Remote Sensing Electronic Device for Hydrogen Sulphide in the Atmosphere: An Investigation

This report was produced for the Urban Water Research Association of Australia, a now discontinued research program.

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Report No UWRAA 29

February 1995

SYNOPSIS

Odours from sewage plants are a continuing source of community complaints. Since hydrogen sulphide (H₂S) is commonly the major odorous component of sewage, it is a major cause of these complaints. At present, only expensive, slow response devices are available for the measurement of low (ppb)concentrations of hydrogen sulphide in the atmosphere in odour plumes and of nearby communities, and are unsuitable for detecting and quantifying these rapidly fluctuating levels. Current devices, therefore, are unsuitable for use as early warning monitors that would indicate when the concentration of hydrogen sulphide in the environment surrounding sewage plants was approaching annoyance level and that preventative measures should be undertaken at the plant. At present, therefore, it is difficult for plant operators to initiate odour reduction measures until after a community complaint has been received.

The objective of this study was to construct a device that (i) will measure and monitor rapidly fluctuating low concentrations (ppb) of hydrogen sulphide in the atmosphere that are at the threshold levels detectable by the human nose, and (ii) can be interfaced to a central microprocessor in the sewage plant which would activate odour reduction processes.

In pursuit of these aims, a number of prototype sensors were constructed and tested. These included:

Conductive polymer electrodes using cyclic voltammetry of modified polymers and AC cyclic voltammetry.
Quartz crystal microbalances (QCM) with sulphide-specific coatings. A purpose built dual QCM designed to minimise interference from temperature and humidity.
Gold film resistance methods using both glass and plastic backings were tested.
Flow injection liquid analysis using amperometric methodology.

As indicated later in this report, lack of funds prevented the fuller development of a sensor using one of these approaches. However, the results achieved indicate that the most promising sensor techniques for the further development of a hydrogen sulphide sensor appear to be conductive polymer micro-electrodes, quartz crystal microbalances and the associated surface acoustic wave devices.

Finally, a hydrogen sulphide gas delivery system was developed using a permeation tube technique. This apparatus was used for the calibration of sensor devices in the ppm – ppb range and should find wide use in the sewage and chemical industries for the calibration of H₂S and other gas detection devices that are currently in use. The system is available at CSIRO.

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