This standard provides criteria for the process design of activated sludge systems used for treating sewage and biodegradable industrial wastewater. It covers various modifications of the process, including conventional, extended aeration, and contact stabilization, detailing key design parameters like F/M ratio, sludge age, and oxygen requirements.
Specifies the criteria for the design of activated sludge process used in sewage and industrial wastewater treatment.
Quick Reference Values
F/M Ratio (Conventional Process)0.2 - 0.4 kg BOD/kg MLVSS/day
MLSS Concentration (Conventional Process)1500 - 3000 mg/l
Hydraulic Retention Time (HRT) (Conventional Process)4 - 8 hours
Sludge Age (Extended Aeration)20 - 30 days
Volumetric Loading (Extended Aeration)0.16 - 0.40 kg BOD/m³/day
Surface Overflow Rate (Secondary Clarifier)12 - 20 m³/m²/day
Key Formulas
F/M = (Q * So) / (V * X) — Food to Microorganism Ratio
θc = (V * X) / (Qw * Xr + Qe * Xe) — Sludge Age or Mean Cell Residence Time (MCRT)
Volumetric Loading = (Q * So) / V — Organic loading rate per unit volume of aeration tank
Practical Notes
The design values provided are typical and must be adjusted based on treatability studies for specific wastewater characteristics.
Proper design of the secondary clarifier is as crucial as the aeration tank design for achieving the desired effluent quality and ensuring good sludge settling.
Pay close attention to sludge recirculation and wasting rates, as they directly control the sludge age (MCRT) and overall process stability.