sustainable consumption on a large scale”? As organizations that serve every flushing customer, which is everybody, we could ask them to choose products and practices that improved the quality of their community’s biosolids, earning them the privilege to “close the loop.”  

To date we have been strangely silent in the kind of debate that was reported in Helsinki of how to deal with persistent pollutants, but we can reverse that silence, and put ourselves on the side of the activists as beneficiaries of reduced use of persistent organic chemicals in consumer products.

We need New Ideas to Close the Circle. 

The Great Turning with Biosolids

Joanna Macy, 86-year-old Buddhist environmental activist, was featured in a podcast this week introducing her  “The Great Turning.”  By this she means a turning away from exploitation and extraction, and toward a uniting of people with their Earth.  I think her global vision can speak to us biosolids managers, where the nutrients we gather from people are reunited with Earth.

I have embraced “closing the circle” as a positive paradigm for biosolids resource recovery. Macy’s exhortation for a wholehearted commitment to humanity’s just and safe relationship to Earth reminded me of two issues that, with biosolids recycling to soil, niggle at me, just a little – microbial risks and persistent organic pollutants.

I am entirely confident that the scientific record exonerates biosolids today from meaningful risk of harm to humans and the environment and entirely supports my commitment to recovering biosolids for the purpose of soil improvement.  Yet, I also read of the performance of innovative technologies that enable us, tomorrow more so than yesterday, to eliminate microbial risks and organic pollutants. Perhaps these targets are not mandated by regulation, in particular not the 23-year-old Part 503 regulations. And, perhaps these new technologies are more costly and risky than those our industry have used for 100 years. But they are compelling in their high quality performance and biosolids product.

The promise of a leap forward in technology was the big message of Bill Barber’s presentation to the MABA Summer Technical Symposium in Baltimore. He had me “rethinking” the creative potential ahead of us to deploy high-performance processes as a turning toward a wholehearted commitment to highly stable biosolids.  There is not just one way to do this. In fact, Barber suggests that our fascination with thermal hydrolysis pretreatment for digesters is akin to putting decorative decals on a Model T Ford. You can see Barber’s MABA’s presentation on what may lie ahead for us in digester technology:  “RETHINKING ANAEROBIC DIGESTION TO COMPLEMENT 21ST CENTURY DRIVERS”. 

In diving deeper into Barber’s concepts, I came across the European-based “ROUTES” initiative, which has evolved as a tool to achieve Europe"s “safe sludge matrix.” The global conversation around ROUTES was sparked in October 2012 with a technical gathering in Rome, Italy. NOVEL PROCESSING ROUTES FOR EFFECTIVE SEWAGE SLUDGE MANAGEMENT.  I learned in the paper ROUTES: innovative solutions for municipal sludge treatment and management that the “project is addressed to discover new routes in wastewater and sludge treatment which allow: (a) to prepare sludge for agricultural utilization by transforming it in a very clean and stabilized product with respect to hygienic aspects and phytotoxicity;….” To my ear, this sounds all the world like the principal motivation for the WE&RF High Quality Biosolids research project.

The European champions of ROUTES have put out some extraordinary publications that take us toward “closed circle” goals in the stabilization of biosolids. 

The report by prolific female researcher from Italy, Camille Braguglia, and her associates, Quality assessment of digested sludges produced by advanced stabilization processes, found that: “Removals of conventional and emerging organic pollutants were greatly enhanced by performing double-stage digestion (UMT and AA treatment) compared to a single-stage process as TT; the same trend was found as regards toxicity reduction.”

Double-stage digestion is neither new nor extremely risky. Reaffirming Bill Barber’s assertion in his paper from Baltimore, the ROUTES team concluded: “These results confirmed that temperature-phased anaerobic digestion systems could show better performances and higher process stability than single-stage mesophilic or thermophilic processes, carried out under the same operative conditions.”

The ROUTES team looked at a wide variety of other digestion approaches.  One approach was to attempt higher organic loadings to the digester, meaning smaller digesters and more room for co-digestion of sludges with trucked-in wastes.  In the article The impact of sludge pre-treatments on mesophilic and thermophilic anaerobic digestion efficiency: Role of the organic load the authors wrote that “at higher organic loads, the TAD [thermophilic anaerobic digestion] yields were significantly higher with respect to the MAD [mesophilic anaerobic digestion] ones, assuring the sustainable economic benefit of operating smaller anaerobic digesters to obtain higher methane production.

