what is total organic carbon?

The amount of carbon found in an organic compound is commonly referred to as Total Organic Carbon, or TOC for short.

Calculating Total Organic Carbon

TOC is a term regularly used in both the clean water and wastewater industries to indicate water quality. One typical methodology of TOC measurement in water is to first ascertain the total carbon (TC) and so-called ‘inorganic carbon’ (IC) present. By then subtracting the IC from the TC, the amount of TOC can be calculated.

TOC can also be determined using surrogate measurements such as UV254 correlations. The UV absorption of the sample at UV254nm wavelength correlated against known TOC standards provides a continuous method of measurement, without the need for a chemical reagent based technique.

Water quality measurement

TOC is a long-established method of measuring the quality of drinking water during the purification process. Decaying Natural Organic Matter (NOM) such as fulvic acid and urea are commonly found in water sourced for drinking. The NOM in any specific source water is responsible for creating the TOC of that water.

At the same time, synthetic sources can also affect the level of TOC in water. Detergents, fertilisers, pesticides and industrial chemicals are prime examples. These synthetic sources, combined with natural sources create complex samples which are very challenging to monitor. Reliable and robust instrumentation, such as the ORAKEL UV254 is essential.

TOC and water treatment

All drinking water must be treated at a water treatment facility before it can be deemed fit for consumption. Understanding the TOC in the water that is being treated also informs the amount of NOM. By analysing both the TOC and the NOM, the water treatment facility is able to determine the correct component disinfectant (and the dosage) required to safely treat the water in order to ensure it is potable.