Hexavalent chromium (Cr(VI)) was proved to be a carcinogen to organisms and threaten health of human beings through food chains. In order to detect a more economical and efficient method to remove Cr(VI) from contaminated sites, a Cr(VI) reducing strain named TH-1 was isolated from aerobic activated sludge and identified as Escherichia sp. by 16 S rDNA sequence analysis. The Cr(VI) removing performance of TH-1 was elucidated under different environmental conditions (temperature, pH, initial Cr (VI) concentration and metal ions) to detect the optimum condition, and the potential mechanisms of Cr(VI) reduction were explained including micro-characterization and stability test of reduction product. As the result, while inhibited by Cd²⁺ existence, TH-1 could grow and remove Cr(VI) in a wide range of temperature and pH (optimum at 37 ℃ and pH7.0), with the process being promoted by Cu²⁺, Ni²⁺ and Fe³⁺. The results of X-ray Diffraction, X-ray photoelectron spectroscopy confirmed that the reduced Cr(VI) product was mainly organic-Cr (III) complex, and Fourier Transform infrared spectroscopy showed that functional groups such as –OH, -COOH and CO etc. were Cr binding sites. Afterwards, the stability of the organic-Cr (III) complex reduced by strain TH-1 were much more stable than Cr (III) chemically reduced by FeS, the stability of which decreased significantly from pH 9 to pH 14, but rarely changed under near-neutral and acidic condition. Hence, TH-1 had great prospects for reducing Cr (VI) under different environmental conditions with long-term effect, which was significant for the remediation of Cr (VI) influenced environmental sites.

六价铬（Cr(VI)）被证明是一种对生物体的致癌物，并通过食物链威胁人类的健康。为了寻找一种更经济、更有效的去除污染场地 Cr(VI) 的方法，从好氧活性污泥中分离出一株名为 TH-1 的 Cr(VI) 还原菌株，并鉴定为Escherichia sp.。通过 16 S rDNA 序列分析。阐明了在不同环境条件（温度、pH、初始 Cr（VI）浓度和金属离子）下 TH-1 的 Cr(VI) 去除性能，以检测最佳条件，并解释了 Cr(VI) 还原的潜在机制包括还原产物的微观表征和稳定性测试。结果，虽然被 Cd ^2+抑制TH-1可以在较宽的温度和pH范围内（37 ℃和pH7.0最佳）生长和去除Cr(VI)，其中Cu ²⁺、Ni ²⁺和Fe ³⁺促进了该过程。X射线衍射、X射线光电子能谱结果证实还原后的Cr(VI)产物主要是有机-Cr(III)配合物，傅里叶变换红外光谱表明-OH、-COOH和C等官能团O等是Cr结合位点。之后，菌株 TH-1 还原的有机-Cr (III) 配合物的稳定性比 FeS 化学还原的 Cr (III) 稳定得多，其稳定性从 pH 9 到 pH 14 显着下降，但在接近中性和酸性条件。因此，TH-1在不同环境条件下具有长效降低Cr(VI)的前景，对Cr(VI)影响的环境场地修复具有重要意义。