A Sludge

1. Solids separated from suspension in a liquid.
2. A residual semi-solid material left from industrial, water treatment, or wastewater treatment processes.
3. A sediment of accumulated minerals in a steam boiler.
4. A mass of small pieces of ice on the surface of a body of water.
5. (uncountable, music) sludge metal

(separated solids): mud, mire, ooze, slush