Changes in air flow patterns using surfactants and thickeners during air sparging: bench-scale experiments

Area of Science:

• Environmental Engineering
• Hydrogeology
• Chemical Engineering

Background:

• Air sparging is a common in-situ remediation technology for contaminated aquifers.
• Typically, injected air flows upward driven by pressure gradients and buoyancy.
• Natural hydrogeologic conditions dictate the unpredictable air flow paths.

Purpose of the Study:

• To present a novel method for controlling air flow paths during aquifer air sparging.
• To investigate the influence of aqueous phase viscosity and surface tension on air flow.
• To enhance contaminant removal efficiency by directing air flow to target zones.

Main Methods:

• Altered hydrodynamic parameters (viscosity, surface tension) using water-soluble reagents prior to air sparging.
• Conducted experiments using one-, two-, and three-dimensional physical models packed with water-saturated sand.
• Measured air intrusion velocity and air flux distribution using gaseous flux meters.

Main Results:

• Increased aqueous viscosity retarded air front velocity and acted as an air flow barrier.
• Decreased surface tension directed air flow selectively through the low-surface tension region.
• Air flow was significantly influenced by localized changes in viscosity and surface tension.

Conclusions:

• Manipulating aqueous phase viscosity and surface tension offers a method to control air flow during sparging.
• Creating low-surface tension zones can enhance air delivery to contaminated areas for improved remediation.
• High viscosity zones can effectively block air flow, preventing unwanted de-saturation.