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The Gene and Linda Voiland School of Chemical Engineering and Bioengineering

Research of Nehal I. Abu-Lail

Multiscale Investigations of Biofilm-Mineral Interactions

⬅ Back to Dr. Abu-Lail’s List of Research Projects

Problems

  1. Soil erosion
  2. Need for effective and environmental friendly solutions (toxicity, weather, and contamination)
  3. Cost

Goal

Quantify biofilm interactions with minerals and optimize conditions needed for biofilm use to improve mechanical properties of soil.

Figure

Soil sample being examined using laser beam, cantilever and photodiode detector; graphs
AFM experiments

Graphs showing transport experiments
Transport experiments

Lab equipment used
Macroscale column experiment

Soil particles through microscope
TEM image of biofilms

Close-up of particles
TEM image of biofilms

Questions:

  • How do bacterial cells interact with soil particles at nanoscale?
  • Which environmental conditions (pH, IS, starvation) are more favorable for their initial attachment?
  • Do surface properties affect this adhesion?
  • What affects bacterial transport?
  • How does biofilm formation affect soil mechanics?

Impact

Enhanced soil mechanics

Research Details

For many years, conventional methods such as planting and use of synthetic polymers have been utilized to improve stability of soil. Chemical cements also have been often used to increase the shear strength or reduce water conductivity in soil. Although practical, each technique suffers from a shortcoming. For example vegetative covering of the soil is not permanently effective for all seasons of a year. Also the use of cement or chemicals for soil improvement is not sustainable over the long term because production and implementation of these materials in soil are expensive. Moreover, concerns regarding toxicity of chemicals represent other drawbacks.

Therefore alternative sustainable solutions to enhance soil mechanics are needed. Because of their natural presence in soil bacterial biofilms are being explored to provide sustainable solutions to many soil problems. In situ biofilm formation in soil can result in reduction of hydraulic conductivity due to bioclogging of pore spaces or increasing the shear strength by improving the grain-grain contacts. Bioclogging is especially important in controlling contaminant flow from spreading to groundwater by reactive biobarriers.
Many lab-scale experiments show the ability of biofilm in solving soil problems. However, the use of biofilms in field studies is challenging. To overcome the challenges towards applying biofilms in soil, fundamental understanding of what controls bacterial interactions with soil particles as well as bacterial transport in environmental conditions of interest is needed. As such and in collaboration with Dr. Muhunthan in Civil Engineering at WSU, our lab is interested in investigating the effects of environmental condition (pH, ionic strength and nutrient limitation) on bacteria-mineral surfaces interactions.

To reach our goal, transport of bacteria in lab-scale sand columns studied at different environmental conditions. Once retention of bacteria in sand columns are studied at macroscale, atomic force microscopy technique is used to quantify the adhesion forces between the bacteria and mineral surfaces at nanoscale in different environmental conditions. Moreover, to investigate the effects of nutrients’ limitations on durability and applicability of bioclogging processes in soil, biofilms are formed in small sand columns under poor and rich nutrient conditions for a long period and their carbohydrate and protein content is quantified. X-ray computed microtomography, geophysical monitoring, and triaxial strength testing are also being used to assess effects of biofilm formation in soil on soil macroscale mechanical properties. The obtained results of our experiment are expected to contribute to fundamental knowledge that can facilitate the design and engineering of upscale processes of biofilm-associated soil.

Funding Acknowledgements

NSF - National Science Foundation