Product category:
Testing, analysing and monitoring equipment
News Release from: ABB Automation Tech (Instrumentation + Automation) | Subject: AV400 analysers
Edited by the Engineeringtalk Editorial
Team on 22 March 2006
Monitors keep check on trihalomethanes
Dissolved organics monitors help Yorkshire Water safeguard the health of its customers by preventing the formation of regulated compounds known as trihalomethanes.
Dissolved organics monitors from ABB are helping Yorkshire Water safeguard the health of its customers by preventing the formation of regulated compounds known as trihalomethanes (THMs) Enabling real-time monitoring of organic compounds, ABB's AV400 analysers are helping ensure that THM levels never exceed the legal limit of 100ug/litre
This article was originally published on Engineeringtalk on 17 Jul 2008 at 8.00am (UK)
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The TTF350 temperature transmitter is suitable for heavy-duty applications in industries such as oil and gas, power, cement, waste incineration and chemical processing.
THMs can be formed by the reaction of organic matter with the chlorine used in the later stages of potable water treatment.
Where THMs are likely to form, water samples are regularly taken for laboratory analysis to ensure that levels of dissolved organic matter are being properly controlled.
Such testing, however, can present a problem for water companies because it takes up to a week to get the results of direct analytical tests.
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The AV400 monitors measure the absorption of ultraviolet light at 254nm commonly known as UV254, which is directly related to the level of organic matter in the water.
Modelling the relationship between the level of organic matter and the subsequent formation of THMs has allowed Yorkshire Water's engineers to control THMs by setting safe limits for organic material in the partially treated water heading for chlorination.
According to Jenny Banks, Project Engineer for R and D with Yorkshire Water, various changes to the upstream process, such as changing dose rates, adjusting pH or improved mixing, can all have an impact on the amount of organic matter getting through.
"Coagulation removes around 95% of organic matter before chlorination, but the ABB monitors allow us to fine tune the treatment process and ensure that we are complying with the THM limit at all times", she said.
Before the advent of UV254 technology, colour was the only contender for measuring organic matter in real time.
The organic compounds commonly found in water abstracted from moorland, for example, typically give the raw water a characteristic yellow colour.
But according to Banks, this approach was not accurate enough to apply to partially treated water.
"The level of colour is so low at that stage in the treatment that the resolution is poor", she said.
"UV254 provides a much more accurate indicator".
The monitors give a resolution of 0.01mg/litre of dissolved organics over a range of 0-20mg/litre.
The transmitter incorporates the latest technology to provide a highly reliable yet flexible, device for process monitoring and control applications.
The measured value is updated every 2s when the UV lamp is flashed and is calculated from over 200 readings that are taken during the brief flash duration, delivering more accuracy than conventional colour testing technology.
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