Investigating the Effect of Important Parameters in a One-Dimensional Numerical Model of Pollutants Transmission in the Presence of Colloid in a Saturated Porous Medium

Document Type : Research Paper

Authors

1 PhD Candidate of Environmental Engineering-Water Resources, School of Environment, College of Engineering, University of Tehran, Tehran, Iran

2 Assoc. Prof., of Environmental Engineering, School of Environment, College of Engineering, University of Tehran, Tehran, Iran

Abstract

Transmission of pollutants to high vulnerability groundwaters is significant due to the uncontrolled growth of water harvesting from wells in recent years. One of the significant parameters for the pollutants transfer to groundwater is the presence of colloidal particles. These particles often facilitate the transfer of pollutants to lower soil depths in saturated conditions. However, in particular circumstances, they also delay the transmission of pollutants. Therefore, it is necessary to study the effect of various parameters on the transfer of pollutants in the presence of colloids. In this research, in order to investigate the effect of various parameters and the effect of colloid presence on pollutant transfer, first, a hexavalent chromium transmission experiment was performed in the presence of bentonite colloidal particles in a saturated porous medium column. Then a one-dimensional numerical model has been developed based on three-phase equations and interactions of soil, colloid particles, and pollutants in a saturated porous medium. The equations in this research include six differential equations that have six unknown parameters. These equations are solved with finite difference method, which uses two points reverse differential approximation for derivatives of time and central difference approximation for spatial derivatives. The numerical model was calibrated with experimental results with a determination coefficient of 0.98 and constant coefficients of the equations were optimized. Investigation of the important parameters showed that by increasing the deposition rate of colloidal particles on the solid matrix, less pollutant content was transferred, which is a fact for the effect of colloidal particles on pollutant transport. Also, increasing the rate of pollutants absorption by colloidal particles and increasing the flow velocity, increases the pollutant transport. The results indicated that doubling the hydrodynamic diffusion coefficient of the contaminant and colloidal particles increased transmission by more than 100 times at the beginning of the experiment and by approximately 15% at the end of the experiment. Finally, the increase in porosity increases the gap between the particles and the chromium transmission. The results of this study indicate the significant effect of bentonite colloidal particles in facilitating and enhancing chromium transport in saturated porous media. Also, the diffusion coefficient has the most influence on chromium transport in the presence of colloidal particles in the saturated porous media. As a result, the presence of colloidal particles in groundwater-contaminated environments should be monitored and the effects of parameters in that environment should be determined by modeling to take the necessary measures to control it.

Keywords

References

Bekhit, H. M., El-Kordy, M. A. & Hassan, A. E. 2009. Contaminant transport in groundwater in the presence of colloids and bacteria: model development and verification. Journal of Contaminant Hydrology, 108(3-4), 152-167.
Bekhit, H. M. & Hassan, A. E. 2005. Two-dimensional modeling of contaminant transport in porous media in the presence of colloids. Advances in Water Resources, 28(12), 1320-1335.
Bradford, S. A. & Leij, F. J. 2018. Modeling the transport and retention of polydispersed colloidal suspensions in porous media. Chemical Engineering Science, 192, 972-980.
Burri, N. M., Weatherl, R., Moeck, C. & Schirmer, M. 2019. A review of threats to groundwater quality in the anthropocene. Science of the Total Environment, 684, 136-154.
Chen, C., Liu, K. & Shang, J. 2018. Effects of ionic strength, electrolyte type, pH, and flow rate on transport and retention of atmospheric deposition particles in saturated porous media. Journal of Soils and Sediments, 18(3), 1066-1075.
Corapcioglu, M. Y. & Jiang, S. 1993. Colloid‐facilitated groundwater contaminant transport. Water Resources Research, 29(7), 2215-2226.
De Jonge, L. W., Kjærgaard, C. & Moldrup, P. 2004. Colloids and colloid-facilitated transport of contaminants in soils. Vadose Zone Journal, 3(2), 321-325.
Energy, I. R. O. I. M. O. 2018. Iran Water Statistical Yearbook. (In Persian)
He, J., Wang, D. & Zhou, D. 2019. Transport and retention of silver nanoparticles in soil: Effects of input concentration, particle size and surface coating. Science of the Total Environment, 648, 102-108.
Hunter, R. J. 2001. Foundations of Colloid Science, Oxford University Press.
Katzourakis, V. E. & Chrysikopoulos, C. V. 2014. Mathematical modeling of colloid and virus cotransport in porous media: application to experimental data. Advances in Water Resources, 68, 62-73.
Kheirabadi, M., Niksokhan, M. H. & Omidvar, B. 2017. Colloid-associated groundwater contaminant transport in homogeneous saturated porous media: mathematical and numerical modeling. Environmental Modeling and Assessment, 22(1), 79-90.
Li, X., Zhang, W., Qin, Y., Ma, T., Zhou, J. & Du, S. 2019. Fe–colloid cotransport through saturated porous media under different hydrochemical and hydrodynamic conditions. Science of the Total Environment, 647, 494-506.
Malgaresi, G., Zhang, H., Chrysikopoulos, C. & Bedrikovetsky, P. 2019. Cotransport of suspended colloids and nanoparticles in porous media. Transport in Porous Media, 128(1), 153-177.
Mccarthy, J. F. & Mckay, L. D. 2004. Colloid transport in the subsurface: past, present and future challenges. Vadose Zone Journal, 3(2), 326-337.
Mills, W. B., Liu, S. & Fong, F. K. 1991. Literature review and model (COMET) for colloid/metals transport in porous media. Groundwater, 29(2), 199-208.
Roy, S. B. & Dzombak, D. A. 1997. Chemical factors influencing colloid-facilitated transport of contaminants in porous media. Environmental Science and Technology, 31(3), 656-664.
Saiers, J. E. 2002. Laboratory observations and mathematical modeling of colloid‐facilitated contaminant transport in chemically heterogeneous systems. Water Resources Research, 38(4), 3-1-3-13.
Saiers, J. E. & Hornberger, G. M. 1999. The influence of ionic strength on the facilitated transport of cesium by kaolinite colloids. Water Resources Research, 35(6), 1713-1727.
Sen, T. K. & Khilar, K. C. 2006. Review on subsurface colloids and colloid-associated contaminant transport in saturated porous media. Advances in Colloid and Interface Science, 119(2-3), 71-96.
Sen, T. K., Nalwaya, N. & Khilar, K. C. 2002. Colloid‐associated contaminant transport in porous media: 2. Mathematical modeling. AIChE Journal, 48(10), 2375-2385.
Sen, T. K., Shanbhag, S. & Khilar, K. C. 2004. Subsurface colloids in groundwater contamination: a mathematical model. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 232(1), 29-38.
Šimůnek, J., He, C., Pang, L. & Bradford, S. A. 2006. Colloid-facilitated solute transport in variably saturated porous media: numerical model and experimental verification. Vadose Zone Journal, 5(3), 1035-1047.
Speight, J. G. 2019. Natural Water Remediation: Chemistry and Technology, Butterworth-Heinemann.
Valsala, R. & Govindarajan, S. K. 2019. Co-colloidal BTEX and microbial transport in a saturated porous system: numerical modeling and sensitivity analysis. Transport in Porous Media, 127(2), 269-294.
Journal of Water and Wastewater; Ab va Fazilab ( in persian )
Volume 31, Issue 5 - Serial Number 129
November and December 2020
Pages 91-102

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