Optimization Strategies for in Situ Groundwater Remediation by a Vertical Circulation Well Based on Particle-Tracking and Node-Dependent Finite Difference Methods

摘要

Both theory and application of multispecies reactive transport for in situ groundwater bioremediation involving a vertical circulation well (VCW) are not fully understood despite its importance and common usage in aquifer remediation practices. This study proposes novel approaches including two methods for design and remediation prediction of a VCW system, which involves multispecies, multiphase, and microbially enhanced reactive transport process. One is particle-tracking method, which depicts the trajectories of particles released from an injection chamber; the other is node-dependent finite difference (NDFD) method, which describes the advection-dispersion process based on the inflow and outflow directions at each node. The numerical results demonstrate that the particle-tracking method works well by yielding a useful index, that is, the recovery ratio, which helps optimize the in situ preliminary remediation screening. When biochemical parameters, dispersivities, and in situ contaminated conditions are known after the preliminary screening, the NDFD method performs better than the conventional Laplace transform finite difference method in terms of describing multispecies reactive transport with multiple phases in a VCW system. The proposed particle-tracking method and NDFD methods are employed to elucidate different effects of factors such as injection mode, hydraulic conductivity anisotropy ratio, distance between injection and extraction screened intervals, and injection/extraction rate on recovery and removal ratios. Our findings suggest that both methods are effective tools for optimization and prediction of VCW remediation in an anisotropic aquifer.