RemoteSensing Electronic Device for Hydrogen Sulphide in the Atmosphere:

AnInvestigation

ReportNo WSAA 90

February 1995

SYNOPSIS

Odoursfrom sewage plants are a continuing source of community complaints. Sincehydrogen sulphide (H₂S) is commonly the major odorous component ofsewage, 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 ofnearby communities, and are unsuitable for detecting and quantifying theserapidly fluctuating levels. Current devices, therefore, are unsuitable for useas early warning monitors that would indicate when the concentration ofhydrogen sulphide in the environment surrounding sewage plants was approachingannoyance level and that preventative measures should be undertaken at theplant. At present, therefore, it is difficult for plant operators to initiateodour reduction measures until after a community complaint has been received.

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

Inpursuit of these aims, a number of prototype sensors were constructed andtested. These included:

·        Conductive polymer electrodes using cyclic voltammetry of modifiedpolymers and AC cyclic voltammetry.

·        Quartz crystal microbalances (QCM) with sulphide-specific coatings. Apurpose built dual QCM designed to minimise interference from temperature andhumidity.

·        Gold film resistance methods using both glass and plastic backings weretested.

·        Flow injection liquid analysis using amperometric methodology.

Asindicated later in this report, lack of funds prevented the fuller developmentof a sensor using one of these approaches. However, the results achievedindicate that the most promising sensor techniques for the further developmentof 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 tubetechnique. This apparatus was used for the calibration of sensor devices in theppm – ppb range and should find wide use in the sewage and chemical industriesfor the calibration of  H₂Sand other gas detection devices that are currently in use. The system isavailable at CSIRO.

Copiesof the Report are available from WSAA, price $A20. Orders may be placed throughthe Bookshop at www.wsaa.asn.au or by email to info@wsaa.asn.au.