Md. Code, Environment § 12–402

(a) Except as provided in subsection (b) of this section, each waterworks, wastewater works, and industrial wastewater works shall be under the supervision of a superintendent who is certified in the appropriate classification.

(b) A waterworks, a wastewater works, and an industrial wastewater works may have a certified operator serve in responsible charge instead of a certified superintendent if approved by the Department and if the facility:

(1) Serves fewer than 500 persons;

(2) Has minimal treatment requirements as determined by the Department; and

(3) Employs no more than two operators.

(c) The Department shall enforce this section.