(a) The bonds issued under this chapter shall not be general obligations of the municipality or county but shall be special obligations. In no event shall the bonds constitute an indebtedness of the municipality or county within the meaning of any constitutional or statutory limitation.
(b) It shall be plainly stated on the face of each bond that the same has been issued under the provisions of this chapter, and that it does not constitute an indebtedness of the municipality or county within any constitutional or statutory limitation.
(c) The principal of and interest on the bonds shall be secured by a pledge of, and shall be payable from, revenues derived from the pollution control project acquired, constructed, reconstructed, extended, or improved, in whole or in part, with the proceeds of the bonds.
(d) In addition, the municipality or county is authorized to pledge to and use for the payment of the principal of and interest on the bonds, together with other expenses in connection therewith, surplus revenues derived from water, sewer, gas, and electric utilities owned by the municipality or county.
(e) Surplus revenues, as used in this section, are defined to mean revenues remaining after adequate provision shall have been made for expenses of operation, maintenance, and depreciation and all requirements of ordinances, orders, or indentures securing bonds, theretofore and thereafter issued to finance the cost of acquiring, constructing, reconstructing, extending, or improving the utilities, have been fully met and complied with.