Mirko Trionfini

I everyone, I have to admit I'm kind of a newbie in WEST.
I'm testing an activated sludge plant with a membrane separation, instead of the classic secondary clarifier.
I'm struggling with the fact that the parameters of the membrane set a constant Qout.
I'm using the ideal membrane (without fouling)
I tried to use a control to set a constant concentration in the SST of the concentrate, but it gave me an error (system error: Model contains one or more algebraic loops)
I have put a loopbreaker and this happens only if the PI_control is present.
If I don't put the control, though, I struggle with the fact that the membrane works in the opposite way of a clarifier (you set the Qout instead of the underflow).
If anyone could help me I'd find it very useful, thank you.