// multi-utility computation suite · offline · instant · precise
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eng.activated-sludge-SRT Calculator
Calculates activated sludge process parameters including SRT, HRT, aeration tank volume, and sludge production from wastewater characteristics. The Solids Retention Time (SRT or sludge age) controls nitrification — nitrifying bacteria need SRT above 10 days at 20°C.
Inputs
Influent Bod Mg L
Reference formula or conversion factor shown for context.
Effluent Bod Mg L
Reference formula or conversion factor shown for context.
Mlss Mg L
Reference formula or conversion factor shown for context.
Hrt Hr
Duration of the process. Make sure units match the rate inputs (seconds, minutes, or hours).
Results
SRT (solids retention time, days)
The computed duration or time value.
BOD removal efficiency
Useful output divided by total input, as a percentage. True 100% efficiency is impossible — losses appear as heat. LEDs: 30–50%. Electric motors: 85–97%. Switching supplies: 85–95%.
F/M ratio (food:microorganism)
The proportional relationship between two quantities.
typical SRT range
The difference between the maximum and minimum values.
typical F/M
Reference formula or conversion factor shown for context.
sludge production (g VSS/g BOD)
The result of multiplying all input values together.