Scaling-up of a zero valent iron packed anaerobic reactor for textile dye wastewater treatment: a potential technology for on-site upgrading and rebuilding of traditional anaerobic wastewater treatment plant

Anaerobic digestion (AD) is a cost-effective technology for the treatment of textile dye wastewater with clear environmental benefits. However, the need to improve process feasibility of high treatment efficiency as well as to shorten hydraulic retention time has raised interest on several intensification techniques. Zero valent iron (ZVI) packed anaerobic digesters have the potential to become an on-site upgrading wastewater treatment technology through building a ZVI bed in a traditional AD plant. However, the experiences and knowledge of scale-up are limited. In this study, a pilot-scale ZVI packed upflow anaerobic sludge bed (ZVI-UASB) was built up and operated for actual dye wastewater treatment in a textile dye industrial park. Results showed that the treatment performance of this digester is higher than that of a traditional AD plant in terms of chemical oxygen demand (COD) removal and color removal. During 90 days of operation, the average COD removal and color removal in ZVI-UASB was maintained at around 19% and 40%, respectively, while it was only 10% and 20%, respectively, in the traditional AD plant.