An electronic nose consisting of twelve polypyrrole conducting polymer sens
ors was evaluated for its ability to monitor quiescent sewage liquors at th
ree wastewater treatment works. Samples collected from the works inlet. the
settlement rank and the final effluent outlet over an 8-month period, show
ed that a non-specific sensor array can distinguish between sewage samples
of different type and from different treatment works. The correlation of th
e electronic nose responses with the 5-day biochemical oxygen demand (BOD5)
using canonical correlation (a statistical reduction technique), showed th
at no generalised relationship can be found between these parameters for ra
w sewage, settled sewage and final effluent samples from three treatment wo
rks. However. when samples From a single works are compared separately, str
ong correlations can be produced between the electronic nose responses and
BOD5 for time intervals of approximately 4 weeks. These relationships show
that it is possible to fit single lines between the response patterns of an
electronic nose and BOD5 for sewage samples at a single treatment works. T
he results suggest that it may bt:feasible to use an electronic nose to mon
itor and/or control the biochemical activities of a wastewater treatment pr
ocess. (C) 1998 Elsevier Science Ltd. All rights reserved.