What is the formula for calculating the seed correction factor in BOD testing?

The seed correction factor in Biochemical Oxygen Demand (BOD) testing is essential for accurate measurement, especially when dealing with the unseeded sample. The formula used for this calculation accounts for the influence of the seed, which is necessary to provide the right amount of microorganisms to promote biological activity.

By taking the BOD of the unseeded sample—essentially a measure of how much oxygen is required by microorganisms to decompose organic matter in a previously untreated sample—this ensures that any discrepancies arising from the added seed can be offset. The seed volume is included in the formula to ensure that the result is appropriate for the amount of the seed added.

The specific use of the factor 300 in the formula allows for a standardized calculation that takes into consideration the expected dilution and the effect of the seed on the overall result. Thus, the formula that combines the BOD of the unseeded sample with the seed volume divided by 300 accurately reflects the correction necessary to arrive at the true BOD value. This way, when assessing the overall organic load of wastewater, the resultant BOD is a representative measure of the system's capability to break down organic materials under biological conditions.