Bacterial bioassay evaluation of foundry residuals for use as construction materials
Abstract
The constructive reuse of foundry residuals represents a decidedly beneficial goal with economic and environmental benefits. Results of foundry residual leachate characterization to date strongly suggest that many iron foundries are discarding sands whose quality is fully amenable to their future use with embankment construction and related high-volume highway development activities. Potential end users, however, are reluctant to accept these residuals given concerns regarding unforeseen environmental liabilities. In order to assess the potential for such long-term environmental impact, therefore, the Microtox$\sp{\rm TM}$ bioassay has been used to quantify the response of living organisms (i.e., the luminescent microorganism, Vibrio fischeri) to ferrous foundry residual leachates. Leachates from the majority of the iron foundries which participated in this study caused less inhibition of light production by the Microtox$\sp{\rm TM}$ bacteria than did virgin sands. Furthermore, for these sands, no appreciable 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 foundry wastes had released a contaminating toxin or toxins into the leachate waters, resulting in a quantifiable depression in observed microbial activity. This innovative bioassay application thus appears to offer an efficient and expedient approach to the identification of foundry operations 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, casting temperature) and bacterial impact, such that foundries could potentially utilize bioassay response data in pollution prevention efforts.
Degree
Ph.D.
Advisors
Alleman, Purdue University.
Subject Area
Civil engineering|Sanitation|Environmental science
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