The removal of antibiotic metronidazole (MNZ) in aqueous solution by nanoscale zero-valent iron (NZVI) particles was investigated. The experimental results showed that MNZ was completely removed by NZVI. MNZ solution at 80 mg L-1 was rapidly removed by NZVI within 5 min, at initial solution pH 5.60. NZVI dose of 0.1 g L-1. Influencing factors such as NZVI dosage, initial MNZ concentration and initial solution pH were systematically studied, and the removal process of MNZ followed a pseudo-first order kinetics model. The removal efficiency was enhanced with increasing NZVI dosage while it was decreased with the increase of initial MNZ concentration and initial solution pH. The removal of MNZ in a nitrogen bubbling system (NZVI/N-2 process) and in an air bubbling system (NZVI/air process) was compared, and the results showed that the removal rate in the NZVI/air process was slightly higher than that in the NZVI/N-2 process. The removal efficiencies of MNZ by using NZVI and commercial iron powder were investigated as well, indicating that MNZ removal efficiency by NZVI was about 49 times higher than that by commercial iron powder under the same dosages. This study demonstrates that the NZVI technology could be a promising approach for antibiotic wastewater treatment. (C) 2010 Elsevier B.V. All rights reserved.