Tackling challenges posed by odorous emissions at the IWA conference

8th Odour and VOC/Air Emissions Conference

The 8th Odour and VOC/Air Emissions Conference, organised by the International Water Association (IWA) was held on 14–16 October in Hangzhou, China – the first time that this series of biennial conferences has been held in the country.

The focus is broad, and covers odour and VOC regulations, monitoring and mitigation. Interest was high, with around 200 delegates attending the workshop and the conference. The conference was held just a few blocks away from the beautiful West Lake, a UNESCO World Heritage site west of the city of Hangzhou.

The pressures of urbanisation

The management and abatement of odours was a major topic at this year’s conference. One factor in this is increasing urbanisation, which especially in China has led to a spotlight being thrown upon odorous emissions from wastewater treatment plants, industry and livestock.

Identifying the sources and managing emissions from such facilities are key factors in planning and selecting locations for housing, but also for improving the sustainability of these industries in the future.

The need for standardisation

In his keynote address, Professor Richard Stuetz from the University of New South Wales, Australia, noted a few of the challenges facing the odour management community.

One of these is that different sampling strategies and analytical methods make it difficult to compare odour studies – making the need for standardisation of prime importance. However, he highlighted the progress that has been made, with the EU standard EN 13725 allowing odour concentrations of gaseous samples to be determined by dynamic olfactometry using human testers.

Variation in odour perception

Another interesting presentation was that by Professor Mel Suffet from the University of California, who explained some subtleties about odour perception. He explained that although in general the intensity of an odour is proportional to the logarithm of its concentration; different odours can cause different associations at different concentrations in different people.

Professor Mel Suffet (right) discusses with me how modern VOC analytical technologies can be used to monitor odours at the very low levels needed.

Consequently, odour perception is a very personal experience, and Professor Suffet described how the use of odour-profiling methods with trained panels can help to address this issue and provide some consistency. Key metrics that can be identified are the odour threshold (when an odour is detected) and the recognition threshold (when an odour can be identified). In conjunction with analytical systems, these thresholds can then be associated with an actual concentration.

Odour removal strategies

The organiser of the conference, Professor Dezhao Liu, from Zhejiang University, Hangzhou, discussed strategies for removing odorants.

Spraying water is frequently used to reduce odour from pig houses, but it’s usually rather ineffective, and the large volumes of water required are problematic in themselves. However, where this approach is appropriate, Professor Liu described how the efficiency of odour removal can be improved by adding a microbial agent and citric acid.

Odour emission testing

Because the human nose is so good at detecting low levels of odorous compounds, it can be quite challenging to determine the actual VOC concentrations analytically.

At our stand (pictured below), my colleagues and I explained how our thermal desorption equipment can reach the ultra-low detection limits required, by using a focusing trap to concentrate the analytes prior to injection into a GC.

Ready to discuss sampling and preconcentration using our Centri® platform at the Markes international booth at IWA.

In fact, in a recent study we achieved method detection limits of 1–3 ng/L for five target odorants in the headspace above a water sample. These values are close to or below the odour thresholds in each case. The target compounds included geosmin and 2-methylisoborneol (2-MIB), which are the two odorous compounds that are most often the source of complaints to water companies.

To find out more about using thermal desorption technologies to detect odorants at such low levels, Application Note 255 is a great introduction – you can download it here.