They 'flushed' impurities from the system. = They 'flushed' impurities out of the system.
She published her first novel while still 'in the flush of' youth. [=while still young]
The committee succeeded in 'flushing out' [='finding'] several good candidates.
(..) on that one. Call. One hundred and fifteen million in the pot. Gentlemen, showdown, please. Flush. Ace, king, queen. Full house. Eights full of aces. A higher full house. Aces full of sixes. Monsieur Bond. Five and seven of spades. A straight flush. Four to the eight. The high hand. Monsieur Bond wins. -For you. -Thank you very much. (..)2006 Casino Royale