The ROUTE group looked at pre-treatment ahead of digesters, noting the different functionality of different processes: “Thermal hydrolysis enhanced the release of lipids and long chain fatty acids, while ultrasounds application resulted in proteins being the main component of the released matter.”

With the ROUTE group objective of meeting multiple goals for product stability, energy balance and dewaterability, but also importantly hygienization, they described in Enhanced Versus Conventional Sludge Anaerobic Processes: Performances and Techno-Economic Assessment the following findings: “The TPAD [two-phased anaerobic digestion] proved to improve the overall process by enhancing the individual steps (Francioso et al., 2010), and had the advantage to be operated at high loading rates (Azbar et al., 2001). At the same time the short thermophilic step did not guarantee total hygienization (Huyard et al., 2000). For this reason, in this work, an inverse TPAD (meso/thermo) is proposed, where the mesophilic acidogenic step is followed by an intense methanogenic step in thermophilic conditions aimed to achieve higher methane yields, obtaining a final hygienized product suitable for land application.”

In one experiment, WAS is treated with a physical disintegration process, sonication, and then put through temperature-phased anaerobic digestion (TPAD), but inversed, as described above, to have the feedstock treated with a mesophilic acid phase followed by a high temperature gas phase.  In a second experiment involving dual digestion, primary sludge is treated with wet oxidation, and the secondary sludge is treated with thermal hydrolysis, then combined for thermophilic digestion.

Wet oxidation?  I needed to look that up (Wet oxidation of sewage sludge: full-scale experience and process modeling).

One key driver for ROUTES is hygienization.  Standards of treatment go beyond indicator fecal coliform to include a higher test of virus inactivation.  Researchers concluded that viral inactivation requires higher temperatures in the thermophilic digester than those conventionally targetted: “…our study confirmed the higher resistance to thermal treatments of viral particles with respect to bacteria indicating the low reliability of bacteria as an indicator of virus fate at temperature greater than 55 °C…. In contrast to what was observed with bacterial indicators, the removal of viral indicators to below detection limit was observed only at high temperature in the TH+TAD [thermal hydrolysis followed by thermophilic anaerobic digestion] processes confirming, in agreement with other studies, that temperatures above 80 °C are necessary for an efficient inactivation of viruses.” 

ROUTES also showed that biosolids quality made a difference to the evaluation of technologies.  The lowered cost of disposal of the high-quality biosolids and the greater recovery of energy for biogas released during digestion were two factors that justified the more costly equipment.  Measures of phytotoxicity and the soil-like quality of the residuals sold the biosolids for agricultural users. Even though new treatment practices required electricity input, the extra biogas production yielded electricity production above that additional need.

Yet, the ROUTES researchers worked through some troublesome areas.  Thermophilic systems can be harder to operate, harder to keep stable and difficult to avoid foaming and rapid rise.  The ROUTES paper Microbial diversity in innovative mesophilic/thermophilic temperature-phased anaerobic digestion of sludge explained that “thermophilic communities may be therefore more susceptible to sudden changes and less prompt to adapting to operative variations.” They also pointed to the release of difficult-to-dewater COD.  The impact of sludge pre-treatments on mesophilic and thermophilic anaerobic digestion efficiency: Role of the organic load  noted that “Nevertheless, the colloidal charge increase during thermophilic digestion impaired the sludge filterability much more rapidly than in mesophilic conditions.”

The mind boggles at all of the combinations and complex options for stabilization that have emerged recently for serious consideration by public agencies.  The most notable for its recent U.S. implementation is Cambi’s Thermal Hydrolysis Process at DC Water, but Trinity River Authority outside Dallas and Hampton Roads Sanitation Authority in Virginia Beach have announced plans to move ahead with Cambi. At the MABA meeting, GE Power described its Monsal biological hydrolysis system, and Ovivo provided case studies of six high-tech aerobic digesters. At last November’s MABA Annual Meeting, Veolia described European examples of advanced digestion, and we heard there also of Suez’s TPAD (temperature phased digestion) at the Hermitage (PA) Municipal Authority, where it is deployed for a very serious program of co-digestion.

