A Non-dimensional Analysis of Permeability Loss in Zero-Valent Iron Permeable Reactive Barrier (PRB)

Abstract

Zero-valent iron (ZVI) permeable reactive barrier (PRB) is a treatment wall filled with ZVI as a reactive material that is installed perpendicular to the groundwater flow in the subsurface. To aid design of these PRBs, a non-dimensional analysis of the permeability reduction has been carried out in this work where the dimensionless equation has been identified to correlate different variables. Additionally, the change in physical features of ZVI PRB has been identified using the inspection system of X-ray microcomputer tomography and it has shown that the particle size is expanding, thus reducing the permeability. The change in chemical composition that impacts the surface reactivity has been confirmed using X-ray diffraction, and the corroded products of maghemite and magnetite have been identified. Flow experiments have been conducted to observe and measure the changes in permeability, where the pressure at various points of the experimental rigs has been measured for the calculation of permeability values. The reduction in permeability could be observed from both small- and large-scale experiments. For example, the flow experiments indicated that the permeability value has been significantly reduced for coarse particle, e.g. in small-scale experiment, it reduced from 7.04E−8 to 3.09E−9 cm2. It can also be seen that the permeability is decreased by 95.6% for small scale (coarse particle) and by 79.5% for large scale.