This INDOT-JTRP project examined an innovative strategy for mitigating, and possibly obviating, the environmental impact of wintertime salt release within INDOT yard areas specifically associated with the generation and release of salt truck wash waters, whereby these waste streams may be beneficially reused in the manufacture of salt brine solutions suitable for subsequent pre-wetting and anti-icing applications. The associated environmental problem stems from the fact that these wash waters carry high-level (e.g., from 100's of mg/L to percentile-level) salt concentrations whose uncontrolled release via local surface or ground waters will have to be discontinued pursuant to the onset of tightened environmental regulations. Specifically, current Indiana Water Quality Standards restrict total dissolved solids in natural waters to 750 mg/L. Reusing these salt-laden truck wash waters will, therefore, not only resolve, either in part or wholly, this environmental problem but will also save material cost in preparation of valuable salt brine solutions. Six (6) key aspects were identified for this proposed activity, including: 1) wash water collection, 2) wash water pretreatment, 3) temporary wash water storage, 4) brine manufacturing hardware and operational details, 5) product brine storage, and 6) brine application procedures and timing. The first five of these aspects are addressed within this report; relevant details regarding the sixth item (brine application, etc.) are given in the "Manual of Practice for an Effective Anti-Icing Program: A Guide For Highway Winter Maintenance Personnel," published by the Federal Highway Administration (i.e., as referenced in this report). Lastly, a condensed, Web-based synopsis of this project is available at the following URL: http://rebar.ecn.purdue.edu/Salt-Wash-Reuse/
Considerable savings are available to the metal casting industry through the development of reuse applications for waste foundry sand (WFS). Departments of Transportation (DOTs) that are facing increased pressure to reuse waste materials may also save from using low-cost WFS as a source material in transportation construction. In 1996, the Indiana Department of Transportation (INDOT) and Purdue University constructed a demonstration embankment using WFS from a ferrous foundry. WFS and control embankments were instrumented to monitor geotechnical and environmental performance during and after construction. Stockpile WFS samples were also tested. The geotechnical performance of the WFS was comparable to that of natural sand, with small internal deformations and a high-standard penetration resistance. However, the WFS had a hydraulic conductivity considerably lower than that of natural sand and cannot be considered as freely draining. Minor problems were encountered during construction due to foreign objects and dust in the WFS. Environmental testing consisted of Microtox™ and Nitrotox bioassays, ion chromatography, and inductively coupled plasma testing for metals. Bioassay results indicate the WFS has not resulted in inhibitions (toxicity) higher than those expected from natural sands. Ion migration from the WFS into the foundry sand lysimeter and down-gradient wells was found but at concentrations below regulatory reuse criteria. Metal concentrations also were below regulatory reuse criteria and typically below drinking water standards. The WFS did not result in a negative environmental impact at the site.
Considerable savings are possible for the metal casting industry through the development of reuse applications for waste foundry sand (WFS). State departments of transportation face increased pressure to reuse waste materials in transportation construction. In 1996, the Indiana Department of Transportation and Purdue University constructed a demonstration embankment by using WFS from a ferrous foundry. WFS and control embankments were instrumented to monitor geotechnical and environmental performance during and after construction. Stockpile and jobsite WFS samples also were tested. The geotechnical investigation demonstrated that WFS can perform well as a structural fill, having strength and deformation characteristics comparable to natural sand. The compacted WFS has a hydraulic conductivity considerably lower than that of natural sand and generally cannot be considered as freely draining. Environmental testing consisted of Microtox and Nitrotox bioassays, ion chromatography, and inductively coupled plasma testing for metals. Bioassay results indicate the WFS has not leached contaminants at concentrations higher than those expected from natural sand and is not likely to have a negative environmental impact at the site. Ion migration from the WFS into the foundry sand lysimeter was found, supporting bioassay data, but at concentrations below drinking water standards or reuse regulatory criteria. Metal concentrations typically were below detection levels.
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