Hydraulic Performance of the Horizontal Reactive Media Treatment Well: Pilot and Numerical Study

Abstract

This study is focused on a passive treatment system known as the horizontal reactive treatment well (HRX Well®) installed parallel to groundwater flow, which operates on the principle of flow focusing that results from the hydraulic conductivity (K) ratio of the well and aquifer media. Passive flow and capture in the HRX Well are described by simplified equations adapted from Darcy's Law. A field pilot‐scale study (PSS) and numerical simulations using a finite element method (FEM) were conducted to verify the HRX Well concept and test the validity of the HRX Well‐simplified equations. The hydraulic performance results from both studies were observed to be within a close agreement to the simplified equations and their hydraulic capture width approximately five times greater than the well diameter (0.20 m). Key parameters affecting capture included the aquifer thickness, well diameter, and permeability ratio of the HRX Well treatment media and aquifer material. During pilot testing, the HRX Well captured 39% of flow while representing 0.5% of the test pit cross‐sectional volume, indicating that the well captures a substantial amount of surrounding groundwater. While uncertainty in the aquifer and well properties (porosity, K, well losses), including the effects of boundary conditions, may have caused minor differences in the results, data from this study indicate that the simplified equations are valid for the conceptual design of a field study. A full‐scale HRX Well was installed at Site SS003 at Vanderberg Air Force Base, California, in July/August 2018 based on outcomes from this study.

Screening of organic substrates for a permeable biobarrier to remediate nitrate contaminated groundwater

“…have increased the effectiveness and life time of treatment zone (Singh et al, 2020; US Air Force, 2008). Different configurations like permeable vertical unpumped well or permeable horizontal well systems have been developed and applied on field scale (Divine et al, 2018; Freethey et al, 2003; Nzeribe et al, 2020).…”

Field Demonstration of the Horizontal Treatment Well (HRX Well®) for Passive In Situ Remediation

“…where K A is the average hydraulic conductivity of the targeted aquifer zone, b A is the targeted aquifer zone thickness, and i A is the regional aquifer hydraulic gradient (outside the influence of the HRX Well). In general i HRX < i A , however, as the length of the HRX Well and the screen sections increase, i HRX /i A approaches unity and therefore for most field appli-cations, i HRX can be practically assumed to be similar to the ambient aquifer hydraulic gradient, i A (Divine et al 2011(Divine et al , 2018cNzeribe et al 2020). The approximate average flow velocity v HRX and minimum average residence time t R of groundwater within the treatment media can be estimated by:…”

“…The HRX Well concept, laboratory-and pilot-scale physical testing, and detailed numerical modeling are presented elsewhere in the literature (Divine et al 2011(Divine et al , 2013(Divine et al , 2018a(Divine et al , 2018b(Divine et al , 2018cNzeribe et al 2020). This paper presents results of the first full-scale field demonstration of the HRX Well to passively treat chlorinated solvents (primarily trichloroethene [TCE]) via in situ chemical reduction with ZVI treatment media.…”