How to Correlate UV254 to Other Organics Parameters (TOC, BOD, COD) - Measurements - UV254Sense

UV254 Sensor (UV254Sense) from Pi, for more information please visit: https://www.processinstruments.co.uk/....

UV254 is an optical technology which utilises light in the UV at a wavelength of 254nm and is able to detect organic matter in the water. Typically, its measurement is presented as a calculation of UV absorbance (UVA) or UV transmittance (UVT). Absorbance measurements are very common in the laboratory and in the field since absorbance at a given wavelength is linearly proportional to the concentration of any substances in the water that are known to absorb light at the given wavelength.

Light at 254nm wavelength is of particular interest since it is a wavelength that is very readily absorbed by organic matter in the water. Because the UV254 absorbance parameter is proportional to the concentration of organics in the water, it is a simple process to determine a linear correlation factor that relates the UV254 parameter to other water quality parameters that provide a measure of organic matter in the water. There are several such water quality parameters including total organic carbon (TOC), chemical oxygen demand (COD), biological oxygen demand (BOD) and colour (Hazen). All these parameters have slightly different biases to different types of organic matter. UV254 can often be linearly correlated to all of these parameters.

Please note that it is possible for there to be no correlation between UV254 absorbance and other water quality parameters if that parameter on a particular water source does not contain UV254 absorbing substances. An example of this would be a water supply counting a lot of dissolved sugar, as sugar won’t absorb UV254 but will have a high Chemical Oxygen Demand (COD).

FAQs:
How good is the correlation between UV254 and TOC?
TOC (Total Organic Carbon) is a difficult and expensive measurement to make online and UV254 can often be used as a surrogate measurement. This requires the user to build a correlate between TOC and UV254 offline and then enter the relationship between the two into the analyser which can then output as TOC (effectively, correlating the UV254 output to TOC). How good this correlation is will depend on what makes up the TOC. If the TOC is made up entirely of UV254 absorbing organics then the correlation will be excellent. If not the correlation will become predictably poorer until TOC is made up entirely of non-absorbing organics when the correlation will be 0. Typically, municipal water and waste water have very good correlations.

For more information about your TOC, BOD or COD measurement application, please contact us. All of our contact details can be found at: https://www.processinstruments.co.uk/....

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