Sewage treatment works odour measurement

Public concern over odours from sewage treatment works is increasing. More people are being exposed to odours, due to development around existing works or the construction of new works. Raised awareness of both the environment and individual rights has meant people are now more likely to complain. Odour abatement and control is a major issue for sewage works operators. To control odours, they must first be measured. This is no easy task as response to odours is subjective and our understanding of the sense of smell is incomplete. In assessing an odour nuisance, odour formation, emission, dispersion and perception must be considered. There is no single measure that is suitable for this purpose. Odour measurements fall into two classes. Analytical measurements characterise odours in terms of their chemical composition and are more suited to formation, emission and dispersion models. Unfortunately, they tell us little about the perceived effect of the odour. Sensory measurements employ the human nose and characterise odours in terms of their perceived effect. A link between analytical and sensory measurements is clearly needed. In this paper data collected from odour surveys at 17 different wastewater treatment sites are evaluated to explore possibilities for linking analytical and sensory measures. The relationship between hydrogen sulphide concentration and odour concentration as measured by threshold olfactometry explored. Correlations suggest power-law relationships between hydrogen sulphide and odour concentration. with r(2) values as high as 0.69. This paper will assess the use of hydrogen sulphide (H2S) and olfactometry measurements for a range of unit operations and abatement technologies.