For constructing or acquiring any water supply, wastewater transportation, or treatment system for the authorized purposes of the authority, or necessary or incidental thereto, and for constructing improvements and extensions thereto, and also for reimbursing or paying the costs and expenses of creating the authority, the governing body of any such authority is hereby authorized to borrow money from time to time and in evidence thereof issue the revenue bonds of such authority. Such revenue bonds are hereby made a lien on the revenues produced from the operation of the authority's system, but shall not be general obligations of the public agencies participating in the agreement. All revenue bonds issued under this article shall be signed by the president of the governing body of the authority and attested by the secretary of the governing body of the authority and shall contain recitals stating the authority under which such bonds are issued and that they are to be paid by the authority from the net revenue derived from the operation of the authority's system and not from any other fund or source and that said bonds are negotiable and payable solely from the revenues derived from the operation of the system under control of the authority: Provided, That in the case of a regional water and wastewater authority, the statutory lien created hereby shall only be a lien on the revenues of that service funded by the proceeds of the sale of the bonds, it being understood that such combined authority shall maintain separate books and records for its water and wastewater operations. Such bonds may be issued in one or more series, may bear such date or dates, may mature at such time or times not exceeding forty years from their respective dates, may bear interest at a rate not exceeding two percent above the interest rate on treasury notes, bills or bonds of the same term as the term of the bond or bonds the week of closing on the bond or bonds as reported by the treasury of the United States, may be payable at such times, may be in such form, may carry such registration privileges, may be executed in such manner, may be payable at such place or places, may be subject to such terms of redemption with or without premium, may be declared or become due before maturity date thereof, may be authenticated in any manner, and upon compliance with such conditions, and may contain such terms and covenants as may be provided by resolution or resolutions of the governing body of such authority. Notwithstanding the form or tenor thereof, and in the absence of any express recital on the face thereof, that the bond is nonnegotiable, all such bonds shall be, and shall be treated as, negotiable instruments for all purposes. Bonds bearing the signatures of officers in office on the date of the signing thereof shall be valid and binding for all purposes notwithstanding that before the delivery thereof any or all of the persons whose signatures appear thereon shall have ceased to be such officers. Notwithstanding the requirements or provisions of any other law, any such bonds may be negotiated or sold in such manner and at such time or times as is found by the governing body to be most advantageous, and all such bonds may be sold at such price that the interest cost of the proceeds therefrom does not exceed three percent above the interest rate on treasury notes, bills or bonds of the same term as the term of the bond or bonds the week of closing on the bond or bonds as reported by the treasury of the United States, based on the average maturity of such bonds and computed according to standard tables of bond values. Any resolution or resolutions providing for the issuance of such bonds may contain such covenants and restrictions upon the issuance of additional bonds thereafter as may be deemed necessary or advisable for the assurance of the payment of the bonds thereby authorized.