Enrico Remigi WEST Product Owner

See image attached

If you select the Block, in the WEST layout, and [b]press the F1 key[/b], the Model Guide will start up, showing the description of that specific model.

Anyhow, "given" the actual DO in the tank, the tank volume and the sludge age (all are to be given as input signals to the aerator), it will return the kLa.
The aerator is [u]not a control model[/u]: it is a simple aerator. Thus it needs to be integrated in a 'control loop' with e.g. a PI control model.
The PI controller will receive the DO measurement as input; and return (output signal 'u') the necessary 'Q_Air' (so it is to be linked to the manipulated variable 'Q_Air' of the aerator).
The aerator will receive the SRT from a calculator (or you could use a constant value, if SRT is relatively constant); it will also receive DO and V_ASU from the tank, as input; and it will return the kLa.

This is not clear to me: [b]maybe you can elaborate further?[/b]

[quote author=iacopod link=topic=2452.msg5652#msg5652 date=1431081913]
.. imposing constant Kla and constant flow air ..
Essentially I would check that you have consumption of DO in the tank when the biodegradable load changes in input plant ..
[/quote]
[list]
[li]if kLa (and/or the air flow rate) is constant, you're not controlling anything, right?[/li]
[li]you could quantify the effect of the variation of the organic load by comparing the (steady-state) DO levels perhaps?[/li]
[/list]
In either case, you don't need a controller but rather work with the existing state variables of the AS tank.

Alternatively, you may want to control DO (e.g. by a PI controller). You're right: the DO will be maintained around the set-point. So you could quantify the effect of the organic load by comparing the kLa's generated by the controller, or the air flow rate required, to maintain the DO.

Either way, I don't see the need to modify a base model (or create a new model).

Very true: you can indeed do sort of the same, by running a Scenario Analysis.
You see, what a Virtual Experiment does is varying a set of model [b]parameters[/b] in-between simulations. In other words, it does [b]automatically[/b] and sequentially, what you would do manually (plus, of course, evaluate the overall outcome of the experiment). And it acts on model parameters, that are otherwise constant during the course of a simulation.
This is very appropriate, if you are to compare the outcome at different sludge ages.

The solution I was suggesting is considerably more complex (it requires that you write some MSL) but would allow you to evaluate [b]dynamically[/b] the effect of varying sludge ages. If this is not necessary, then your solution is certainly a better option.

I cannot advice on the most appropriate settling model for low SRT / loading rates - hopefully other users will be able to assist you on this.

What I can suggest though is a practical solution to the issue you describe, i.e. "[i]how to automatically have the settling properties of the sludge vary with the sludge age[/i]".

What you actually need is to control (via a custom control model) the settling properties based on e.g. SRT.
So, the first thing you need is to implement such control model in MSL.

But, in order for the settling properties to be "controllable", they are to be defined as [b]manipulated variables[/b] (= input interface variables, flagged as [i]manip[/i]) - and this is generally NOT the case, if I recall well: e.g. 'v0', 'v00' and 'r_P' are all [b]parameters[/b] in the Takacs model.
So, you need to modify the base implementation by: i) moving the definitions of these OBJ's to the interface section of the model (and adapting the definition, by e.g. indicating the causality, terminal, etc.); and ii) modifying the equations in which they are used by replacing "parameters.[NAME]" by "interface.[NAME]"

You can in fact include the [b]whole layout[/b] (and a variety of other project items) in a Report that you can generate via the menu Project / Reports.

However, if what you really need is the image of a [b]single icon[/b], I suggest you take it from the Icon Library to have the best possible image resolution.
Proceed as follows:
[list]
[li]start the [b]Block Editor[/b][/li]
[li]open the high resolution icon library of WEST: "\data\blocks\WESTforOPTIMIZATION\Icons\WEST.[b]VectorGraphics[/b].IconLib.xml[/li]
[li]select and open (double-click on) the icon of interest[/li]
[li]get rid of the grid (menu View/Grid lines)[/li]
[li]resize (zoom) and take a snapshot[/li]
[/list]

Hi,
the error message reads: "Unable to open include file 'Tornado/ME/MSLU/MSLUpHASMG1pH.h" and "Externally executed command has returned error code: 1"

This generally indicates that the external library is either not properly included (Libs property of the BlockLib.xml file) or not present at that particular location (it's quite easy to make mistakes when using "\.." in relative paths).

Your association PumpingEnergy <-> Backwash is definitely wrong, because a) the two quantities have different units and b) Backwash is an integer, limited between 0 and 1.

One option would be:
[list]
[li]use a Timer22, i.e. 2 phases and 2 outgoing signals[/li]
[li]link one signal (u1) to the pump flow rate of the buffer tank (I am assuming you're using the pump for back-washing)[/li]
[li]link the other signal (u2) to the "Backwash" (interface variable) of the sand filter[/li]
[/list]

In a timer model with 2 phases, T1 and T1 indicate the length of each phase, e.g. 10 h and 10 min.
In a timer model with 2 phases and 2 outgoing signals, u11, u12, u21 and u22 indicate the values of the first and second outgoing signals during the first and the second phase respectively.

The "[b]Backwash[/b]" you see as (interface) input variable is in fact a switch (i.e. backwashing state): 0 or 1 for non-backwash and backwash phase respectively.
What you could do is connect this to a timer, in order to switch backwashing on/off. And synchronise this with the other interface input variable, "[b]Inflow_Backwash[/b]" that is to receive your backwash flow (and composition, i.e. the usual ASMx state vector) [u]precisely[/u] during the backwashing phase.

[quote]Primary Clarifier
the available parameters will depend on the model you have selected for the primary clarifier.[/quote]
Depending on the model you select for the specific block (this is evidently true for any block, not just for a PST) in the Properties pane (prop: [b]ClassName[/b]), the parameters (and variables) displayed in the Block Details pane will be different. For instance, if you select the "PrimaryTakacs", you will need to indicate, the surface and average depth of the settling tank.

[quote]I want to control SRT with the aim of achieving sufficient nitrification. Oxygen level should be controlled by ammonium feedback and set point should vary between 1 to 2mg/l.[/quote]
Maybe I misunderstand: but maintaining a constant DO by means of a "cascade" control logic (the ammonium controller on the effluent regulates the DO set-point of the aeration controller) is, or may be, independent from a SRT controller (which may, for instance, regulate the sludge wastage based on the desired SRT).
The first type of logic may consist of an On-Off controller for ammonium followed by a PI controller for DO. The second, may be a PI controller for the flow rate of sludge wastage based on the computed SRT.

As Youri pointed out, the inclusion of biological processes in a Sand Filter may be tricky.
The suggested solution of "coupling" the Sand Filter to a mixing tank which a) receives the iron dosage and b) hosts the biological reactions may be the easiest.