Mo. Rev. Stat. § 250.020

Any such city, town or village is hereby authorized to acquire, construct, improve or extend, maintain and operate a combined waterworks and sewerage system. Any such combined waterworks and sewerage system may consist of an existing sewerage system, and existing waterworks, a sewerage system to be acquired or to be constructed or a waterworks to be acquired or constructed or any combination thereof and may include any improvements or extensions to be acquired or constructed either to an existing sewerage system or to an existing waterworks or to both.