Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: 10/1/2008
Publication Date: 12/15/2008
Citation: Allred, B.J. 2008. Laboratory Testing of Foundry Sands as Bulking Agents for Porous Media Filters Used to Treat Agricultural Drainage Waters. American Geophysical Union. Interpretive Summary:
Technical Abstract: Foundry sands are industrial byproducts that may have potential application as bulking agents that when mixed with small amounts of more chemically reactive materials (i.e. sulfur modified iron, fly ash, etc.) can be used to produce porous media filters capable of removing contaminants from agricultural drainage waters. Foundry sand bulking agents are attractive primarily as a low cost means to maintain the hydraulic efficiency of a filter. Secondarily, the foundry sands themselves may have some capacity for removal of agricultural nutrients and pesticides from water. Consequently, a laboratory study was initiated to quantify hydraulic efficiency and agricultural contaminant removal abilities of six foundry sands. Of the six foundry sands tested, all were obtained in central Ohio, three from iron casting foundries, two from steel casting foundries, and one from an aluminum casting foundry. Hydraulic efficiencies of the foundry sands were assessed by measuring hydraulic conductivity with twice replicated falling-head permeability tests. Batch tests were employed to evaluate foundry sand potential to treat water containing nitrate and phosphate nutrients, along with the pesticide, atrazine. Five of the six foundry sand samples had measured hydraulic conductivity values from 7.6 x 10-3 cm/s to 3.8 x 10-2 cm/s, which is in the range of hydraulic conductivity values found for clean sand. The one foundry sand that was an exception had much lower measured hydraulic conductivity values of 2.75 x 10-5 cm/s and 5.76 x 10-5 cm/s. For the batch tests conducted, none of the nitrate was removed by any of the six foundry sands; however, conversely, almost all of the phosphate was removed by each foundry sand. Batch test atrazine removal results were much more varied. Compared with baseline batch tests, one foundry sand removed two thirds of the atrazine, one foundry sand remove about one half of the atrazine, three foundry sands removed about a third of the atrazine, and one foundry sand removed none of the atrazine. Overall, these laboratory results generally indicate that foundry sand bulking agents can be used to maintain the hydraulic efficiency of porous media filters used to treat agricultural drainage waters, and as an added benefit, the foundry sand bulking agents may even be able, by themselves, to remove some nutrient and pesticide contaminants.