AOA sewage treatment process and sewage treatment system based on circulation clarifier

Abstract

The invention provides an AOA sewage treatment process based on a circulation clarifier and a sewage treatment system, and relates to the field of sewage treatment. The treatment process comprises the following steps: sequentially arranging an anaerobic zone, an aerobic zone and an anoxic zone, inoculating sludge into the three zones, fixedly mounting at least one circulation clarifier at the upper part of the anoxic zone, and arranging an auxiliary circulation assembly on the outer side of the circulation clarifier; enabling to-be-treated sewage to sequentially pass through the anaerobic zone and the aerobic zone to form a sludge-water mixture; the auxiliary circulation assembly generates a gas stripping effect on the two sides of the circulation clarifier at the upper part of the anoxic zone, so that circulation is formed to promote biochemical reaction and mud-water separation, and a nitrogen stripping effect is realized; a stirring effect is generated at the lower part of the anoxic zone, so that the biochemical reaction of a mud-water mixture is promoted; the sludge-water mixture subjected to the biochemical reaction enters the circulation clarifier to be subjected to sludge-water separation, separated supernate is discharged, and separated sludge falls back to the lower part of the anoxic zone; and sludge at the lower part of the anoxic zone flows back to the anaerobic zone.

Description

Technical Field

[0001] The present invention relates to the field of sewage treatment, and in particular to an AOA sewage treatment process and a sewage treatment system based on a circulation clarifier. Background Art

[0002] The A2O (anaerobic-anoxic-aerobic) process is the most common activated sludge treatment process used in existing municipal wastewater treatment plants. This process performs both denitrification and phosphorus removal in a single sludge system, offering simple operation and a proven track record. However, competition for carbon sources between denitrifying and phosphate-accumulating bacteria in the A2O system, as well as the conflict between maintaining denitrification efficiency through the return of nitrification liquid and damaging the anoxic denitrification environment, result in low simultaneous denitrification and phosphorus removal efficiency, high operating energy consumption, and the need for high carbon source dosage. The AOA (anaerobic-aerobic-anoxic) process breaks through the traditional A2O process flow by pre-positioning the aerobic stage. This allows for deep denitrification and phosphorus removal from domestic wastewater with low C / N ratios without the need for an external carbon source. Consequently, the AOA process has become a hot topic of research in the wastewater treatment field.

[0003] The operating principle of the AOA process is as follows: sewage flows through the three biochemical treatment units of anaerobic, aerobic, and anoxic in sequence. In the anaerobic section, microorganisms use the organic matter in the sewage to convert it into an internal carbon source, and a phosphorus release process occurs; in the aerobic section, aerobic nitrification and phosphorus absorption processes occur; in the anoxic section, microorganisms use the internal carbon source stored in the anaerobic section to carry out internal denitrification, achieving deep denitrification; finally, the treated sewage enters the secondary sedimentation tank, and the settled sludge is returned to the anaerobic and anoxic sections through the return system to maintain the system sludge concentration. From this, it can be seen that, on the one hand, the effluent from the anoxic section of the existing AOA process directly enters the secondary sedimentation tank. However, the sludge settling performance of the anoxic section is poor, which easily entrains the nitrogen microbubbles generated by the denitrification reaction and easily forms an anaerobic environment in the secondary sedimentation tank, inducing sludge floating in the tank body, resulting in a high concentration of suspended solids in the effluent and unstable effluent effect. On the other hand, existing AOA processes typically utilize a dual sludge recirculation system. Studies have shown that increasing the sludge recirculation ratio increases the inflow velocity of the secondary sedimentation tank, causing the vortex area in the secondary sedimentation tank to shift upward, thus affecting the sludge-water separation efficiency of the secondary sedimentation tank. Furthermore, the secondary sedimentation tank in biochemical treatment processes occupies a large area, resulting in high capital investment costs. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention provides an AOA sewage treatment process and sewage treatment system based on a loop clarifier, which reduces the concentration of water suspended matter, improves the efficiency of biochemical reactions, and eliminates the need for a secondary sedimentation tank, thereby solving the problems of the existing technology in which the secondary sedimentation tank is prone to sludge leakage, occupies a large area, and has high investment costs.

