ABSTRACT
Biochemical oxygen demand (BOD) is an empirical test that measures the amount of oxygen required for the microbial oxidation of organic compounds in aqueous samples. Such a test measures the amount of oxygen utilized during a specific incubation period for the biochemical oxidation of organic materials and oxidizable inorganic ions. The concentration of dissolved oxygen (DO) before and after incubation is measured. The DO in water may be determined by the following two methods: iodometric titration (Winkler method) and electrode method. Oxygen-sensitive membrane electrodes are commercially available. The electrode in such a system is covered with an oxygen-permeable plastic membrane, thus protecting it from impurities. The current is proportional to the activity of the dissolved molecular oxygen, and at low concentration, to the amount of DO. Before the measurement of DO in the sample, the electrodes are calibrated using standards of known DO concentrations. The BOD reaction follows first-order kinetics. BOD may also be calculated by the graphical method.
