Performance of a ZVI-UASB reactor for azo dye wastewater treatment

BACKGROUND: Zero valent iron (ZVI) is expected to be helpful for creating an enhanced anaerobic environment that might improve the performance of the anaerobic process. Based on this idea, a ZVI packed upflow anaerobic sludge blanket reactor (ZVI-UASB) was developed to enhance azo dye wastewater treatment. RESULTS: The ZVI-UASB reactor was less influenced by a decrease in the operational temperature from 35 degrees C to 25 degrees C than a reference UASB reactor that did not contain ZVI. In addition, chemical oxygen demand (COD) and color removal efficiencies of the ZVI-UASB reactor at an HRT of 12 h exceeded those of the reference reactor at an HRT of 24 h. The hydraulic circulation in the ZVI bed enhanced the function of ZVI so that it improved the COD and color removal efficiencies. Moreover, fluorescence in situ hybridization experiments revealed that the abundance of Archaea in the sludge of the ZVI bed was significantly higher than that at the reactor bottom, which made the reactor capable of greater COD removal undertow temperature and short HRT conditions. CONCLUSION: This ZVI-UASB reactor could adapt well to changes in the operational conditions during wastewater treatment. C) 2010 Society of Chemical Industry