Sludge Age
The F/M ratio is related to sludge age, or mean cell residence time. The concept here is that the wastewater goes through the aeration process only once, but the sludge (solids) go through several times due to the sludge recycle process. Aeration time in a conventional activated sludge system is in the order of 3 to 30 hours; the sludge age is typically in the order of several days.
Age of Sludge = [(V) (MLSS)] / [(TSSe) (Qe) + (TSSw) (Qw)]
Where:
Sludge age equals the average cell residence time in days.
V = Liquid volume in the aeration basin in millions of gallons (cubic meters)
MLSS = Mixed liquor suspended solids concentration in milligrams per liter (grammes per cubic meter).
TSSe = Suspended solids concentration in the effluent of the reactor in mg/L (grams/m3)
Qe = Effluent flow rate in millions of gallons per day (cubic meters per day)
TSSw = Suspended solids concentration in the waste activated sludge (the sludge sent to the digesters) in mg/L (grams/m3)
Qw = Waste activated sludge flow rate in millions of gallons per day (cubic meters per day)
Sludge age can also be expressed in terms of volatile suspended solids concentrations, rather than total suspended solids. If the F/M ratio is being calculated using MLVSS then it is useful to maintain consistency and to use MLVSS for the sludge age calculations, as well.
Salam...is there a mistake there
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