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The Effect of Degree of Recycle on the Nitrifier Growth Rate
Author(s) -
Jimenez Jose,
Melcer Henryk,
Parker Denny,
Bratby John
Publication year - 2011
Publication title -
water environment research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.356
H-Index - 73
eISSN - 1554-7531
pISSN - 1061-4303
DOI - 10.2175/106143010x12609736967008
Subject(s) - degree (music) , environmental science , growth rate , environmental engineering , chemistry , mathematics , physics , geometry , acoustics
The nitrifier maximum specific growth rate, μ A,max , is a critical parameter for the design and performance of nitrifying activated sludge systems. Although many investigations studied μ A,max , only a few have dealt with the effect of the reactor configuration on this important kinetic parameter. Bench‐ and full‐scale trials were devised to study the effect of the internal mixed‐liquor recycle (IMLR) on the nitrifier growth rate constant. The nitrifier growth rate constant for an existing activated sludge plant was determined at different operational conditions using the high food‐to‐microorganism ratio (F/M) test and by process model calibration. Overall, the results obtained during this study indicate that high IMLR values have a negative effect on μ A,max . Based on the results obtained during this investigation, a 15% decrease in μ A,max was observed at an IMLR of 4 Q or higher. It is surmised that, at high IMLRs, the reactor behavior shifts from a plug‐flow configuration to a “quasi” complete‐mix configuration, influencing either the species selection in activated sludge population or at least the adaptation of specific species. These results have a tremendous effect on the design of activated sludge processes that incorporate IMLR for denitrification, such as the Bardenpho, Modified Ludzack‐Ettinger (MLE), University of Cape Town (UCT), and Phoredox or anaerobic‐anoxic‐aerobic (A 2 /O) processes.