Activated Sludge Aeration & Solids Retention Time (SRT) Calculator

Determine Mean Cell Residence Time (SRT / MCRT), Food-to-Microorganism ($F/M$) ratio, hydraulic retention time ($HRT$), waste sludge flow ($Q_w$), and biological oxygen demand.

Influent Flow & Substrate Loading

Influent Flow Q (m³/day):

Aeration Tank Volume V (m³):

Influent BOD₅ S₀ (mg/L):

Effluent BOD₅ S (mg/L):

MLSS Concentration X (mg/L): Mixed liquor suspended solids

Waste Sludge MLSS X_w (mg/L): Underflow / RAS concentration

Target Solids Retention Time SRT θ_c (days): Typical: Conventional 5-15d, Extended Aeration 20-30d

Biological Performance & Waste Sludge Flow

Food-to-Microorganism (F/M)

Daily WAS Pumping Rate (Q_w)

Hydraulic Time HRT (θ)

Volumetric BOD Load

BOD Removal Efficiency

Total Aeration Basin Solids & Oxygen Demand

Basin Solids Inventory: -- kg MLSS | Daily Oxygen Demand: -- kg O₂/day

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Activated Sludge Aeration & Solids Retention Time (SRT) Calculator

Influent Flow & Substrate Loading

Biological Performance & Waste Sludge Flow

Frequently Asked Questions