Microbial Communities Shape Chemical Fate during Wastewater Treatment: Implications for Low-Cost Treatment Optimization

Municipal
wastewater effluent is a major conduit of contaminants
of emerging concern (CECs) to the environment. While advanced technologies
remove CECs more effectively than biological treatment, their high
costs limit widespread adoption. Optimizing microbial communities
within existing infrastructure could provide a low-cost stopgap until
such technologies become more accessible. We quantified changes in
the suspect and nontarget chemical composition associated with microbial
communities, determined by 16S rRNA sequencing, during biological
wastewater treatment across 12 Oregon utilities. Samples were collected
from three conventional systems: activated sludge (AS), biological
nutrient removal (BNR), and lagoons (LAG). Although the influent composition
was similar across sites, treatment system types shaped microbial
communities, which in turn drove distinct chemical transformation
patterns in the effluent. For example, LAG systems more effectively
transformed umbelliferones, while AS and BNR systems showed better
removal of isoflupredone and cocamidopropyl betaine. Eleven chemical
classes and seven subclasses were significantly associated with the
treatment position and system type. These findings suggest that operational
conditions can be adjusted to shift microbial communities toward states
that enhance the removal of specific contaminants, offering a scalable
and cost-effective strategy to improve treatment performance without
major infrastructure upgrades.