Question

What is tge relationship between dissolved oxygen (DO) and Biological oxygen demand (BOD)?

Answer 1

The DO (dissolved oxygen) has a direct relationship with the BOD (biochemical oxygen demand) in that it is determine to test the level of the BOD in water, especially in wastewater when microorganisms and an available food supply are present in water body. The DO is consumed in the process of oxidation of waste in water. Oxygen consumed in the decomposition process robs other aquatic organisms of the oxygen they need to live. Organisms that are more tolerant of lower dissolved oxygen levels may replace a diversity of more sensitive organisms. Normally, oxygen is not a very soluble gas and the DO concentrations are particularly very low in wastewaters. To determine the BOD, sample wastewater is tested for the DO on the first day of the sample and the sample water is incubated at 20°C for five days it is again determined at the end of 5 days. The difference in dissolved oxygen between the initial measurement and the fifth day measurement represents the BOD.

Suppose, initial and final determinations of the DO both are zero, naturally the biochemical oxygen demand (BOD) will be very high and what ever there is the demand of oxygen for oxidation of a given amount of waste in given volume of water.