Relevant design parameters for a reactor used in P removal with ZVI-based materials

Abstract

Phosphate (P) retention onto zero valent iron (ZVI) particles and on iron oxyhydroxides has been widely investigated as a treatment process for domestic wastewater. Since such a process is less expensive and requires less maintenance than typical biological and physicochemical methods, it could provide a viable path to reaching high P removal capacities. This manuscript provides up-to-date information on P retention mechanisms, with the main ones being adsorption, precipitation and co-precipitation. The major experimental parameters affecting these mechanisms and ZVI reactivity are summarized. Through a review of batch studies and continuous reactor experiments, the P retention capacities of ZVI-based materials have been collated and compared according to test operating conditions, such as pH, initial adsorbate concentrations or hydrodynamic conditions. ZVI and its byproducts have already demonstrated high P retention capacities (up to 264 mg P/g ZVI). Methodological recommendations are provided to design reactor for phosphorus removal in wastewater treatment plants.