Broad\nMicrobial\nCommunity Functions in a Conventional\nActivated Sludge System Exhibit Temporal Stability

Wastewater microbial communities\nwithin conventional\nactivated\nsludge (CAS) systems can perform hundreds of biotransformations whose\nrelative importance, frequency, and temporal stability remain largely\nunexplored. To improve our understanding of biotransformations in\nCAS systems, we collected 24 h composite samples from the influent\nand effluent of a CAS system over 14 days, analyzed samples using\nhigh-resolution mass spectrometry (HRMS), and conducted a nontarget\nanalysis of our HRMS acquisitions. We found that over 50% of the chemical\nfeatures in the influent were completely removed, and the daily number\nof detected features exhibited low variability with a coefficient\nof variation of 0.07. Additionally, we found 352 Core chemical features\npresent in every sample at both locations. We used chemical features\nto search for evidence of 19 potential biotransformations and detected\n9 of these biotransformations at a frequency of over 80 times per\nday, where evidence for <i>dehydrogenations</i>, <i>hydroxylations</i>, and <i>acetylations</i> was most\nfrequently detected. The daily number of detections for the 9 biotransformations\nexhibited coefficients of variation ranging from 0.13–0.20,\nrevealing the broad temporal stability for these wastewater microbial\ncommunity functions. This stability contrasts with the previously\nobserved temporal variability for micropollutant biotransformations,\nsuggesting that micropollutant biotransformations are linked to specialized\nmicrobial community functions.