Nutrient and Pesticide Removal from Laboratory-Simulated Tile Drainage Discharge

Abstract

Excess nutrient and pesticide transport through subsurface tile drainage is well documented. One approach being considered to reduce the amount of these contaminants in subsurface drainage waters is the use of end-of-tile filters. Materials used in such filters are often comprised of natural minerals and industrial wastes or by-products that have a significant capacity for binding or sorbing nutrients and pesticides (e.g., activated carbon, fly ash). In this laboratory study, the feasibility and efficacy of an activated carbon, zeolite (clinoptilolite), and activated alumina filter to reduce nitrate-nitrogen (NO3-N), dissolved reactive phosphorus (DRP), metalaxyl, and chlorothalonil concentrations in simulated drainage waters was determined. Hydrographs having peak flow rates of 0.63, 1.26, and 1.89 L s-1 were simulated in a laboratory environment and replicated three times. Across all flow rates, the cartridge-type filter system produced average load reductions of 4.7% for NO3-N, 51.6% for DRP, 58.2% for chlorothalonil, and 28.8% for metalaxyl. The filter effectiveness was dependent on flow rate and position on the hydrograph. The findings from this study suggest that the end-of-tile filter approach could be adapted as a best management practice to reduce nutrient and pesticide transport in subsurface tile drainage where the contributing area and flow rates are relatively small. Additionally, the findings support further investigation into alternative sorbent materials and delivery designs that permit larger drainage areas and greater flow rates to be filtered.