Odour measurements for sewage treatment works.

Public concern over odours from sewage treatment works is increasing. More people are being exposed to odours, due to development around existing works or construction of new works. Increased 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. Our understanding of the sense of smell is incomplete, and there is no single measure that will directly relate to the likelihood of complaint. Odour measurement has often been regarded as an art as opposed to a science. Odour measurement techniques fall into two classes. Sensory measurements employ the human nose and measure the effects of the odour as perceived by an observer. Analytical measurements characterise odours in terms of their chemical composition and attempt to quantify the odorants present. Both methods are less than ideal--sensory measurements can be overly subjective and the interpretation of results requires care. Analytical measurements are complicated by the large number of odorants present, often at concentrations close to detection limits. Our incomplete understanding of odour perception makes linking analytical and sensory measurements difficult. This paper reviews the methods applied to sewage treatment works odour measurement. Sensory and analytical measurements are reviewed, along with a recent development, the electronic nose.