Exploring biofilms in three dimensions in porous media is a long-standing challenge. X-ray tomography allows for visualization of a variety of porous materials and associated processes, but because of the absence of a significant photon cross-section for biofilms (it rather closely resembles the aqueous phase in porous media), getting at the architecture of biofilms in porous media is challenging. However, by innovative use of contrast agents, it is possible to separate biofilm from porous medium and aqueous phase, and to make a variety of measurements in support of the overall objective of better understanding how biofilms grow and function in a variety of applications such as groundwater bioremediation, clogging of trickling filters, and fouling of medical implants.
In past work, we have used micro-imaging to study the effects of flow rate (Re number) on three-dimensional growth of biofilm in porous media. The images allow us to gain a better understanding of how biofilms grow and interact with the pore geometry, nutrients, and the fluid flow environment in the subsurface, and paves the way to more systematic studies of the structure-function relationships involved in biofilm growth in porous media.
We’re now taking this methodology to the next level by sending bacteria to space, to explore how gravity and capillarity affect biofilm growth and architecture. Under unsaturated conditions, meaning when pore spaces are only partially filled with water, capillary forces (as what holds water in a straw or sponge) will dominate fluid flow relative to gravity. This can have a significant impact on how biofilms survive and thrive since they need water to deliver nutrients and oxygen to them. The overarching goal of this new research project is to use the microgravity environment on the International Space Station to study the respective roles that gravity and capillary forces play in the development of biofilms in porous media on Earth. By conducting biofilm growth experiments in space/microgravity and on Earth, we can isolate the effects of gravity and capillarity, forming a better understanding of the role that each play in the development of biofilms in the absence of the other. This will allow us to better understand how biofilm 3D shape and function are affected by either of these forces and will allow better designs of systems that make use of biofilms to do work for us, or to prevent biofilms from fouling systems where that is undesirable.
Dr. Wildenschild is a Professor of Environmental Engineering in the School of Chemical, Biological, and Environmental Engineering at Oregon State University, and the Jon and Stephanie DeVaan Chair and Executive Director for Clean Water Initiatives at OSU. Her research focuses on flow and transport in porous media, with the goal of answering questions of relevance to subsurface water pollution and energy-related storage challenges. Recent work includes optimization of geologic storage of anthropogenic carbon dioxide; colloid-facilitated transport of contaminants in groundwater; exploration of biofilms in porous media using high-resolution 3D imaging, and fundamental investigations in support of more effective groundwater remediation techniques. She is the recipient of the 2023 Interpore Society’s Honorary Lifetime Award, and was the 2014 Henry Darcy Distinguished Lecturer in Groundwater Science.