NO x monitoring of a simultaneous nitrifying–denitrifying (SND) activated sludge plant at different oxidation reduction potentials
Simultaneous nitrification–denitrification (SND) allows biological nitrogen removal in a single reactor without separation of the two processes in time or space but requires adapted control strategies (anoxic/aerobic conditions). In this study, the formation of gaseous nitric oxide (NO G) and nitrog...
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Published in | Water research (Oxford) Vol. 41; no. 2; pp. 397 - 405 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
Elsevier Ltd
2007
|
Subjects | |
Online Access | Get full text |
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Summary: | Simultaneous nitrification–denitrification (SND) allows biological nitrogen removal in a single reactor without separation of the two processes in time or space but requires adapted control strategies (anoxic/aerobic conditions). In this study, the formation of gaseous nitric oxide (NO
G) and nitrogen dioxide (NO
2G) was monitored for SND in relation to the oxidation-reduction potential (ORP) and nitrogen removal in a lab batch reactor and a pilot membrane bio-reactor (MBR). In addition hospital wastewater (COD/N
tot>6:1) was treated on site for 1 year. The highest total nitrogen removal rates of max 90% were reached at 220–240
mV ORP (given as
E
h) with corresponding maximal NO
G emissions rates of 0.9
μg
g
−1
VSS
h
−1. The maximal emission rates of NO
2G (0.2
μg
g
−1
VSS
h
−1) were reached at the same ORP level and the NO
2G emissions correlated to the nitrite accumulation in the activated sludge up to 5
mg
l
−1
NO
2L-N. It was shown that this correlation was due to biological production and not due to pH-dependent chemical conversion. Therefore, NO
2G can be used as additional control loop for ORP-controlled SND systems to avoid the inhibition of denitrification and high nitrite concentrations in the plant effluent. |
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ISSN: | 0043-1354 1879-2448 |
DOI: | 10.1016/j.watres.2006.10.034 |