text: Background BOD or benthic oxygen demand is the diffuse source of BOD represented by the decay of organic matter that has already settled on the bottom. This will give rise to a constant diffuse input thus the change in BOD over time will be
  where
  *  is the rate for oxygen consumption by BOD, usually in .
  *  is the BOD from organic matter in the water .
  *  is the background BOD input .