Determination of Bod Kinetic Parameters and Evaluatoin of Alternate Methods

Abstract

Biodegradable organic matter is one of the important pollution parameter for water and wastewater. Being heterogeneous (suspended colloidal and dissolved forms) and being composed of a wide variety of compounds, it is very difficult to have a single direct method for estimating its organic matter concentration in any water or wastewater sample. Because of this reason, indirect methods, like BOD, COD, etc. are dependent upon for the measurement of organic matter concentration. These methods measure the organic matter concentration through estimating the amount of oxygen required for its complete oxidation. Methods like COD are quite accurate and take very less time for estimating the organic matter concentration. But they cannot differentiate biodegradable organic matter from non-biodegradable organic matter. Further, COD is not capable of accurately estimating volatile organic matter and organic matter with nitrogen bases. Because of these reasons, BOD is preferred over COD. In the BOD test microorganisms are used for bio-oxidation of the organic matter in the presence of oxygen. The amount of oxygen utilized in the bio-oxidation process is measured and expressed as organic matter concentration in terms of oxygen. This method actually estimates the amount of biodegradable organic matter rather than the total organic matter present in water or wastewater sample. In this method, the sample is diluted to appropriate level, seeded with sufficiently acclimatized microbial populations, aerated and then filled in the air proof BOD bottles and incubated under favaourable conditions. Through measuring the initial and final dissolved oxygen present in the incubated sample, the amount of oxygen consumed in the bio-oxidation process is estimated. Fig.1.1 shows the fate of biodegradable organic matter during the incubation in the BOD test.