The use of zero-valent iron (ZVI)–microbe technology for wastewater treatment with special attention to the factors influencing performance: A critical review

Abstract

ABSTRACTIn recent years, the use of zero-valent iron (ZVI) coupled with microorganisms has attracted considerable attention for the removal of diverse contaminants from wastewater, and the performance of bio-ZVI systems under diverse conditions is of particular interest. This paper comprehensively reviews the recent developments related to (1) the effects of the iron surface area, operating conditions, coexisting ions, and contaminant concentrations on the performance of bio-ZVI systems; (2) the potential mechanisms of the major factors affecting the ZVI–microbe performance; and (3) the effects of ZVI on the characteristics of the microorganisms, including both enhancing and deteriorating effects. All these factors can have notable impacts, which are contaminant-specific and highly dependent on the removal mechanisms of the respective pollutants, and on the performance of the bio-ZVI system in terms of contaminant removal. Additionally, the stimulating effects of ZVI on the growth and diversity of microorganisms are reasonable considering the synergistic effects of the combined system on pollutant removal, although inhibitory effects of ZVI on bacterial activity have also been proposed. Based on these findings, further efforts should be made to establish feasible strategies to improve the engineering design and performance of integrated ZVI–microbe systems.