Broad Microbial Community Functions in a Conventional Activated Sludge System Exhibit Temporal Stability

Wastewater microbial communities
within conventional
activated
sludge (CAS) systems can perform hundreds of biotransformations whose
relative importance, frequency, and temporal stability remain largely
unexplored. To improve our understanding of biotransformations in
CAS systems, we collected 24 h composite samples from the influent
and effluent of a CAS system over 14 days, analyzed samples using
high-resolution mass spectrometry (HRMS), and conducted a nontarget
analysis of our HRMS acquisitions. We found that over 50% of the chemical
features in the influent were completely removed, and the daily number
of detected features exhibited low variability with a coefficient
of variation of 0.07. Additionally, we found 352 Core chemical features
present in every sample at both locations. We used chemical features
to search for evidence of 19 potential biotransformations and detected
9 of these biotransformations at a frequency of over 80 times per
day, where evidence for dehydrogenations, hydroxylations, and acetylations was most
frequently detected. The daily number of detections for the 9 biotransformations
exhibited coefficients of variation ranging from 0.13–0.20,
revealing the broad temporal stability for these wastewater microbial
community functions. This stability contrasts with the previously
observed temporal variability for micropollutant biotransformations,
suggesting that micropollutant biotransformations are linked to specialized
microbial community functions.