Configuring passive wells with reactive media for treating contaminated groundwater

Abstract

Passive (nonpumped) wells filled with reactive media may be an effective alternative to permeable reactive barriers for treating contaminated groundwater in deep aquifers. This study's objective was to evaluate alternative passive well configurations for treating contaminated groundwater in a simulated aquifer. Six configurations of 17 wells were tested, each well screened across the saturated zone. Passive wells occupied various locations on monitoring transects. Five configurations involved one or more monitoring transects perpendicular to regional groundwater flow, positioned downgradient of a contaminant plume. In a sixth configuration, monitoring transects were ±45° to groundwater flow, joined downgradient of the contaminant plume. A numerical mass transport model, accounting for advection and hydrodynamic dispersion, tested the ability of each passive well configuration to reduce contaminant concentrations and prevent offsite contaminant migration. For a fixed number of wells, relatively effective strategies include: (a) spanning the lateral width of a contaminant plume; (b) multiple monitoring transects, with relatively close well spacing along upgradient transects; and (c) 45° monitoring transects. Overall, the 45° structure was most effective. © 2008 American Institute of Chemical Engineers Environ Prog, 2008

Configuration of Non-Pumping Reactive Wells Considering Minimum Well Spacing

“…A diagonal arrangement of reactive wells (zigzag array) was proposed as a more efficient well configuration (Figure 1d) in which the zigzag array transect consists of linear segments arranged at a 45-degree angle with respect to the direction of groundwater flow. This configuration performed effectively in terms of reducing the maximum concentrations, as well as the residual plume area [31].…”

“…With the development of drilling technology, NPRWs are easier to construct than the existing trench-type PRBs for use in deep subsurface environments. In previous studies, various configurations of NPRWs have been developed, such as those employing a single transect, a 45-degree structure transect [31], and multi-transects in the shape of a zigzag [28] (Figure 1). Each non-pumping well filled with reactive media had a capture width larger than its diameter when the hydraulic conductivity of the reactive material was higher than that of the surrounding geologic media.…”

“…The multi-transect configuration can capture the contaminant plume completely by repeated treatment in the reactive wells on the second and third transects. However, the performance of NPRWs in preventing pollution is affected by several configuration factors such as well spacing, distance between transects, and number of wells and transects [28,31].…”

“…Wilson et al [28] studied configurations of an array of nonpumping wells with single-and multi-transects for remediating contaminated groundwater. Hudak [31] compared contaminant blocking in groundwater according to the number of transects (single, double, and triple transect) of non-pumping wells. He also studied triple transect consisting of linear segments arranged at 45-degrees with respect to the direction of groundwater flow and evaluated a nonlinear array of non-pumping wells [26,31].…”

“…Hudak [31] compared contaminant blocking in groundwater according to the number of transects (single, double, and triple transect) of non-pumping wells. He also studied triple transect consisting of linear segments arranged at 45-degrees with respect to the direction of groundwater flow and evaluated a nonlinear array of non-pumping wells [26,31]. Freethey et al [30] proposed a configuration of possible DART well arrays for contaminant removal in a circular arrangement by combining them with pumping wells.…”