Biosolids Roots

Roots, I have really been into them this past year – roots of all kinds. Science articles describing fungal networks that connect tree roots within a forest have thrilled me (Social Life of Forests). I planted 3.5-inch diameter white oaks, one in honor of each grandchild, in hopes that the oaks grow into future legacy trees connecting my “roots” to the next century. I also provided the grandkids a chart that connects them to their roots 11 generations back to 14-year-old John Cooke on the Mayflower in 1621.

My interest in roots extend also to biosolids. I have been tracking the hypothesis that the special effects of biosolids on plant growth are through its benefits to root growth. The article Biosolids Impact Antioxidant Metabolism Associated with Drought Tolerance in Tall Fescue opines that “ the biosolids may enhance plant antioxidant defense systems through providing certain BAS such as auxin to the soil or by providing organic substrates for soil microbial production of growth hormones… improving turfgrass performance when faced with periodic abiotic stresses such as drought.” I am also tracking the hypothesis that pathways of potential environmental and human health effects from toxic organic compounds (TOrCs) are mediated by their interaction with plant roots. The research team at MWRD of Greater Chicago authored A Framework to Predict Uptake of Trace Organic Compounds by Plants, and this work was extended in 2020 by Water Research Foundation report Knowledge Gap Analysis for Plant Uptake Models. The big picture is that a rather narrow number of contaminants of concern in biosolids are likely to pass into plants via root membranes. Unfortunately, perfluoroalkyl substances (PFAS) are among that narrow number.

PFAS is a “root cause” for today’s anxiety with biosolids management. A public WRRF that receives via its sewer system or by tank truck wastewater that is laden with PFAS is at risk of having its biosolids be a source of PFAS contamination to water sources, plants and animals on the farms receiving the biosolids. Plant roots are no barrier to uptake in harvestable crops. Of special concern to me was the surprising evidence, contrary to my expectations, of significant plant root uptake of PFAS compounds by field crops grown on contaminated soils. Maine DEP's biosolids coordinator presented results to the EPA’s December National Biosolids Meeting from its summer 2020 investigation into a PFOS/PFOA contaminated dairy farm in central Maine. This investigation discovered dry weight concentrations of PFOA and PFOS in grass and hay that were nearly equivalent to concentrations in soil. This is a significant finding!

Aside from PFAS, is the biosolids profession at risk of discovering other contaminants of concern to crop and livestock? Assessing that risk is “at the root” of the US EPA’s “reinvestment” into the federal government’s biosolids program. Responding to a 2017 Office of Inspector General’s report, the Office of Water embarked on a program to create new tools to evaluate unregulated pollutants in biosolids and their potential for harm to public health and the environment. EPA has rolled out a Risk Assessment program and has an announced a Request for Assistance -- The National Priorities: Evaluation of Pollutants in Biosolids. The agency has mobilized a research team to evaluate methods and develop working hypotheses, particularly around PFAS and its pathways to crops and livestock. EPA has held a Land Application Field Study webinar and its National Biosolids Meeting, summarized by Ned Beecher at NEBRA.

Even though this $6 million federal investment in biosolids research is long overdue and holds promise of some important new understandings, I worry it will not provide meaningful help to biosolids practitioners. I returned to a Biosolids TOPICs I wrote in April 2020, Existential Risks in Biosolids Management, which drew inspiration from the work of philosopher Toby Ord. His book, The Precipice: Existential Risk and the Future of Humanity, was released in the U.S. on the eve of the global lockdown in March. The top existential risks Ord describes in his book are artificial intelligence unaligned with human values and engineered pandemics far worse than SARS-CoV-2. A writer for the New Yorker recently interviewed Ord for an updated viewpoint, reported in the article How Close Is Humanity to the Edge?  Ord said he was both “frightened and encouraged by our response to the pandemic.” He sees, as does the World Health Organization (Coronavirus: Worst could be yet to come, WHO warns), the SARS-CoV-2 as a “warning shot.” Ord is encouraged by the scope of international cooperation and he is frightened by the U.S.’s isolationism. His view is that existential risks ought to be understood by a global collective of people and governments, such that concerted actions to alter such risks can be made, without respect to governmental boundaries in space and, importantly, with a long view to future generations as the beneficiaries.

In my response to Ord’s The Precipice and the fragility he reported in the global economic and health systems, I observed that biosolids management in the U.S. is likewise fragile. I concluded that the “root causes” of biosolids program risks are technology failures, worker negligence and sloth, and illegal toxic releases. Answers to these risks were collaborative technology assessments, worker training and standards, and innovative means of sensing influent contamination. When I consider Ord’s recent comments, I see that in the wastewater industry we accommodate deficiencies in infrastructure maintenance and replacement, we accept inequitable resources for worker training and skills development, and we fail to persuade the public of the value of wastewater systems for the ecosystem services they provide. I believe these are the "root causes" for the major risks to our biosolids programs. EPA’s “reinvestment” in the study of unregulated organic compounds of concern are unlikely to significantly improve prospects for successful resource recovery from wastewater, as the TOrCs are not a root cause of biosolids risks.

