The initial ultimate BOD after mixing of the River is 12.0 mg · L−1. The DO in the River after the wastewater and river have mixed is at saturation. The river temperature is 10◦C. At 10◦C, the deoxygenation rate constant (kd) is 0.30 day−1, and the reaeration rate constant (kr) is 0.40 day−1. Determine the critical point (tc) and the critical DO.

Respuesta :

Answer:

[tex]t_c = 2.87\ DAYS[/tex]

Explanation:

Given data:

Initial BOD level is [tex]12 mg l^{-1}[/tex]

temperature of river is 10 degree C

Rate constant is [tex]kd = 0.30 day^{-1}[/tex]

Reaeration rate constant is kr [tex]0.40 day^{-1}[/tex]

As DO in river is at saturation hence initial Da is zero

critical temperature is calculated as

[tex]t_c = \frac{1}{K_r - k_d} ln[ \frac{k_r}{k_d}(1 -Da\frac{k_r -k_d}{k_d L_a})][/tex]

[tex]t_c = \frac{1}{K_r - k_d} ln[ \frac{k_r}{k_d}(1 -0)][/tex]

[tex]t_c = \frac{1}{0.40 - 0.30} ln[ \frac{0.40}{0.30}(1 -0)][/tex]

[tex]t_c = 2.87\ DAYS[/tex]

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