The future of odour and H2S monitoring at wastewater treatment plants

The wastewater treatment industry has come a long way since its inception, playing the role of an unsung hero in our lives. According to a report by Melbourne Water, the Greater Melbourne alone accounts for the process of 860 megalitres of wastewater influx every day.

Wastewater facilities are a core foundation for growing urban communities around the world. However, it’s becoming a challenge for plants operating in urban areas to sustain environmental balance. Unfortunately, plants with encroaching communities can impact their neighbours with odour emissions, predominantly caused by H₂S. This can lead to complaints, a damaged reputation and lengthy investigations that further steer to inconclusive results.

The growing need to monitor H₂S and odour emissions

H₂S is a by-product of wastewater treatment and makes up a large amount of most odour emissions. H₂S along with other odorous gases can affect the quality of life for residents in the area and more importantly, their health. Even at levels as low as 0.4 parts per billion (ppb), H₂S can be noticeable and considered a particularly offensive odour. The absolute threshold concentration (ATC) for H₂S, which is defined as the minimum concentration that can be detected, stands at 0.00047 ppm while the maximum allowable concentration (MAC) is set at 50 ppm and 37.5 ppm for the US and the UK, respectively.

Urban population growth is creating a growing urgency for the wastewater operations to ensure continuous H₂S and odour monitoring systems are operating efficiently, but also as effectively as possible 24/7. This is now becoming a priority at any treatment facility in addition to managing site odour emissions by measuring H₂S levels at the fence line or boundary of the treatment plant.

The introduction of small-sensor technologies for odour monitoring

Nowadays, small-sensor technologies enable businesses to configure cost-effective sensor networks around wastewater facilities to map odour emissions for a fraction of the cost — what once would have required operators to spend hundreds of thousands of dollars. The technology for measuring H₂S has evolved from ultraviolet (UV) fluorescence spectrometers combined with catalytic converters to small electrochemical sensors, despite the former still being the reference method. Electrochemical sensors that used to take environmental readings in a ppm range are now jumping in the ppb bracket, while minimising the business expense.

‘Enoses’ are part of a growing trend of small-sensor technologies that can measure ‘odour intensity’ on a scale of 1-4 to provide decision support for wastewater operators.

Businesses can now rely on less accurate yet more cost-effective sensors because of the software platforms, artificial intelligence and machine learning algorithms. The wastewater treatment industry is adapting to the new methods of odour mitigation with the implementation of a real-time odour monitoring system.

The inevitable: real-time analysis of odour monitoring networks and local weather data

Growing communities and tightened compliance regulations by relevant environmental authorities have put wastewater operators on the hunt for more proactive odour management solutions. Environmental intelligence systems are now providing a single source of truth for site level emissions through real-time analysis of meteorological conditions and odour monitoring networks. Data insights can inform, simulate and refine incident response plans with predictive modelling tools, along with capabilities of stakeholder engagement.

Wastewater operators can plan for high-risk shifts up to 72 hours in advance with insights from odour emissions modelling and local weather data.

One the UK’s biggest water utilities — Southern Water — is now using an EI platform across its multiple sites to understand the connection between wastewater facility status and odorous emissions more effectively. According to the case study, Southern Water implemented the Envirosuite platform to gain on hour-by-hour forecast of risk level for odour impact up to 72 hours ahead. Envirosuite’s odour monitoring network was also implemented to provide instant diagnoses about the likely sources of community complaints.

There are now a growing number of organisations around the world following in their stride — indicating that the implementation of EI-powered H₂S and odour management systems is essential going forward.

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