An upflow anaerobic sludge blanket (UASB) reactor was successfully applied to continuous degradation of ferric ethylene diamine tetra acetate (Fe-EDTA) as a typical xenobiotic substance contained in photo-processing wastewater. The sludge in the UASB reactor had an abundance of sulfate-reducing bacteria (SRB), which had been anaerobically cultivated in a sulfate-rich culture medium including Fe-EDTA and yeast extract as the carbon sources. Since the prominent reductions of Fe-EDTA and sulfate ion were observed, the contribution of SRB to Fe-EDTA degradation in the UASB reactor was confirmed. The aggregated sludge in the UASB rector became gradually large, reaching steady state with an equivalent diameter of 60-90, μm after 92 days operation. An increase of the amount of yeast extract addition to feed solution, which contained 100 mg-C/l of Fe-EDTA, improved the Fe-EDTA removal efficiency up to 90%. Moreover, approximately 80% of intermediate compounds were mineralized by O₃/H₂O₂ oxidation process. When the combination of SRB treatment and O₃/H₂O₂ was applied to an actual fixing wastewater, approximately 80% of Fe-EDTA and 70% or more of dissolved organic carbon (DOC) in thefixing wastewater were degraded.