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Evaluation of the impact of lime softening waste disposal in natural environments
Citation:
Blaisi, N., J. Roessler, W. Cheng, T. Townsend, AND S. Al-Abed. Evaluation of the impact of lime softening waste disposal in natural environments. R. Cossu (ed.), WASTE MANAGEMENT. Elsevier Science Ltd, New York, NY, 43:524-532, (2015).
Impact/Purpose:
The objective of this study is to further examine the leaching of trace elements from lime softening WTR by utilizing experimental procedures that better assess element behavior in the natural environments of question. Several of the procedures employed are from a new suite of leaching protocols developed for the United States Environmental Protection agency (US-EPA), and patterned after European leaching tests. As these protocols do not address some conditions that may be encountered in the natural environment [e.g., anaerobic conditions, the presence of NOM], the authors examine possible modifications of standardized protocols to address use-specific conditions. Although this paper provides value to the specific waste reuse question at hand, perhaps of even more importance is the evaluation of how existing leaching protocols can best be applied to the beneficial use, risk assessment process. This paper highlights how the broader suite of recently adopted leaching tests can be used to generate a more thorough assessment of leaching risk, but also identifies limitations within these tests. The use of modified leaching procedures illustrates to the reader additional opportunities for refinement of leaching tests to address site-specific conditions and allow for a better interpretation of results.
Description:
Drinking water treatment residues (WTR), generated from the lime softening processes, are commonly reused or disposed of in a number of applications; these include use as a soil amendment or a subsurface fill. Recently questions were posed by the Florida regulatory community on whether lime WTR that contained a small percentage of other treatment additives could appropriately be characterized as lime WTR, in terms of its total element content and leachability. A study was done using a broad range of leaching tests, including a framework of tests recently adopted by the United States-Environmental Protection Agency (EPA) and tests that were modified to account for scenario specific conditions, such as the presence of natural organic matter (NOM). The results of these additional leaching tests demonstrated that certain applications, including disposal in a water body with NOM or in placement anaerobic environment, did result in increased leaching of elements such as Fe, and that a site specific assessment should be conducted prior to using WTR in these types of applications. This study illustrates the importance of leaching test selection when attempting to provide an estimation of release in practice. Although leaching tests are just one component in a beneficial use assessment and other factors including aquifer and soil properties play a significant role in the outcome, leaching tests should be tailored to most appropriately represent the scenario or reuse application being evaluated.
