Citation:
M.D. Butler, Y.Y. Wang, E. Cartmell, T. Stephenson, Nitrous oxide emissions for
early warning of biological nitrification failure in activated sludge, Water
Research, Volume 43, Issue 5, March 2009, Pages 1265-1272
Abstract:
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 receiving