This is just a start, I believe. I predict that within 20 years the common practices for biosolids stabilization will include a number of sequential digester systems that we see today as experimental.  This is inevitable because the early results in the lab, at pilot plants, at reference facilities, and in full scale in Europe, in terms of mass reduction, pathogen control, pollutant reduction, and product stability are very compelling, far above and beyond Part 503 standards requirements, but so much closer to our vision as environmental stewards toward “closing the circle” in our community.  I feel underway the Great Turning to High Quality Biosolids.

One Water, One Residual

WEFTEC in New Orleans introduced me to a new theme in our water industry: ONE WATER.

This was the main theme for the new WERF, that is WE&RF: the new Water Environment and Reuse Foundation.  Most of you recognize WERF as the Water Environment Research Foundation. But you may not know the other Alexandria- based group called WRRF, or the Water ReUse Research Foundation. Two groups with such homonymous and mission similarities would make a synergistic merger as WE&RF seem, in retrospect at least, obvious. And that is what they did this summer. This important development is described in a recent WEF article: WERF and WateReuse Merge To Advance Concept of One Water.

The new executive director for WE&RF, Melissa Meeker, said in a WEF article: “for the utility of the future that seeks to maximize recovery and deliver fit-for-purpose water…[a] “One Water’ concept emphasizes that water quality is our focus, not the history of where the water has been … [This] will have a positive impact on the public’s understanding of water quality issues in general.”
But do biosolids, in the case of wastewater, and brine, in the case of reuse processes, fit into ONE WATER? Not really.

How about “ONE RESIDUAL”? 

Many of us have already played with the notion that biosolids deserves to play in the same sandbox as manure and other organic residuals. We took on many years ago the regulatory discrimination of biosolids made part of the USDA’s National Organic Program, and lost, salving our feelings with the notion that this was a marketing decision, not a science-based decision.
More recently there was Whole Foods. We were alerted to its pending “policy” on biosolids [Whole Foods to stop selling produce grown in human sewage sludge], which was pressed on them by the same group, PR Watch, that brought you Toxic Sludge is Good for You program. But we again faced a marketing campaign that had no interest in considering scientific and rational arguments. A quick tour of the CDC’s Food Safety News will give you the source of real health risks from food (General Mills flour and E coli…. Hmmm, how did that happen?), and that risk isn’t from biosolids. Occasionally “organic” products show up in the CDC site. But when it comes to biosolids, the marketing people at the USDA and Whole Foods just aren’t interested in science.

So we sucked up the National Organic Program and Whole Foods, and moved on. Perhaps we would find better public acceptance if we were to partner our biosolids with food scraps and yard wastes. The current enthusiasm for co-digestion and “intensification of resource recovery” as features of municipal WRRF services may well be more than a play for tipping fees, but arise from a sincere desire to be of greater service, to be in a bigger tent to achieve community sustainability.

There are examples of big-tent organizations, and composting seems to attract them. I like the unifying approach of the California-based Association of Compost Producers. Its executive director Dan Noble has been a champion for a “one organics” approach, at least with respect to the feedstocks used in composting. He focuses the ACP, which is a state chapter of the US Composting Council [if you don’t know of the USCC’s quality assurance program, the Seal of Testing Assurance, or its program to train and certify composters, check it out], on the quality of the output compost product and on its soil-building performance. The focus of this organization is captured in the inspiring tagline -- “We Build Healthy Soils.” Noble argues for the “one-ness” of the feedstock, and he defuses the tendency of some composters among ACP's membership to market products with a “contains no sewage sludge” feature on the label. He also focuses on the BENEFITS of the output, not on the character of the input. This is a lesson the biosolids profession is still learning.

Noble is also the conceptualizer of a “bioproducts market,” with feedstock, technology and products comprising three legs. His background analysis contains estimates that show biosolids is a mere 1 percent of the total organic biomass available for conversion into useful bioproducts for the marketplace. He estimates that over two-thirds of the biomass in the US and Canada is animal manures. Our industry’s paltry 7 million dry tons annually of biosolids contrasts to the 500 million dry tons of animal manures.
Oh my! How can we confirm this wide gap in tonnages when there is no “Manure Environment Federation” nor a “National Manure Partnership?” 500 million tons annually of manure apparently is not sufficient to cause a professional organization to be formed, as we have with wastewater and biosolids. This is sarcasm.

