Removal of chromium (VI) in tannery wastewater by Bacillus cereus

Abstract

Bacillus cereus was used to remove Cr(VI) in tannery wastewater containing medium at different initial Cr(VI) concentration, temperature, pH and biomass to get better conditions. At the optimu m condition, the Cr(VI) in tannery wastewater was treated by each component of the cells to detect the capacity of the components for the Cr(VI) reduction. Also, the Bacillus cereus was continuous cultured to test the durative ability for the Cr(VI) removal. After treating 20mg /L Cr(VI) in tannery wastewater for 48h , the Bacillus cereus was observed by SEM, with the strain grown in Luria broth for 48h as control. The results showed that the removal rate of Cr(VI) was the higher when 37°C, pH=7.0-9.0, 20g/L of the biomass and less than 50mg /L of the initial Cr(VI) concentration; at the optimu m conditions, the removal rate of Cr(VI) for the cell-free extracts reached 92.70 %, nearly the same as the whole-cells(96.85 %), indicating the Cr(VI) reductase generated by the Bacillus cereus was mainly intracellular. In the process of continuous culture, the strain showed consecutive growth and removal ability of Cr(VI). Also, the SEM images showed that the Bacillus cereus treating Cr(VI) grew well and had the same size, compared with its grown in Luria broth. The experiments demonstrated that the Bacillus cereus could be selected as a new biomaterial to remove Cr(VI) in tannery wastewater.