Citation:
Callister, S., Stephenson, T., Butler, M. and Cartmell, E.; N-Tox® - Early
warning of nitrification toxicity for activated sludge treatment. Presented at
4th CIWEM (Chartered Institute of Water and Environmental Management) Annual
Conference held 12-14 September 2006, Newcastle
Abstract:
N-Tox® is a new technique for evaluating the nitrification efficiency in
industrial or municipal activated sludge systems, using direct measurement of
nitrous oxide (N20) as an indicator of nitrification failure. Research using
pilot-scale activated sludge plants treating real settled wastewater has
demonstrated that detection of increased N2O concentration in the aeration tanks
by N-Tox® is able to provide early warning of nitrification failure. The N-Tox®
monitor relies on non-invasive gas-phase detection which avoids sampling of
activated sludge and eliminates associated probe fouling problems and
maintenance issues. Nitrification failure detection by N-Tox® is rapid, giving
plant operators the time to take remedial action before possible release of
ammonia. Recently presented data has shown the effectiveness of N-Tox® in
providing early warning of nitrification inhibition following loss of aeration
and ammonia overloading events. New data is now presented to demonstrate the
effectiveness of N-Tox® in providing early warning of nitrification failure for
a number of well-known toxic chemicals. These include the organic compound
phenol, the nitrification suppressant allylthiourea (ATU) and the inorganic
fungicide and herbicide, sodium azide. N-Tox® was able to detect nitrification
failure when the first step of nitrification was inhibited, resulting in a rise
in effluent ammonia, and when the second step was inhibited, resulting in a rise
in effluent nitrite. The pattern of N2O emission indicated the failure mode: a
sharp peak indicated ammonia breakthrough whereas a sustained increase in N2O
indicated nitrite formation. The N-Tox® device can also be used to quantify
emissions of N2O, a powerful greenhouse gas, from wastewater treatme