70 ILCS 2805/4.3

A sanitary district may, by ordinance, combine and jointly operate the district's waterworks and sewerage systems. A sanitary district operating a combined waterworks and sewerage system may: (i) improve and extend that system; (ii) impose rates and collect charges for the use of that system; and (iii) issue obligations and bonds under the same terms and conditions that it may issue obligations or bonds for a waterworks system or for a sewerage system and may pledge revenues from the combined waterworks and sewerage system in payment of the obligations or bonds.