Sludge
Sludge means any solid, semi-solid, or liquid waste generated from a municipal, commercial, or industrial wastewater treatment plant, water supply treatment plant, or air pollution control facility exclusive of the treated effluent from a wastewater treatment plant.
Source
40 CFR § 260.10
Scoping language
When used in parts 260 through 273 of this chapter, the following terms have the meanings given below: