The performances of sulphur fluidized bed reactors (SFBRs) were evaluated and compared with those of sulphur packed-bed reactors (SPBRs). SFBR-1 fed with 20 mg/l NO3--N showed a denitrification efficiency greater than 91.7% up to a loading rate of 2.53 kg NO3--N/m(3) day, with a corresponding empty bed contact time (EBCT) of 0.19 h. For SFBR-2 fed with 700 mg/l of NO3--N, denitrification efficiency was greater than 98% up to a loading rate of 2.68 kg NO3--N/m(3) day (EBCT of 6.1 h). Nitrogen removal rates of SFBRs were significantly higher than those of SPBRs. The nitrous oxide content in the produced gas was also much lower in SFBRs than in SPBRs. Good mass transfer of nitrate to the biofilm on sulphur surfaces and absence of clogging problems could be the main reasons for the higher nitrogen removal rate in the SFBRs. The present findings suggest that SFBRs are suitable for post-denitrification when higher loading rates and shorter EBCTs are preferred. (C) 2003 Elsevier Ltd. All rights reserved.