domestic sewage

Domestic sewage Overview of domestic sewage and typical domestic sewage quality
Domestic sewage refers to the wastewater produced by urban agencies, schools and residents in daily life, including toilet feces, laundry and bath water, kitchen and other household drainage, as well as commercial, hospital and Drainage of playgrounds, etc.
The quality of domestic water has changed after use, and organic matter, suspended solids and pathogenic bacteria have increased in the water. In typical domestic sewage water quality, the biochemical oxygen demand is generally /, the chemical oxygen demand is generally /, the suspended matter is generally /, and the value is.
The typical complete process of domestic sewage treatment is as follows?
Sewage pre-treatment biochemical secondary sedimentation tank disinfection effluent
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Sludge treatment system
Pre-treatment is also called Commonly used pretreatment technologies include grilles or grids, regulating tanks, grit settling tanks, primary settling tanks, etc.
Since the core of domestic sewage treatment is the biochemical part, we call the sewage treatment process specifically refers to this part such as contact oxidation method, method, / method, etc. The biochemical method, including anaerobic and aerobic treatment of domestic sewage, is currently the most economical and applicable sewage treatment process. Choosing different sewage treatment processes based on the volume, quality and on-site conditions of domestic sewage is decisive for investment and operating costs. Influence. The following is an introduction to the currently commonly used domestic sewage treatment processes.
, No energy consumption underground small domestic sewage device
The process flow of the improved septic tank is as follows?
Sewage anaerobic hydrolysis tank anaerobic filter tank oxidation ditch effluent
Anaerobic The hydrolysis tank is the national standard septic tank, the anaerobic filter tank is the built-in filler of the anaerobic contact oxidation tank, and the oxidation ditch uses drainage ditches and forced ventilation. The process of dissolving oxygen in the air into the sewage occurs naturally. This sewage treatment process is suitable for domestic sewage treatment in a single residential building and can be used in combination with national standard septic tanks. Its biggest advantage is that the operating cost is zero. The effluent water quality can reach the second level standard in the national "Integrated Wastewater Discharge Standard".
This process is suitable for sewage treatment projects with a sewage volume less than 1/2, and can be used in wealthier rural areas.
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The anaerobic and aerobic sewage treatment process is as follows?
Sewage pre-treatment anaerobic hydrolysis tank contact oxidation tank sedimentation tank filter tank effluent
|_Sludge return _|
Design points?
The anaerobic hydrolysis tank adopts the form of an upflow anaerobic sludge bed reactor, and the designed hydraulic retention time is ~ hours.
The lower part of the anaerobic tank is the sludge bed area, and the thickness of the sludge bed is usually controlled within In a suspended state. The average concentration of the sludge bed is, then the sludge load is
. The biological contact oxidation process is a sewage treatment process between the activated sludge process and the biofilm process. There is filler in the tank, and part of the microorganisms are fixed on the surface of the filler in the form of biofilm, while part of the microorganisms are suspended in the water and grow in the form of floc. Therefore, it has the characteristics of both the activated sludge method and the biological filter.
The aeration system can use a blast or jet aeration and oxygenation system. Investment and operating costs must be considered during design. In order to cultivate different dominant strains of microorganisms, it is effective to divide the contact oxidation tank into two compartments. The effective hydraulic retention time of the first grid is when, the effective hydraulic retention time of the organic load is The mud expansion and mud discharge volume are very small, and it has a good denitrification effect. The / and / sewage treatment processes derived from the / method are similar in principle.
, method
The intermittent activated sludge method is currently widely used in sewage treatment projects because it has a series of characteristics that are superior to ordinary activated sludge methods. The aeration tank in France also has the function of sedimentation, and anaerobic and aerobic processes are also carried out in the same tank. Its operation consists of five processes: inflow, reaction, precipitation, discharge and standby. By adjusting the time of each process, the effect of phosphorus and nitrogen removal can be achieved.
Filtered water from pre-treatment reactor
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Sludge disposal
Design points? Theoretically, the volumetric load of the reactor has a relatively high range. However, for safety reasons, it is generally Low values, as on the right. The highest water level and the lowest water level. The highest water level is the water level during the reaction. The lowest water level refers to the water level at the end of the discharge process. The lowest water level must ensure that when the water is discharged at this level, the precipitated sludge will not be lost with the supernatant liquid.
The main features of the process include better effluent quality, less floor space, no sludge expansion, and good phosphorus and denitrification effects.
, Oxidation ditch
Oxidation ditch is a variant of the activated sludge method. The tank body is long and narrow, so it is called oxidation ditch. There are many structural types of oxidation ditches. The typical ones are the Carrousel type and the Obar type. The alternating working oxidation ditch, aeration and sedimentation integrated oxidation ditch.
Oxidation ditch technology has been widely used in large and medium-sized urban sewage treatment plants, with scales ranging from a few hundred cubic meters to tens of thousands of cubic meters per day. The technology is becoming more and more perfect, and its structural types are also increasing.
Its main features are simple water inlet and outlet devices, and the flow pattern of sewage can be regarded as a completely mixed type. Because the tank body is long and narrow, it is similar to a push flow type, with low load, good water quality, and low sludge yield. The sludge discharge volume is small, the sludge age is long, and it has the function of denitrification.
Design points The suspended solids concentration of the mixed liquid is /, the average residence time of biosolids, when removing, takes ~ days, when nitrification reaction is required, take ~ days, the hydraulic retention time is,,,, based on the requirements for the quality of the treated water It is determined that the load is the volumetric load, the sludge return ratio is ~, the flow rate of the mixed liquid in the ditch is, and the flow rate at the bottom of the ditch is.