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Measuring COD / BOD in a multiparameter analyzer : 6/1/2015

In our last article, we discussed about smart ways of monitoring water pollution due to industrial effluents. In this article we will be discussing about how some of the parameters are measured in these analyzers.

When it comes to multiparameter analyzer, it is important to know how some of the important parameters can be measured in it.

COD measurement principle

The preferred measuring principle for COD measurement is based on the UV VIS Absorption Spectroscopy.

[C] = k log (Iin/Iout)

Where [C]: sample concentration

k : absorption coefficient (specific to each molecule)

Iin : light intensity at the input of the sample

Iout : light intensity at the output of the sample,

It is important that turbidity, suspended solids or dirt on the flow cell should to be automatically compensated by a differential measurement with a second detector at a reference wavelength.

The UV absorption can be considered as an alternative method for lab COD (Chemical Oxygen Demand) when fast, reliable and inexpensive measurements with very low maintenance are required.

The above method is in accordance with the DIN38404-C3 standard and can be considered as an alternative method referring to the AFNOR XPT90-210 standard.

BOD measurement principle

The preferred measuring principle for BOD measurement is based on UV VIS Absorption Spectroscopy using Beer - Lambert conversion law;

[C] = k log (I in / I out)

With:[C]:Sample concentration;

k:UV absorption and BOD linear correlation coefficient ;

I in: Incidence light intensity;

I out: Transmission light intensity

Reliability of application:

The chart shows the typical linear relationship between the river water (water quality ingredients more stable) UV and TOC/BOD value.Even in the water quality of the more complex cases, there is a typical linear relationship between the river water (water quality ingredients more stable) UV and TOC/BOD value.

In our next article, we will see some of the important functions of a multiparameter analyzer that can make it more reliable & user friendly.

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