Chicago Stickney Sewage Treatment Plant is the largest sewage treatment plant in the world. It is located in the southwest of Chicago, USA. It is a 90-year-old sewage treatment plant. Its intake pumping station and primary treatment capacity exceed 5 million m3/d. Its secondary treatment capacity averages 4.55 million m3/d and the maximum is 5.45 million m3/d. In addition to the sludge produced by the plant, the sludge treatment capacity also bears the sludge from the northern sewage treatment plant and two other advanced treatment plants. The traditional activated sludge process is adopted. At present, the actual water treatment capacity is 2.71 million m3/d.

The plant is actually composed of two branches. The West Plant began operation in 1930 and the Southwest Plant in 1939. Its intake pumping station is the world's largest underground sewage lifting pumping station, sewage from the underground tunnel 90 meters deep to the sewage treatment plant. The factory is so large that it has even built a railway transportation system.

Process conditions:

Stickney Wastewater Treatment Plant was built and put into operation in 1930. It is a first-class treatment plant consisting of three sets of double-deck sedimentation tanks and 12 sludge natural drying beds.

With the development of the city and the improvement of water source protection standards, the southwest sewage treatment plant with activated sludge process as the main treatment process was built in the southwest side of Xichang in 1935 and put into operation in 1939. Two expansion projects in 1949 and 1975 resulted in a scale of 4.55 million m3/d secondary treatment. In sludge treatment, wet oxidation station, medium temperature digestion tank and vacuum dewatering unit were added after several expansion projects, which made the facilities of the plant more perfect. For historical reasons, its sewage treatment facilities include old double-deck sedimentation tank and sludge natural drying bed, as well as novel aeration tank, sludge digestion tank and wet oxidation device.

The factory is located in the central area of the city, the land is limited, and the layout of the buildings in the factory is very compact. In wastewater treatment process, the traditional activated sludge process is used as the main means of secondary treatment. The volume of aeration tank with rectangular reflux tank is over 800,000 m3, which is measured by the average daily flow of 4.55 million m3, and the residence time is more than 4 hours. The secondary sedimentation tank is composed of 96 radial flow sedimentation tanks with a diameter of 38.4m, and the surface hydraulic load is 40.7m3/(m2 d).

Stickney Sewage Treatment Plant adopts a variety of sludge treatment processes. Initial sludge is digested at room temperature in the lower part of the double-deck sedimentation tank. After digestion, part of the sludge is naturally dried in the drying bed, and part of the sludge is transferred to the sludge pond for stabilization. All the surplus activated sludge is concentrated and then dried in the medium-temperature digestion tank. Some of the digested sludge is dewatered by vacuum filter and Dry fertilizer is made, and the other part is concentrated and transported to the sludge pond under pressure for further stabilization and dehydration, and then shipped to the Suburban Farmland for fertilization.

As early as 40 years ago, Sitckney Sewage Treatment Plant achieved stable removal of ammonia nitrogen by prolonging sludge age. The average HRT of Stickney Sewage Treatment Plant is 8 hours, the peak HRT is less than 4 hours, the effluent BOD5 and S S are less than 10 mg/L, and the effluent ammonia nitrogen is less than 1 mg/L.

Stickney Sewage Treatment Plant is facing the problem of upgrading, upgrading and transformation need to achieve phosphorus removal. The authorities plan to use biological phosphorus removal and add an anaerobic zone to the existing aeration tank. They do not plan to use fillers. The main reasons are: (1) the population of Chicago is no longer growing; (2) the sewage treatment industry is developing in the direction of resource recovery and energy recovery. At present, the application of anaerobic ammonia oxidation technology in sidestream process is being studied. Compared with the traditional nitrification and denitrification technology, anaerobic ammonia oxidation technology only consumes 40% of the energy, and denitrification does not need carbon source.