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A city continuously disposes of effluent from a wastewater treatment plant into a river. The minimum flow in the river is 130 m3/s, and the discharge from the treatment plant is 37 m3/s. Upstream from the outfall, the background concentration is 0.69 mg/L. The maximum allowable concentration in the river is 1.1 mg/L. What is the maximum concentration that of the pollutant (in mg/L) that can be safely discharged from the wastewater treatment plant

Answer :

BOFFEEMADRIDGO

Answer:

[tex]2.54\ \text{mg/L}[/tex]

Explanation:

C = Allowable concentration = 1.1 mg/L

[tex]Q_1[/tex] = Flow rate of river = [tex]130\ \text{m}^/\text{s}[/tex]

[tex]Q_2[/tex] = Discharge from plant = [tex]37\ \text{m}^3/\text{s}[/tex]

[tex]C_1[/tex] = Background concentration = 0.69 mg/L

[tex]C_2[/tex] = Maximum concentration that of the pollutant

The concentration of the mixture will be

[tex]C=\dfrac{Q_1C_1+Q_2C_2}{Q_1+Q_2}\\\Rightarrow C_2=\dfrac{C(Q_1+Q_2)-Q_1C_1}{Q_2}\\\Rightarrow C_2=\dfrac{1.1(130+37)-130\times 0.69}{37}\\\Rightarrow C_2=2.54\ \text{mg/L}[/tex]

The maximum concentration that of the pollutant (in mg/L) that can be safely discharged from the wastewater treatment plant is [tex]2.54\ \text{mg/L}[/tex].

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