The gap in attention to the elephant in the room of biomass -- manure -- is not because science has shown manure to be safe and without environmental effects. The gap more likely arises, in my opinion, as the end-game of a political sacred cow. Research into manure's environmental and health effects is thereby not well funded. Google Scholar, when I searched for “environmental effects of biosolids” came up with 16,400 references, and when searched for “environmental effects of animal feedlots” (which I liken to municipal treatment plants) came up with 15,100 references. Seventy times the biomass, but a lower count on research.

Where can we learn of the effects of manure on the environment and human health?
Few national summary reports are available on the topic of environmental effects of concentrated animal feedlots. One such is Understanding Concentrated Animal Feeding Operations and Their Impact on Communities, prepared by the National Association of Local Boards of Health. It concludes that local health officials have very many reasons to be alert to CAFOs.

What about the effects of manure on the safety of food crops? 

The FDA has the regulatory authority for leadership in this area, but this terrain has proved a political minefield. For some insight, look at “What Is FDA Doing to Promote the Safe Use of Manure and Compost on Crops? Questions and Answers with Michael Mahovic” (head of FDA’s Consumer Safety Division). FDA originally proposed regulations calling for manure stabilization prior to manure's use as fertilizer for human food crops, but FDA was compelled to back off until "more science" could be supplied.
The science of manure and the science of biosolids should share considerable common ground. For instance, how does research into manure compare to research on biosolids on the lively topic of TOrCs (Toxic Organic Compounds)? In biosolids we have many dozens of papers, and WE&RF has a couple of projects completed and in the pipeline. But what is known about TOrCs in manure? 

Not as much as one might hope. This is from an abstract of a literature review for December 2016 publication (already?!), Occurrence and transformation of veterinary pharmaceuticals and biocides in manure: a literature review : “Within the 27 evaluated publications, 1568 manure samples were analyzed and 39 different active substances for VMPs [veterinary medicinal products]and 11 metabolites and transformation products of VMPs could be found in manure. Most often, the samples were analyzed for sulfonamides, tetracyclines, and fluoroquinolones. Not one study searched for biocides or worked with a non-target approach. For sulfadiazine and chlortetracycline, concentrations exceeding the predicted environmental concentrations were found.”

Similarly, In the 2015 paper, Human health risk assessment of pharmaceuticals and personal care products in plant tissue due to biosolids and manure amendments, and wastewater irrigation, researchers say health risks are de minimus, which is good, but qualify that with “work needs to be done to assess the risk of the mixture of PPCPs that may be present in edible tissue of plants grown under these three amendment practices.” Yes, and we know that the avenues of inquiry are numerous, but from where will the research funds come except from interest groups demanding more research into impacts of manure.

The new WE&RF is not likely to take on manure research, even if it would be a help for advancing the science behind biosolids recycling. Our professional association is already aligned with manufacturers and suppliers to the agricultural and food industries. We already have a media champion in this area, BioCycle Magazine. This encourages me to boldly recommend that biosolids professionals reach out to other sectors beyond WEF and the WateReuse Association and develop its own organizational champion to cover the bioproducts marketplace, say the National Organics Recovery Association (this is for you, Nora Goldstein) perhaps embracing the tagline: One Residual.

Ancient Network Intelligence

I was enthralled by the interview with forest scientist Suzanne Simard on the Radiolab podcast From Tree to Shining Tree, in which she boldly claimed that the communications network of fungi and tree roots constituted a type of “intelligence.”  Then I discovered her TEDTalk, How trees talk to each other,  which has had over 1 million viewers. This is exactly my kind of story; where had I been?  Her research has shown that “trees talk, often and over vast distances.” Importantly, they share “resources” in the form of carbon and nutrients over wide swatches of forest.  Mediating this amazing underground communication network are fungi. Their networks hidden in the soil are analogous to the nerve networks in the human brain, according to Simard.

