Application of zero valent iron coupling with biological process for wastewater treatment: a review

As a promising technology, zero valent iron (ZVI) coupling with microorganisms has attracted extensive attention for contaminants removal from wastewater. The current paper provides a comprehensive review on recent developments in: (1) the chemical behavior of ZVI and potential mechanisms of integrated bio-ZVI technology in contaminants removal; (2) synergistic effects of bio-ZVI towards various common environmental pollutants in wastewater, including inorganic oxyanions, organic compounds, heavy metals and dyes; (3) promotion effects of ZVI on the biologically anaerobic digestion of waste sludge; (4) operating factors affecting the effectiveness of bio-ZVI process; (5) measures developed to enhance the long-term performance of the bio-ZVI technology. The chemical behavior and stimulating roles of ZVI playing in the growth and diversity of microorganisms is reasonable for the synergistic effects of the combined system. It was demonstrated that combined bio-ZVI system showed appreciable removal efficiencies for several types of contaminants. Additionally, the formation of passive layer on the ZVI surface can be avoided by the means of electrochemical and microbial method. Lastly, this review highlighted the research gaps to improve the sustainability of this technology. Based on these understandings, further efforts should be made to expand the applications of this combined technology and establish some feasible strategies to provide opportunities for the engineering applications.