Many industrial processes can now make use of precise, compact gas chromatography based monitoring systems. Now available as small compact rack mounted devices, the systems are very robust, extremely sensitive, offer rapid sampling times and reduce operator intervention time, improving overall plant and process efficiency. A typical application is for monitoring of H2S from water treatment processes.

As a result of the enclosed nature of waste water stations, toxic components such as H2S increased in the working environment, posing a health hazard to operators. Safety of employees on such working sites has therefore become a major problem. To combat this hazardous pollution, air filtering systems have been installed. For the station managers, personal safety coupled with the need for constant air quality control and targeted filter changes has become an important task.

The solution is provided via a Medor sampling system, the building from where the waste water is distributed water into 5 digestors is continually inhabited by the technicians on site. The micro-biological activity including the fermentation of the organic material results in the production of toxic sulphur compounds (H2S). It is therefore of the utmost importance to screen this work zone for safety reasons. The air MEDOR, placed in this hostile and difficult environment, provides a solution to this problem by supplying a constant ambient measurement system of the mercaptans (H2S, methyl-SH, DMS+DMDS).
Coupled with a stream selector the air MEDOR gives the necessary data to provide the optimum time at which to change each of the 5 H2S filters (one at every digestor) thus providing both cost savings and preventing saturation of the filters leading to pollution episodes. This system offers increased operation efficiencies, increased safety for personnel and substantial cost savings in filter changes.

The air MEDOR is a continuous gas chromatograph dedicated to sulphur compound analysis. 
A unique electro-chemical detector allows the specific detection of sulphur species.
Deodorisation is also a recurring issue for treatment works. Nuisance odours are caused by  bacteriological fermentation of sulphides into H2S.

Successive chemical cleaning in the deodorisation towers eventually neutralises these odours. Highly odorous air is captured and neutralised by chemical stripping process. It is important to measure the effectiveness of this control process.

The correct amount of chemical products needed to neutralise the polluted air has to be calculated.
An air Medor sampling unit placed at the outlet of the stripping process, measures the H2S concentrations and pilots the dosage of calcium nitrate, a process that supplies excess oxygen to the bacteria which in turn prevents sulphate transformation into sulphides.

This automatic control and regulation of odours, reduces operator time to manage process and again offers cost savings due to lower levels of calcium nitrate being used.

All systems for process control need to be robust, extremely sensitive with detection levels down as low as ppb. Rapid sampling times are essential to offer immediate control of the pollutants. All on line monitoring systems have to be stable, simple to operate and require minimal servicing and operator input to operate and maintain. It is important that all monitoring systems comply with the relevant ISO standards.
(The model used here complies with the norms ISO 6326/2.)

Many other environments can be measured utilising chromatographs, including indoor or outdoor air quality, natural or calibration gas purity and controlling ambient emissions.

For further information please contact;

Casella Measurement Limited
Wolseley Road 
Kempston
Beds
MK42 7JY UK

Phone: 01234 844100
Fax: 01234 841490

Web: www.casellameasurement.com

E-mail: info@casellameasurement.com