Composting and planning for wastewater infrastructure

Health Through Biosolids Composting

I engaged in “forest bathing” last week. I was looking for peacefulness amidst horror-striking environmental news.  More correctly, I undertook a “forest therapy walk,” of the kind advocated by The Association of Nature and Forest Therapy Guides and Programs. I chose to walk Philadelphia’s new “restoration trail,” an amazing project involving park managers, a mountain bike club, nature scientists, and philanthropists; the soft, winding path, encircling a fenced “deer exclusion zone,” is set amidst towering beech and tulip poplars. It is serene and comforting, yet close to home. My faith was restored that community (and, amazingly, the Philadelphia community) can create beauty for generations yet unborn. During my walk, I re-generated an idea that connects me to the wider world and the many threats it faces.

My connection?  Composting. The vision statement of the U.S. Composting Council says it so well: “We believe compost manufacturing and compost utilization are central to creating healthy soils, clean air and water, a stable climate, and a sustainable society.”

But for me, the amazing capacity of composting is its ability to transforms “waste” organic residuals, like biosolids, into health-giving soil ingredient. Composting mineralizes many trace organic “pollutants” common to our biosolids, manures, and other organic residuals, utilizing them as food and rendering them harmless. Composting is a barrier to contamination, and a very worthy part of any biosolids treatment scheme.

I had an NPR “driveway moment” with compost this past week when the local station broadcast “Soil Instead Of Ashes: Human Composting Is About To Become Legal In Washington State.” If you were to survey any one of my four offspring and asked what they understood to be my “final instructions,” I am sure they would say “Dad wants to be composted.” Does this story mean I have to move to Washington? But, somewhat sadly, I had this thought: “I wonder if my body burden of PFAS is too high for me to become a marketable compost?”

There is was, the thought that had been the instigating stressor, the impact of PFAS on biosolids recycling. PFAS (perfluoroalkyl substances) has been taking over far too much of my attention. It was one of the recurring topics at the WEF/IWA 2019 Residuals and Biosolids Conference last week in Fort Lauderdale.  News of PFAS is hard to ignore.  This recent article in Science, Citizen sleuths exposed pollution from a century-old Michigan factory, with nationwide implications, describes how 3M’s Scotchgard, largely comprised of perfluorooctanesulfonic acid (PFOS), a particularly recalcitrant type of PFAS, was used to waterproof leather that went into shoes and boots manufactured  by Wolverine (including Hush Puppies) along the banks of the Rogue River, up river of Grand Rapids, Michigan, resulting in well-water PFOS concentrations averaging 400 times that of EPA advisory level of 70 ppt. OMG!

But PFAS was not the only environmental horror story in the world. Perhaps you heard of the 414 million pieces of plastic on the shoreline of the remote, sparsely settled Cocos Island in the Indian Ocean (414 million pieces of plastic found on remote island group in Indian Ocean) or the plastic pollution found in the most remote spot on the ocean floor (Diver finds plastic bag on seafloor in deepest known point on Earth).  If plastic is not enough, how about the potential climate catastrophe that is the rapid thinning of the Thwaites Glacier in Antarctica (Instability spreading in West Antarctic ice sheet). Have you heard of the devastating African Swine Fever outbreak?

The WEF RBC conference did offer up some positive environmental news.  At the RBC Workshop D on “current and emerging regulatory trends,” Dr. Dilek Sanin, from Turkey, spoke on research into emerging pollutants. One of her slides read “Contaminants such as PAH, LAS, DEHP, NP, NPE, PCB and PCDD are degraded better in composting than in anaerobic digestion; Contaminants such as bactericides, fragrances, vulcanizers, flame retardants, plasticizers are reduced significantly;… combination with anaerobic digestion suggested.”

This was my best conference “take-away,” the reminder that composting not only results in a dependably “saleable” biosolids products but is an important means by which many organic micropollutants in sewage are degraded and eliminated from the environment.  

In the very large field of environmental remediation, the role of composting processes is widely understood and promoted, including the composting of biosolids. Some examples are these reports:

Organic Waste and Pollutants Reduction Through Composting: “During composting, the biodegradable organic carbon, micropollutants, and nuisance gases from the organic fractions are biologically transformed into a stabilized product.”

Application of compost for effective bioremediation of organic contaminants and pollutants in soil: “Compost addition can thus be considered as a ‘super-bioaugmentation’ with a complex natural mixture of degrading microorganisms, combined with a ‘biostimulation’ by nutrient containing readily to hardly degradable organic substrates. It also improves the abiotic soil conditions, thus enhancing microbial activity in general.”