Dr. Simard offhandedly commented that fungi are a complex life form. I checked with Wikipedia, and learned several amazing things.  I read that in today’s understanding of the “tree of life,” while bacteria and archaea each occupy its own domain, the domain of multi-cellular life, the eukaryotes, are now categorized by supergroups (modern classification experts are moving away from the term “kingdom”). One supergroup contains plants, and another supergroup contains animals and also, believe it or not, fungi. Get this, according to the International Society of Protistologists, (reported in Wikipedia) humans have more in common genetically with fungi that they do with an oak tree.

The key to Dr. Simard’s work is micorrhizal networks, or the mediation by fungi of the movement of food and of other signals between plants vascular plants.  In her 2004 research paper Mycorrhizal networks: a review of their extent, function, and importance  she asserts “mycorrhizal networks have the potential to influence patterns of seedling establishment, interplant competition, plant diversity, and plant community dynamics, but studies in this area are just beginning.”  And she has continued to work prodigiously over this past decade.

In digging into this topic, I learned another amazing fact.  These mycorrhizal networks are as old as dirt, literally.  According to Four hundred-million-year-old vesicular arbuscular mycorrhizae “… the existence of arbuscules in the Early Devonian indicates that nutrient transfer mutualism may have been in existence when plants invaded the land.”

The importance of fungi to the health of ecosystems is now understood to have been a big deal for a very long time.

And this got me thinking of some of the recent work on soil health, a topic which has become very fashionable.  Cornell just released its Comprehensive Assessment of Soil Health – The Cornell Framework Manual (3rd edition 2016).  The tests offered in this protocol included microbial respiration rate and a measure of an esoteric parameter glomalin, first described by scientists just a mere twenty years ago. Here is Cornell’s definition:  “Glomalin is a glycoprotein produced abundantly on hyphae and spores of arbuscular mycorrhizal (AM) fungi in soil and in roots.”  Ah, hah! Glomalin is a measure of fungal activity.

Arbuscular mycorrhizal fungi, AM fungi, by most accounts are the organisms doing the heavy lifting in connecting plants to soil and to nutrients in a healthy ecosystem.  Apparently, if you have lots of glomalin you have lots of AM fungi and you have healthy soil. At least that is hypothesis, one not fully vetted.

The question for us: does land-applied biosolids improve or hurt AM fungal populations and, hence, glomalin levels in soil?

The recent research findings have been good to biosolids. A first pass at the question had raised some concern that biosolids suppressed AM fungi, but this was not seen in subsequent study. In the recent study,  Temporal variation outweighs effects of biosolids applications in shaping arbuscular mycorrhizal fungi communities on plants grown in pasture and arable soils, researchers determined that “biosolids application in agroecosystems did not affect mycorrhizal fungi diversity, [nor did biosolids] affect percent root colonisation of arbuscular mycorrhizal fungi.” 

Other researchers looked specifically at persistent toxic compounds in biosolids for an effect on AM fungi, and again no adverse effects were seen. In, Effect of biosolids-derived triclosan and triclocarban on the colonization of plant roots by arbuscular mycorrhizal fungi,  researchers showed: “A relationship between the concentration of triclosan or triclocarban and colonization of plants roots by AMF was not observed. Biosolids-derived triclosan and triclocarban did not inhibit the colonization of crop plant roots by AMF. [Further,] biosolids had a positive effect on the colonization of the roots of lettuce plants.”
The bottom line is that, if good fungal functioning is an important parameter of soil quality, then biosolids is at least not a negative factor.

Many of us who work with biosolids believe the case is just the opposite, that biosolids is a strong positive ingredient when applied to soil.

We know from generations of agronomic researchers that, at a minimum, biosolids can meet most basic crop nutrient needs.  This is well documented, as in Washington State’s “Managing Nitrogen in Biosolids.”    

