Wednesday, March 23, 2011

Innovations in the Biosolids Fields

A “fevered pitch” may be a bit hyperbolic a description for technology advances in biosolids stabilization. A review of the agenda at recent conference will reveal a swing toward advanced digestion and chemical treatment processes to improve pathogen destruction, biogas production, and odor reduction. Yet, articles on our fundamental mission area, land spreading of biosolids, have almost disappeared. So it is a good thing to read that breakthrough new approaches are being studied for delivering solid byproducts to soil for crop fertilization in new ways.

Those of us engaged in biosolids application to farm fields have shared some concern for the uneasy relationship between agricultural practices associated with no-till and conservation tillage and the use of biosolids. No-till farming achieves the protection of soil structure and soil infiltration capacity, but at the expense of reliance on aggressive chemical weed control. Biosolids on such no-till fields may be surface applied, as are manures in the same practice, but with the risk that nutrients and organic matter might be carried to surface waters during heavy storm events.

The drive to address the issue of solid manure spreading while minimizing risk of environmental releases has been focused in sensitive watersheds, notably those within the Chesapeake basin. The drive has produced innovation. And reports of successful new approaches are now being released.

A recent JEQ article (see; discusses novel manure application methods to reduce N and P losses in no-till systems of agriculture. This article introduces the positive qualities of a new subsurface applicator for poultry litter, which is the first subsurface applicator available for solid manures. The biosolids profession should be among early adopters of equipment that advances the goal of reduced nutrient losses while conserving soil structure.

PBDEs and Biosolids

A decade has passed since I first heard the term “PBDEs.” Having been intimately engaged in a response to illegal discharge of PCBs to Philadelphia sewers a few years prior, I had experience which informed my intuition that this class of compounds, disconcertingly alliterative with PCBs, would prove to be no friend to biosolids.

Science has now provided a picture of the exposures to PBDEs in the world environment. The recent issue of Environmental Science & Technology contains an article by David Trudel, et al, “Total Consumer Exposure to Polybrominated Diphenyl Ethers in North America and Europe” (Environ. Sci. Technol. 2011, 45, 2391–2397; It synthesizes an enormous body of work across the world and across ecological systems—water, air and land.

Trudel’s article sparked in me some sharp memories from a full ten years ago. In July 2001, against the backdrop of the crashing waves in Ocean City, MD, on an outdoor patio on which biosolids folks gathered to confer, Rhonda Bowen from Hampton Roads took a cellphone call from her boss. A researcher at the Virginia Marine Institute, Rob Hale, had a Nature magazine article reporting concentrations of a class of persistent organic pollutants known as “PBDEs” in sediments from the same watershed in which land application of biosolids had been practiced. Dr. Hale had intended to implicate biosolids as a source, although even with the meager information available to us on such pollutants, a meaningful link seemed farfetched. A response by the biosolids profession was needed. A full year would go by before the scientific community would see a thorough, peer-reviewed article sources and potential pathways of this class of contaminants (De Wit, C. A. “An overview of brominated flame retardants in the environment.” Chemosphere 2002, 46, 583–624. ).

The present article in ES&T, based on the vigorous response by the scientific community, has now put the issue in perspective. Biosolids is nowhere to be found in the article, as household dust and widespread atmospheric deposition on animal-grazed fields are now understood to be major sources.

I take solace in the observation that biosolids both concentrates persistent organics like PBDEs as well as concentrates the scientific community’s attention to emerging issues, like society’s use of high production chemicals.

Perhaps, the biosolids profession should take a leadership role in advocating responsible stewardship by industries in their choices for chemical inputs to consumer products that may persist in the environment. While the biosolids profession may be the unwitting recipients of the residuals from manufactured goods, all too often the profession takes the public blame for its presence in the environment. Against this tendency we need to have a strategy that deploys sound science and risk assessment, and one that anticipates, rather than merely reacts to, issues of public concern.