Because of the design of the sewage treatment plant of the total size of 80000 tons / day, so I choose Carlo Sal oxidation ditch process. Pulp surface aerator installed vertically using Carrousel oxidation ditch process, each ditch the installation of a unified, are installed in the end, forming the anoxic zone aeration device and the outer ring of the upstream and
downstream near the aerator oxygen enriched region, not only conducive to biological cohesion, but also conducive to the sedimentation of activated sludge. The BOD5 removal rate can be as high as 95% ~ 99%, nitrogen removal rate can reach 90%. Carrousel oxidation ditch anaerobic, anoxic, aerobic process in a pool, the wall separate self-contained, but with each other and connection, make full use of sewage in oxidation ditch circulation flow, good aerobic zone and anoxic zone organically, realize unpowered reflux, saving energy consumption.