Streeter-Phelps model

The Streeter-Phelps model allows the estimation of the DO sag in the stream as a function of distance. This equation may be developed by considering a stream, initially saturated with oxygen, which receives a wastewater discharge containing BOD. As the water moves downstream, the BOD is assumed to decay at a first-order rate, KBOD, typically on the order of 0.2/day ... 

This special case of the Streeter—Phelps model neglects photosynthesis, as well as oxygen consumption by the bottom sediments and by nitrification... 

The Streeter-Phelps model. Dissolved oxygen profiles in a river with a steady influx of a pollutant. 

In the case of oxygen-depleted streams, such as typically occur downstream of wastewater outfalls, the flux of O2 is from the atmosphere into the streams. In a stream with steady, uniform flow and no sources or sinks of oxygen other than the atmosphere, an oxygen deficit decays exponentially with downstream travel time. The classic Streeter-Phelps model, discussed in Section 2.5, considers not only dissolution of O2 into a stream but also simultaneous O2 consumption due to microbial degradation of organic waste within the stream. By tradition, the reaeration coefficient in Streeter-Phelps modeling is designated fCoj. 

More general applications of Streeter-Phelps modeling include photo-s)mthesis and benthic O2 demand (Metcalf and Eddy, 1991). 

---