Bacteria build dikes

Miranda van Wijngaarden-van Rossum

Site of the project:
Stieltjesweg 2
2628 CK Delft

start of the project: September 2007

In February 2008 the Interim Thesis has been appeared and a presentation has been given. Presentation at NWO Bessensap Nemo, Amsterdam, May 26, 2008.

The Master project has been finished in July 2008 by the completion of the Masters Thesis and a final presentation has been given.

For working address etc. we refer to our alumnipage.

Summary of the master project:

For large buildings a good foundation is needed. In various parts of the Netherlands the surface of the earth consists of sand. It is well known that sand is not alway a good foundation for heavy structures. In the subsurface it happens that micro-organisms transform sand into sandstone. These micro-organisms glue the sand grains together by the formation of calcite. In nature this takes several centuries since feeding substances are scarce deep in the subsoil. The idea is to inject feeding substances for the micro-organisms in these layers, which speeds up the formation of sandstone. This leads to a cement-like structure of the sand layers. Another appllication is to contruct 'bio-dikes', where these bacteria with feeding substances are used to strenghten weak dikes. To keep dikes strong is very important in the Netherlands, where most of the land is below sea level.

In this project we shall make a mathematical model for the injection of bacteria with food. The injection is done by using a high pressure. This leads to a convection-diffusion equation. The growth of bacteria and calcite (CaCO3) is modelled by a reaction-transport equation. The model consists of a system convection-diffusion-reaction equation. The flow is convection dominated, which implies that the finite element method should be adapted such that there are no wiggles in the solution. The reaction-terms lead to a stiff system of ordinary differential equations, so a suitable time integration method should be used.

Sandstone formation

SEM photomicrographs of samples subjected to Myxococcus xanthus-induced calcite precipitation.

Contact information: Kees Vuik

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