InterPore2025

Stochastic modeling of bacterial transport and retention in porous media

19 May 2025, 11:25

15m

Oral Presentation (MS06-B) Interfacial phenomena across scales MS06-B

Speaker

Juan J. Hidalgo (IDAEA-CSIC)

Description

Bacteria and microorganisms retention during water filtration allows to improve water quality and quantity. For that reason, the mechanisms affecting the propagation and fate of microbial populations need to be study to assess the risks for human health of water renovation technologies as managed artificial recharge.
In this work we study bacteria transport in porous media by means of column experiments. Two columns were built. One containing only sand and another with a mixture of sand, compost and wood chips. A punctual injection of tracers (rhodamine and amino-G acid) and bacteria consortium collected from the effluent of a wastewater treatment plant was made. Columns’ outflow was sampled and analyzed to obtain breakthrough curves of the tracers and the different amplicon sequence variants (ASVs) of bacteria to determine the influence of columns’ composition on the retention of bacteria. Bacteria and tracers displayed a strong anomalous behavior with late arrival peaks and long tails.
A continuous time random walk (CTRW) transport model was used to interpret the experimental results. The model characterizes transport in terms of mobile-immobile domains. Bacteria are transported with the mean flow and experience transitions from and to low mobility zones with a certain frequency. Transport is described in terms of four parameters, namely, the mean flow velocity, the dispersion coefficient, the trapping rate, and the mean residence time in the immobile zones. The model was able to reproduce satisfactorily the observed breakthrough curves of over 470 measured ASVs. A clustering analysis of the breakthrough curves was applied to establish a relation between the model parameters and bacteria physiology. The analysis showed that breakthrough curves form two clusters. One cluster was characterized by breakthrough curves with heavy tails and it was formed by small, motile, gram-negative bacteria. The other cluster displays strong peaks and a relatively weaker tailing. CTRW parameters are able to predict the cluster in which a certain ASV belongs.