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Midwestern Cornbelt Nutrient Sequestration: Fine Tuning Treatment Technology

Lu Zhang and Joe Magner

Woodchip bioreactors have proven effective in removing nitrate-nitrogen (NO3-N) from agriculturally drained water in the Midwest USA region. Both NO3-N and phosphorus can lead to algal bloom and hypoxia in the receiving surface waters and degrade the water quality. This study explored the effectiveness of bioreactor technology in removing NO3-N and orthophosphate. Three types of media were examined in a pilot-scale lab experiment: deciduous mixed hardwood chips, biochar chips (created from the same type of woodchip) and corn cobs. Chemically formulated water was fed through each system using a residence time of 24 hours. NO3-N reduction occurred in all three media, although biochar showed a relatively longer lag time. An average of 90% NO3-N reduction was observed from the 24 hours retention time. An average of 80% of the orthophosphate was sequestered, with the biochar media providing the most reduction in outflow orthophosphate concentration. Given the recent development of state-wide nutrient management plans to reduce nutrient concentrations in surface water, study results of these technologies will help the row-crop producer community manage nutrient export to surface water.