### ASIM User Forum - [ASM1 orig adapted for ASIM]

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**From**: Javier Climent (jcliment@uji.es)

**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 et.al 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
ASIM_orig:
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
Regards

**Reply #1**

**From**: Eberhard Morgenroth (eberhard.morgenroth@eawag.ch)

**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.
Best,
Eberhard.

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