The removal of 2,4-dichlorophenoxyacetic acid (2,4-D) from an agricultural mineral soil containing organic matter (4%) and clay (48%) was evaluated in lab-scale slurry bioreactors under aerobic and anaerobic (sulfate-reducing) conditions, both with and without an additional carbon source (sucrose). The soil was sterilized and spiked with 300 mg 2,4-D/kg dry matrix prior to introduction to the slurry bioreactors, both of which received bacteria (20%, v/v) acclimated to 2,4-D from aerobic and sulfate-reducing continuous complete-mix reactors. The investigators found that aerobic conditions were more favorable for the degradation of 2,4-D in terms of the overall removal efficiency (93%) compared to 25% under sulfate-reducing conditions during a 14-day treatment period, but the specific removal rate in the sulfate-reducing bioreactor was significantly higher than that in the aerobic bioreactor. This difference was attributed to the fact that the aerobic inoculum was much denser than the sulfate-reducing inoculum. Aerobic removal was not affected by the sucrose supplementation, whereas the sulfate-reducing bioreactor removed 2,4-D to a slightly greater extent with sucrose than without. Overall, the slurry bioreactor bioremediation technique achieved effective removal of the herbicide from mineral agricultural soils characterized by a fine texture and high content of organic matter.