Although
microorganisms play significant roles in bioremediation,
their contributions to long-term site characteristics during and
after active treatment need to be fully elucidated. This study described
microbial ecology dynamics in 1,4-dioxane- and chlorinated solvents-contaminated
groundwater in laboratory microcosms. Bioaugmented Pseudonocardia
dioxanivorans CB1190 improved 1,4-dioxane removal, with increased
carbohydrate and amino acid metabolism, but was eventually outcompeted
by native microbes. The original microbiomes were perturbed and divergent
but tended to be similar over time. Dechlorinating bacteria co-existed
in the same niche, whereas CB1190 had more negative interactions in
the shared niche. Multiple regression and classification machine learning
models were built by using microbial taxa to predict the degradation
process; the ensemble regression model provided most accurate prediction
of 1,4-dioxane concentrations (R
2 = 0.81
± 0.17). Among the classification models, the support vector
machine performed the best in differentiating the contamination levels
(accuracy at 0.67 ± 0.07, kappa at 0.56 ± 0.10). The ensemble
model predicted the 1,4-dioxane concentrations and relative duration
of contamination with independent microbial datasets from a field
study, and the results aligned with the geographic and hydrological
information from monitoring wells. This study introduces the application
of machine learning in microbiome-based diagnostics for groundwater
remediation and evaluation, providing valuable methods for future
research and practice.