Model-Based Approach to Determine Critical Design Parameters for Tandem Circulation Well Remediation Systems.

Abstract

Aerobic bioremediation enhanced by tandem circulation well (TCW)-generated aeration in a groundwater circulation systems has emerged as a novel, environmentally friendly, and cost-effective remediation approach with growing recognition. For TCW, previous investigations have been limited to few laboratory experiments, simulation precision, acquisition of reaction kinetic parameters, and effective guidance for technology optimization. In this work, we employed regionalized sensitivity analysis with Latin Hypercube Sampling (LHS) to identify the most sensitive parameters in laboratory TCW experiments, reducing the number of parameters to estimate. The estimated parameters were utilized to construct a reactive transport model with periodic boundary conditions, enhancing its universality for in-situ trichloroethylene (TCE) bioremediation through electrolysis considering mutual interactions among well clusters. The results revealed the influence mechanisms of the operating parameters and well spacing on remediation performance. Besides, it was found that degradation efficiency was limited by DO oversaturation in the wellbore. However, it could be promoted by optimization of operation parameters, using an optimization index, the ratio of current to pumping rate ( $\alpha$ ). Finally, simulation results implied two suggestions for well spacing: (1) Designing a remediation site with a higher aspect ratio will enhance the performance of this technology. (2) With a larger area, both current intensity and pumping rate need to be proportionally increased in alignment with the enlarged area to ensure optimal efficiency. This work improves the precision of characterizing the TCW system, guiding the determination of reaction kinetics parameters and optimization of critical design parameters, including operational parameters and well spacing, in remediation sites, thereby achieving superior remediation performance in field applications.