(a) A certificate approved by the board and issued by the department shall authorize the individual to whom it is issued to operate a water system in accordance with the following classifications:

“Class A certificate.” Water systems of all types and capacities.

“Class B certificate.” Water systems serving an average of not more than five million gallons per day.

“Class C certificate.” Water systems serving an average of not more than one million gallons per day.

“Class D certificate.” Water systems serving an average of not more than one hundred thousand gallons per day.

“Class E certificate.” This certificate covers the distribution portion of water systems only.

(b) In order to be eligible for certification, an applicant shall have had sufficient experience acceptable to the board in the operation of water systems. In determining whether minimum experience requirements are met, the board may make reasonable allowance for education and training in the field of water system operation and for training and experience in allied fields.

(c) In order to be eligible for renewal of certification, in addition to submitting an application and the appropriate fee, an applicant:

(d) No operator shall make any process control decisions unless he or she is in possession of a valid certificate for the applicable classification and subclassification assigned to the water system.