What is the purpose of adding a nitrification inhibitor in BOD testing?

The purpose of adding a nitrification inhibitor in Biochemical Oxygen Demand (BOD) testing is to prevent oxygen consumption by nitrifying bacteria. In BOD tests, the goal is to measure the amount of oxygen consumed by microorganisms during the decomposition of organic matter over a specified period. If nitrifying bacteria, which convert ammonia into nitrite and then into nitrate, are present, they can consume additional oxygen, leading to skewed results that do not accurately reflect only the organic pollution's oxygen demand.

By inhibiting these nitrifying bacteria, the testing focuses solely on the organic matter that the typical BOD test is designed to measure, providing a more accurate reflection of the sample's biodegradable organic content. This ensures that the results are representative of the true aerobic activity attributable to the organic waste present. The accurate measurement of BOD is crucial for assessing the potential environmental impact of wastewater on aquatic ecosystems.