Dombrowski, P. | Search bioRxiv

bioRxiv2023

Revisiting the role of Acinetobacter sp. in EBPR systems

Side-stream Enhanced biological phosphorus removal (S2EBPR) has been incorporated with B-stage process to enable simultaneous phosphorus and nitrogen removal. However, the dominating phosphorus accumulating organisms (PAOs) in this novel configuration has not been evaluated. The dominance of Acinetobacter was confirmed by 16S sequencing. In addition, single cell Raman spectrum (SCRS) analysis in couple with in situ fluorescence in situ hybridization (FISH) was applied to obtain the feature spectrum and verify the phosphorus release/uptake activity of Acinetobacter spp. The phenotypic profiling further suggested the dominance of Acinetobacter-like organisms among all poly-phosphorus containing organisms and only certain phenotypic Acinetobacter (oligotype 1) contribution to P-removal in a unique HRAS-P(D)N-S2EBPR system. The findings suggest that Acinetobacter may outcompete other heterotrophic organisms in EBPR systems due to their sensitivity to operational conditions. However, stable P-removal was only observed during a specific section of the operation period, coinciding with an increase in the VFA/P ratio. Further research is needed to identify the phenotypes of Acinetobacter responsible for P-removal in EBPR systems. The study contributes to a better understanding of the microbial ecology and engineering aspects of EBPR systems and wastewater treatment in general.

bioengineering↗

bioRxiv2023

Comammox and Unknown Candidate AOBs Contribute to Nitrite Accumulation in An Integrated A-B stage process that Incorporates Side-stream EBPR (S2EBPR)

A novel integrated pilot-scale A-stage high rate activated sludge, B-stage short-cut biological nitrogen removal and side-stream enhanced biological phosphorus removal (A/B-shortcut N- S2EBPR) process for treating municipal wastewater was demonstrated with the aim to achieve simultaneous and carbon- and energy-efficient N and P removal. In this studied period, an average of 7.62 {+/-} 2.17 mg-N/L nitrite accumulation was achieved through atypical partial nitrification without canonical known NOB out-selection. Network analysis confirms the central hub of microbial community as Nitrospira, which was one to two orders of magnitude higher than canonical aerobic oxidizing bacteria (AOB) in a B-stage nitrification tank. The contribution of comammox Nitrospira as AOB was evidenced by the increased amoB/nxr ratio and higher ammonia oxidation activity. Furthermore, oligotyping analysis of Nitrospira revealed two dominant sub-clusters (microdiveristy) within the Nitrospira. The relative abundance of oligotype II, which is phylogenetically close to Nitrospira_midas_s_31566, exhibited a positive correlation with nitrite accumulation in the same operational period, suggesting its role as comammox Nitrospira. Additionally, the phylogenetic investigation suggested that heterotrophic organisms from the family Comamonadacea and the order Rhodocyclaceae embedding ammonia monooxygenase and hydroxylamine oxidase may function as heterotrophic nitrifiers. This is the first study that elucidated the impact of integrating the S2EBPR on nitrifying populations with implications on short-cut N removal. The unique conditions in the side-stream reactor, such as low ORP, favorable VFA concentrations and composition, seemed to exert different selective forces on nitrifying populations from those in conventional biological nutrient removal processes. The results provide new insights for integrating EBPR with short-cut N removal process for mainstream wastewater treatment.

bioengineering↗