Treatment capacity as a sink arc (source code)

= Treatment capacity as a sink arc

In a <flow network> for treatment facilities, the amount treated at a facility is represented by a directed arc from it to the sink, with that arc's capacity equal to its treatment limit. Untreated fluid may pass through the facility independently of how much is treated there. Thus the treatment limit is not a bound on total incoming flow. <Flow conservation> at a facility equates incoming flow with outgoing untreated flow plus its sink-arc flow.