Further, our research into the microbiology of biosolids recycling has us address the synergy between biosolids and soil, as when soil microbes assist with the attenuation of biosolids-borne organisms.  Even though it is a well-known process, we can be gratified that recent research confirms this: Influence of soil type, moisture content and biosolids application on the fate of Escherichia coli in agricultural soil under controlled laboratory conditions reports that “soil ecological mechanisms are implicated as having a critical role in the fate of enteric organisms introduced into temperate agricultural soil in sewage sludge.”
How biosolids affects soil health is “fertile” research ground even today.   While we intuitively understand biosolids benefits, scientists are looking for performance measures in soil health. This is not just for biosolids, but also for a full sweep of agricultural practices and nutrient sources.  As explained in Understanding and Enhancing Soil Biological Health: The Solution for Reversing Soil Degradation  “biological relationships are by far the most complex with large deficiencies in basic understanding. Many new tools and techniques have been or are being developed, thus making it more feasible to unravel these complex systems. desperately needs to meet the rapidly increasing food, feed, fiber, and fuel needs of an expanding global population.”

Research is underway today on this topic of how biosolids effects soil health.  Virginia Tech agronomist Greg Evanylo has devoted his research career to this topic, not only for biosolids, but for a wide array of fertilizers, composts, manures and residuals. An example of a practical application of his research is: “Agricultural Management Practices and Soil Quality: measuring, assessing and comparing laboratory and field test kit indicators of soil quality attributes.”  Dr. Evanylo is on the WERF High Quality Biosolids project research team that is exploring several specific biosolids formulations. His project is intended to show how biosolids can be prepared for use in improving the health of urban soils.  With DC Water launching its new biosolids product, Bloom, this research has special relevancy.

Exciting times are ahead as we illuminate how biosolids helps sustain communications between soil and roots, which, when mediated by our cousins the fungi, is, in my mind, a wonderous manifestation of an ancient Network Intelligence.

The Miracle of Life... in Digesters!

RadioLab’s program Cellmates this past week was mind-blowing. UK biogeochemist Nick Lane put forth the hypothesis (The Vital Question: Energy, Evolution, and the Origins of Complex Life) that the explosion of multicellular life some 2 billion years ago was a singular event in Earth’s history, an event of vanishingly small probability, having never again occurred over the 2 billion years. This event was the merging of an archaea-type organism and a bacteria-type organism, resulting in a successful, collaborative union. This solitary union, a singular event, gave rise to all plant and animal multicellular life on Earth, from ferns to jelly fish to me. What is more, the chance of such a collaboration is so improbably small that it might not be expected to occur anywhere else in the universe. At least, that is how I understood Dr. Lane.

The improbability of multi-cellular life is, in my mind, even more mind-blowing than the explanation of the origins of life itself, put forth by George Mason University earth scientist Robert Hazen in his Great Courses lecture series (The Origin and Evolution of Earth: From the Big Bang to the Future of Human Existence). Hazen describes a global oceanic soup replete with nucleic acid polymers, formed by chemical reactions on reactive minerals surfaces, existing for a hundreds of million years, in which by an exceedingly rare chance event a self-replicating “living” DNA strand was formed, which then exploded across the face of Earth. This emergence of “life” occurred some 3.5 billion years ago, evolving over some 1.5 billion years into a soup of prokaryotic cells, many within the remarkable kingdom of life, Archaea. Also in that primordial soup were Bacterium, that other great “domain” of single-cell, non-nucleated prokaryotes.  It was the merger of a single archaea organism with a single bacterium of which Dr. Lane spoke on RadioLab.

Archaea… this is the kingdom that includes the methanogens we have embraced with child-like enthusiasm, as evidenced at our recent WEF specialty conference in Milwaukee.  I am probably the only one who stepped back from our profession’s precious attention to biogas and contemplated with wonderment that human beings are a highly evolved form of a bacteria-infected archaea cell.

Archaea are indeed pretty special.  We have learned a lot about them since science first uncovered their existence four decades ago.  But I believe we have many surprises ahead for their potential role in wastewater and biosolid treatment.

Between papers at Milwaukee, I rudely poked my head over the shoulders of Josh Mah, PhD candidate from Virginia Tech, and Peter Loomis, CDMSmith, both working with DC Water’s digesters, as they pored over charts of qPCR results of sludge samples from within DC Water’s digester start up. Communities of archaea and bacteria are still evolving inside those new DC tanks, and with that evolution comes the possibility of directing their path into highly-effective methane-producing communities. For Mah, this is a task still in need of financial support (hint, hint). Nearby in that WEF conference room sat Marquette’s professor Daniel Zitomer, a key researcher into the biology of digesters, and the first person from whom I learned several years back that each digester harbored unique microbial populations. We are still in the infancy of our understanding the significance of this observation.

