Abstract
A simple method is described for the continuous determination of chemical oxygen demand (COD) in wastewater samples by flow injection analysis. Samples are injected into a water stream which merges with an acidic dichromate carrier solution. After reaction in a PTFE coil at 120°C, absorbances are measured at 445 nm. D-Glucose is satisfactory as a standard substance for COD in a variety of wastewaters. A sampling rate of 15 samples per hour can be achieved, and the detection limit and precision are 5 mg l -1 as COD and 0.4%, respectively. Chloride concentrations of ⩾ 100 mg l -1 interfere slightly unless silver and/or mercury salts are added. COD values for various wastewater samples correlate well with those obtained by standard methods using dichromate or permanganate.
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