ADM1 parameters

Hello everybody!

I'm using Anaerobic Digestion Model (ADM1) in WEST; I set all the parameters of the model but I don't understand the meaning of the parameter f_X_Out (fraction of the biomass that leaves the digester).

Does anybody know which is a typical value of this parameter and in which ADM1 equations it is considered ?

thank you

The parameter f_X_Out in the ADM1 model is used to retain the sludge in the digester, i.e. to mimic the behaviour that more solids are retained within the digester than the soluble fractions.

If you set f_X_Out to 1, then the quantity of solids and solubles are percentage wise the same. When you set f_X_Out to zero than all solids are retained within the system.

Ideally you should compare your effluent values with the values that you get from your simulations. You can also try to match the (wanted) sludge retention time in the digester.

You also ask about the specific equation.
f_X_Out is used to calculate the "outflux" (the outgoing flux) of solids, as follows:

OutFlow[j] = f_X_Out * ( C[j] * Q )

where:
- 'j' denotes the j-th particulate component
- Q the flow rate

so I guess the default value should be 1. Do you agree ?

Correct: the default value is indeed 1.
However, f_X_Out = 1 translates in ALL solids leaving the digester. You may want to "decouple" SRT and HRT and therefore rather use f_X_Out <1 (which by the way was the very meaning of the parameter in the original ADM1 implementation, if I recall well).