Numerical modeling purification performance of pot test

Abstract

A three-dimensional mathematical model was developed to simulate the pollutant removal efficiency of the soil and plants in the pot test. The advection, dispersion, diffusion, adsorption, biochemical reaction and plant uptake processes were taken into account in the model. The three-dimensional modified Richards equation was used in simulating flow field. The mass balance law was employed in deriving the equation for pollutant transport, where the diffusion and dispersion were described with the Fick-type law, the adsorption was macroscopically expressed as form isotherm, and the bio-chemical degradation process was assumed to follow the Monod kinetics. The mathematical model was descretized by the finite element numerical method. In the pot test, the hydraulic loading was assumed to have the intermittent pattern simulating the rainfall duration and the occurrence of frequency, and the concentrations of pollutants in the influent and effluent were measured. The computed overall removal rates for the COD Cr and TN in four cases are in the range of 90.62% − 95.43% and 85.01% − 96.46%, respectively. The differences between the computed and tested overall removal rates for the COD Cr and TN are smaller than 5%. The time-varying oscillation pattern of the concentrations of the COD Cr and TN were rationally simulated, which showed that the model presented in this article could be used to assess the pollutant removal efficiency of the soil and plants in related cases.