What percentage of oxygen is recommended in dilution water for a BOD test?

The recommended percentage of oxygen in dilution water for a Biochemical Oxygen Demand (BOD) test is approximately 90%. This high percentage is important because the BOD test measures the amount of oxygen consumed by microorganisms while decomposing organic matter in a water sample. To ensure that the microorganisms have sufficient oxygen to respire and accurately assess the oxygen demand, the dilution water must have a high dissolved oxygen concentration.

Using a dilution water with around 90% oxygen saturation helps to minimize the potential for oxygen-limiting conditions during the test, which could lead to inaccurate results. It ensures that the respiration of the microorganisms is not artificially restricted, allowing for a true representation of the BOD in the sample being analyzed.