All water treatment plants and water distribution systems, whether publicly or privately owned, shall be under the supervision of an operator whose competency is certified to by the Energy and Environment Cabinet in a grade corresponding to the classification of the water supply system to be supervised. All operators holding valid and effective certificates issued under existing regulations of the State Board of Health on June 16, 1966, may, within the discretion of the Energy and Environment Cabinet, be issued new certificates without examination for any appropriate new classifications that may be established by the regulations adopted hereunder or such certificates may be continued in effect.