"Role of Solids Retention Time on Complete Nitrification: Mechanistic U" by Guoqiang Liu and Jianmin Wang
 

Abstract

Effects of solids retention time (SRT) on both steps of the nitrification process (e.g., ammonia oxidation and nitrite oxidation) and the nitrifier community in a complete-mix activated sludge process were studied. At a SRT less than or equal to 20 days, the effluent ammonia concentration was lower than the effluent nitrite concentration. At the 40-day SRT, however, the effluent nitrite concentration became equal to or less than the effluent ammonia concentration. Quantitative Polymerase Chain Reaction (QPCR) assays indicated that increasing SRT significantly increased nitrite-oxidizing bacteria/ammonia-oxidizing bacteria (NOB/AOB) ratio. Further investigation indicated that Nitrosomonas europaea/eutropha were the dominant AOB for ammonia oxidation under all SRTs. However, for nitrite oxidation, Nitrobacter-like NOB played the key role at low SRTs, while Nitro Spira-like NOB played the key role at high SRTs. Modeling results indicated that, for AOB and NOB, the values of maximum specific growth rate (μ) were 0.24 and 0.18/day, respectively, while the values of decay coefficient (Kd) were 0.066 and 0.045/day, respectively. The half-velocity constants (KS) for both AOB and NOB were approximately 0.02 mg/L, and the maximum specific substrate utilization rate (k) for AOB and NOB were 1.3 and 3.0 g-N/g-VSS-day, respectively. These values suggest that AOB had an advantage over NOB at a lower SRT, mainly because AOB grew faster than NOB did. On the contrary, the increased NOB/AOB ratio at a longer SRT was likely due to NOB having a smaller kd. The very low KS values for both AOB and NOB imply that a plug-flow reactor may not have much kinetic advantage over a complete-mixed reactor for a complete nitrification process. The mass concentrations of AOB and NOB in the activated sludge can also be calculated based on the measured nitrification capacity and their k value. © 2014 American Society of Civil Engineers.

Department(s)

Civil, Architectural and Environmental Engineering

Comments

Fonds National de la Reserche Luxembourg, Grant None

Keywords and Phrases

Kinetic parameter; Modeling; Nitrification; Nitrifying bacterial community; Solids retention time

International Standard Serial Number (ISSN)

0733-9372

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2024 American Society of Civil Engineers, All rights reserved.

Publication Date

01 Jan 2014

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