All classified water treatment plants whether publicly or privately owned, used, or intended for use by the public or private persons, shall at all times be under the direct supervision of an individual whose competency is certified to by the director in a classification corresponding to the classification of the water treatment plant to be supervised. All classified distribution systems, whether publicly or privately owned, used, or intended for use by the public or private persons, shall at all times be under the supervision of an individual whose competency is certified to by the director in a classification corresponding to the classification of the distribution system to be supervised.