Abstract:The resistance to Cr(VI) and regeneration character of biological iron sulfide composites were studied. The composites consisted of sulfate reducing bacteria(SRB) and nanosized iron sulfide produced by SRB. A new reduction-regeneration recirculation process for treating chromium-containing wastewater and reclaiming chromium was developed with the regeneration character of the composites. The SRB still survived after treating wastewater containing Cr(VI), which could regenerate biological iron sulfide composites by using Fe3+, sulphur as electron acceptor. Furthermore, the SRB could also resist 600mg/L Cr(VI) and remove it gradually. The results of reduction-regeneration recirculation process for treating wastewater indicated that the contaminants in the effluent could meet the discharge standard, i.e. the concentration of total chromium less than 0.929mg/L, Cr(VI) less than 0.019 mg/L. After 10 cycles, the Cr2O3 content in sludge reached 40.47%, and the ratio of Cr2O3/FeO was 6.98. The sludge reached the chemical and metallurgical(hydrometallurgy) grade of chromite ore, which could be reclaimed again.