Aeration Tank - Sludge

1. Calculate Wastage of Sludge Q_W

Y Q_Ad (gal/day) S₀ (mg/l) S (mg/l) y

K_d(1/day) q_c (day) MLVSS/MLSS SS_eff(mg/l)

P_X (lb/day) Q_W (lb/day)

2. Return Sludge Rate

R � Return sludge ratio = Q_r/Q

Q_r � Return sludge flowrate from bottom of secondary settling tank to the inlet of aeration tank

Select thickened sludge concentration at clarifier bottom

7,500 ~ 11,000 mg/l, which depends on the operation condition of secondary settling tank

When Q = 5 mgd




q (hr) qc (day) X_r (mg/l)

MLSS (mg/l) MLVSS/MLSS Q (gal/day)

Return Sludge Ratio, R Q_r (gal/day)

Select R = 0.54 for the following hydraulic calculation.

When Q = 10 mgd