Dominant denitrifying bacteria are important hosts of antibiotic resistance genes in pig farm anoxic-oxic wastewater treatment processes

Water Environment Research

Zheng

Wang

et al. 2021

Dissolved organic nitrogen (DON) is a component of wastewater with a negative influence on the environment. The removal of DON is conducted through the anoxic/oxic (A/O) and anammox processes. However, the mechanisms and chemical preferences in the removal of DON compounds have not been understood and compared so far. This study, for the first time, comparatively investigated the molecular‐level characteristics of DON during both processes by using FT–ICR MS (Fourier transform ion cyclotron resonance mass spectrometry). The results indicated that the number of DON formulas increased from 1844 to 1935 during A/O process, and from 2784 to 3242 during anammox process, highlighting the increase in complexity of DON after undergoing both processes. DON with high saturation and aliphatic structures was removed by A/O process, whereas highly unsaturated and aromatic structures were removed by anammox process. For DON without S atom, Lignin‐like and tannin‐like ones were resistant to both processes and protein‐like and condensed aromatic structures were resistant to anammox process. The complementarity of these two processes provided a sequential combination with sufficient theoretical support to improve DON removal efficiency. Practitioner points Molecular components of dissolved organic nitrogen characterized by ESI FT–ICR MS. DON removal preferences of A/O and anammox processes evaluated. A/O and anammox processes are effective to remove aliphatic and aromatic DON, respectively. Complementarity in removal preferences of A/O and anammox processes can remove recalcitrant DON of each other. Sequential A/O and anammox processes can improve DON removal.

Section: Resultsmentioning

confidence: 64%

Molecular characterization of dissolved organic nitrogen during anoxic/oxic and anammox processes using ESI FT–ICR MS

Water Environment Research

Zheng

Wang

et al. 2021

“…In contrast with the samples discussed above, dominant bacteria in the microbial sample of T2 were Thermomonas (15.12%), Steroidobacter (3.76%), Ferruginibacter (2.33%), Rhodobacter (2.32%), and Phenylobacterium (2.07%). While Thermomonas and Steroidobacter are typical anaerobic denitrifying bacteria (He et al, 2018; Yang et al, 2020), Ferruginibacter typically functions in anoxic/oxic/membrane reactors (AO/MR) where extracellular polymeric substances (EPS) can release carbon sources to promote denitrification (Han et al, 2018). What is more, Rhodobacter and Phenylobacterium are involved in the degradation of organic macromolecules (Simona et al, 2022; Wang, Liu, et al, 2021).…”

Section: Resultsmentioning

confidence: 99%

Nitrogen removal and microbial mechanisms in a novel tubular bioreactor‐enhanced floating treatment wetland for the treatment of high nitrate river water

Cui

Yang

Water Environment Research

et al. 2022

A novel tubular bioreactor‐enhanced floating treatment wetland (TB‐EFTW) was developed for the in situ treatment of high nitrate river water. When compared with the enhanced floating treatment wetland (EFTW), the TB‐EFTW system achieved 30% higher total nitrogen removal efficiency. Further, the average TN level of the TB‐EFTW effluent was below the Grade IV requirement (1.5 mg/L) specified in Chinese standard (GB3838‐2002). Microbial analysis revealed that both aerobic and anoxic denitrifying bacteria coexisted in the new system. The relative abundance of aerobic and anoxic denitrifiers were 42.69% and 22% at the middle and end of the tubular bioreactor (TB), respectively. It is reasonable to assume that effective nitrogen removal can mainly be attributed to the addition of solid carbon source and the spatial difference in DO distribution (oxic–anoxic areas in sequence) inside the TB. The initial investment cost and operating costs associated with the TB‐EFTW system are approximately 14,000 and 3500 yuan per 1000 m3 river water, respectively. Considering its low cost, minimal maintenance requirements, and effective nitrogen removal, this newly developed system can be regarded as a promising technology for treating high nitrate river water. Practitioner Points A novel TB‐EFTW system was developed to upgrade traditional in situ treatment techniques. The TB‐EFTW could achieve 30% higher nitrogen removal efficiency than EFTWs. Both aerobic and anoxic denitrifying bacteria coexisted in the system. The system shows better technical and economic performance compared with routine techniques.

“…48 The enhanced abundance of denitrifying bacteria with ARGs and pathogenic ARB indicates higher microbiological risks. 10,11 although the DB treatment greatly reduced TN and some PPCPs in wastewater, its microbial risks associated with antibiotic resistome and virulence factors should not be neglected.…”

Section: ■ Discussionmentioning

confidence: 99%

“…For instance, a recent study reported that indigenous activated sludge denitrifiers in WWTPs were important living hosts and hotspots of ARGs. 11 Pesticide WWTPs that utilized enhanced biological treatment also showed high abundances of ARGs and mobile genetic elements (MGEs) in both sludge and effluents. 12 However, the influence of enhanced biological treatment on the antibiotic resistome, pathogenicity, and bacterial hosts in wastewater still needs further investigation.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Among the TWTPs, enhanced biological treatment processes can efficiently degrade refractory pollutants in wastewater through enriching functional microbes, which may simultaneously harbor resistance genes and easily cause biological risks when capturing VFGs. For instance, a recent study reported that indigenous activated sludge denitrifiers in WWTPs were important living hosts and hotspots of ARGs . Pesticide WWTPs that utilized enhanced biological treatment also showed high abundances of ARGs and mobile genetic elements (MGEs) in both sludge and effluents .…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Tertiary Wastewater Treatment Processes Can Be a Double-Edged Sword for Water Quality Improvement in View of Mitigating Antimicrobial Resistance and Pathogenicity

Jia

Gao

et al. 2022

Environ. Sci. Technol.

Despite the high removal efficiency for chemical pollutants by tertiary wastewater treatment processes (TWTPs), there is no definite conclusion in terms of microbial risk mitigation yet. This study utilized metagenomic approaches to reveal the alterations of antibiotic resistance genes (ARGs), virulence factor genes (VFGs), their co-occurrence, and potential hosts during multiple TWTPs. Results showed that the TWTPs reduced chemical pollutants in wastewater, but the denitrifying biofilter (DB) significantly increased the absolute abundances of selected antibiotic-resistant bacteria and ARGs, and simultaneously elevated the relative abundances of ARGs and VFGs through the enrichment of multidrug resistance and offensive genes, respectively. Moreover, the co-occurrence of ARGs and VFGs (e.g., bacA–tapW, mexF–adeG) was only identified after the DB treatment and all carried by Pseudomonas. Then, the ultraviolet and constructed wetland treatment showed good complementarity for microbial risk reduction through mitigating antibiotic resistance and pathogenicity. Network and binning analyses showed that the shift of key operational taxonomic units affiliating to Pseudomonas and Acinetobacter may contribute to the dynamic changes of ARGs and VFGs during the TWTPs. Overall, this study sheds new light on how the TWTPs affect the antibiotic resistome and VFG profiles and what TWTPs should be selected for microbial risk mitigation.