School of Mechanical Engineering Asaf Ben Neriah

School of Mechanical Engineering Seminar
Wednesday, June 20, 2018 at 14:00
Wolfson Building of Mechanical Engineering, Room 206

Groundwater remediation by air sparging: improving efficiency by inducing mixing

Asaf Ben Neriah

 PhD. student of Dr. Amir Paster

Groundwater contamination due to leakage, designated or accidental releases of volatile organic compounds is a major problem worldwide. Remediating the contaminated water is crucial for maintaining groundwater as a drinking source, and preventing the expansion of the contaminant plume into clean water.

Air sparging is a relatively simple and inexpensive remediation technique, commonly applied for removing volatile organic compounds from the water. Since the 1980s, air sparging was successfully used at sites where the contaminants are located at the upper part of the aquifer and the soil is relatively permeable (i.e., sandy soils).

Air sparging is commonly applied for long time periods. One important observation, seen in laboratory and field conditions, is that as the system approaches steady state, the remediation efficiency decreases. The decrease in efficiency was linked to the nearly stagnant conditions in the aquifer and very limited mixing, which characterize prolonged operation. This research was aimed at improving the remediation efficiency by utilizing the transient stages of air sparging, in which mixing is significant.

Using a 2D laboratory model and a numerical code (T2VOC, TOUGH2), several approaches for enhancing the groundwater remediation process were studied. These approaches include periodically changing the air injection rate, applying short duration- high pressure- pulses to the injection system, and establishing a methodology for estimating the optimal system characteristic time. Results from the current study highlight the significance of mixing to the remediation process, and the importance of planning an injection scheme which fits the specific characteristics of the remediated site. They also show that the optimal frequency of periodic injection can be approximated by the characteristic time of the relaxation of a large pressure perturbation in the aquifer..