Screening, Identification And Characteristics Of A Strain With High Cr (Ⅵ) Degradation Capacity

The treatment of industrial wastewater contaminated Cr(Ⅵ) is a difficulty in the whole world. In recent years, the researches on the Cr (Ⅵ) removal show that indicated that microbial treatment has the advantages of being low investment, less secondary pollution and simple craft, and has become one of the hottest research topics in water treatments. The chromium-containing waste water was cleaned by the microbial method. Though a series of researches inculding screening, isolating, acclimating and UV treating, a high Cr(Ⅵ)-removal strain was obtained from the eight Cr(Ⅵ)-tolerancing strains that screened from the chrome sludge at Xiawan harbor of Zhuzhou city, Hunan province. According to the morphological, physiological and biochemical characteristics, as well as sequence analysis of16S rDNA, the strain was identified as Enterobacter cloacae subsp. cloacae, which was signed as ECsC.The effects of removal time, temperature, pH, inoculation amount and shaking speed on reductive degradation rate of the active ECsC strain and absorption removal rate of inactive ECsC strain were studied, respectively. The synthetic wastewater containing initial Cr(Ⅵ) concentration200mg/L was treated by the active ECsC strain under the conditions of pH6.5and inoculation amount14%with50r/min at35℃for10h, where the reductive degradation rate reached92.5%. The sorption removal rate of the inactive ECsC strain can reach86.2%after treating the wastewater with50mg/L initial Cr(Ⅵ) concentration in the optimizing conditions:pH6.0, inoculation amount2.0g/L and120r/min at25℃for8h. In order to achieved national standard of wastewater contaminated Cr(Ⅵ), In order to hit the state emission standards of the wastewater contaminated Cr(Ⅵ), the two-step method combining the active ECsC reducing degradation and inactive ECsC adsorption was carried out. The result showed that the residual Cr(Ⅵ) concentration in the treated wastewater was0.12mg/L, which was lower than the value of stipulated by government (0.2mg/L). The wastewater treated using the two-step method is directly discharged into the environment.