Journal
ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH
Volume 27, Issue 32, Pages 40483-40494Publisher
SPRINGER HEIDELBERG
DOI: 10.1007/s11356-020-10030-9
Keywords
Single-stage packed bed; Partial nitritation-anammox; Bio-carrier; Metagenomics and metatranscriptomics; Nitrite-accumulated denitrification; Nitrite loop
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Funding
- Fundamental Research Funds for the Central Universities [2019XKQYMS79]
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The single-stage partial nitritation-anammox (PN/A) process is severely limited by a long start-up time and unstable removal efficiency. In this study, PN/A was developed in 67 days in a novel packed bed equipped with porous bio-carriers by gradually increasing the influent nitrogen loading rate (0.15-0.73 kg-N m(-3).d(-1)) and controlling the dissolved oxygen (< 1.2 mg L-1). An average ammonium nitrogen removal efficiency (ARE) and total nitrogen removal efficiency (TNR) of 87.01 and 72.41%, respectively, were obtained. This represents a reliable alternative method of achieving rapid PN/A start-up. The results of 16S rRNA sequencing showed that Proteobacteria and Planctomycetes, with which ammonia-oxidizing bacteria and anammox bacteria were affiliated, accounted for 38.8%, representing the dominant phylum in the system after acclimation. The abundance of Nitrosomonas and Candidatus Brocadia increased by 16 and 1.79%, respectively. The results of metagenomics and metatranscriptomics revealed that the nitrite oxidation process was blocked by the transcriptional suppression of nitrite oxidoreductase and the entire nitrogen metabolism process was dominated by the partial nitritation and anammox process. Moreover, a high abundance of heterotrophic bacteria with potential for nitrogen removal was detected. In the nitrogen cycle, a widespread nitrite-accumulated denitrification helps to form a nitrite loop, which promotes the efficiency of total nitrogen removal. This is crucial for further improving the nitrogen removal mechanism in the PN/A system.
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