Variable-component, energy-efficient technology for groundwater remediation

ABSTRACT

A groundwater flow and mass transport model was used to evaluate energy-efficient alternatives for remediating a contaminated, unconfined aquifer. Alternatives were a two-well scheme featuring a downgradient extraction and upgradient injection well pumping at the same rate, and a two-well scheme augmented with passive (non-pumping) wells equipped with treatment (reactive) media. The augmented two-well scheme was the same as the plain two-well scheme, but for the addition of passive wells. The passive wells occupied a linear transect oriented perpendicular to the local hydraulic gradient and offset downgradient of the extraction well. Various combinations of passive well spacing and downgradient offset were evaluated in augmented schemes. The two-well scheme required a slightly higher pumping rate to contain and remove the contaminant plume; however, it removed the plume in less time than augmented schemes. In this case, “removed the plume” meant that simulated concentrations dropped below 1 mg/L at all model cells. Augmented schemes contained and removed the plume at a lower pumping rate, while removing less water and contaminant mass. Small differences in transect location and well spacing had substantial impact on the performance of augmented schemes. Overall, results of this study suggest that two-well and augmented schemes may be effective low-energy alternatives for remediating contaminated groundwater in some settings.

KEYWORDS:

• Energy efficient
• groundwater
• passive wells
• remediation