The data of the wastewater treatment plant comes from a typical case. The construction project of a small-scale wastewater treatment plant at the county level mainly includes the comprehensive office building, coarse screen, lift pump house, fine screen, aeration grit chamber, improved oxidation ditch, secondary settling tank, type D filter, sludge treatment system, and supporting comprehensive equipment rooms. The plant is divided into different functional areas: living and auxiliary production area (front area of the plant), wastewater treatment area (production area). The construction of the plant's structures is mainly based on a framework structure. The sewage treatment plant covers a total area of 57110 square meters and mainly treats domestic sewage from the county. The design treatment capacity of the sewage treatment plant is 20,000 cubic meters per day. The sewage treatment adopts the \"modified oxidation ditch + D-type filter pool\" process. The treated sewage is discharged after reaching the Class A standard of the \"Pollutant Discharge Standards for Urban Wastewater Treatment Plants\" (GB18918-2002).