This work is one of attempts to implement coupled ROCKFLOW-PHREEQC to reactive transport modelling. The model is designed for virtual aquifer. A two-dimensional model for homogenous systems under natural conditions was developed to observe the groundwater flow pattern and to simulate contaminant reactive transport in sandy, slightly porous aquifer system having square form, with sides 300 m and 500 m, thickness 6 m. With grid spacing of 10 meters in both directions. This study is concerned with the reactive transport of contaminants in groundwater. The analysis includes the instantaneous propagation of the contaminant from the emplaced source. This work presents a recapitulation of the processes of contaminant reactive transport in groundwater systems and develops a two-dimensional numerical approach for biodegradation of emplaced contaminant source in a porous sandy aquifer. The book can be interesting to audience interested in modelling with ROCKFLOW-PHREEQC.