Laboratory Batch Test Evaluation of Five Filter Materials for Removal of Nutrients and Pesticides from Drainage Waters

Abstract

Where subsurface drainage practices are employed, fertilizer nutrients and pesticides applied on farm fields and municipal locations are commonly intercepted by the buried drainage pipes and then discharged into local streams and lakes, oftentimes producing adverse environmental impacts on these surface water bodies. Various filter materials have the potential to remove nutrient and pesticide contaminants from subsurface drainage waters before these waters are released offsite. For this study, laboratory batch tests were conducted to evaluate the contaminant removal effectiveness and efficiency of five potential filter materials. The five materials, isolated from previous screening tests, were steam activated carbon, high calcium oxide - high carbon fly ash, iron sulfide, sulfur-modified iron, and surfactant-modified zeolite. Filter material effectiveness was tested against initial contaminant solution concentrations that varied between 10 and 200 mg L-1 for nitrate-N, 0.1 and 1.0 mg L-1 for phosphate-P, and 0.1 and 0.5 mg L-1 for atrazine, while filter material efficiency was evaluated with respect to exposure time by varying test durations from 1 to 24 h. Sulfur-modified iron proved best for treating nitrate, based on reductions greater than 95% across the range of initial concentration levels and exposure times. Surfactant-modified zeolite and high calcium oxide - high carbon fly ash affected the greatest removal of phosphate, 50% or more in all cases. For atrazine, the most promising results were obtained with steam activated carbon and high calcium oxide - high carbon fly ash, which removed almost 100% of this particular pesticide regardless of initial concentration level and exposure time. Consequently, there are several filter materials, when used either alone or in combination, that show promise for removing mixed contaminants from subsurface drainage water; however, more laboratory testing followed by field experiments are needed to completely evaluate their feasibility for widespread use.