A mechanistic model (BCC‐PSSICO) to predict changes in the hydraulic properties for bio‐amended variably saturated soils

The accumulation of biofilms in porous media is likely to influence the overall hydraulic properties and, consequently, a sound understanding of the process is required for the proper design and management of many technological applications. In order to bring some light into this phenomenon we prese...

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Bibliographic Details
Published in:Water resources research 2017-01, Vol.53 (1), p.93-109
Main Authors: Carles Brangarí, Albert, Sanchez‐Vila, Xavier, Freixa, Anna, M. Romaní, Anna, Rubol, Simonetta, Fernàndez‐Garcia, Daniel
Format: Article
Language:English
Subjects:
Accumulation
Bacteria
bioclogging
biofilm swelling
Biofilms
Biomass
Capillary tubes
Cells
Colonies
Consortia
Data
Design analysis
Displacement
Displays
Distribution
Enginyeria civil
Extracellular
Geotècnia
Hydraulic properties
Hydraulics
Laboratories
Light
Light effects
Management
Mathematical analysis
Mathematical models
mechanistic model
Mecànica de sòls
Membrane permeability
Methods
Microorganisms
Modelling
Moisture content
Permeability
Phases
Porositat
Porous media
Properties
relative permeability
Retention
Saturated soils
Soil
Soil amendment
Soil infiltration
Soil permeability
Soil properties
Sound
Sòls
Tubes
vadose zone
Water content
Water flow
water retention curve
Àrees temàtiques de la UPC
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Summary:The accumulation of biofilms in porous media is likely to influence the overall hydraulic properties and, consequently, a sound understanding of the process is required for the proper design and management of many technological applications. In order to bring some light into this phenomenon we present a mechanistic model to study the variably saturated hydraulic properties of bio‐amended soils. Special emphasis is laid on the distribution of phases at pore‐scale and the mechanisms to retain and let water flow through, providing valuable insights into phenomena behind bioclogging. Our approach consists in modeling the porous media as an ensemble of capillary tubes, obtained from the biofilm‐free water retention curve. This methodology is extended by the incorporation of a biofilm composed of bacterial cells and extracellular polymeric substances (EPS). Moreover, such a microbial consortium displays a channeled geometry that shrinks/swells with suction. Analytical equations for the volumetric water content and the relative permeability can then be derived by assuming that biomass reshapes the pore space following specific geometrical patterns. The model is discussed by using data from laboratory studies and other approaches already existing in the literature. It can reproduce (i) displacements of the retention curve toward higher saturations and (ii) permeability reductions of distinct orders of magnitude. Our findings also illustrate how even very small amounts of biofilm may lead to significant changes in the hydraulic properties. We, therefore, state the importance of accounting for the hydraulic characteristics of biofilms and for a complex/more realistic geometry of colonies at the pore‐scale. Key Points A new mechanistically based model to estimate the impact of complex biofilms on the soil hydraulic properties We derive a set of analytical equations for water retention and relative permeability The model is corroborated by using real data from laboratory experiments and previously existing models
ISSN:0043-1397
1944-7973
DOI:10.1002/2015WR018517