With the improvement of people's living standards, domestic sewage discharge is becoming more and more serious. In this form, the domestic sewage treatment process is also improving. Now let's learn about the domestic sewage treatment process.

1. Biological aerated filter

Brief introduction of domestic sewage treatment process: biological aerated filter is to set up fillers in the biological filter treatment device, and make a large number of microorganisms grow on the fillers through artificial oxygen supply. This sewage treatment process unit is composed of filter bed, air distribution device, water distribution device, drainage device, etc. The aerator adopts a special aerator, and the small and medium-sized bubbles generated are cut repeatedly by the filler, which is close to the effect of micro-control aeration. Due to the high concentration of sludge in the reaction tank and the compact treatment facilities, it can greatly save the floor area and reduce the reaction time.

2. SBR process

Brief introduction of domestic sewage treatment process: The main reason for eutrophication of water body is that human beings discharge a large amount of ammonia nitrogen and phosphorus into the water body, and phosphorus is the most important factor for eutrophication of water body. Throughout the domestic sewage treatment process, phosphorus removal technology has always been a difficult problem for the operation of sewage treatment plants. The traditional physical-chemical phosphorus removal technology needs a lot of chemicals, which has the disadvantages of high operating cost and large sludge output; Pre-anaerobic biological phosphorus removal process has the advantage of low operating cost, but it is difficult to meet the requirements of national sewage treatment process because it is completely dependent on the phosphorus uptake and release of microorganisms. When considering the reuse of reclaimed water, it is more difficult to meet the requirements.

3. A/O biological filter

Brief introduction of sewage treatment process: due to the scattered residential areas in small towns and the large number of sewage source distribution points, the scale of urban sewage plants is mostly less than 10000 tons/day. At present, the sewage treatment processes often used by domestic large and medium-sized urban sewage treatment plants include traditional activated sludge process, A2/O, SBR, oxidation ditch, etc. If these technologies are used to build small urban sewage treatment plants, they will cause high operating costs and cannot operate normally. It is necessary to adopt a process with low investment, low operation cost, stable and reliable technology and relatively simple operation and management according to the characteristics of small towns.

The modern domestic sewage treatment process can be divided into primary, secondary and tertiary treatment according to the treatment degree.

Primary treatment is mainly used to remove suspended solid pollutants in sewage. Most physical treatment methods can only meet the requirements of primary treatment. After primary treatment, BOD can be removed by about 30%, which can not meet the discharge standard. The primary treatment is the pretreatment of the secondary treatment.

The secondary treatment is mainly used to remove the colloidal and dissolved organic pollutants (BOD, COD) in the sewage, with a removal rate of more than 90%, so that the organic pollutants meet the discharge standard.

Three-level treatment, further treatment of refractory organic matter, nitrogen, phosphorus and other soluble inorganic substances that can lead to eutrophication of water body. The main methods include biological nitrogen and phosphorus removal, coagulation sedimentation, sand filtration, activated carbon adsorption, etc.

The whole process is that the raw sewage passing through the coarse screen is lifted by the sewage lift pump, passes through the screen or sand filter, and then enters the grit chamber. The sewage passing through the sand-water separation enters the primary sedimentation tank. The above is the primary treatment (i.e. physical treatment). The effluent from the primary sedimentation tank enters the biological treatment equipment, including activated sludge method and biological membrane method, (The reactor of the activated sludge process includes aeration tank, oxidation ditch, etc., and the biofilm process includes biological filter, biological rotary table, biological contact oxidation method, and biological fluidized bed). The effluent of the biological treatment equipment enters the secondary sedimentation tank, and the effluent of the secondary sedimentation tank is discharged after disinfection or enters the tertiary treatment. The end of the primary treatment is the secondary treatment. The tertiary treatment includes biological nitrogen and phosphorus removal method, coagulation sedimentation method, and sand filtration method, Activated carbon adsorption method. Part of the sludge from the secondary sedimentation tank flows back to the primary sedimentation tank or biological treatment equipment, part enters the sludge thickening tank, and then enters the sludge digestion tank. After the dehydration and drying equipment, the sludge is finally used.