BOD analysis should begin no later than how many hours after sampling?

The appropriate timeframe for initiating biochemical oxygen demand (BOD) analysis after sampling is crucial to obtaining accurate and reliable results. BOD is a measure of the amount of oxygen that microorganisms will consume while decomposing organic matter in water at a specific temperature and time.

Starting the analysis within six hours after sampling helps to preserve the integrity of the sample, ensuring that the biological activity and chemical composition remain representative of the original water quality. If the analysis is delayed beyond this window, microbial activity can change significantly, leading to inaccurate BOD measurements, potentially resulting in a lower reading than would be representative of the sample at the time of collection. This timeframe is widely recognized in standard methods for water and wastewater examination, aligning with best laboratory practices to ensure consistency and reliability in results.

Thus, beginning BOD analysis within six hours provides a balance that minimizes changes due to respiration and other biological processes, making it the most suitable choice in this context.