Biosolid n. (1977):
The Mid-Atlantic Biosolids Association vision is that biosolids is recognized everywhere as a valuable community resource.
Science is Behind Biosolids Recycling
Even those of us who have for decades been dealing with public concerns need to be reassured that science is on the side of biosolids recycling. Two scientist in our region give their perspective on the issues raised recently in our region. Over their many years of research, these scientists understand the complexity of the biosolids matrix, the science of pollutant fate and transport, the geochemical behavior of soil, the interactions of plants, soil and water, and the tools for assessing environmental and human health risks.
A long list of elemental and organic compound constituents theoretically end up in sewage sludge. For all but the currently regulated pollutants (As, Cd, Cu, Hg, Mo, Ni, Pb, Se, and Zn), there are data that show that they are either present in such low concentrations or in such a chemical form as to not pose a hazard (and, therefore, not require monitoring), or, they are no longer produced and thereby not accumulating to any extent (and, therefore, also not require monitoring)..
The greatest unknown today is the potential for synergistic, additive, or multiplicative effects. These have not been demonstrated, but are routinely conjectured as concerns. For perspective, we need to remember that pathways for many of these products from source (e.g., flame retardants in carpets, computers, chair cushions) to human is much more direct from the products that incorporate these chemicals than from land where biosolids are applied.
Soil elements are mostly so insoluble that they are not taken into plants even at the low parts per billion level. We actually measure some elements in plant samples to estimate the soil contamination of crop samples from windblown dust, or soil contact during harvest -- elements such as titanium, zirconium, yttrium, chromium and most of the rest of the rare earth elements. Even with soils geologically rich in these elements, plants do not accumulate the element, but dust contamination can be estimated by analysis of several of the elements compared to levels in the fine particles of soil.
In testing uptake by plants, some scientists add fresh spikes of soluble metal salts. But research has clearly shown results from such testing are severely flawed and have no bearing on uptake of elements equilibrated and weathered in soils, or those applied in stabilized biosolids. Huge errors have been reported in research purported to represent biosolids but instead have used spiked element additions. Some elements do reach edible plant tissues grown on biosolids amended soils, and those that are common in biosolids were subjected to risk assessment and development of the 503 regulations. There is simply no information which shows that, after long term use of biosolids as a fertilizer, foods grown on the amended soil would comprise risk to highly exposed individuals based on the home garden model (which gives much more potential for exposure than the general agricultural market model).
One of the important lessons of risk from lipophilic compounds came from study of PCBs. In the 1970s, science discovered PCB contamination from common commercial use of PCBs without attention to industrial pretreatment, thereby resulting in some biosolids quite high in PCBs. Study of pure chemical PCBs spiked to soils showed some uptake to the peel of carrots, and lesser-chlorinated PCBs even volatilized from soil to shoots of plants. But when biosolids-borne PCBs were examined, even transfer to carrot peels was significantly lower than occurred from spiked soils. Eating soil by livestock was the only way for detectable levels of biosolids-applied PCBs to reach livestock tissues.
Risk assessment of other biosolids-borne xenobiotic thus needs to test potential uptake from soils amended with appropriate levels of the xenobiotic in biosolids. Tests preferably should not have 1000-times higher concentrations than is commonly found in US biosolids, as has been the case in some "scare" experiments. Based on this view of appropriate experimental tests, no xenobiotics listed as health concerns comprise risk to humans. There is likely not even a risk to soil organisms, because the compounds are so sufficiently insoluble that they are bound strongly by the organic matter in soil and when added with biosolids.
Biosolids Use in Mine Reclamation
The use of biosolids in the MABA region goes back to the early 1970s, predating the ban on ocean disposal and to the early days of a national research focus on beneficial biosolids recycling to landacapes. Restoration of scarred coal mine lands was an early commitment of EPA and agencies in Pennsylvania. The extensive number of projects in western Pennsylvania were studied for water, soil and habitat impacts. These studies led to the adoption of regulations in Pennsylvania that accommodated mine land use of biosolids in closure activities under mining rules news to at the time. We have a few project summaries that show how these projects were successfully carried out. The Philadelphia Water Department was a major player in this work, and a summary of 25 years of reclamation work was put together in 2003, and work continues to today.
This is a executive summary of a report commissioned by the USEPA and published in 1990. The full report will be later added to the MABA website. But a good first start is this summary.
The Pennsylvania Game Commission has been the recipient of a great acreage of lands that had been subject to both surface and deep coal mining. Many of these sites do not arise to their wildlife production capacity without the benefit of aggressive reclamation efforts. The deployment of biosoliids is an important tool available to the commission in achieviing great habitats The Rattler Run project is an example of a successful project with numerous stakeholders znd collaborators.
The very excxllent biosoiids from the city of Harrisburg plant and the urgent need of a property owner with a denuded site resulted in a happy marriage and a great reclamation result This approach uses recyclable products and saves both participants signficant money,
Mine companies in eastern Pennsylvania retain ownership of their coal land holding and look for ways to extract long term value from the reclamation work. Borrowing on research in Maryland and in British Columbia, Reading Anthracite Company's reclamation arm took on showcasing the use of biosolids for hybrid poplar farming using a technique called deep row trenching. One of the values of this approach is that it minimizes surface applications of biosolids that can give rise to odor emissions,
One of the best documented uses of biosolids for reclamation in the MABA region was the EPA-monitored project to reduce heavy metal contamination of the borough of Palmerton by historic industiral production of zinc. Blue Mountain overlooking Palmerton and the zinc smelter had become entirely denuded by toxic deposits of zinc, lead, cadmium and nickel, and these same compounds had settled into the valley and waste sediments that washed into streams. A long-standiing program of recycling biosolids for use in reclaimiing the hillsides has largely eliminated exposure pathways rsking human and environmental health.
Stafford County Airport -- Revisited!
The Virginia Biosolids Council has prepared a case study report on the return of lime amended biosolids to this unique landscape. The development of the Stafford County (VA) regional airport resulted in the exposure of an acid sulfate soil with a uniquely damaging quality of barring vegetative growth and damaging surface waters. DC Water supplied lime-amended biosolids to both neutralize acidity and support vegetative growth, with a heavy dose of site supervision by Dr. Lee Daniels of Virginia Tech. In 2013, the team returned with biosolids to treat a few areas that showed signs of deterioration. The VBC has provided an interesting review of this project, and for your convenience, you can download it here.
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