An electronic nose on a drone collects air for odor measurement.

Maria Deseada Esclapez

Spanish researchers have designed a portable electronic nose (electronic nose) that is almost as sharp as a human nose to smell the stench of sewage treatment plants. Coupled with a drone, the lightweight electronic nose can measure the concentration of different odors, predict odor intensity, and produce a real-time odor map of the plant for management. The method appears on November 16 in the journal iScience.

Conventionally, the smell of a wastewater treatment plant is measured by dynamic olfactometry, where a human panel sniffs and analyzes the air sacs collected from the plant. Although the method has been considered the gold standard, the process is expensive, slow, and infrequent, making it difficult for operators to respond quickly to issues or identify the root of the stench.

“I live two kilometers from a sewage treatment plant and every now and then you can’t even open the window because the smell is awful,” says lead author Santiago Marco de l ‘Institute of Bioengineering of Catalonia. “The impact on the quality of life of the people around these facilities should not be underestimated, and there are also physical and psychological consequences of being exposed to bad smells.

To better monitor odor emissions from wastewater treatment plants, Marco and his team designed a portable electronic nose for real-time data monitoring and visualization using artificial intelligence (AI). The team collected air sacs from a plant and trained the electronic nose to detect pungent chemicals such as hydrogen sulfide, ammonia, and sulfur dioxide, which respectively smell like rotten eggs, l urine and burnt matches. The electronic nose is also equipped with a carbon dioxide sensor, an indicator of bacterial activity. In the laboratory, the electronic nose worked almost as well as the human nose.

Researchers then attached the 1.3 kilogram (2.9 pound) electronic nose to a drone and sent it into the sky at a mid-size wastewater treatment plant in southern Spain between January and June. Flying over various plant facilities, the “sniffer drone” draws air through a ten-meter (33-foot) tube and analyzes the air in a sensor chamber.

“What is tricky about measuring odors is that it is a human perception and that it is not well defined”, explains co-author Maria Deseada Esclapez of Depuración de Aguas del Mediterráneo, a sanitation and sanitation service company. “We are not only trying to quantify particular or individual components of the emission, but also to predict the intensity of odors perceived by humans.”

The results demonstrated that the electronic nose on a drone was feasible for monitoring wastewater odors. When analyzing the same air samples in a field test, 10 of the 13 measurements of the electronic nose matched the human panel evaluations. Aided by the drone’s mobility and the AI ​​algorithm, the team also mapped the temporal and spatial concentration of odors and, for the first time, predicted the intensity of the odor from the drone measurements.

“We are extremely happy with the results, but we need more validation and to make the device more robust for actual plant operation,” says Marco. The team plans to reduce the additional weight of the electronic nose and develop a standardized process for the method. They also plan to further optimize the device against the influence of temperature, humidity and other environmental conditions that can affect accuracy.

“The work can also have implications for other facilities like landfills, composting factories or even large farms with cattle and pigs which are also known to produce all types of bad smells,” says Marco.

“We can’t wait to see what impact this work would have on the industry,” adds Esclapez.


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