The continued widespread contamination of the subsurface environment by microbial
pathogens and chemical wastes has resulted in an increased interest in the factors that
influence microbial transport through porous media.
In this work a numerical study is undertaken to determine the influence of various
processes that contribute to microbial transport in porous media. The evaluations were
conducted by the simulation of a typical macroscopic transport model, using a novel
numerical technique referred to as the Green Element Method (GEM). This
computational method applies the singular boundary integral theory of the Boundary
Element Method (BEM) to a discretised domain in a typical Finite Element Method
(FEM) procedure.
Three models are presented to evaluate the effects of the various parameters and
factors: a constant porosity model was formulated to verify the GEM formulation against
an analytical solution, a variable porosity linear model was developed and used for the
simulation of the transport process involving first order type clogging, and a variable
porosity nonlinear model used to evaluate effects of nonlinear type clogging. All three
models were validated by simulations in specific applications in which analytical or
deduced solutions were available. The parameters and factors evaluated included the
effects of substrate concentrations, decay rates, source concentrations (boundary
conditions), flow velocity, clogging rates, dispersivity, point and distributed sources,
and nonlinear clogging.
The results show that the trends predicted were consistent with the trends expected
from theory. The conditions that enhanced bacteria transport included high velocities,
low decay rate constants, high substrate concentrations, and low clogging rates. The
range of dispersivities investigated showed little variation in the bacteria concentration
in the longitudinal direction. Reduction in porosity resulted in retardation of the
migrating plume. Conditions that led to significant loss in porosity are high bacteria
loadings and high growth rates.
The GEM formulation showed no restrictions or limitations in solving transient linear
and transient nonlinear applications. In the nonlinear application, the Newton Raphson
algorithm was successfully used for the iterative solution procedures. In addition, the
GEM formulation easily facilitated the application of distributed and point sources in the
problem domain. / Thesis (M.Sc.Eng.)-University of Durban-Westville, 2000.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/8996 |
| Date | January 2000 |
| Creators | Ramsuroop, Suresh. |
| Contributors | Onyejekwe, O. O. |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
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