BIOEFGM II: Two-dimensional meshless model to simulate the aerobic and anaerobic biodegradation of BTEX contaminant through multiple electron acceptors in groundwater

In the present study, a meshless BIOEFGM II model is proposed to simulate the natural attenuation of BTEX contaminant (benzene, toluene, ethylbenzene, and xylenes) through multiple aerobic and anaerobic electron acceptors in the two-dimensional groundwater system. This model is the extension of the BIOEFGM I model for aerobic BTEX degradation. In BIOEFGM II, the meshless element-free Galerkin method (EFGM) is applied to governing groundwater flow and reactive transport equations. The weak-integral form of EFGM is also applied to the Darcy law equation to compute the groundwater velocity directly at scattered field nodes representing the aquifer domain. This step allows the easy coupling of flow and transport models with both regular and irregular nodes in BIOEFGM II, unlike grid/mesh-based models. The proposed model is the first multispecies model that can simulate natural BTEX degradation using regular/irregular field nodes. In this study, proposed BIOEFGM II-RG and BIOEFGM II-IRG for regular and irregular nodes respectively are applied to a hypothetical aquifer and field-type large heterogeneous aquifer, and results are verified with the benchmark RT3D model. The results of this study reveal that aerobic and anaerobic processes contribute to 30%–40% and 60%–70% of the total BTEX degradation respectively.