Just as the key to life on Earth was the unlikely joining of cells, so too is the key to WEF’s Residuals and Biosolids Technical conference the unlikely joining of biosolids insights.  AECOM’s Bill Barber displayed a provocative PowerPoint slide (given in his presentation April 6, 2016, Session 14, 9 AM, “Alternative Configurations of Anaerobic Digestion and Thermal Hydrolysis To Enhance Performance”) equating the use of thermal hydrolysis with digesters to that of a Model T Ford decaled with racing flames. I had an “Ah-Hah!” moment when Barber pointed out the wrong-headedness of our industry’s practice of continuously overflowing slow-growing, hard-working archaea methanogens out of the anaerobic digesters, in contrast to our careful cultivation of activated sludge bugs. So, this put an exclamation point to the reasonableness of Alan Cooper’s proposal to use recuperative thickening (April 6, Session 14, 10 AM, “Achieving Advanced Digestion Using Recuperative Digestion Options”), in a return of both bugs and organic food to the digesters.  The “over-the-top” attention at the WEF conference for co-digestion makes more sense now to me as a way of balancing the nutrient and energy needs of archaea organisms in the digesters rather than as a way of boosting electricity production and struggling with waste heat.

Microbial science is the future of biosolids and, more generally, wastewater treatment.  The inquiry is clearly international and has burgeoned forth in the scientific literature over this past year. I already mentioned Marquette’s Dan Zitomer.  His 2015 paper “Relating Methanogen Community Structure and Anaerobic Digester Function” demonstrates the immediate relevancy of this microbial work: “nearly identical digesters can produce more methane than others because the microbial communities are more suited to produce methane rapidly.“ In a similar vein, Japanese researchers say it straight away in their article title: Canonical correlation analysis and variance partitioning analysis implied that bacterial and archaeal community variations were significantly affected by substrate and the operation conditions.  An Italian team explains “the applied method is suitable to describe microbiome into the anaerobic reactor, moreover methanogen concentration may have potential for use as a digestion optimisation tool (Traversi, et al. Application of a real-time qPCR method to measure the methanogen concentration during anaerobic digestion as an indicator of biogas production capacity.)  A Chinese researcher team asserts that “[t]he knowledge garnered would facilitate to develop more efficient full-scale anaerobic digestion systems to achieve high-rate waste sludge treatment and methane production” (Dissecting microbial community structure and methane-producing pathways of a full-scale anaerobic reactor digesting activated sludge from wastewater treatment by metagenomic sequencing).  

This current research on the microbiology of anaerobic digestion soon may have direct impacts on process design.  Again, Bill Barber, who is back in the States from a stint in Australia, explained in his review presentation in Milwaukee that superior sludge digester performance occurred with the sequencing of mesophilic digesters, even when compared to pre-treatment with thermal hydrolysis. That this effect aligns with the emerging science of microbial populations is borne out by research in Singapore. The research report Determination of the archaeal and bacterial communities in two-phase and single-stage anaerobic systems by 454 pyrosequencing  evaluated the microbial communities of “2-Phase anaerobic digestion (AD), where the acidogenic phase was operated at 2 day hydraulic retention time (HRT) and the methanogenic phase at 10 days HRT.” 

The application of microbial science will also help with co-digestion.  A recent journal article reported on an 18-month long monitoring period for a co-digestion facility by a Welsh team: “Monitoring methanogenic population dynamics in a full-scale anaerobic digester to facilitate operational management.” The message for me was that without use of new tools for studying microbial communities, our foray into co-digestion will be sub-optimal and trial-and-error at best.

I have no doubt that the future design and operation of anaerobic digestion and co-digestion at wastewater facilities will be dictated by new scientific tools that measure and monitor the behavior of microbial communities. The engine of these communities are microbes that are newest to our understanding of the evolution of life on Earth, and newest to our understanding of sludge digestion, but among the very oldest on Earth, the Archaea. Oh my, the life in biosolids is a miracle!