Although the constructive reuse of foundry residuals represents a decidedly beneficial goal with distinct economic and environmental benefits, potential end-users are nonetheless reluctant to use these residuals, given an inherent concern about potential unforeseen environmental liabilities. Results of foundry residual leachate characterization to date strongly suggest that many ferrous foundries are discarding sands whose quality is fully amenable to their future use with embankment construction and related high-volume highway development activities. In order to provide additional assurance as to the environmental impact of foundry residual reuse, the MicrotoxTM bioassay has been used to quantify the response of living organisms (e.g., the microorganism, Vibrio fischeri) to ferrous foundry residual leachates. This response has been compared with the response of the organism to “virgin” sands used in the foundry industry and as construction materials. Leachates from the majority of the ferrous foundries tested caused less inhibition of light production by the MicrotoxTM bacteria than did virgin sands. Taken literally, it appears that these sands are truly, “cleaner than dirt.” Furthermore, for those sands, no real differences were seen between system sands and fresh or aged waste sands. In a limited number of instances, however, there were clear and consistent indications that the tested waste foundry sands had released a contaminating toxin or toxins into the leachate waters, thereby resulting in a quantifiable depression in observed microbial activity. This innovative bioassay test appears to offer an efficient and expedient approach to ‘fingerprinting’ foundry locations for which constructive waste sand reuse could subsequently be pursued without undue concern about negative environmental impacts. Additionally, there appears to be a correlation between casting process (e.g., core binders, casting size, and casting temperature) and bacterial impact, such that foundries could potentially utilize bioassay response data in focusing pollution preventive efforts.

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waste foundry sand, core binders, greensand, bioassay, Microtox, waste reuse, environmental quality, leachate testing, highway construction, HPR-2006

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Performing Organization

Joint Highway Research Project

Publisher Place

West Lafayette, IN

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