WATER QUALITY IMPROVEMENT FROM MANAGEMENT PRACTICES IN AGRICULTURAL WATERSHEDS
Location: Agroecosystems Management Research Unit
Title: Herbicide and antibiotic removal by woodchip denitrification filters: Sorption processes
Submitted to: Water, Air, and Soil Pollution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 13, 2011
Publication Date: December 27, 2011
Citation: Ilhan, Z., Ong, S., Moorman, T.B. 2011. Herbicide and antibiotic removal by woodchip denitrification filters: Sorption processes. Water, Air, and Soil Pollution. Available: http://www.springerlink.com/content/4xp097310327271m/fulltext.pdf.
Interpretive Summary: Nitrate loss from the upper Mississippi River basin has been implicated in the development of hypoxia zones in the Gulf of Mexico. Wood chip bioreactors and denitrification walls convert nitrate to nitrogen gas and are a promising method for removing nitrate in subsurface tile drainage before this drainage enters rivers and streams. Drainage water also carries herbicides and veterinary antibiotics. This research was conducted to determine if these organic chemicals would bind to wood chips, thus possibly improving water quality. The herbicide atrazine, and three veterinary antibiotics, enrofloxacin, monensin, and sulfamethazine were used in the research. More than 65% of adsorbed atrazine, 70% of sulfamethazine, 90% of enrofloxacin and 80% of monensin were found to be retained in the wood chips, even after repeated exposure to water. This retention indicates that wood chip-based bioreactors can simultaneously remove nitrate, herbicides and pharmaceuticals from drainage water. Scientists, conservationists, and Agencies responsible for water quality will benefit from this research.
Batch sorption and desorption experiments to evaluate the retention of the agrichemicals onto wood chips from an in situ wood chip denitrification wall were conducted for atrazine, enrofloxacin, monensin and sulfamethazine. Estimated Freundlich distribution coefficients (Kf) showed that the order of sorption from highest to lowest was enrofloxacin > monensin > atrazine > sulfamethazine. Of the four chemicals tested, enrofloxacin was found to desorb the least while monensin desorbed the most. In comparison with surface and subsurface soils obtained from the same site as the wood chips, the sorption of atrazine and sulfamethazine onto wood chips were found to be higher than the sorption onto the surface and subsurface soils. The apparent hysteresis index (AHI) value for atrazine was lower than that for enrofloxacin and sulfamethazine indicating greater sorption-desorption hysteresis for atrazine than enrofloxacin and sulfamethazine. Following consecutive steps of water desorption and organic solvent extraction, more than 65% of adsorbed atrazine, 70% of sulfamethazine, 90% of enrofloxacin and 80% of monensin were found to be retained in the wood chips. The results of the study showed that wood chips denitrification walls or biofilters can retain atrazine, sulfamethazine, enrofloxacin and monensin, and therefore reduce their concentrations in tile water.