The Commission shall deposit all funds collected under the system development charge into a system development charge fund. The system development charge fund is a special fund that may not revert to general funds of the Commission. The Commission may use the funds collected from the system development charge only to: pay for new treatment, transmission, and collection facilities, the need for which is directly attributable to the addition of new service and the construction of which began after July 1, 1993; or amortize any bond that is issued in connection with the construction of those new facilities. Other costs of enhancement, maintenance, or environmental regulation on existing or new systems shall be borne equally by all ratepayers.