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Pathogenic Bio Colloids Transport In Groundwater Flows

Congress: 2015
Author(s): Tushar Sen (Perth, Australia), Tushar Sen
Curtin University Perth1

Keyword(s): Sub-theme 2: Surface water and groundwater,
AbstractIntroduction There are several classes of subsurface colloids, abiotic and biotic. Biotic pathogenic organic colloids can be viruses, bacteria and protozoa collectively called bio colloids or macromolecular organic matter (when being smaller than 45 ìm often termed dissolved organic matter, DOM) falls under these colloidal size ranges. Ground-water contamination from biocolloids has been reported over the decades. These subsurface bio colloids pose a great risk in water resources and have caused large outbreaks of waterborne diseases. The transport of these pathogenic biocooloids is of significant interest, from the perspective of protection of groundwater supplies from contamination, assessment of risk from pathogens in groundwater and for the design of better water treatment systems to remove biocolloids from drinking water supplies. There are several basic processes such as physical, chemical, and biological -- all affect the transport of biocolloids. These factors include advection and dispersion as well as diffusion through water, straining and physical filtration through the porous media as the biocolloids move, adsorption, and biological processes such as adhesion/detachment, survival, and chemotaxis which are important in biocolloid transport. Here author will be presented the up-to-date developments on various biocolloidal microorganisms transport model based on physical, chemical and biological processes through saturated and unsaturated porous media and their role on groundwater contamination. Author here also will be presented their own research work on the development of pathogen transport model in groundwater contamination. Finally, author here will present the future research direction based on his critical review on biocolloid transport model in saturated and unsaturated porous media. Modelling To better understand the process controlling the transport of microbes in groundwater flows, models of microbe transport have been developed and tested against laboratory and field experiments which have been compiled by many researchers time to time. All these transport models incorporate advection, dispersion and a variety of terms accounting for microbe removal and growth, kinetic attachment, equilibrium attachment which is represented by transport equation (1). For viruses, the additional terms include attachment, release and inactivation. Physical and mathematical model for describing the fate of bacteria in porous media has been developed by few researchers. Investigators are identified several environmental factors such as cell concentration, substrate concentration, captured to and release from the porous medium surfaces, growth and inactivation, chemotaxis and advection and dispersion which having strong effects on bacterial fate and transport in porous media. Model has been developed based on coupling of microbial and substrate conservation equations, transient conditions, convective transport etc. Results and Discussion Most of the developed pathogenic transport model gives simultaneous numerical solution to the set of partial differential equations (such as equation 1) along with boundary and initial conditions. Most of the model including author's own model simulations shows that with the increase of flow velocity, inlet cell concentration, substrate concentration, enhancement of microbial breakthrough takes place and it is also found that chemotactic played a significant role in microbial transport. This subsurface microbial transport also dependence on various geochemical conditions that alter capture and release coefficients of adsorbed cells. Conclusion Understanding the fate and transport of pathogenic biocolloids in environmental systems is quite important because they pose a serious water quality risk. In order to estimate the potential health risk associated with aquifers contaminated by various biocolloids, the prediction of biocolloidal pathogenic fate and transport is necessary. Our ability to accurately simulate pathogenic biocolloid transport and retention in subsurface aquifers and especially in the unsaturated vadose zone is currently limited by our lack of basic understanding of the governing subsurface processes that might control the pathogenic biocolloids transport. This paper presented our current understanding of various physical, chemical, geochemical and biological processes that strongly affects the subsurface bio colloids transport and hence groundwater contamination Some of the future research areas such as subsurface charge heterogeneity, nutrient availability, survival stress, mixed microbial cells, vadose zone transport remain a fertile area of research on subsurface bio colloids transport. 1. Auset M and Keller A.A. (2004) Pore-scale processes that control dispersion of colloids in saturated porous media.Water Resour Res 40, 3503-3510 2. Sen, T. K. and Khilar, K. C. (2009) Mobile Subsurface Colloids and Colloid-mediated Transport of Contaminants in Subsurface Soil", Handbook of Surface and Colloid Chemistry, 3rd Edition, Taylor & Francis Group, CRC Press, pp 107-130 3. Sen, T. K. (2011) Processes in pathogenic biocolloidal contaminants transport in saturated and unsaturated porous media: a review-Water, Air and Soil Pollution, 216 (1), 239-256 (DOI 10.1007/s11270-010--503-0)
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