Outdoor in situ monitoring of volatile emissions from wastewater treatment plants with two portable technologies of electronic noses

This paper reports the test of portable electronic noses for outdoor air monitoring of sewage odours directly in the field. Two commercial devices with two different gas sensor technologies were tested: conducting polymer (CP) and metal oxide semiconductor (MOS) in order to select the most appropriate one for this application. As a means to improve the classification ability, the influence of environmental parameters in different data pre-processing algorithms was studied. The algorithm that permitted the least humidity, temperature and day correlation as judged with partial least squares (PLS) was selected. The effectiveness of the systems to discriminate between samples was observed using principal component analysis (PCA). The results indicated that CP sensors appear to be unacceptable for this application while MOS sensors tested were better for discriminating between the different odours. Correlation between the sensor responses and CH3SH concentration in water shows that location of samples for MOS sensors depends on the water quality.