SBR Sewage Treatment Design

Classic SBR process sizing — reactor volume, oxygen demand (AOR/SOR), excess sludge, nitrogen removal check and aeration system.

Design conditions

Design flow Q (m³/d)

Summer temp T1 (°C)

Winter temp T2 (°C)

Nitrification factor K

Effluent DO (mg/L)

Atm. pressure p (Pa)

Water quality (mg/L unless noted)

In COD

In BOD₅ S₀

In TN

In NH₄-N

In TP

In alkalinity

In SS

In VSS

Out COD

Out BOD₅ Sz

Out TN

Out NH₄-N

Out TP

Out SS Ce

Sludge kinetics & reactor

Kd(20) (1/d)

Sludge age θc (d)

Yield Y

MLSS X (mg/L)

Out VSS/SS f

N in cells

K₂

Reactors n₁

Cycle time t (h)

Decant time td (h)

Decant height h₁ (m)

Safety ε (m)

Water depth H (m)

Nitrification & aeration parameters

μm(15) (1/d)

Dissolved O₂ half K₀

KN(15) (mg/L)

bN(20) (1/d)

a′ (carbon)

b′ (sludge)

Aerator offset (m)

O₂ transfer EA

CS(25) (mg/L)

CS(20) (mg/L)

CS(10) (mg/L)

Aerator O₂ qc (kg/h)

Line loss h₁ (MPa)

Local loss h₂ (MPa)

Aerator loss h₄ (MPa)

Margin Δh (MPa)

Sludge moisture

Flow, cycle & reactor volume

Total change Kz

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Flow (m³/h)

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Flow (m³/s)

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Cycles n₂

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Per-cycle water (m³)

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Feed time te (h)

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Settling u (m/h)

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Settle ts (h)

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Aeration ta (h)

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Reaction ratio e

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Out soluble BOD (mg/L)

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Reactor volume V (m³)

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Decant h₁ (m)

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Sludge load (kg/kg)

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Excess sludge & nitrogen

ΔXv (20°) kg/d

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ΔXv (10°) kg/d

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Anorganic ΔXs kg/d

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ΔX (20°) kg/d

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ΔX (10°) kg/d

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Wet sludge (m³/d)

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Wet sludge (10°) m³/d

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Out BOD (mg/L)

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Out NH₄ (10°) mg/L

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Out NH₄ (20°) mg/L

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Nitrified NH₄ eff (mg/L)

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Oxygen demand & aeration

Carbon O₂ kg/d

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Nitrify O₂ kg/d

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Denitrify O₂ kg/d

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AOR kg/d

—

AORmax kg/d

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O₂/BOD kg/kg

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SOR(25) kg/h

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SORmax kg/h

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Air QF(25) m³/h

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Max air m³/h

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Air pressure MPa

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Aerators n₁

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Service area m²

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Classic SBR per GB 50014. Per-cycle water = Q/n₂/n₁; feed time te = 24/n₁n₂; settling velocity u = 46000·X⁻¹·²⁶; ts = (h₁+ε)/u; ta = t−te−ts−td; reactor volume V = Y·θc·Q·(S₀−Se)/(e·X·f·(1+Kd·θc)); Se = Sz−7.1·Kd·f·Ce. Excess sludge ΔXv = Y·Q·(S₀−Se)/1000 − e·Kd·X·V·f/1000; anorganic ΔXs = Q·(1−fb·f)·(SSin−SSout)/1000. Total oxygen AOR = carbon + nitrification − denitrification; AORmax = Kz·AOR. Standard SOR converts to field conditions by α, β, CS and altitude.