Kari Wolf Presentation.

The presence of nitrate (NO₃) in tile water is one of the major environmental challenges facing Midwestern agriculture. This project evaluated the feasibility of using industrial anion exchange resin to remove NO₃ from tile water. The resin is commonly used by water works departments and can be repeatedly recharged with a solution containing chloride ions. Common practice in the industry is to recharge the resin with sodium chloride (NaCl) solution and then dump the waste water containing sodium nitrate (NaNO₃) back into the river. The premise of this testing was to capture and recycle NO₃ desorbed from the resin during its recharge. Starting 2015, field studies were undertaken to assess the effectiveness of two different resins to remediate tile water. The testing was done by passing tile water from a soybean field through 11 liters of resin contained in a 76.2 cm tall PVC column with 15 cm diameter.  Instead of NaCl, columns were recharged with the potash (KCl) solution, thus recovering adsorbed NO₃ as potassium nitrate (KNO₃). The results showed that resins were effective in capturing about 46 percent of the nitrate in tile water over a 50 day period.  An analysis of the recharge water containing KNO₃ showed no high concentrations of heavy metals. Other testing in 2015 included laboratory leaching of 100 mg L^-1 NO₃ solution through a 50 mL resin column. The results showed retention of 13.3 g of NO₃ per kilogram of the resin. Breakthrough curve showed the center of the mass appearing at 310 pore volume with a partitioning coefficient of 141; a nearly instantaneous retention. In 2016, field testing of the resin was again undertaken but with tile water from a hog manure applied corn field. We are currently in the process of analyzing water samples from this testing. In this presentation, we will present results of the above testing and the challenges one faces in the use of anion resin under agricultural settings.  We will also show the effectiveness of horizontal compared to vertical resin beds in remediating tile water.