In intelligent septic tanks, the sewage treatment subsystem is the core link and plays a crucial role in connecting the previous and the next. It undertakes the preliminary sedimentation and separation of sewage, and uses biological, chemical and other treatment processes to remove various pollutants such as nitrogen, phosphorus, organic matter, etc. from the sewage, so as to meet the discharge standards or reuse requirements. The system workflow has the following four stages.

Sewage collection and pretreatment stage: The intelligent septic tank first collects sewage from households, commercial places, etc. These sewage first enter the grid well, and through coarse and fine grids, intercept larger floating and suspended solids in the sewage, such as tree branches, plastic bottles, tissues, etc., to prevent them from entering the subsequent treatment unit and causing equipment blockage. Subsequently, the sewage flows into the sedimentation tank and utilizes the principle of gravity settling to settle inorganic particles such as sand particles in the sewage, reducing the subsequent treatment load.

Biological treatment stage: The pre treated wastewater enters the biological treatment tank, which is the core process. The pool is filled with activated sludge, which contains a large number of microorganisms. Through different environments such as anaerobic, anaerobic, and aerobic, the metabolism of microorganisms is utilized to decompose organic pollutants in sewage. During the anaerobic stage, anaerobic bacteria break down large organic compounds into small molecules; During the anoxic stage, denitrifying bacteria undergo denitrification reactions; During the aerobic stage, aerobic microorganisms further decompose residual organic matter and complete nitrification reactions, converting ammonia nitrogen into nitrate nitrogen.

Deep treatment stage: The sewage after biological treatment enters the deep treatment unit, where residual pollutants and microorganisms are further removed through processes such as filtration and disinfection. Common filtration methods include sand filtration and membrane filtration, which can remove fine suspended solids and some soluble substances. Disinfection uses methods such as ultraviolet radiation and chlorine dioxide to kill pathogenic microorganisms in water and ensure that the effluent quality meets standards.

Discharge and reuse stage: A portion of the water that has been deeply treated to meet standards is directly discharged into natural water bodies or municipal sewage pipelines; The other part can be recycled for non drinking purposes such as irrigation and flushing, achieving the recycling of water resources. At the same time, the sludge generated during the treatment process will be transported to the sludge treatment unit for dewatering, drying, and other treatments to reduce the impact on the environment.