Discussing porosity loss of Fe0 packed water filters at ground level

The use of granular metallic iron (Fe-0) as filter material is gaining acceptance in the field of water treatment. Few works have been directed at developing design guidance for efficient Fe-0 filters. This note consolidates earlier works and provides the scientific basis for the design and evaluation of Fe-0 filters for water treatment at any scale. The approach assumes uniform corrosion of individual Fe-0 particles and utilizes the radius loss (X = R-0 - R) to asses the extent of porosity loss in the whole system. Results corroborate that, for R-0 <= 1.0 mm, sustainable filters must content less than 53% Fe-0 (v/v). A universal equation of Fe-0 filters is provided given X as a function of the initial radius R-0, the initial volume of Fe-0, the initial porosity of the filter and the coefficient of volumetric expansion (O-2 availability). This equation should be routinely incorporated in simulations for modeling the hydraulic conductivity of Fe-0 filters. The model improves the discussion of published data on porosity loss. (C) 2014 Elsevier B.V. All rights reserved.