The Wallet Scrubber is used to sell currencies on your exchange that are too small to sell.

how does the scrubber work?

The wallet scrubber takes the left over amount (Dust) and creates a limit buy order, filling that perticular balance to a point the exchange accepts it as a trading pair.
Afterwards, the hopper will sell all the funds, and leave no dust behind, this way the scrubber literaly "scrubs" your wallet and only leaves your base currency !