First constructed in 1930, the Lima Wastewater Treatment Plant consisted of screening, grit removal, primary sedimentation, and anaerobic digestion. Throughout the years, secondary treatment, tertiary treatment and additional sludge digestion were added. In 1973, the plant was expanded to an average dry weather flow capacity of 18.5 million gallons per day (MGD), and a peak flow capacity of 53 MGD. The design concept called for secondary and advanced treatment processes of the plant to operate at a peak rate of 33 MGD, with any remaining flow receiving primary settling and chlorination. Since 1973 the plant has provided primary, secondary and tertiary treatment, as well as biosolids and digester gas recycling.