The city treasurer shall install and maintain a proper system of accounting, showing the amount of revenue received from the sewerage system and the application of that revenue, and such account shall be audited properly at least once a year. The keeping of such records and the audit thereof shall be further governed by the provisions of any ordinance which may hereafter be adopted authorizing the issuance of bonds payable from the revenues of the sewerage system. (Prior code § 38-4-9)