Microbial Clogging of Saturated Soils and Aquifer Materials: Evaluation of Mathematical Models

Abstract

Bacterial reductions of the saturated hydraulic conductivity of natural porous media appear to be caused by a wide range of mechanisms, few of which have been carefully studied. Nevertheless, a number of mathematical models have been developed in recent years to describe the microbial clogging process, based on the assumption that bacterial cells form impermeable biofilms uniformly covering pore walls. In the present study, two independent sets of experimental data available in the literature are used to test the existing bioclogging models. To broaden the scope of the assessment, an additional model, initially developed to describe the deep filtration of suspended colloids, is also included in the comparisons. Analysis of the experimental data reveals a clear relationship between the texture of a porous medium and the ability of a given level of biomass to reduce its saturated hydraulic conductivity; at equal biomass, clogging is much more pronounced in fine-textured materials than in coarse-textured ones. In addition, the results of the model comparisons suggest that none of the existing models can predict satisfactorily the saturated hydraulic conductivity reductions observed in fine sands, whereas they fare somewhat better in coarser materials. It is argued that this inadequacy of existing models is due to the continuous biofilm assumption on which they are founded. Indeed, a simplistic model that assumes the biomass to be distributed as plugs instead of as continuous biofilms produces quantitatively much improved predictions of the saturated hydraulic conductivity reductions. Reference is made to the consequences of this observation in terms of future research.

Simulations of two‐dimensional modeling of biomass aggregate growth in network models

“…Permeability decrease due to aggregate growth is more pronounced than that predicted by biofilmbased models for the same porosity reduction. This overall behavior has been indicated by Vandevivere et al [1995], who noted that aggregate clogging better approaches observations than biofilm clogging. The explanation is that an aggregate can occlude a pore without filling it, while a continuous biofilm must completely fill it [Rittmann, 1993;Vandevivere et al, 1995].…”

“…This overall behavior has been indicated by Vandevivere et al [1995], who noted that aggregate clogging better approaches observations than biofilm clogging. The explanation is that an aggregate can occlude a pore without filling it, while a continuous biofilm must completely fill it [Rittmann, 1993;Vandevivere et al, 1995]. Porosity-permeability curves for different random realizations are quite similar.…”

Mineral Transformation and Biomass Accumulation Associated With Uranium Bioremediation at Rifle, Colorado

“…For example, the initial bioavailable Fe(III) content was changed from 5.0 mol/g in the column experiments to 2.5 mol/g in the field. This is likely due to the fact that the column experiment used the <4 mm fraction of the sediment, which Multiple studies have shown that it is easier to clog a porous medium with fine-grained materials (29)(30)(31). The current estimate is based on the assumption that the system is a homogeneous system with uniform distributions of aquifer properties.…”

Coupling distributed stormwater collection and managed aquifer recharge: Field application and implications

“…2), when well-developed crops and other vegetation may have stabilized soil and reduced the amount of sediment available for transport. Carefully managing sediment as part of MAR operations is critical to maintain longterm effectiveness (Behnke, 1969;Okubo and Matsumoto, 1983;Schuh, 1990;Vandevivere et al, 1995;Bekele et al, 2013;Barraud et al, 2014). Beneficial practices include applying source control measures to reduce erosion in the drainage area, retaining sediment in a detention basin with adequate size and residence time, and/or removing accumulated fine sediment annually (prior to tilling).…”