Septic tank is a small-scale sewage primary treatment structure that utilizes the principles of sedimentation and anaerobic microbial fermentation to remove suspended solids, organic matter, and pathogenic microorganisms from fecal sewage or other domestic sewage. Most suspended solids (SS) can be removed from sewage through sedimentation in septic tanks, and some organic matter (CODcr, BOD5) can be degraded through anaerobic fermentation of microorganisms. The sludge deposited at the bottom of the tank can be used as organic fertilizer. Pre treatment of septic tanks can effectively prevent sewage pipelines from being blocked and reduce the organic pollution load of subsequent treatment units. However, the treatment effect of septic tanks is limited and generally cannot be directly discharged into water bodies. It needs to be further treated by subsequent aerobic biological treatment units or ecological technology units. Septic tanks should be treated with waterproofing, anti-seepage, and anti-corrosion measures to prevent groundwater pollution and ensure the water treatment capacity of subsequent sewage treatment units. Septic tanks should be regularly cleaned to maintain smooth inflow and outflow of water. The cleaned materials should be treated as solid waste or used for fertilization in farmland. The advantages of septic tanks include simple structure, easy construction, low cost, easy maintenance and management, no energy consumption, low operating costs, and good hygiene effect. Shortcomings of septic tanks: excessive sedimentation of sludge, requiring regular cleaning; Low biogas recovery rate and low comprehensive benefits; The treatment effect of septic tanks is limited and generally cannot be directly discharged into water bodies. It needs to be further treated by subsequent aerobic biological treatment units or ecological technology units. Scope of application of septic tanks: They can be widely used for the pretreatment of rural domestic sewage within the province, especially for the pretreatment of feces and urine in ecological sanitary toilets. Type and Structure
According to the different building materials and structures, septic tanks can be mainly divided into brick septic tanks, cast-in-place reinforced concrete septic tanks, prefabricated reinforced concrete septic tanks, glass reinforced concrete septic tanks, etc. According to the shape of the tank, it can be divided into rectangular septic tanks and circular septic tanks. Rural septic tanks can be divided into double grid septic tanks and triple grid septic tanks according to the number of users (as shown in Figure 8-1). Septic tanks should be used in places where water is used to flush toilets, and should be located downstream of household pipes for easy cleaning. 【 Septic Tank 】 Principle+Design+Construction+Management
