- lack of reliable wet weather application sites;
- restrictive local permitting requirements and new fees related to land application sites;
- dwindling availability of qualified, responsive contract haulers; and
- a significant decrease in Class B land application sites in rural communities surrounding Orlando, similar to many counties and regions across the country.
For these reasons, the city decided to install an innovative sludge oxidation process, supercritical water oxidation (SCWO), which is currently being refined and improved at the Iron Bridge Regional Water Reclamation Facility. This article presents an analysis of the costs and benefits of alternatives considered by the city and the reasons for selecting SCWO.
The Carbon Footprints of Various Biosolids Treatment Processes
William P.F. Barber
A wide variety of processes are capable of treating biosolids to comply with pathogen reduction requirements as defined by 40 CFR 503 regulations. However, within Europe, long-term sustainability and carbon impacts are becoming more influential, including economic incentives in the form of taxes and levies to prevent the release of greenhouse gases (GHGs). GHGs have been classified by the Intergovernmental Panel on Climate Change to include, among others, carbon dioxide, methane, nitrous oxide, tetraflouromethane, sulfur hexafluoride, hydrofluorocarbons, and chlorofluorocarbons.
Saving Drinking Water and Costs
Isotope tracing nudges one utility to drop chemical fertilizers and go full time with biosolids
David J. Heckler, Somnath Basu, Jeremy Bowser, and Holly Weatherhead
A negative aspect of land application is the potential for groundwater contamination by various pollutants. Digested biosolids contain high concentrations of ammonia, both in free and ionized forms. Upon land application, aerobic soil bacteria oxidize the ammonia to nitrate ions that dissolve in water from rain or irrigation sources. As this water gradually seeps through the soil, it ultimately may reach the groundwater table. Any excess nitrate ions left after the uptake by the plants are also transported down with the seeping liquid toward the groundwater table.
Scientists and engineers in the field of groundwater hydrogeology increasingly have been using isotope distributions of nitrogen and oxygen as tracers to determine sources of contamination with good success. However, to the best of the authors’ knowledge, this technique has never been applied to monitor the fate of nitrogen originating from the land application of digested treatment plant residuals for farming. In a recent study, the authors determined the source of nitrates in groundwater in Ohio. This led to the elimination of chemical fertilizers, and the use of biosolids solely on feed crops has allowed the Tri-Cities Authority (TCA) near Dayton, Ohio, to cut costs and risks and reduce groundwater contamination.
NEWS
Mission Accomplished
With no funding and scarce time, Virginia biosolids panel manages to make recommendations for future regulations
Cathy Vidito
In a final report released in January, a biosolids expert panel assigned by the Virginia General Assembly made numerous recommendations, including ways to handle complaints from residents near land application sites, but did not add any new findings to the current body of literature.
Despite the testimony of residents who claimed their health was adversely affected by their proximity to land application sites, the panel “uncovered no evidence or literature verifying a causal link between biosolids and illness, recognizing current gaps in the science and knowledge surrounding this issue,” it stated in the final report.
Drought Tolerance: Another Biosolids Benefit
Steve Spicer
Crops planted in biosolids-amended soil seem to weather droughts better than crops in fields without biosolids. Now, researchers at Virginia Polytechnic Institute and State University (Blacksburg) think they’ve figured out why.
The answer is indole acetic acid. This compound, which is also called auxin, is a plant hormone that spurs plants to use their excess energy to grow new roots. Indole acetic acid is produced in biosolids as the bacteria degrade organic matter, according to Erik Ervin, an associate professor of turf grass physiology who has been conducting this research.
DEPARTMENTS
In Brief
Summaries of national and regional news items of interest to biosolids and residuals managers.
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