Md. Code, Environment § 9-353

(a) In this part the following words have the meanings indicated.

(b) (1) “Industrial user” means:

(i) A person who is engaged in manufacturing, fabricating, or assembling goods; or

(ii) A member of any class of significant producers of pollutants identified under regulations adopted by:

1. The Secretary; or

2. The Administrator of the U.S. Environmental Protection Agency.

(2) “Industrial user” does not include the federal, State, and local governments.

(c) “PFAS chemicals” means a class of fluorinated organic chemicals that contain at least one fully fluorinated carbon atom, including perfluoroalkyl and polyfluoroalkyl substances.

(d) “Pretreatment permit” means a document issued by the Department or the Department’s designee that authorizes a significant industrial user to introduce industrial wastes into a publicly owned treatment works in compliance with the pretreatment requirements under COMAR 26.08.01.01B(69).

(e) (1) “Significant industrial user” means an industrial user that:

(i) Is subject to categorical pretreatment standards under 40 C.F.R. Part 403.6;

(ii) Discharges an average of 25,000 gallons per day or more of processed wastewater to a publicly owned treatment works, not including sanitary, noncontact cooling, and boiler blowdown wastewater;

(iii) Contributes processed wastewater that makes up 5% or more of the average dry–weather hydraulic or organic capacity of the publicly owned treatment works; or

(iv) Is designated as a significant industrial user by the publicly owned treatment works on the basis that the industrial user has:

1. A reasonable potential for adversely affecting the wastewater treatment plant’s operations and sewer system; or

2. Violated a pretreatment standard or requirement.

(2) “Significant industrial user” does not include the federal, State, and local governments.

(f) “Waters of the State” includes:

(1) Both surface and underground waters within the boundaries of the State subject to its jurisdiction;

(2) That portion of the Atlantic Ocean within the boundaries of the State;

(3) The Chesapeake Bay and its tributaries;

(4) All ponds, lakes, rivers, streams, public ditches, tax ditches, and public drainage systems within the State, other than those designed and used to collect, convey, or dispose of sanitary sewage; and

(5) The floodplain of free–flowing waters determined by the Department on the basis of the 100–year flood frequency.