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. 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: Serves fewer than 500 persons; Has minimal treatment requirements as determined by the Department; and Employs no more than two operators. The Department shall enforce this section.