Formula that I've seen is Flow x BOD/ Volume UNDER AERATION x Volatile Suspended Solids. A colleague says its actually total volume of all basins including anoxic. Which is right?
If you are using an anoxic tank for phosphorus removal, you should leave it out of the calculation.
The F/M ratio is a process control number that helps you to determine the proper number of microorganisms for your system. To do this calculation, you will need the following information:
Influent Flow into your activated sludge system (Flow MGD)
Influent CBOD (mg/l) concentration into your aeration tank.
Mixed Liquor Volatile Suspended Solids Concentration (mg/l) Volume (in gallons) of your aeration system
F= Influent Flow (MGD) X Influent CBOD Concentration (mg/l) X 8.34
M= Aeration System Volume (in Millions of Gallons) X MLVSS X 8.34