Input signal is a flow measurement. Output is a control signal between -1 and 1. Parameters: Qmin - minimal allowed return acticated sludge (RAS) flow Qdry - flow until dry weather is assumed Qmax - maximum flow the treatment plant can handle Qrain- RAS flow at Qmax RAS_ratio - RAS/Inflow ratio during dry weather This component is only used for the complex plant example. Therefore no further documentation.