Abstract

In the activated sludge process, reducing the operational dissolved oxygen (DO) concentration can improve oxygen transfer efficiency, thereby reducing energy use. The low DO, however, may result in incomplete nitrification. This research investigated the long-term effect of low DO on the nitrification performance of activated sludge. Results indicated that, for reactors with 10- and 40-day solids retention times (SRTs), complete nitrification was accomplished after a long-term operation with a DO of 0.37 and 0.16 mg/L, respectively. Under long-term low DO conditions, nitrite oxidizing bacteria (NOB) became a better oxygen competitor than ammonia oxidizing bacteria (AOB) and, as a result, no nitrite accumulated. Real-time PCR assays indicated that the long-term low DO enrich both AOB and NOB in activated sludge, increasing the sludge nitrification capacity and diminishing the adverse effect of low DO on the overall nitrification performance. The increase in the population size of nitrifiers had likely resulted from the reduced nitrifier endogenous decay rate by a low DO. Under long-term low DO conditions, Nitrosomonas europaea/eutropha remained as the dominant AOB, whereas the number of Nitro Spira-like NOB became much greater than Nitrobacter-like NOB, especially for the 40-day SRT sludge. The enrichment and shift of the nitrifier community reduced the adverse effect of low DO on nitrification; therefore, low DO operation of a complete nitrification process is feasible. © 2013 American Chemical Society.

Department(s)

Civil, Architectural and Environmental Engineering

International Standard Serial Number (ISSN)

1520-5851; 0013-936X

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2024 American Chemical Society, All rights reserved.

Publication Date

21 May 2013

PubMed ID

23631354

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