a2/o
the a2o method, also called aao method, is an abbreviation of the first letter of anaerobic-anoxic-oxic (anaerobic-anoxic-aerobic method) in english. it is a commonly used secondary sewage treatment process and can be used for secondary sewage treatment or the tertiary sewage treatment, as well as the reuse of water, has a good effect of nitrogen and phosphorus removal. the law was developed in the 1970s by some american experts on the basis of the ao process nitrogen removal process.
each reactor unit function
1. the anaerobic reactor, the original sewage and the phosphorus-containing return sludge discharged from the sedimentation tank enter at the same time. the main function of the reactor is to release phosphorus, and at the same time partial organics are subjected to ammoniation;
2, anoxic reactor, the main function is to remove nitrogen, nitrate nitrogen is sent by the aerobic reactor through the internal circulation, the circulation of a large amount of mixed liquid, generally 2q (q is the original sewage flow);
3. aerobic reactor - aeration tank, this reaction unit is multi-functional, bod removal, nitrification and phosphorus absorption are all carried out here. the flow of the 2q mixture from here back to the anoxic reactor. the
4. sedimentation tanks, the function of which is separation of sludge and water. part of the sludge is returned to the anaerobic reactor and the supernatant is discharged as treated water. the
process characteristics
1. this process can be called the simplest synchronous nitrogen and phosphorus removal process on the system, and the total hydraulic retention time is less than other types of processes;
2. under anaerobic (anaerobic) and aerobic conditions, filamentous bacteria can't proliferate in large quantities, and the filamentous swelling of the sludge is not easy to occur. the svi value is generally less than 100;
3. the sludge contains high phosphorus and has high fertilizer efficiency;
4. do not need to be administered during the operation. the two a-stages only use lightly stirring to increase the dissolved oxygen, and the operating cost is low.
there are pending problems:
1. the effect of phosphorus removal is difficult to increase, sludge growth has a certain limit, and it is difficult to increase, especially when the p/bod value is high;
2. the nitrogen removal effect is difficult to further improve. the internal circulation volume is generally limited to 2q and should not be too high;
3. the treated water entering the sedimentation tank must maintain a certain concentration of dissolved oxygen, reduce the residence time, prevent the occurrence of anaerobic conditions and the phenomenon of phosphorus release from the sludge, but the dissolved oxygen concentration should not be too high to prevent circulation of the mixture to the shortage. oxygen reactor interference.
sbr
the batch type activated sludge method is an activated sludge wastewater treatment technology that operates in a time intermittent aeration mode.
advantage
1. the ideal push-flow process will increase the driving force of biochemical reactions and increase the efficiency. the anaerobic and aerobic conditions in the pool are in an alternating state and the purification effect is good. the
2. the operation effect is stable, and the sewage is settled under the ideal static state, which requires short time, high efficiency and good water quality. the
3, impact load, the pool of treated water retention, dilution of the sewage, buffering, effective resistance to water and organic dirt impact. the
4. each process in the process can be adjusted according to the quality of water and water, and the operation is flexible. the
5, less processing equipment, simple structure, easy operation and maintenance management. the
6. there is a concentration gradient of do and bod5 in the reaction pool to effectively control the expansion of activated sludge. the
7. the sbr method itself is also suitable for modular construction methods, which facilitates the expansion and reconstruction of wastewater treatment plants. the
8, nitrogen and phosphorus removal, appropriate control of the operating mode, to achieve aerobic, anoxic, anaerobic state alternate, with a good effect of nitrogen and phosphorus removal. the
9, simple process, low cost. the main equipment only has one sequencing batch reactor, no secondary sedimentation tank, and sludge return system. the regulating tank and primary sedimentation tank can also be omitted. the layout is compact and the area is saved. the
insufficient
1, high automation control requirements. the
2. the drainage time is short (at the time of intermittent drainage), and the sedimentation sludge layer is not required to be agitated during the drainage. therefore, a special drainage device (decanter) is required, and the requirements for the decanter are high. the
3, post-processing equipment requirements: if the disinfection equipment is large, the contact pool is also very large, drainage facilities such as drainage pipes are also large.
4. the depth of muddy water is generally 1~2m. this part of the head loss is wasted and increases the total head. the
5. because there is no primary sedimentation tank, scum is easy to generate and the scum problem has not been properly solved. the
technology
due to the above technical features, the sbr system has further broadened the scope of use of the activated sludge process. with regard to recent technical conditions, the sbr system is more suitable for the following situations:
1) domestic sewage from small and medium cities and towns and mines, and industrial waste water from factories and mines, especially where there is a large gap between intermittent discharges and discharges. the
2) places where higher water quality is required, such as scenic resorts, lakes and harbors, not only remove organic matter, but also require phosphorus and nitrogen removal from the water to prevent eutrophication of rivers and lakes. the
3) where water resources are scarce. the sbr system can be materialized after biological treatment, and no additional facilities are needed to facilitate the recycling of water. the
4) places where the land is tense. the
5) renovation of established continuous-flow sewage treatment plants. the
6) it is very suitable for the treatment of small water volume, intermittent discharge of industrial wastewater and scattered point source pollution.
cass
the circulating activated sludge method divides the reaction pool of sbr into two parts along the length direction. the former part is the biological selection area also called the pre-reaction area, and the latter part is the main reaction area. in the rear of the main reaction zone, a decanter device that can be raised and lowered is installed to realize the periodic cycle operation of the continuous water intermittent drainage, and the aeration precipitation and drainage are integrated.
oxidation ditch
the feature is: the mixed liquid continuously circulates in the ditch, forming anaerobic, anoxic and aerobic sections.
biofilm method
1, contact biological method
the contact biological method is a new biochemical treatment method for sewage which is characterized by both the activated sludge method and the biofilm method. the main equipment of this method is the biological contact oxidation filter. the impervious aeration tank is filled with coke, gravel, plastic honeycomb and other fillers. the filler is invaded by water and aerated and aerated with a blower at the bottom of the packing.
2. membrane bioreactor
it is a new type of water treatment technology that combines a membrane separation unit and a biological treatment unit.
anaerobic anaerobic biological treatment utilizes the metabolic characteristics of anaerobic microorganisms. under the condition that no external energy is provided, the reduced organic matter is used as a hydrogen acceptor, and methane gas with energy value is generated at the same time.
1, septic tank
2, uasb
3, ic internal circulation reactor
4. advanced treatment on the basis of primary and secondary treatment, further treatment of refractory organics, phosphorus, nitrogen and other nutritive substances. it mainly includes filtration and disinfection.
1) activated carbon filter
2) chlorine dioxide generator
article source: i love bayern munich - personal library
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