BACKGROUND: Ciprofloxacin (CIP) is an antibiotic largely used to treat bacterial infections and found in sewage treatment plant (STP) effluent. Zero valent iron (ZVI, Fe2+) technology has great potential for the degradation of residual pharmaceuticals. The effect of some parameters (anaerobic/aerobic, particle size, iron ligands and anions) were evaluated for CIP degradation in distilled water (DW) and finally compared to that obtained in STP effluent. RESULTS: The smaller ZVI particle (200 mesh) resulted in a lower degradation rate than the larger particle (20 mesh) in both anaerobic and aerobic treatment. This is due mainly to the fast generation of Fe2+, hindering the degradation process due to (OH)-O-center dot scavenging. A linear increase of CIP degradation ratewas observed when the reactionwas carried out with increasing EDTA concentrations. The Cl- anions had a positive effect on CIP degradation in the ZVI process. On the other hand, the presence of NO3- resulted in a decrease of degradation rate, both with 20 and 200 mesh particles. CIP could be degraded in two STP effluents mediated by ZVI (20 mesh). CONCLUSIONS: The ZVI process can be used efficiently for the degradation of CIP in two types of STP effluent (anaerobic treatment or anaerobic/aerobic treatment), revealing a possible applicability of the ZVI process to this type of matrix. (C) 2017 Society of Chemical Industry