Activated sludge: aeration tank (BOD removal)

Description

Complete-mix activated sludge reactor for carbonaceous BOD removal, sized from the sludge age $\theta_c$ and the volatile suspended solids concentration in the reactor $X_v$.

Biodegradable fraction of the VSS:

$f_b = \frac{f_b'}{1 + (1 - f_b') K_d \theta_c}$

Reactor volume:

$V = \frac{Y \theta_c Q (S_0 - S)}{X_v (1 + f_b K_d \theta_c)}$

Biological sludge production as VSS, converted to TSS by the VSS/TSS ratio:

$P_{xv} = \frac{Y Q (S_0 - S)}{1 + f_b K_d \theta_c}$

Excess sludge flow withdrawn from the reactor:

$Q_{ex} = \frac{V}{\theta_c}$

Oxygen demand for carbon removal:

$RO_c = a' Q S_r + b' X_v V$

$a' = \frac{1}{f} - 1.42 Y, \qquad b' = 1.42 f_b K_d$

$S$ is the soluble effluent BOD5. When the effluent suspended solids are given, the particulate BOD5 they carry and the total effluent BOD5 are also calculated.

Reference

VON SPERLING, M. Lodos ativados. Princípios do tratamento biológico de águas residuárias, v. 4. Belo Horizonte: DESA/UFMG.