sludge
Sludge is a mud containing a lot of organic matter precipitated in the bottom of rivers, swamps, ponds and lakes, oceans, and so on. It is called sediment. The sludge of a river is also called river sediment quality. Sludge is sometimes written as false, but the etymology is not certain. There is also the theory that the word meaning muddiness is the etymology in the dialect of Tsukui-gun, Kanagawa prefecture (now part of Sagamihara city), such as ash (Yellow) or Suda (Yorodori) is accented. Although the phrase "sludge" is Japanese, it is rare that kanji is absent and is conventionally written in katakana. ...