Below the Surface: Measuring Organic Sum Parameters in Water

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Therefore, it is common to use a combination of measuring sum parameters for organic matter and for toxicity in river monitoring. With this method it is at least possible to obtain information whether the increase in organics is caused by a more dangerous or harmless substance. The following sum parameters should be taken into account:

1. Chemical Oxygen Demand — COD

2. Total Organic Carbon — TOC

3. Dissolved Organic Carbon — DOC

4. Total Oxygen Demand — TOD

5. Toxicity

Chemical Oxygen Demand COD

Although the permanganate method is still used widely, it is internationally approved that this method is definitely not suitable for this river monitoring. In a survey of the „Institute for water, soil and air of the German EPA“ dating back to 1983, it was established that the oxidation power of this method is much too low. Test results show that there are too many substances which go undetected. Also the recovery rates of many other substances are somewhere between 0 and 100 %. For the survey the institute analyzed the recovery rates of approx. 600 substances, the majority of which could not be detected.

The so-called COD di-chromate method may not be left unmentioned. However, its most considerable disadvantage is the necessity of extremely dangerous reagents that produce hazardous waste. Despite the fact that the recovery rates are not always 100 %, the slow response time alone makes this method unsuitable for river monitoring.

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