### Question
Can you define what sludge means?


### Answer
**Sludge** is defined as the following in *49 U.S.C. § 10908*:

> 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

#### Citation:
  - *49 U.S.C. § 10908*
  - Heading: **SUBTITLE IV-INTERSTATE TRANSPORTATION > PART A-RAIL > CHAPTER 109-LICENSING**

