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.