Smart environmental monitoring solutions

Quick summary

Odour is a potentially contentious environmental issue due to the often subjective nature of odour complaints.

Wastewater treatment plants are commonly a source of odour nuisance. Complaints emanating from residential and tourist areas range from unpleasantness and psychological discomfort to headache and dizziness complaints.


Odour emissions to the environment can vary and depend on sewage quality and technological solutions at the wastewater treatment plant. Biological changes occur within the process systems at the plant and influence the type of odour produced. Odour is most often a result of the breakdown of organic matter under anaerobic conditions. The presence of oxygen is an essential factor in feeding the bacteria that break down organic matter, thus reducing the formation of odorous compounds.

Odours are likely to be generated when there are long retention times in sewerage components. Sewage catchment points, pump stations, syphons and sludge management facilities are all points of high odour susceptibility. A combination of factors within the infrastructure influences odour emissions, including uneven and low flow, combined with inadequate ventilation, high temperatures, and thus the emergence of anaerobic conditions.

Meteorological conditions also alter variability in odour emissions, such as atmospheric pressure and air turbulence over the sources. Odorous complaints related to wastewater infrastructure may even double in summer as opposed to winter.

Odour emissions consist of many individual components of complex mixtures. The most common odour constituents in a wastewater treatment plant are hydrogen sulphide gas, dimethyl sulphide, methyl mercaptan, ammonia and volatile organic compounds (VOC’s). Besides odour issues, these chemical compounds can also impact operating infrastructure – thus addressing odour emissions may also improve facility management. Hydrogen sulphide gas management using carbon filters and chemical dosing reduces both odour emissions and infrastructure corrosion within wastewater treatment plants.

There is no universally accepted method of odour measurement or quantification of odours; however, measurement at is by sensory or analytical methods.

Sensory analysis of odour is open to considerable uncertainty. An individual’s response to odour is highly subjective. People find different odours offensive at different concentrations. Therefore, it is necessary to have a team of trained persons to assess the smell in odour assessment.

Analytical methods are more advantageous as they determine concentrations of individual components of the malodorous mixture and identify and quantify chemical compounds emitted at the emissions source.

Analytical methods can use real-time data to examine amount, duration, rate and characteristics of emissions and the environmental sensitivity to assess odour emissions and complaints.

Monitoring data is a useful tool in mitigating odour issues achieved through the design, construction and operational processes at a wastewater treatment plant.

Choosing the right monitor is essential to accurately identify odours early for the comfort of employees and the community and the efficient operation of the wastewater treatment plant.

Norditech Pty Ltd provides innovative solutions for all your odour monitoring needs. Effective monitoring is key to achieve your work health and safety objectives and meet your compliance requirements. Give us a call for further information on 1300 572 872.

Published December 18, 2020



Gebicki J, Byliński H, Namieśnik J. Measurement techniques for assessing the olfactory impact of municipal sewage treatment plants. Environ Monit Assess. 2016;188(1):32. doi:10.1007/s10661-015-5024-2

Pochwat, Kamil & Kida, Małgorzata & Ziembowicz, Sabina & Koszelnik, Piotr. (2019). Odours in Sewerage—A Description of Emissions and of Technical Abatement Measures. Environments. 6. 89. 10.3390/environments6080089.

Zarra, Tiziano & Naddeo, Vincenzo & Belgiorno, Vincenzo & Reiser, Martin & Kranert, Martin. (2008). Odour monitoring of small wastewater treatment plant located in sensitive environment. Water science and technology: a journal of the International Association on Water Pollution Research. 58. 89-94. 10.2166/wst.2008.330. (PDF) Odour monitoring of small wastewater treatment plant located in sensitive environment (

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