To describe the organic load of water, the standard parameters COD (chemical oxygen demand) and DOC (Dissolved Organic Carbon) as well as TOC (Total Organic Carbon) or BOD (biochemical oxygen demand) are used. The most important standard parameter is the chemical oxygen demand (COD). It contains all substances that can be solubilized by chemical oxidation and it is the conventional parameter for the calculation of wastewater. To specify the discharge, COD values have to be determined and documented according to the standard DIN 15705. This includes, inter alia, the photometric determination by cuvette tests.
Previously, a time consuming digestion procedure according to DIN 38409-H41 (148 °C / 2 hours) is necessary. Meanwhile, different optical reagent free (OptRF) measurements are available for self-monitoring of municipal wastewater treatment plants.
Fluctuations in concentrations and peak loads can be documented continuously by stationary systems with reagent free online sensors. The photometric reagent free measurement is a fast and cost-effective control without use of reagents.