What is the maximum time a BOD test can be preserved if cooled to the appropriate temperature?

The correct response indicates that the maximum time a Biochemical Oxygen Demand (BOD) test can be preserved at a temperature of 4 degrees Celsius is 48 hours. This is significant because holding samples for too long can lead to alterations in the organic matter concentration due to microbial activity and other factors.

At refrigerated temperatures, the growth of bacteria is slowed, thus allowing for a more accurate assessment of the BOD when the samples are eventually analyzed. However, it is important to remember that even at these cooler temperatures, there is still some degree of biological activity, which is why preserving the sample for just 48 hours is permitted. This time frame optimizes the integrity of the sample while minimizing changes in the concentration of biodegradable materials.

Understanding this aspect is crucial for wastewater operators, as BOD is an essential measurement used to evaluate the organic pollution in wastewater, and accurate results are necessary for effective treatment and compliance with environmental regulations.