Measuring and testing – Gas content of a liquid or a solid – Particular separator
Patent
1996-08-28
1998-03-03
Williams, Hezron E.
Measuring and testing
Gas content of a liquid or a solid
Particular separator
73 6447, 73 6173, 73 3102, 210640, 422101, G01N 1300, G01N 2740, C08G 7704
Patent
active
057237697
DESCRIPTION:
BRIEF SUMMARY
THIS INVENTION relates to a diffusion cell.
This invention has been developed for use in an in-situ monitoring device which is utilised for the environmental and process monitoring, determination and/or measurement of gaseous or volatile products in a bulk medium. For instance, such an in-situ monitoring device is useful for determining the concentration of products such as methane or dissolved oxygen in subsurface ground water, or for determining the levels of products that may be considered to be contaminants of such ground water.
While the present invention is not to be limited only to use with contaminants it is noted that in recent years there has been a growing awareness of the need to develop techniques for the rehabilitation of soils and ground waters that have been contaminated with a range of inorganic and organic materials, such contamination being generally due to improper waste disposal, and spillages and leakages of chemicals from existing or disused industrial sites.
An important aspect of the evolution of these particular rehabilitation techniques has been the development of devices which are capable of sensing contaminants, such as volatile organic compounds and gases (for example, oxygen) in ground waters, industrial effluents and contaminated soils. The volatile organic compounds (VOC's) are often in the form of organic solvents and petroleum fuels, and in particular are substances such as aromatic hydrocarbons, chlorinated ethanes and ethenes. Specifically, volatile organic compounds which are common ground water pollutants are benzene, toluene, ethylbenzene, xylenes (BTEX's), dichloroethane, carbon tetrochloride, chloroform, trichloroethylene (TCE) and tetrachloroethylene (PCE).
Furthermore, it is also known that high concentrations of dissolved methane can occur in some natural ecosystems from leakage of hydrocarbon deposits and also from biogenic sources. The formation of methane by microbial breakdown of organic matter (methanogenesis in anoxic sediments) is common and is known in marine, estuarine and fresh water systems. In deeper subsurface environments such aquifers, methanogenesis can also occur, often being associated with ground water contaminated by waste leachates. Thus, it an be seen that high concentrations of dissolved methane in ground water is a useful indicator of such contamination.
Development of in-situ monitoring devices has also arisen through projects aimed at determining the levels of dissolved oxygen in ground waters, surface waters, affluents and treatment plants. For example, by developing an in-situ monitoring device capable of sensing dissolved oxygen in surface waters, it may be possible to obtain an early warning of the build-up of nuisance algal blooms or waste discharges which deplete dissolved oxygen and affect in-stream eco-systems.
In general, in-situ devices capable of providing real-time data are particularly useful for environmental monitoring, where concentrations and conditions change significantly with time, for example due to diurnal effects or from intermittent contamination. Such devices may be used to monitor and measure the degree of contamination, or may be used to simply attend to constant compliance monitoring of existing facilities which use substances such as organic nonaqueous phase liquids (for example, storage, waste disposal and recovery plants) in order to avoid the contamination problem evident from past experience.
Normally, the techniques used to determine the extent of any contamination would involve the drilling of a network of observation boreholes to allow direct sampling of ground water. However, considerable effort and expense are inevitably involved in such exercises as the techniques for recovering samples are generally extremely labour intensive. Further, and particularly when VOC's are being measured, extensive decontamination procedures are required in order to avoid difficulties associated with cross contamination of samples by VOC's which are easily absorbed from contaminated ground water by flexible (polymer) pu
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Barber Christopher
Hannon Patrick
Patterson Bradley Mark
Trefry Michael George
Commonwealth Scientific and Industrial Research Organisation
Greenspan Technology Pty Ltd.
Wiggins J. David
Williams Hezron E.
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