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This researcher helps take the stink out of biosolids

Odour management at wastewater treatment plants is becoming increasingly nuanced, thanks to research being conducted into the chemical and microbial processes responsible for nuisance smells.

University of New South Wales (UNSW) School of Civil and Environmental Engineering Lecturer Dr Ruth Fisher said the approach to mitigating problematic smells depends on the source of the problem.

“Odours only become a problem when we smell them. And there's a whole different series of stages utilities can take to minimise nuisance emissions,” she said.

Fisher is part of UNSW’s Odour Laboratory, an extension of the Water Research Centre, which works to identify the make-up of complex emissions.

The Odour Laboratory comprises a group of academics from varying research backgrounds, with Fisher responsible for analysing emission composition in order to link the specific odorant to operating conditions.

“I’m looking for the chemical and the microbial processes responsible for the odorants,” Fisher said.

“We do this using both analytical and sensorial methods; we use machines and our noses.”

Fisher’s methodology starts with identifying the odour’s source and composition. 

“If we understand what the compounds are, it can help us identify specifically what stage of the treatment process [the odour is] from,” she said.

“For example, with biosolids from wastewater treatment plants, we can identify if the smell is coming from the primary settlers, or if it is coming from the dewatered biosolids.

“Then, if we can understand what compounds they are, we can look at why they would be present, taking into account the chemical and microbial processes.”

Having worked alongside Sydney Water, Hunter Water and Suez, Fisher said the approach to mitigating nuisance odours depends on the individual site and its processes.

“The majority of the work we do is minimise the odours being formed in the first place, or dealing with them once they are there,” she said.

“Once we know what is there we can suggest actions to troubleshoot or change the process, such as reducing septicity through decreasing retention times or addition of iron chloride” she said. 

While source and composition is a large part of mitigating nuisance smells, Fisher said the biggest challenge is accounting for human subjectivity in terms of interpreting smells.

“The biggest challenge in terms of odours is that they are a human response,” she said. 

“There is so much variability and uncertainty, even in the measurements that we are conducting.

“Some people are really sensitive to odours and they're the ones who are more likely to complain and be affected. So we need to make sure that we take that into account when we are measuring.”

Fisher’s work with the UNSW Odour Lab is set to continue in the Transformation of Australia’s Biosolids Resource Training Centre funded by the Australian Research Council.

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