Screening and Diversity Analysis of Aerobic Denitrifying Phosphate Accumulating Bacteria Cultivated from A2O Activated Sludge

Yong Li,Jianqiang Zhang,Jiejie Zhang,Siyuan Zhao,Yang He,Rong Ge

doi:10.3390/pr7110827

Abstract

The aerobic denitrifying phosphate accumulating bacteria (ADPB) use NO3− as an electron acceptor and remove nitrate by denitrification and concomitant uptake of excessive phosphorus in aerobic conditions. Activated sludge was collected from the A2O aerobic biological pool of the sewage treatment plant at Hezuo Town, Chengdu City. The candidate ADPB strains were obtained by cultivation in the enriched denitrification media, followed by repeated isolation and purification on bromothymol blue (BTB) solid plates. The obtained candidates were further screened for ADPB strains by phosphorus uptake experiment, nitrate reduction test, metachromatic granules staining, and poly-β-hydroxybutyrate (PHB) staining. The 16 sedimentation ribosome deoxyribonucleic acid (16 S rDNA) molecular technique was used to determine their taxonomy. Further, the denitrification and dephosphorization capacities of ADPB strains were ascertained through their growth characteristics in nitrogen-phosphorus-rich liquid media. The results revealed a total of 25 ADPB strains screened from the activated sludge of the A2O aerobic biological pool of the sewage treatment plant at Hezuo Town. These strains belonged to two classes, four orders, and five genera. Among them, the strain SW18NP2 was a potentially new species in the Acinetobacter genus, while the strain SW18NP24 was a potential new species in the Pseudomonas genus at the time of their characterization. The Acinetobacter was the dominant genus. The obtained ADPB strains demonstrated a rich diversity. The ADPB strains had significant variations in denitrification and dephosphorization capacities. Twenty-three strains exhibited a total phosphorus removal rate of above 50%, and 19 strains exhibited a total nitrogen removal rate of above 50%. The strain SW18NP2 showed the best denitrifying phosphorus removal (DPR) capacity, with a dephosphorization rate of 82.32% and a denitrification rate of 73.73%. The ADPB in the A2O aerobic biological pool of the sewage treatment plant at Hezuo Town demonstrated a rich diversity and a strong DPR capacity.

Highlights

Nutrients such as nitrogen and phosphorus in excess have been recognized as the primary cause of eutrophication
The discovery of Denitrifying phosphate-removal bacteria (DPB) indicated the direction for the development of denitrifying phosphorus removal (DPR) technique, so that it may overcome the drawbacks of the conventional processes, including insufficient carbon source, the competition of flora, hard to control mud age, and reflux of mixed liquid [3]
Compared with the aerobic DPB (ADPB) isolated by Xie et al [27] from wetland sediments, the ADPB isolated from this study demonstrated a high DPR activity and a good diversity

Summary

Introduction

Nutrients such as nitrogen and phosphorus in excess have been recognized as the primary cause of eutrophication. The conventional processes for combined nitrogen and phosphorus removal face several problems, such as insufficient carbon source, the competition of flora, difficulty in controlling sludge age, and reflux of mixed liquid [1,2]. The discovery of DPB indicated the direction for the development of denitrifying phosphorus removal (DPR) technique, so that it may overcome the drawbacks of the conventional processes, including insufficient carbon source, the competition of flora, hard to control mud age, and reflux of mixed liquid [3]. Kuba et al [4] reported the cultivation of a type of facultative anaerobe in the alternating anaerobic-anoxic sequencing batch reactor (SBR) This type of anaerobe, the DPB, could use both O2 and NO3 − as electron acceptors to remove phosphorus and simultaneously carry out denitrification. In their study of DPR using the anaerobic-anoxic SBR (A2 SBR), Ng et al [5]

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Discussion

Conclusion