ASIM User Forum - [ASM1 orig adapted for ASIM]

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From: Javier Climent (
Date: 12/16/2014

Hello ASIM Community,

I am using ASIM_orig model to validate my own model. I 
have several problems with results from rho9 and rho10, 
that is, Hydrolysis of entrapped organic nitrogen process 
adapted from Henze to ASIM. 

I would like to communicate my doubt using these two 
expressions as follows:

Here we have the expression 1, two terms from Hydrolisis 
of Henze model which should appear in rho9 and rho 10 of 

       TERM 1              * TERM 2

(Xs/Xbh) / [Kx + (Xs/Xbh)] * Xnd/Xs 	= expression 1

They are implemented together in ASIM by means of the 
following Adsorption Process located in Kinetics of Part. 
Species as:

*(X1    /X2  ) / (Kx + (X1/   X2   )) or
*(Xnd /Xbh   ) / (Kx + (Xnd/ Xbh   ))  = expression 2

The expression 1 and the expression 2 should be the same 
but they don't; so I would like to ask you the reason 
they are implemented in this way (two terms simplified  
in one Adsorption term).

Thank you in advance

Reply #1
From: Eberhard Morgenroth (
Date: 12/19/2014
For clarification: In the original ASM1 the process of
hydrolysis of X_S and X_ND are separate processes and are
processes number 7 and 8, respectively.

Your question is about the hydrolysis of X_ND and not of X_S
where in ASM1 rho_8 = rho_7 * X_ND/X_S.

If you multiply (Xs/Xbh) / [Kx + (Xs/Xbh) by X_ND/X_S then
you have a adsorption saturation expression in terms of
X_ND/X_BH. This is what is implemented in ASIM. Note that
the value of K_X must be adjusted depending on whether you
choose the direct saturation with X_ND/X_BH or whether you
follow the ASM1 description.

I hope this helps.

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