(a) Wastewater districts formed pursuant to this chapter shall be operated without profit, but the rates, fees, rent, or other charges for wastewater disposal and other facilities, supplies, equipment, or services furnished by the wastewater district shall be sufficient at all times:
(1) To pay all operating and maintenance expenses necessary or desirable for the prudent conduct of its affairs and the principal of and interest on the obligations issued or assumed by the district in the performance of the purposes for which it was organized;
(2) For the creation of adequate reserves.
(b) The revenues of the wastewater district shall be devoted first to the payment of operating and maintenance expenses and the principal and interest on outstanding obligations and, thereafter, to such reserves for improvements, new construction, depreciation, and contingencies as the board may prescribe from time to time.
(c) Revenues not required for the purposes set forth in subsection (b) of this section shall be returned from time to time to the customers of the wastewater district on a pro rata basis, according to the amount of business done with each customer during the period for which the return is made, either in cash, in abatement of current charges for wastewater disposal, or otherwise as the board determines. The return may be made by way of a general rate reduction to customers if the board so elects.