Biosolids and Catastrophism

I blame the Amazon gift card and Amazon app on my iPhone. Together, they make my impulsive purchase of another book of environmental catastrophism far too easy. I was primed for this purchase by the sense of dread from reading on my cellphone the NY Times environmental news briefing. The story What Was Said at Davos on Climate Change, led to How trees could help to save the climate, and then to the discouraging why tree planting is a bad idea. So, when I was presented with a push notification for Climate Leviathan, my mindless, fear-based reaction was to perform an Amazon “one-click” and the next day the book was at my door. I started in:  “The political problems we face cannot be fixed by simply delivering science to the masses.” Well, yes, science may be an inadequate tool for overcoming the growing sense of environmental catastrophe, but without science, we are lost, right??!

I had just revisited my article in NYWEA’s winter 2019 ClearWaters magazine, “Biosolids: Understanding the Invisible Evils that Keep Us Awake.” The magazine also well covers the “numero uno” cause of biosolids catastrophism, namely polyfluoroalkyl substances (PFAS), a class of compounds present everywhere, but also in biosolids. My noble aspiration was to prove that, even with so fearsome an opponent as PFAS, soil processes, when combined with our wastewater treatment system, can be an effective barrier to the flow of so many of society’s TOrCs, or toxic organic chemicals.

As for PFAS, science shows us that loadings of PFAS to wastewater plants and the consequent concentration levels in most biosolids are low (Mass Loading and Fate of Perfluoroalkyl Surfactants in Wastewater Treatment Plants  ), below levels constituting a risk. But even at the relatively low concentrations present in biosolids, PFAS can leach from biosolids and arguably contribute to existing PFAS loads in the groundwater. See these articles: Loss and in situ production of perfluoroalkyl chemicals in outdoor biosolids–soil mesocosms and Environmental risk assessment of perfluoroalkyl substances and halogenated flame retardants released from biosolids-amended soils.  Research has shown uptake into plants and animals.  See, for example, Uptake of perfluoroalkyl substances and halogenated flame retardants by crop plants grown in biosolids-amended soils and Bioaccumulation of emerging organic compounds (perfluoroalkyl substances and halogenated flame retardants) by earthworm in biosolid amended soils). Biosolids-specific research on PFAS is arguably incomplete, and environmental catastrophism generates the political pressure to take regulatory action even without science.

Could it be that PFAS in biosolids is just one more of the biosolids pollution “fads” we have witnessed over the years? When I checked in with Ned Beecher, our biosolids protector in the field of PFAS, he suggested that, as a broad awareness of PFAS had begun to consume society, the focus on biosolids has, too, somewhat subsided. For the time being, public concern for PFAS has, in a way, “sucked the air out of the room” for consideration of other contaminants.

I had this thought. While the spotlight is on PFAS as an environmental catastrophe, ought biosolids practitioners strive to get ahead with research on other biosolids-borne TOrCs, and their impacts on soils and crops? I reviewed the eminent 2010 report Trace Organic Chemicals in Biosolids-Amended Soils: State-of-the-Science Review (WERF Report SRSK5T09). In italics, in the final chapter, the report concluded: “Very few studies were identified that were intentionally designed to address the fate, transport, bioaccumulation, and toxicity of TOrCs in biosolids-amended soils under well-controlled conditions. The most significant data gap, however, is the absence of human toxicological and ecotoxicological data as well as biotransfer data for ecological receptors.”

When I went to my favorite science source, Google Scholar, I could find few articles that demonstrate that our profession took up this recommendation in any serious way. When it came to the environmental fate of PPCPs (pharmaceutical and personal care products), for instance, the number of research papers that have been published globally around biosolids and PPCPs has pretty much flat-lined over the decade at about 300. One science colleague observed: “the general hysteria on that front is gradually subsiding… There has also been a general recognition that potential for human harm is nonexistent.”

Still there has been progress. Over the decade since 2010 report, a few of the notorious, persistent TOrCs have been given additional study. These include compounds such as triclocarban (Fate of triclocarban in agricultural soils after biosolid applications), PCBs (Four decades since the ban, old urban wastewater treatment plant remains a dominant source of PCBs to the environment), and polybrominated diphenyl ethers (PBDEs) (Polybrominated diphenyl ethers: Residence time in soils receiving biosolids application).  

