Spatial and Temporal Shifts in Bacterial Communities and Nutrient Removal in Two Springfield Wastewater Facilities

Bacterial communities play a central role in the biological nutrient removal and overall performance of wastewater treatment plants (WWTPs). However, very few is known about the spatial and seasonal dynamics of these communities. This study explores the spatial and seasonal variations in bacterial community composition across multiple treatment stages in two municipal WWTPs—Southwest (SWTP) and Northwest (NWTP)—in Springfield, Missouri. Using 16S rRNA gene amplicon sequencing, I analyzed 87 samples collected during summer and winter of 2024 from influent, sludge, aeration basins, clarifiers, and final effluent stages. I retrieved 16.4 million (summer) and 3.2 million (winter) sequences. Proteobacteria dominated both seasons (42 % summer; 49 % winter), followed by Firmicutes, Bacteroidota, Actinobacteria, Planctomycetes. Non-metric multidimensional scaling (NMDS) and Bray-Curtis similarity analyses revealed distinct microbial community transitions across treatment processes and seasons. Seasonal shifts were evident, with summer and winter samples forming distinct clusters, suggesting that temperature and water chemistry significantly influence bacterial community structure. Physicochemical parameters (e.g. DO, COD, NO₂⁻, NO₃⁻, metals), revealed clear stage-specific bacterial community shifts. Family-level taxonomic analysis highlighted functional groups like Comamonadaceae, Moraxellaceae, and Lachnospiraceae, which varied significantly across both spatial and temporal gradients, reflecting their roles in organic degradation, nutrient cycling, and resistance to disinfection. Overall, this study underscores the dynamic interplay between operational parameters, environmental conditions, and bacterial community structure in WWTPs, offering valuable insights for improving treatment efficacy and potential bacterial pathogen risk management.