Treatment of high-concentration chromium-containing wastewater by sulfate-reducing bacteria acclimated with ethanol

In order to solve the problem of difficult treatment of high-concentration chromium-containing wastewater, sulfate-reducing bacteria (SRB) with a high tolerance of hexavalent chromium and a strong ability to reduce the compound were isolated from sludge from a sedimentation tank in a leather industrial park and was identified as Desulfovibrio by morphological observation, routine physiological and biochemical determination, 16S rDNA sequencing and phylogenetic tree construction. After ethanol acclimation, a strain of SRB that could reduce chromium (CR-1) was selected as the research object. The optimum growth conditions for hexavalent chromium removal by the strain were determined by single-factor analysis. The chromium removal mechanism of the strain was analyzed, and a kinetic model of the reduction process was established. The chromium-reducing ability of the strain was 500 mg/L, the optimum pH value was 7, the optimum temperature was 35 °C, the optimum cultivation time was 24 h, and the optimum ratio of bacteria to waste (volume ratio of bacterial solution dosage and chromium-containing wastewater) was 1:5. The mechanism of treatment of Cr(VI) by this strain is mainly based on the reduction of Cr(VI) by H₂S accumulated in the cultured bacterial solution and the small amount of H₂S generated by bacterial reductase, bacterial growth and SO₄ ^2- reduction in the waste liquid.