From where might come the human ingenuity to address the genuine root causes of biosolids risks? A different kind of “root” has been an important step to addressing risks, and this is Project Routes. Project Routes was a program funded by the European Union (EU) from 2010 through 2014 that “aimed to discover new routes in sludge stabilization treatments leading to high-quality digested sludge, suitable for land application.” Its summary report Novel processing routes for effective sewage sludge management and full report Final Report Summary - ROUTES (Novel processing routes for effective sewage sludge management laid out a variety of innovations in sewage treatment that accomplished key objectives of dewaterability, disinfection, odor control, and, importantly, micropollutant degradation. Dozens of journal articles and conference presentations came out of this inter-governmental research effort in Europe. Here in the United States, this “Route” had metaphorically no soil in which to grow, and we seemingly learned little from it.

The “route” charted by the EU managed wastewater, with its long view to recovery of biosolids resources, also provided a barrier to flow of TOrCs. The report Quality assessment of digested sludges produced by advanced stabilization processes offers double-stage digestion with an aerobic element as a promising technology for reduced micropollutants. Others have looked at composting for the ability of aerobic treatment to reduce antibiotics and other commodity chemicals (see Relevant approach to assess performances of wastewater biosolids composting in terms of micropollutants removal). Capital investments made in 2020 may reasonably operate for 20 to 30 years, so treatment technology that treats TOrCs, even if not necessary to meet today’s effluent standards, is an appropriate response to a multi-generational commitment to resource recovery and the circular economy (see, for instance, Moving toward a waste-free circular economy by example of biosolids). A US EPA initiative to champion new technology “routes” could have a meaningful effect on reducing risks from TOrCs.

The Covid-19 pandemic has a one bright spot for our profession – deployment of wastewater-based epidemiology (WBE) for managing risks of coronavirus outbreaks. Several microbiologists well-known to our profession are at the forefront of WBE and advocated for techniques for monitoring biosolids for indicators of community health (How the University of Arizona used No. 2 to solve its No. 1 problem: The coronavirus).

WBE has a much larger potentiality for public health than monitoring for coronavirus. Researchers have suggested such deployment as Wastewater Treatment Plants as Chemical Observatories to Forecast Ecological and Human Health Risks of Manmade Chemicals, which can include monitoring for life style activities (Alcohol and nicotine consumption trends in three U.S. communities determined by wastewater-based epidemiology and Assessing the Potential To Monitor Plant-Based Diet Trends in Communities Using a Wastewater-Based Epidemiology Approach) and for community incidence of illegal drugs (Occurrence of illicit drugs in water and wastewater and their removal during wastewater treatment).

But the potential for WBE surveillance of influent for TOrCs could have great benefits for wastewater and biosolids managers. The Arizona State University Biodesign Institute houses the national repository of representative biosolids sample collected by the EPA for several rounds of the National Sewage Sludge survey. This institute has provided bountiful portraits of “unregulated” elements and organic compounds in these samples, leading director Rolf Halden to release a proposal for Using national sewage sludge data for chemical ranking and prioritization. As technology advances for real time sensing for contaminant chemicals in influent and biosolids, public agency managers may one day have information to make on-the-spot decisions for wastewater and biosolids treatment before the biosolids is delivered to farmlands. Once contaminated biosolids reaches the farm, risk mitigation becomes very expensive.

Getting back to the “root causes” of risks from TOrCs in biosolids, we do well to step back for the wide and long view. Biosolids is not a source of organic micropollutants; it is a sink. The use of WBE sensors and the evolution of robust treatment technologies can go only so far in blocking pathways of human and environmental exposure. “Compounds of concern” which will be reviewed in the EPA risk assessment study, if shown to comprise a meaningful risk, need to be controlled at the source of disposal to public sewers, not after biosolids production and delivery to the farm field.

We are at the edge of having an enormous capacity to manage the risks of chemicals to individuals against the benefits of their use by society. EPA maintains awesome databases of chemical use in the United States, as in its EPA: High Production Volume List, from which has been extracted the database for the Chemicals in Biosolids. Environmental releases of toxic chemicals are reported to EPA’s Toxics Release Inventory program by manufacturers around the country. But chemicals required to be reported do not include all TOrCs of concern in biosolids. For our profession, a particular irony is that only in 2020 were manufacturers required to report releases of PFAS chemicals, the class of compounds that is the root cause of the greatest risk today to the biosolids profession. Key to understanding the effects of chemical use and environmental releases is embodied in Fourth National Report on Human Exposure to Environmental Chemicals, a document that demonstrates reductions in blood levels achieved by regulatory restrictions over use in consumer products of chemicals in such biosolids-contaminating classes as brominated flame retardants (PBDEs) and antimicrobials (e.g., triclosan). Understanding the risk of society’s use and release of commodity chemicals to all media -- air, water, and land – are much more possible with today’s data systems than in the past, as is argued in the journal article Data engineering for tracking chemicals and releases at industrial end-of-life activities.

Biosolids is the mostly hidden component of the vast flow of chemicals through our economy and ecosystems. In “before times,” biosolids was at the far end of the conveyor, at the end of the process diagram, dropping into a truck, destination unlabeled. This vagueness is now dispelled. Today’s community of far-thinking engineers and technologists, creating the future of environmental stewardship, are seeing the necessity to interconnect flows of elements and energy, returning vital nutrients to the soil as a primary goal, in a circular economy. This vision includes managing the release of chemicals that interfere with the interconnections, drawing on such principles as product stewardship and extended producer responsibility. While the fate of TOrCs in the soil ecosystem deserves a scientific explanation in the near term, in the long view, life on Earth urgently requires Biosolids at its Roots.