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United States Department of Agriculture

Agricultural Research Service

Title: Laboratory feasibility evaluation of a new modified iron product for use as a filter material to treat agricultural drainage waters

item Allred, Barry

Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: 10/5/2010
Publication Date: 12/14/2010
Citation: Allred, B.J. 2010. Laboratory feasibility evaluation of a new modified iron product for use as a filter material to treat agricultural drainage waters [abstract]. American Geophysical Union.

Interpretive Summary:

Technical Abstract: The removal of excess soil water with a subsurface drainage pipe system is a common agricultural practice employed to improve crop yields, especially in the Midwest U.S. However, fertilizer nutrients (nitrate and phosphate) and pesticides applied on farm fields will frequently leach downwards through the soil profile to be intercepted by the buried drainage pipes and then discharged with drainage water into neighboring streams and lakes, oftentimes producing adverse environmental impacts on local, regional, and national scales. On-site drainage water filter treatment systems can potentially be employed to prevent the release of agricultural nutrients/pesticides into adjacent waterways. A recently developed modified iron product may have promise as a filter material used within this type of drainage water treatment system. Therefore, a laboratory study was initiated to directly evaluate the feasibility of employing this new modified iron product as a filter material to treat drainage waters. Laboratory research included saturated falling-head hydraulic conductivity tests, contaminant (nutrient/pesticide) removal batch tests, and saturated solute transport column experiments. The saturated falling-head hydraulic conductivity tests indicate that the unaltered modified iron product by itself has a high enough hydraulic conductivity (> 0.001 cm/s) to normally allow sufficient water flow rates that are needed to make this material hydraulically practical for use in drainage water filter treatment systems. Modified iron hydraulic conductivity can be improved substantially (> 0.01 cm/s) by using only the portion of this material that is retained on a 100 mesh sieve (particle size > 0.15 mm). Batch test results carried out with spiked drainage water and either unaltered or 100 mesh sieved modified iron showed nitrate reductions of greater than 30% and 100% removal of the pesticide, atrazine. Saturated solute transport columns tests with spiked drainage water provided further insight on the effectiveness and efficiency of utilizing modified iron as a filter material for drainage water treatment. These column tests confirm that the modified iron is capable of nearly complete removal of atrazine, and also significant amounts of nitrate. Furthermore, once the phosphate originally present within the modified iron leaches out, the modified iron then exhibits ability to remove large quantities of phosphate. Consequently, these laboratory findings support employment of this modified iron product for use within on-site agricultural drainage water filter treatment systems; although, field pilot tests are now needed to further document this particular application for modified iron.

Last Modified: 10/15/2017
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