A small lake with volume 10,000 m3 has a stream flowing into it with flow rate 100 m3/day and a Toluene concentration of 1.0 mg/m3. A factory discharges 5 m3/day into the lake with Toluene concentration of 10 mg/m3 – they want to increase effluent to 50 mg/m3. Toluene decays at a rate of 0.01/day. Assume steady-state and completely mixed (CSTR). a) How would this increase in discharge concentration change the lake concentration? b) Field studies show that the same lake would be better represented by dividing the lake into two cells. The first cell having a volume of 2,500 m3 and the second with 7,500 m3. How does this affect the estimate of concentration leaving the lake? Compare with one-cell model. Assume the factory continues to discharge at 10 mg/m3 into the first cell. c) Why does modeling the lake as multiple cells impact the final concentration leaving the lake? What do you expect might happen to the final concentration leaving the lake if we modeled it as more cells? How would the answer change if the reaction rate were higher?
A small lake with volume 10,000 m3 has a stream flowing into it with flow rate 100 m3/day and a Toluene concentration of 1.0 mg/m3. A factory discharges 5 m3/day into the lake with Toluene concentration of 10 mg/m3 – they want to increase effluent to 50 mg/m3. Toluene decays at a rate of 0.01/day. Assume steady-state and completely mixed (CSTR).
a) How would this increase in discharge concentration change the lake concentration?
b) Field studies show that the same lake would be better represented by dividing the lake into two cells. The first cell having a volume of 2,500 m3 and the second with 7,500 m3. How does this affect the estimate of concentration leaving the lake? Compare with one-cell model.
Assume the factory continues to discharge at 10 mg/m3 into the first cell.
c) Why does modeling the lake as multiple cells impact the final concentration leaving the lake? What do you expect might happen to the final concentration leaving the lake if we modeled it as more cells? How would the answer change if the reaction rate were higher?
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