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.