Mechanical processing section
The mechanical (first-level) treatment section includes structures such as grills, grit chambers, and primary sedimentation tanks. The purpose is to remove coarse particles and suspended solids. The principle of treatment is to achieve solid-liquid separation through physical methods to separate pollutants from sewage. This is a commonly used sewage treatment method. Mechanical (primary) treatment is an indispensable section of all wastewater treatment processes (although some processes sometimes omit primary sinks), the typical removal rates of urban wastewater primary treatment BOD5 and SS are 25% and 50%, respectively. In biological dephosphorization and denitrification sewage treatment plants, aerated sedimentation tanks are generally not recommended to avoid the rapid degradation of organic matter. In the case that the quality of the raw sewage is not conducive to the removal of phosphorus and nitrogen, is the setting of the primary sedimentation tank and The setting method needs to be carefully analyzed and considered according to the water quality characteristics and subsequent processes to ensure and improve the incoming water quality of subsequent processes such as phosphorus and nitrogen removal.
Sewage biochemical treatment
Sewage biochemical treatment belongs to the secondary treatment. The main purpose is to remove non-sinkable suspended solids and soluble biodegradable organic matter. The process composition is various and can be divided into activated sludge method, biofilm method, biological stable pond method and land treatment. Law and other four categories. Most municipal sewage treatment plants use activated sludge. The principle of biological treatment is to complete the decomposition of organic matter and the synthesis of organisms through biological action, especially the action of microorganisms, and convert organic pollutants into harmless gas products (CO2), liquid products (water) and organic-rich substances. Solid product (microbiological group or biological sludge); excess biological sludge is separated by solid-liquid precipitation in a sedimentation tank and removed from the purified sewage. It can be seen that the role of the sewage treatment process is only through biodegradation and solid-liquid separation. While the sewage is purified, the pollutants are concentrated in the sludge, including the primary sedimentation sludge produced in the primary treatment section, Residual activated sludge from the secondary treatment section and chemical sludge from the tertiary treatment. Because these sludges contain a large amount of organic matter and pathogens, and are extremely prone to decay and odor, it is easy to cause secondary pollution, and the task of eliminating pollution has not been completed. The sludge must undergo a certain volume reduction, volume reduction, stabilization and harmless treatment and proper disposal. The success of sludge treatment and disposal has an important impact on the sewage plant and must be paid attention to. If the sludge is not treated, the sludge will have to be discharged with the treated effluent, and the purification effect of the sewage plant will be offset. The selection and different combinations of various mechanical treatment, biological treatment, and sludge treatment and treatment technology and equipment, as well as the design of structures, constitute a variety of wastewater treatment plant processes and engineering solutions. The responsibility of the designer is to flexibly combine various possibilities according to specific conditions and water quality goals, in order to form an overall economic processing process that is economical and practical, and to avoid simple localized treatment methods. Comparison and selection.