The potential impact on the biodegradation of organic pollutants from composting technology for soil remediation: The technology of soil composting or use of compost as soil amendment can utilize quantities of active microbes to degrade OPs with the help of available nutrients in the compost matrix. It is highly cost-effective for soil remediation. … compost incorporated into contaminated soil is capable of increasing the organic matter content, which improves the soil environment and stimulates the metabolically activity of microbial community.”

The day may be soon coming when a fundamental goal of wastewater treatment will be removal and degradation of organic micropollutants.  If so, then biosolids composting ought to be a key part of such an intentional, effective treatment system.

Liquid side treatment methods are evolving for micropollutant removal   A non-conventional treatment train involving membrane reactors was designed for high removal efficiencies.Elimination and fate of selected micro-organic pollutants in a full-scale anaerobic/anoxic/aerobic process combined with membrane bioreactor for municipal wastewater reclamation reported “[T]he investigated process achieved over 70% removal of the target EDCs and 50%–100% removal of most of the PPCPs, with influent concentration ranging from ng/L to μg/L.”  Similarly, anammox processes for wastewater treatment are being studied for their capacity to remove organic contaminants. The article, Removal of pharmaceuticals and personal care products by ammonia oxidizing bacteria acclimated in a membrane bioreactor: Contributions of cometabolism and endogenous respiration, found that “target PPCPs were degraded in 2 stages, first by cometabolic degradation related to AOB growth, and then by endogenous respiration by microorganisms in the absence of other growth substrate.”

When advanced wastewater treatment has shuttled microcontaminants to biosolids, composting is an effective approach to further degrade them. In one study, Fate of polycyclic aromatic hydrocarbons during composting of activated sewage sludge with green waste, researchers concluded “The treatment by composting led to a decrease of all PAHs mainly in the stabilization phase, but some differences could be observed between PAHs with three or fewer aromatic rings (N ⩽ 3) and those with four or more (N ⩾ 4).”  Another study,  Organic micropollutants’ distribution within sludge organic matter fractions explains their dynamic during sewage sludge anaerobic digestion followed by composting, found “Discontinuous composting allowed to go further on the organic micropollutants’ removal as 34 ± 8%, 31 ± 20%, 38 ± 10%, and 52 ± 6% of fluoranthene, benzo(b)fluoranthene, benzo(a)pyrene, and nonylphenols were dissipated, respectively.”  A third study, Dissipation pathways of organic pollutants during the composting of organic wastes, found that “[T[he dissipation of four 14C-labeled OPs (fluoranthene; 4-n-nonylphenol, NP; sodium linear dodecylbenzene sulfonate, LAS; glyphosate) was assessed during composting of sewage sludge and green waste ….In the final composts, the proportions of water soluble residues of OPs considered as readily available were <11% of recovered 14C-Ops.”

Then there is the PFAS. Though composting knocks way down many toxic organic compounds, it seems to do nothing for the PFOA and PFOS. While these long chain, stable chemicals are no longer being manufactured for use in no-stick cookery and fabric waterproofing, their legacy in the environment looms large and a risk to our biosolids future. To get the best overview of this issue, spend some time with the PFAS page at the NEBRA website, and look for the NEBRA report on  “best management practices” and how to be part of the push for public action to reduce sources of PFOS and PFOA.

But, PFOS aside, there is still much that composting can do, particularly for biosolids. The WEF conference was a forum for several composting technologies and composters. These companies include:  Sustainable Generation / Gore Covers,  represented by Dan Collins, now retired from Chicago and a major compost advocate, and Engineered Compost Systems, represented by Steve Diddy, a compost personality from Seattle and an extraordinary cyclist.  Synagro Technologies  and Denali Water Solutions / WeCare Organics, both exhibitors at WEF’s national conference, operate some of the U.S.’s most successful biosolids composting facilities. McGill Environmental Systems and J.P. Mascaro’s  A&M Compost are mid-Atlantic composters, whom you  will meet at state shows, and both of whom produce branded biosolids composts at their merchant plants (I used Landscapers Advantage from A&M in my gardens this Spring).  Manufacturer BDP Industries represents the IPS Composting System, which is expected to be installed at a new composting facility soon breaking ground in New Jersey.

My intention here is to reconnect us all to composting as a great option  in our planning for wastewater infrastructure. It is not only a technology for a future that demands a response to climate catastrophe, through carbon sequestration and fossil-based fertilizer replacement, but it is a technology at work today to respond to current issues, such as the need to biodegrade micropollutants, to improve soils for stormwater control, and to reduce organics disposal in landfills. I find that thought so comforting. I can take my forest therapy walk with serenity, not thinking of PFAS more than a few times, and I can imagine a world resilient