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Nitrous oxide emissions for early warning of biological nitrification failure in activated sludge.

By M. D. Butler, Y. Y. Wang, Elise Cartmell and Tom Stephenson


Experiments were carried out to establish whether nitrous oxide (N2O) could be used as a non-invasive early warning indicator for nitrification failure. Eight experiments were undertaken; duplicate shocks DO depletion, influent ammonia increases, allylthiourea (ATU) shocks and sodium azide (NaN3) shocks were conducted on a pilot-scale activated sludge plant which consisted of a 315 L completely mixed aeration tank and 100 L clarifier. The process performed well during pre-shock stable operation; ammonia removals were up to 97.8% and N2O emissions were of low variability (<0.5 ppm). However, toxic shock loads produced an N2O response of a rise in off-gas concentrations ranging from 16.5 to 186.3 ppm, followed by a lag-time ranging from 3 to 5 h ((0.43–0.71) × HRT) of increased NH3-N and/or NO2− in the effluent ranging from 3.4 to 41.2 mg L−1. It is this lag-time that provides the early warning for process failure, thus mitigating action can be taken to avoid nitrogen contamination of receivin

Topics: Activated sludge, Early warning, Nitrification, Nitrous oxide, Toxic shocks
Publisher: Elsevier Science B.V., Amsterdam.
Year: 2009
DOI identifier: 10.1016/j.watres.2008.12.027
OAI identifier:
Provided by: Cranfield CERES

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