Detection of Biofilm Forming Microbes Using Electrochemical Methods

• Author / Creator

  Chen, Yongxu

• Microbiologically Influenced Corrosion (MIC) and biofouling are major challenges to operators who manage water systems in the oil & gas and other sectors. The root caused for these threats is the formation and accumulation of biofilms in piping systems due to the agglomeration of both biotic components (e.g. bacteria, archaea and extracellular polymeric substances) and abiotic materials (e.g. inorganic solids). These biofilms adhere to inner pipe wall surfaces and evolve over time, depending on surrounding environmental conditions, eventually lead to corrosion.
  
  In this study, a novel in-situ method to detect the presence of biofilm-forming bacteria in a fluid system has been proposed based on capacitance measurements using the Electrochemical Impedance Spectroscopy (EIS) technique. Two probe types were assessed to detect and measure the growth of bacteria: 1) a parallel plate system, and 2) a small-scale Interdigitated Electrode (IDE) microchip system. Surface areas and gap sizes of the various probes were also evaluated to determine their effect on measuring sensitivities. In both series of tests, Pseudomonas.putida was used as the model bacteria due to its ability to grow rapidly as a biofilm former, and is commonly found in MIC related environments.
  Upon the introduction of the microorganism to the system, EIS patterns collected were correlated to the observed bacterial concentration over time. A model circuit was also developed to determine the effective capacitance and resistances at various bacteria concentrations. Both the parallel plate and IDE systems were able to detect changes in total bacteria concentration (planktonic and sessile) when a threshold value of 108 CFU/ml and 104 CFU/ml was reached, respectively. The effect of the surface area and gap size was seen to play a role in the effective capacitance value obtained during the test. For the parallel plate probe, the 0.5 mm gap size and 2 cm2 surface area had a slightly better response. IDEs made with gold conductors and a gap size of 5µm also had a better response compared to IDE configurations. This “proof of concept” study has demonstrated the potential for a viable, real-time detection method for systems susceptible to bio-fouling and/or MIC.

• Subjects / Keywords

  • Corrosion
  • EIS

• Graduation date

  Spring 2021

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-471c-ev76

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.