Mathematical Description of Nitrification in Rivers: The Key Role of Dissolved Oxygen

A mathematical model is presented to describe the pollution profile along a river downstream of a discharge point. The model incorporates the nitrification process and is based on nitrogen mass balance. It accounts for both substrates and the products of biochemical transformations, in which ammonium is sequentially converted to nitrite and nitrate. Oxygen availability for nitrifying bacteria is identified as a crucial factor governing the dynamics of ammonium along the river.