Numerical experiments on evolution of contaminant plume in groundwater with hydraulic parameter reduction by biomass growth

Abstract

A model of groundwater flow and contaminant transport is proposed that incorporates changes in hydraulic parameters due to biomass growth. The model simulates the coupled transport phenomena of biodegradable organic contaminants such as hydrocarbon compounds, dissolved oxygen, and biomass. The model starts with flow simulation to compute the velocity field, which is used to simulate solute transport by the method of characteristics and the finite difference method. The reaction equation incorporating biodegradation kinetics is solved to compute the biomass increase. The increased biomass is transformed to biofilm thickness, which reduces the porosity and permeability. The porosity and permeability are updated at each time step of the computation. Numerical simulations show that the transport simulations, if the reduction of hydraulic parameters is ignored, are likely to overestimate the extent of contaminant plume and underestimate the peak concentration of the plume.