Impact of Low Dissolved Oxygen and Microbial Community on Pharmaceutical Biotransformations during Wastewater Treatment

Dissolved oxygen (DO) concentration is an important operational parameter in wastewater treatment that can be controlled and minimized to achieve significant energy savings. DO may also impact the extent of pharmaceutical biotransformations that occur during treatment. Low DO treatment can impact pharmaceutical biotransformations by 1) slowing the activity of microorganisms involved in biotransformation because it serves as a limiting substrate; and/or 2) selecting for a community that is more (or less) effective at biotransformation. The objective of this work was to evaluate the impact of low DO conditions on pharmaceutical biotransformations by nitrifying microbial communities. Nitrifiers were a focus in this work because they are thought to be particularly sensitive to DO limitation and because previous studies have observed a positive association between nitrification and pharmaceutical biodegradation. The results reveal a nuanced relationship between DO concentration and micropollutant biotransformation rates, as DO impacts both microbial physiology and microbial community structure.