EVALUATION OF MODIFIED IRON FOR FILTER TREATMENT OF DRAINAGE WATERS
Soil Drainage Research
2013 Annual Report
1a.Objectives (from AD-416):
To develop a filter treatment system (containing modified iron) to remove nutrients and pesticides from agricultural drainage waters.
1b.Approach (from AD-416):
Laboratory contaminant batch tests, saturated hydraulic conductivity tests, and saturated solute transport tests, followed by field pilot tests, will be used to develop filter treatment systems (containing modified iron) capable of removing nutrient and pesticide contaminants from drainage waters.
A new, hydraulically improved porous iron composite (PIC) filter material was evaluated in the laboratory for potential use in agricultural water treatment. Measured saturated hydraulic conductivity values were very high and ranged from 0.03 to 0.11 cm/s, which confirms that the new PIC material can accommodate a water flow capacity that is more than sufficient for use in a filter treatment system. Two saturated column tests were then carried out over an extended period of two months using subsurface drainage water spiked with high concentrations of phosphate and nitrate. Results from these two column tests showed that PIC removed essentially all phosphate, even with when the contact time between PIC and the drainage water was less than 2 minutes. The column tests also showed that PIC could remove almost all nitrate, but to do this a contact time of around 4 hours was needed. Desorption/dissolution batch tests indicate that once phosphate is adsorbed onto PIC particle surfaces, the phosphate becomes fixed and is not readily desorbed back into the drainage water. Finally, in early June 2013, a small filter treatment system containing PIC was installed at a farm near Dublin, Ohio and will be monitored over the next year with respect to the effectiveness of phosphate removal from drainage water discharged by a 7 acre field.
Research related to this project directly supports achieving the overall goal of Sub-Objective 1d for parent project, which is to "develop effective and efficient filter treatment systems capable of removing nutrients and pesticides from waters discharged by small- and large-scale subsurface drainage systems".