The principal work of MSD is to provide sanitary sewer and drainage service and treatment for Louisville and Jefferson County. There are several other small treatment plants that are still operated by private owners and public agencies in Jefferson County. Some of these plants, as well as all individual septic tank installations, were built for relatively short-term operation. The homes served by these plants and septic tanks will eventually be connected to the MSD sewerage system.
Sewage treatment is a recent event in the history of Louisville and Jefferson County.
Though sewer lines themselves date back some 125 years, no treatment was provided until 1958. As the City grew, sewer lines were extended. Louisville's dramatic population and industrial boom during and following World War II finally stimulated treatment planning. Construction of a major wastewater treatment plant began in 1956 and the plant began providing primary wastewater treatment in 1958. There has also been significant sewer line construction.