We have also had research into the fate of soil-applied antibiotics. The article Risk assessment of biosolids-borne ciprofloxacin and azithromycin found “negligible human and ecological health risks from biosolids-borne CIP and AZ under real-world biosolids application scenarios.”  Research with similar approaches was reported in  Rapid and complete degradation of diclofenac by native soil microorganisms and, for fluroquinolones, Dissipation of antibiotics in three different agricultural soils after repeated application of biosolids.

The interest in environmental fate of antibiotics has a corollary with another emerging area for biosolids research. That is “ARG,” or antibiotic resistances genes. This is the genetic material fragments from bacteria exposed to antibiotics, and the human health concern is for the potential for spread of resistance genes among human pathogens. To date, biosolids-borne ARGs seem to be highly vulnerable to the treatment by anaerobic digestion followed by aerated soil microbiome and are readily degraded, but others believe the risk is significant. This is shown in the report: The potential implications of reclaimed wastewater reuse for irrigation on the agricultural environment: The knowns and unknowns of the fate of antibiotics and antibiotic resistant bacteria and resistance genes – A review.  And the most recent contribution to this issue is Long-term application of Swedish sewage sludge on farmland does not cause clear changes in the soil bacterial resistome, concluding: "Taken together, the current study does not indicate risks of sludge amendment related to antibiotic resistance development under the given conditions."

Another new issue for biosolids research is plastic pollution. Plastic production since the 1960s has resulted in release of plastics to the global environment, lands, streams and oceans, in large fragments down to nano-scale particles. For a chilling review of the extent of pollution, the 2017 report Production, use, and fate of all plastics ever made is a “must read.” Microscopic sized plastic beads and fibers are released to wastewater via consumer products and clothes washing (Microfiber release from different fabrics during washing), and, when biosolids is land applied to farm soil, biosolids-borne microplastic become part of the soil-plant system. Thereby, biosolids is one of several sources of plastic contamination that is now routinely incorporated in farm soils (An overview of microplastic and nanoplastic pollution in agroecosystems). The effects of macro- and micro- plastics in the soil-plant system in agriculture are the subject to a blossoming of research, but the effects on soil properties and animal and plant life are still being worked out (Current research trends on plastic pollution and ecological impacts on the soil ecosystem: A review). Whether biosolids-borne plastics is a significant problem for soil health is a matter of dispute, but one that warrants our attention (e.g., Are Agricultural Soils Dumps for Microplastics of Urban Origin?), lest this issue be cast in the light of environmental catastrophism.

Of greater risk than microplastics or the latest TOrC horror to our profession is that we underfund biosolids research into the significant counterbalancing benefits of biosolids, particularly the multiple aspects of recycled nutrients and organic matter supplementation. An example of the importance of making the case for biosolids is the 2019 report out of Sweden, a country which in the past has been an origin of precautionary fears of biosolids. The European Sustainable Phosphorus Platform reported that in late January a key report was issued, the Sweden Enquiry recommends use of sewage sludge on crops. This report, H?llbar slamhantering, strongly supported land application of biosolids for its recycled phosphorus content. While the report is in Swedish, its English summary chapter concluded: “Evidence for a total ban being necessary is lacking, however, research having failed to prove that crops grown with sludge have health impacts or have an adverse impact on ecosystems in agriculture. On the other hand, there is clear evidence that sludge fertiliser application supplies plant nutrients and humus that agriculture demands.” This is a great statement, and ought to substantially address the catastrophism that has surrounded Swedish biosolids programs.

In the end, repeated confirmation of no impacts of TOrCs on soil health and plant growth, and the compelling evidence of vibrant crop production under treatments with biosolids, can win the day. Giving into catastrophism may well trigger an impulsive “one-click” type decision, whether to buy a book or to pass legislation banning biosolids. But we need to remind ourselves that biosolids research delving into the fate of TOrCs and demonstrating soil and crop benefits of biosolids together are the best salve for pitfalls of biosolids catastrophism. The risk is that, when challenged to make a scientific case that the resource benefits of biosolids far outweigh the risks of TOrCs, we fail: that would be the true catastrophe.