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Feasibility of nanoscale zero-valent iron (nZVI) for enhanced biological treatment of organic dyes

Liu, Jing, Liu, Airong, Wang, Wei, Li, Ruofan, Zhang, Wei-xian
Chemosphere 2019 pp. 124470
biodegradability, biodegradation, biological treatment, chemical oxygen demand, decolorization, dyes, iron, membrane bioreactors, organic compounds, pH, redox potential, wastewater, wastewater treatment
Biodegradation of recalcitrant organic contaminants such as organic dyes is a fundamental challenge in wastewater treatment. We report herein the integration of nanoscale zero-valent iron (nZVI) with membrane bioreactors to achieve enhanced degradation of Congo red (CR) in wastewater. nZVI pretreatment converts the large and bio-recalcitrant CR molecules into smaller and more biodegradable organic compounds in continuous flow stirred tank reactors (CFSTR). A nZVI-bio system was experimented continuously for 52 d with a color removal efficiency of 99% and a reduction of chemical oxygen demand (COD) from 167 mg L−1 to less than 70 mg L−1. However, a conventional biotreatment system treating identical wastewater achieved color removal efficiency of just 30–70% and the COD reduction to 116 mg L−1. This suggests that integrated nZVI-bio system has potential for the treatment of recalcitrant organic dyes. On-line measurements of pH and redox potential in the CSFTR can be conveniently used to monitor and regulate treatment performance.