Biochemical oxygen demand (BOD) is a way to assess the amount of oxygen required for aerobic microorganisms to decompose the organic material in a sample of water over a specific time frame. It is the oxygen uptake demand of a source of water. Carbonaceous biochemical oxygen demand (CBOD) is the same method as BOD, but the nitrifying bacteria in the sample are inhibited. Nitrifying bacteria consume nitrogenous materials (compounds with reduced forms of nitrogen) and add to the oxygen demand of the wastewater. Nitrogenous materials are often seen as interference because the purpose of the BOD test is to measure carbonaceous material.