Fabio Polesel

Thank you very much for the very relevant questions, which I will try to address here.

From a thermodynamic standpoint, it is correct that (for the same carbonaceous substrate or wastewater source) the anoxic yield is lower than the aerobic one. This theoretical consideration has been confirmed experimentally for multiple wastewater sources (e.g., Muller et al., Water Res. 2003).

As to yield parameter values, process model implementations in WEST have been made to adhere as much as possible to their original formulation. This means that ASM1, ASM2d(Mod) consider the same value for the aerobic and anoxic heterotrophic yield, while ASM3-based models consider a lower value for the anoxic yield.

This shouldn’t prevent users (and us) from modifying ASM2d(Mod) and implementing a lower anoxic yield to increase the realism of this model. However, this change may affect the extent and the kinetics of other processes (e.g., hydrolysis), and should be therefore accompanied by a new parameterization for these processes.

Thanks for the update.
There may have been some inconsistencies in the 2017 version for Top-Level Quantities (as you have observed), but they have has been fixed in the new 2020 version.

Hi Gamze,

Does the error occur when you drag and drop multiple parameters at once, or also when you drag and drop a single parameter in the Top-Level Quantities dialog?

As you point out, the ASM2dModTemp formulation assumes negligible lysis/decay under ideal anaerobic conditions.
For heterotrophs, for instance, the model considers no net growth under anaerobic conditions since: (i) anaerobic hydrolysis and fermentation do not result in any growth; (ii) lysis/decay is negligible.

In a full-scale system modelled ASM2dModTemp, the anaerobic lysis/decay may not necessarily be null - very low (but not null) S_NO levels may in fact occur in the anaerobic tank depending on the nitrate load being recirculated with the RAS stream.

If you wish to update the current model formulation with a modified expression for the decay rate, you can use the Model Editor and change the expression to:
- b_H · X_H · (S_O/(K_O + S_O) + n_NO_Het_d · K_O/(K_O+S_O))            [assuming that aerobic decay > anoxic decay = anaerobic decay]
- b_H · X_H · (S_O/(K_O + S_O) + n_NO_Het_d · K_O/(K_O+S_O) · S_NO/(K_NO+S_NO) + n_anaer_Het_d · K_O/(K_O+S_O) · K_NO/(K_NO+S_NO))            [assuming that aerobic decay > anoxic decay > anaerobic decay]

The process rate equation for lysis that is currently implemented (with switching function for S_NO) derives from the original model implementation, on which ASM2dModTemp is based. You can find more information in Gernaey and Jørgensen (2004).

On a separate note, this process rate equation described a slower decay under anoxic/anaerobic conditions. This may be the reason why you have obtained higher MLSS concentrations using ASM2dModTemp in your model comparison exercise, and have subsequently increased the parameter value for b_H and b_AUT in order to obtain similar MLSS, X_H and X_AUT concentrations using ASM2dModTemp and ASM1Temp.

[quote author=arspr link=topic=21901.msg28884#msg28884 date=1584441428]
[list][li][b]Decay/Lysis is slower in WEST ASM2d implementation[/b]. But I've been able to more or less compensate it with higher b_H (0.69 vs original 0.62) and b_AUT (0.1675 vs original 0.15) values.[/li][/list][/quote]

The parameterization for theta_K_X is somehow based on originally published K_X values at different temperatures, namely:
[list][li][b]ASM1[/b]: K_X = 0.03 gCOD/gCOD at 20°C, K_X = 0.01 gCOD/gCOD at 10°C, hence theta_K_X > 1[/li]
[li][b]ASM2[/b]: K_X = 0.10 gCOD/gCOD at 20°C, K_X = 0.30 gCOD/gCOD at 10°C, hence theta_K_X < 1[/li][/list]
In the case of ASM2, theta_K_X < 1 indicates a decreasing half-saturation coefficient, thus increasing affinity (and overall hydrolysis rate) with increasing temperature.

The difficulty in defining unique trends for temperature dependence of half-saturation coefficients was already acknowledged by authors of ASM1, who wrote "[i]Because half-saturation coefficients are not rate coefficients, but are parameters which influence the shape of a μ-S ... curve it is more difficult to generalize about the effects of temperature on them[/i]" (Henze et al., 1987).
Therefore, you may also wish to assume negligible temperature effect on K_X and set theta_K_X = 1.

Hi Ilke,
I would recommend you to:
1) copy the project folder from the USB to the path Documents\DHI\WEST\data\projects (i.e. where WEST projects are saved by default)
2) make sure that the project uses the right Block/Model Library. When opening a project with WEST (espeically if loaded from another folder than the default), you're asked to select the Block/Model library used in the project. You should therefore verify that the project uses the default library or a modified version of it - and choose accordingly.
BR