The Sanitary District of Decatur is the regional wastewater treatment authority for central Macon County providing wastewater treatment services to the residents of the City of Decatur, Village of Forsyth, Village of Mt. Zion, and for industrial and commercial users in the Decatur metropolitan area. The Sanitary District of Decatur was formed in 1917 and the original treatment facility was completed in 1924. Major expansions and facility updates were made in 1928, 1957, 1964 and 1976. The current treatment facility, completed in 1990, provides preliminary and primary treatment followed by a two-stage activated sludge biological treatment process with effluent disinfection by chlorination prior to discharge to the Sangamon River. Sludges removed by the treatment process are stabilized by an anaerobic digestion process prior to ultimate disposal by land application on area farms.