At what temperature must BOD samples be preserved?

The preservation of Biochemical Oxygen Demand (BOD) samples is crucial to ensuring that the measurements reflect the actual conditions of the sample when it is analyzed. The correct practice involves maintaining the samples at or below 4 degrees Celsius. This temperature is essential as it helps to slow down microbial activity, thereby minimizing any changes in the sample's composition before testing. Preserving BOD samples at 4 degrees Celsius ensures that the biochemical processes that could alter the oxygen demand over time are inhibited.

In this context, maintaining a temperature at or below 6 degrees Celsius would not adequately preserve the integrity of the samples, as microbial activity could continue to have an effect. Higher temperatures could lead to increased respiration rates of microorganisms, which could consume oxygen and artificially lower BOD results. Similarly, storing samples at room temperature would lead to significant microbial activity, resulting in inaccurate BOD measurements. Therefore, the best practice for preserving BOD samples is to keep them at or below 4 degrees Celsius.