Zero-valent iron mediated biological wastewater and sludge treatment

In quest of meeting the requirements of sustainable development, coupling zero valent iron (ZVI) with microorganisms has attracted extensive attentions for enhancing biological wastewater and sludge treatment in terms of microbial growth, nutrients removal, and resources recovery. Given to the significant role of ZVI playing in biological wastewater and sludge treatment, a thorough evaluation of the associated interactions among ZVI and microorganisms is necessary to further scale-up the application of ZVI-based biotechnologies. To this end, this review comprehensively summarizes the mechanisms of ZVI for enhancing nutrients removal (i.e., C, N, S and P) in several typical biological wastewater treatment processes, discusses the role of ZVI in improving the excess sludge reduction by dewatering or anaerobic digestion for methane production, and analyzes the feasibility of recovering phosphorus from anaerobic sludge digestion system in the form of vivianite through using ZVI. Knowledge gaps regarding the application of ZVI in sludge or wastewater treatment are also identified in this review to facilitate the further development of the ZVI-based biological technology. © 2021 Elsevier B.V.