What If?

Suppose a wastewater treatment plant at a certain location along the stream. After the treatment water is mixed with the upstream water, we find that the water temperature just downstream (after mixing) is °C, the mg/L, the mg/L, and the stream velocity is 20 km/day. The deoxygenation and reaeration rates are the same as the earlier upstream values. Plot the new DO sag curve and identify the critical time, , where the DO is at a minimum and find this minimum value. How far downstream from the treatment plant does this minimum occur? Are there any portions of the stream downstream from the treatment plant where fish cannot survive?

Solution