Newbie WEST questions (oxidation ditch)

Hello,

I'm a beginner in WEST and I use it to simulate a small-scale WWTP for study. It's oval-shaped oxidation ditch with clarifier. I consider C, N removal mainly and use ASM1Template.

Questions:
1) Aeration. Oxygen is supplied by bubble diffusers and surface aerators. I tried to use PI controller blocks to model oxygen supply in compartments, but when I use 2 or more PI a simulations takes ages to finish. I found that aerator Block can be used for diffusers. Is there alternative for surface aerators as well?

2) Chemical precipitation. Both calcium hydroxide and ferrous sulfate are used. What blocks should I use for them?

3) Can I calculate SRT in WEST? If so, how can I do it in my case?

BR,
Artemii

Hello,
[quote author=ArtemiiOs link=topic=21999.msg29085#msg29085 date=1592844633]
1) Aeration. Oxygen is supplied by bubble diffusers and surface aerators. I tried to use PI controller blocks to model oxygen supply in compartments, but when I use 2 or more PI a simulations takes ages to finish. I found that aerator Block can be used for diffusers. Is there alternative for surface aerators as well?
[/quote]
It cannot be related to the use of one or two PI controllers, it must be caused by some other setting. Have you checked the Logging? which integrator are you using?
On a side note, if you use an aerator block (either blower or surface aerator), you may need to use a controller (e.g. PI) upstream to the aerator for regulation.

[quote author=ArtemiiOs link=topic=21999.msg29085#msg29085 date=1592844633]
2) Chemical precipitation. Both calcium hydroxide and ferrous sulfate are used. What blocks should I use for them?
[/quote]
Precipitation of what?
In ASM1, the only chemical dosing blocks are for external carbon ..

[quote author=ArtemiiOs link=topic=21999.msg29085#msg29085 date=1592844633]
3) Can I calculate SRT in WEST? If so, how can I do it in my case?
[/quote]
Yes, you are to use a Calculator block and connect it to the relevant blocks (tanks, effluent and sludge sensors).

1) I read aerator block model description and I wonder how to apply it for surface brush aerator. The only data that I have on brush aerator are oxidation rate (10 kgO[sub]2[/sub]/h-->7.8m[sup]3[/sup]O[sub]2[/sub]/h with O2_air parameter set to 100) and dimensions. What values should I set for the parameters in Group:Tank geometry, i.e., depth, A_sp, and Nd, as they relate to diffusers, but not to brush-type aerator?

2) Chemicals such as [i]calcium hydroxide[/i] and [i]ferrous sulfate[/i] are dosed upstream to influent. The chemical combination forms calcium sulfate and ferric hydroxide, which has high phosphate adsorption capacity. I do not consider P removal, but it affects C N removal anyhow, that's why I asked if there is a way to take into account it in ASM1Temp.

Thanks

Hello
1) you are looking at the default model associated with the icon "aerator". You need to switch to Surface Aerator, via the ClassName property of the block in the Properties pane
2) you most likely need to implement some custom little model then. First, the icon and model for ferric hydroxide are not available when you select ASM1 - but this could switch to ASM2, even if you were not interested in P removal. Second, what kind of impact on C and N removal do you expect? You (we) will have to check whether it is present or not in the model.