The Application of In Situ Air Sparging as an Innovative Soils and Ground Water Remediation Technology

Abstract

Vapor extraction (soil venting) has been demonstrated to be a successful and cost‐effective remediation technology for removing VOCs from the vadose (unsaturated) zone. However, in many cases, seasonal water table fluctuations, drawdown associated with pump‐and‐treat remediation techniques, and spills involving dense, non‐aqueous phase liquids (DNAPLS) create contaminated soil below the water table. Vapor extraction alone is not considered to be an optimal remediation technology to address this type of contamination. An innovative approach to saturated zone remediation is the use of sparging (injection) wells to inject a hydrocarbon‐free gaseous medium (typically air) into the saturated zone below the areas of contamination. The contaminants dissolved in the ground water and sorbed onto soil particles partition into the advective air phase, effectively simulating an in situ air‐stripping system. The stripped contaminants are transported in the gas phase to the vadose zone, within the radius of influence of a vapor extraction and vapor treatment system. In situ air sparging is a complex multifluid phase process, which has been applied successfully in Europe since the mid‐1980s. To date, site‐specific pilot tests have been used to design air‐sparging systems. Research is currently underway to develop better engineering design methodologies for the process. Major design parameters to be considered include contaminant type, gas injection pressures and flow rates, site geology, bubble size, injection interval (areal and vertical) and the equipment specifications. Correct design and operation of this technology has been demonstrated to achieve ground water cleanup of VOC contamination to low part‐per‐billion levels.

Effects of air injection on flow through porous media: Observations and analyses of laboratory‐scale processes

“…40, W09203, doi:10.1029/2003WR002960, 2004 aerobic biodegradation [e.g., Reddy and Adams, 2001;Brooks et al, 1999;Ahlfeld et al, 1994;Ji et al, 1993;Marley et al, 1992;Bruell et al, 1997].…”

Conceptual air sparging decision tool in support of the development of an air sparging optimization decision tool

“…Air sparging can also impact the DO levels by transfer within the saturated zone due to the mixing associated with air sparging system start-up and shut-down. Following several hours of sparging, groundwater DO levels are often observed to increase significantly at one or a number of monitoring points (Marley, et al 1993). Combined air sparging and SVE systems may also influence DO levels as a result of air transport occurring within the unsaturated zone or may contribute to elevated DO levels via equilibrium between the aqueous and air phases.…”

Modeling of air sparging in a layered soil: Numerical and analytical approximations

“…Experimental studies on air sparging on both field [Johnson et al, 1993;Lundegard and LaBrecque, 1995;Marley et al, 1992] and laboratory [Ji et al, 1993;Wehrle, 1990] scales intended to determine the region in the saturated zone where air is present (radius of influence). These studies revealed that variations in soil texture strongly affect the air flow.…”