No person, firm, or corporation, municipal or private, owning or having control of a water pollution control system for which a certified operator is required under rules adopted by the Commission shall allow such system to be operated by any person who does not hold a currently valid certificate in an appropriate grade and type issued by the Commission.  No person shall perform the duties of a water pollution control system operator in responsible charge without being duly certified under the provisions of this Article.  No person shall perform the duties of a water pollution control system operator who has not paid all fees required under this Article. (1969, c. 1059, s. 3; 1979, c. 554, s. 2; 1991, c. 623, s. 11.)