Impact of microbial physiology and microbial community structure on pharmaceutical fate driven by dissolved oxygen concentration in nitrifying bioreactors

Abstract

Operation at low dissolved oxygen (DO) concentrations (<1 mg/L) in wastewater treatment could save utilities significantly by reducing aeration energy costs. However, few studies have evaluated the impact of low DO on pharmaceutical biotransformations during treatment. DO concentration can impact pharmaceutical biotransformation rates during wastewater treatment both directly and indirectly: directly by acting as a limiting substrate that slows the activity of the microorganisms involved in biotransformation; and indirectly by shaping the microbial community and selecting for a community that performs pharmaceutical biotransformation faster (or slower). In this study, nitrifying bioreactors were operated at low (∼0.3 mg/L) and high (>4 mg/L) DO concentrations to understand how DO growth conditions impacted microbial community structure. Short-term batch experiments using the biomass from the parent reactors were performed under low and high DO conditions to understand how DO concentration impacts microbial physiology. Although the low DO parent biomass had a lower specific activity with respect to ammonia oxidation than the high DO parent reactor biomass, it had faster biotransformation rates of ibuprofen, sulfamethoxazole, 17α-ethinylestradiol, acetaminophen, and atenolol in high DO batch conditions. This was likely because the low DO reactor had a 2x higher biomass concentration, was enriched for ammonia oxidizers (4x higher concentration), and harbored a more diverse microbial community (3x more unique taxa) as compared to the high DO parent reactor. Overall, the results show that there can be indirect benefits from low DO operation over high DO operation that support pharmaceutical biotransformation during wastewater treatment.

Impact of external carbon dose on the removal of micropollutants using methanol and ethanol in post-denitrifying Moving Bed Biofilm Reactors

“…As previously described (Section 3.2), the higher microbial richness observed in the biofilm enriched with methanol could have likely contributed to the overall higher micropollutant biotransformation in the methanol-dosed MBBR. Similarly, positive associations between biodiversity and the rates of specific micropollutant biotransformations were observed in activated sludge (Johnson et al, 2015;Stadler and Love, 2016) and MBBR (Torresi et al, 2016).…”

“…Thus, microbial communities in postdenitrifying systems using either of these carbon sources may be fundamentally different and potentially exhibit a different biodiversity and functionality with more or less microbial specialists able to biotransform organic micropollutants. Additionally, biodiversity in terms of species richness (the number of species) and evenness (the relative abundance of the species) (Wittebolle et al, 2009) was shown to positively associate with the biotransformation of a number of micropollutants in aerobic activated sludge (Johnson et al, 2015;Stadler and Love, 2016) and nitrifying MBBRs (Torresi et al, 2016). Further investigation of the impact of biodiversity in different biological treatment systems seems thus required.…”

Elucidating the impact of microbial community biodiversity on pharmaceutical biotransformation during wastewater treatment

“…One way to enhance the loss of compounds that undergo these types of biotransformation processes may be to design WWTPs to support diverse microbial communities and harness specific low‐abundance community members. Recent studies suggest that certain WWTP operational parameters, such as solids retention time (Vuono et al ., 2016), dissolved oxygen conditions (Stadler and Love, 2016), and concentration and composition of dissolved organic matter (Li et al ., 2014) can all influence the degree of microbial biodiversity and the extent of micropollutant removal. Further research is needed to understand the relative importance of these operational parameters and environment conditions and others on WWTP microbial biodiversity and pharmaceutical biotransformation.…”

Design and assessment of species-level qPCR primers targeting comammox

“…1, 2 The discovery of comammox bacteria has redefined a key component of the global nitrogen cycle, initiating a renewed focus of recent nitrogen cycling research in environmental biotechnology. 3–8…”