When used in this division, the following words and phrases shall have the following meanings, respectively, unless the context clearly indicates otherwise:
(1) MUNICIPALITY. A municipal corporation organized under the laws of this state.
(2) SEWER SYSTEM. Any or all of the following: sanitary sewer mains, sanitary sewer laterals and branches, sanitary sewer service lines, sanitary outfall lines, a sewage disposal plant or plants, a sewage treatment plant or plants, and appurtenances to any thereof.