A toothpaste factory situated on a large river disposes of a waste water containing villiamite (NaF) to the river on a continuous basis. The minimum flow in the river is 210 m3/s, and the discharge rate from the treatment plant is 12.5 m3/s. The river temperature averages 18°C and the waste discharge is 80°C.
a. If the maximum acceptable limit for the pollutant is 1.0 ppm in the downstream river, and the background concentration of the pollutant upstream is 0.4 ppm, what is the maximum concentration, in M, that can be safely released from the plant?
b. What is the final river temperature downstream? Assume that the density of the waste stream is 1000 kg/m3.