Abstract
To in situ and noninvasively monitor the biofilm development process by low-field nuclear magnetic resonance (NMR), experiments should be made to determine the mechanisms responsible for the T2 signals of biofilm growth. In this paper, biofilms were cultivated in both fluid media and saturated porous media. T2 relaxation for each sample was measured to investigate the contribution of the related processes to T2 relaxation signals. In addition, OD values of bacterial cell suspensions were measured to provide the relative number of bacterial cells. We also obtained SEM photos of the biofilms after vacuum freeze-drying the pure sand and the sand with biofilm formation to confirm the space within the biofilm matrix and identify the existence of biofilm formation. The T2 relaxation distribution is strongly dependent on the density of the bacterial cells suspended in the fluid and the stage of biofilm development. The peak time and the peak percentage can be used as indicators of the biofilm growth states.
Highlights
Hydrocarbons, heavy metals, and microplastics are serious environmental problems with which governments around the world are concerned
To determine the mechanisms whereby the biofilm development process contributes to the low-field T2 relaxation, four different P. aeruginosa cultivation experiments were conducted in the liquid media and porous media
The results in experiment 1 indicate that the transverse relaxation is related to bacterial growth, especially in the logarithmic period when the bacterial cells are rapidly proliferating
Summary
Hydrocarbons, heavy metals, and microplastics are serious environmental problems with which governments around the world are concerned. The native microbes can be artificially activated by injecting nutrients to form a biobarrier to prevent pollutants’ migration or to promote pollutants’ degrading rate in contaminated soil and aquifers as environmentally friendly, low-cost, and effective methods [1,2,3,4,5,6]. During these processes, the formation of biofilms is crucial for accelerating pollutants’ adsorption and degradation [2,3,7]. Lab-scale experiments focus on evaluating the physical and chemical impacts that dominate biofilm development and the pollutant degradation efficiency through imaging techniques and other analytical methods
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