algae vs sludge

algae

noun
  • A particular kind of algae. 

  • Algal organisms viewed collectively or as a mass; algal growth. 

sludge

noun
  • A mass of small pieces of ice on the surface of a body of water. 

  • A residual semi-solid material left from industrial, water treatment, or wastewater treatment processes. 

  • Solids separated from suspension in a liquid. 

  • sludge metal 

  • A sediment of accumulated minerals in a steam boiler. 

verb
  • To slop or drip slowly. 

  • To slump or slouch. 

How often have the words algae and sludge occurred in a corpus of books? (source: Google Ngram Viewer )