Dissolved Oxygen and Biochemical Oxygen Demand
Introduction
In determining the extent of organic pollution, the two parameters that have been used include (DO) and Biochemical oxygen demand (BOD). The widely used parameter for monitoring organic pollutants in wastewater is BOD. BOD has an international standard method of the five-day assay (BOD5). During the assay, BOD measures the quantity of dissolved oxygen that would be needed for the microbial oxidation of carbon organic matter within specified conditions (Pasco & Hay, 2005). In the presence of organic pollutants, the amount of dissolved oxygen will decline following their decomposition. During the laboratory session, determining the dissolved oxygen (DO0) and the dissolved oxygen in seven days (DO7) are used in estimating the BOD5. The values of DO0 and DO7 will be used in estimating the BOD5.
Dissolved oxygen (DO)
DO is a measure of the actual amount of free oxygen that is dissolved in water. DO is determined by two factors; polluting loading and natural cleaning. Therefore, DO measured in milligram per liter (mg/L), will reflect the extent of water pollution. In the presence of pollutants, decomposition in the water will decrease the amount of dissolved oxygen that will, in turn, threaten the survival of aquatic lives. Although the colorimetric method is commonly used to determine the dissolved oxygen due to its robustness and inexpensiveness, the technique tends to have more errors. In the laboratory, the Winkler method that uses the BOD bottle is used to estimate the dissolved oxygen. Furthermore, Azide-Winkler titration method is used in estimating the dissolved oxygen.
Biochemical oxygen demand (BOD)
According to Pooja et al. (2020), BOD (mg/L) is the quantity of oxygen that aerobic microorganisms need to breakdown the organic matter in wastewater at a specific temperature and time. The determination of BOD requires incubating the sample for five days at 20 0C. The BOD test indicates the pollutional strength of the wastes by determining how much oxygen will be required to generate the end products of CO2 and H2O. The value of BOD5 will be obtained from the dissolved oxygen. In the experiment, the dilution factor will be used to demonstrate the differences in DO in the diluted sample water.
References
Pasco, N. F., & Hay, J. M. (2005). Biochemical oxygen demand and other organic pollution measures. Water Encyclopedia, 2, 37-41.
Pooja, D., Kumar, P., Singh, P., & Patil, S. (Eds.). (2020). Sensors in Water Pollutants Monitoring: Role of Material. Springer Singapore.