A numerical model of controlled bioinduced mineralization in a porous medium

INTRODUCTION

Our aim is to demonstrate the feasibility of microbial protection against corrosion in a porous medium. As a first step, we present a numerical model of controlled bioinduced mineralization in a porous medium as a possible corrosion protection mechanism for subsurface infrastructure such as pipelines or sheet pile walls. Corrosion is a significant economic problem - recent reports evaluate the annual cost of metal corrosion as 3-4% of the gross domestic product (GDP), in both developed and developing countries. As an alternative corrosion control method, bioinduced deposition of protective mineral layers has been proposed [1]. Bioinduced

precipitation has already been investigated for CO2 geological sequestration and soil

improvement [2]. To our knowledge, though, no numerical study of biomineralization for corrosion protection has been published yet.

MICROBIALLY INFLUENCED CORROSION

Netto reaction:

4Fe +SO

+3HCO

+5H

→

FeS +3FeCO

+

4H

O

REACTIVE TRANSPORT

Our model includes three phases - solid, biofilm and mobile water, in the latter are dissolved the reactive elements involved in the precipitation and the biosubstrate:

θ

+θ

+θ

=1

where θw is the water content, θb is the biofilm content, and θs is the solid content. The

reactive transport of solutes is described by:

∂θ

C

∂

t

=∇⋅(

D

∇

C

)−

SS

where Ci is the concentration, Di the diffusion coefficient and SS the source-sink term.

The consumption of substrate in biofilm (such as SO4-2) is described by the Monod

term [4]:

R

=−

q θ

X

C

K

+

C

(3) where q is the substrate utilization rate, X the concentration of bacteria, Cb

concentration of substrate and Kb is the Monod constant. Change in porosity as a result

of precipitation of solids such as FeS is described by:

∂θ

∂

t

=

M

ρ

R

where Ms is the molecular mass, ρs the density of the precipitate and Rs the

precipitation rate.

MODEL VALIDATION

We validate the model using data published by other researchers, such as [2]. Once validated, the model will be used to

compare with the results of our experiments and field measurements. The image below shows an example of a simple experiment - plastic container has been filled with sand and a steel rod has been inserted. The container has been filled with water and incubated for several months. Concentration gradients of the corrosion products are clearly visible

.

IMAGING CORROSION

IN POROUS MEDIA

The distribution of corrosion products, will be imaged in 3D by X-ray computed microtomography (CMT), and compared to the prediction of the model. Due to the similarity in X-ray absorption coefficients the use of pre-coated microspheres and an X-ray contrast agent is required to image biofilm within the experimental matrix using CMT [5]. We will use imaging techniques such as CMT to

non-destructively quantify and map the distribution of corrosion products and biofilms inside a porous medium to evaluate the performance of our numerical models.

OUTLOOK

Future development of the model includes multiple chemical species and reactions, multispecies biofilm that grows and detaches, varying coverage of solid grains by biofilms, and reactive solid phase. The predictive capacities of our model will be used to design experiments that will demonstrate the capacity to prevent corrosion in a porous medium by controlled bioinduced mineralization. Developing biological corrosion protection is a first step in developing the future capacity to use Nature's constructive forces in assembling functioning structures.

REFERENCES

[1] Rongjun Zuo. Biolms: strategies for metal corrosion inhibition employing microorganisms. Applied Microbiology and Biotechnology , 76(6), October 2007. [2] . Ebigbo, A. Phillips, R. Gerlach, R. Helmig, A. B. Cunningham, H. Class, and L. H. Spangler. Darcyscale modeling of microbially induced carbonate mineral

precipitation in sand columns. Water Resources Research , 48(7), July 2012.

[3] Dinh Thuy Hang. Microbiological study of the anaerobic corrosion of iron . PhD thesis, Universität Bremen, 2003.

[4] M. M. Al-Darbi, K Agha, and M R Islam. Comprehensive Modelling of the Pitting Biocorrosion of Steel. Canadian Journal of Chemical Engineering , 83, October 2005. [5] Gabriel C. Iltis, Ryan T. Armstrong, Danielle P. Jansik, Brian D. Wood, and Dorthe Wildenschild. Imaging biolm architecture within porous media using synchrotron-based X-ray computed microtomography. Water Resources Research , 47(2), February 2011.

ACKNOWLEDGEMENTS

This research is supported by the Dutch Technology Foundation STW, which is part of the Netherlands Organisation for Scientific Research (NWO), and which is partly funded by the Ministry of Economic Affairs, Agriculture and Innovation. Other contributants are the Port of Rotterdam, Vopak and Deltares, to all of whom we express our gratitude.

A numerical model of controlled bioinduced

mineralization in a porous medium

Michael Afanasyev

_{, Leon A. van Paassen}

and Timo J. Heimovaara

1

_{Department of Geothechnology, Delft University of Technology}

*

_{Corresponding author, e-mail M.Afanasyev@tudelft.nl}

The bottom side of a small plastic

jar (Ø=3 cm) containing sand, a

steel rod(Ø=2 mm) and water.

Scheme of iron corrosion by Sulphate Reducing Bacteria (SRB) [3]

CMT imaging results of biofilm (green) grown in a