Enhancing the Sustainability of Household Fe 0 /Sand Filters by Using Bimetallics and MnO 2

Filtration systems containing metallic iron as reactive medium (Fe 0 beds) have been intensively used for water treatment during the last two decades. The sustainability of Fe 0 beds is severely confined by two major factors: (i) reactivity loss as result of the formation of an oxide scale on Fe 0 and (ii) permeability loss due to pore filling by generated iron corrosion products. Both factors are inherent to iron corrosion at pH > 4.5 and are common during the lifespan of a Fe 0 bed. It is of great practical significance to improve the performance of Fe 0 beds by properly addressing these key factors. Recent studies have shown that both reactivity loss and permeability loss could be addressed by mixing Fe 0 and inert materials. For a non‐porous additive like quartz, the threshold value for the Fe 0 volumetric proportion is 51%. Using the Fe 0 /quartz system as reference, this study theoretically discusses the possibility of (i) replacing Fe 0 by bimetallic systems (e.g., Fe 0 /Cu 0 ), or (ii) partially replacing quartz by a reactive metal oxide (MnO 2 or TiO 2 ) to improve the efficiency of Fe 0 beds. Results confirmed the suitability of both tools for sustaining Fe 0 bed performance. It is shown that using a Fe 0 :MnO 2 system with the volumetric proportion 51:49 will yield a filter with 40% residual porosity at Fe 0 depletion (MnO 2 porosity 62%). This study improves Fe 0 bed design and can be considered as a basis for further refinement and detailed research for efficient Fe 0 filters.