[0005] The present invention provides an AOA sewage treatment process based on a loop clarifier, the sewage treatment process comprising the following steps: Step S1, sequentially setting up an anaerobic zone, an aerobic zone, and an anoxic zone, and inoculating sludge into the anaerobic zone, the aerobic zone, and the anoxic zone, and fixing at least one circulation clarifier on the upper portion of the anoxic zone, with an auxiliary circulation assembly provided on the outer side of the circulation clarifier; Step S2, allowing the sewage to be treated to pass through the anaerobic zone and the aerobic zone in sequence to form a mud-water mixture; Step S3: The mud-water mixture enters the anoxic zone and performs the following processes in the anoxic zone: Step S3-1, generating an air stripping effect on both sides of the circulation clarifier in the upper part of the anoxic zone by the auxiliary circulation component, thereby driving the mud-water mixture to form a circulation, thereby promoting biochemical reaction and mud-water separation, and achieving a nitrogen stripping effect through the air stripping effect; generating a stirring effect in the lower part of the anoxic zone, thereby promoting the biochemical reaction of the mud-water mixture; Step S3-2: The sludge-water mixture that has undergone biochemical reaction enters the circulation clarifier, where sludge and water are separated, and the supernatant is discharged. The separated sludge falls back to the lower part of the anoxic zone; Step S4: returning the sludge in the lower part of the anoxic zone to the anaerobic zone.

[0006] Furthermore, the circulation effect generated by the gas lift is regulated by adjusting the gas flow of the auxiliary circulation component, and the gas flow is set at 20-80 m3 / h; and / or The circulation effect generated by the air lift action is regulated by adjusting the installation height of the auxiliary circulation assembly, and the installation height of the auxiliary circulation assembly is set between the middle position and the bottom position of the outer side of the circulation clarifier.

[0007] Furthermore, a stirring device is provided at the lower part of the anoxic zone, and the range of the stirring effect is controlled to be at the lower part of the anoxic zone by controlling the stirring rate of the stirring device.

[0008] Furthermore, the sludge concentration in the upper part of the anoxic zone and the lower part of the anoxic zone are stratified, the sludge concentration in the upper part of the anoxic zone is 3g / L~6g / L, and the sludge concentration in the lower part of the anoxic zone is 5g / L~10g / L.

[0009] Furthermore, in step S4, the sludge return ratio in the lower part of the anoxic zone is controlled at 50% to 300%.

[0010] Furthermore, the step S4 also includes returning the sludge in the lower part of the anoxic zone to the front end of the anoxic zone.

[0011] Furthermore, the step S1 may further include: providing an anaerobic / aerobic switching zone between the anaerobic zone and the aerobic zone; and / or An aerobic / anoxic switching zone is provided between the aerobic zone and the anoxic zone.

[0012] According to a second aspect of the present invention, an AOA sewage treatment system based on a circulation clarifier is provided, wherein the sewage treatment system comprises, in sequence: an anaerobic zone, an aerobic zone, and an anoxic zone, and is characterized in that at least one circulation clarifier is fixedly installed on the upper part of the anoxic zone, an auxiliary circulation component is provided on the outer side of the circulation clarifier, and a stirring device and a reflux facility are provided at the lower part of the anoxic zone.

[0013] Furthermore, the circulating clarifier comprises: A shell, an auxiliary circulation assembly is installed on the outside of the shell, a sludge outlet is formed below the shell, and the sludge outlet is communicated with the lower part of the anoxic zone; A sedimentation chamber is formed inside the shell and is surrounded by two vertical plates arranged along the front-to-rear direction of the shell and the front and rear side plates of the shell, and an overflow weir is installed on the upper part of the sedimentation chamber; and A flow guide channel is formed between the shell and the sedimentation chamber.

[0014] Furthermore, the auxiliary circulation assembly includes a first air inlet pipe, an auxiliary circulation pipe and a pipe fixing device, and the auxiliary circulation pipe is installed through the pipe fixing device to any height range from the middle of the outer side of the shell to the outer side of the sludge outlet.

[0015] Furthermore, the sewage treatment system further comprises: an anaerobic / aerobic switching zone, located at the rear end of the anaerobic zone, with a volume of 25% to 50% of the anaerobic zone; and The aerobic / anoxic switching zone is located at the rear end of the aerobic zone, and its volume is 25-50% of that of the aerobic zone.

[0016] The AOA sewage treatment process based on the loop clarifier of the present invention has the following advantages: (1) The present invention develops a circulating clarifier for use in anoxic zones, and utilizes the circulating clarifier to realize the integration of reaction and precipitation in the anoxic zone, thereby achieving an effective combination of the circulating clarifier and the AOA process. Compared with the traditional AOA process, the secondary sedimentation tank is removed, saving at least 30% of the floor space.

[0017] (2) The present invention installs an auxiliary circulation pipe outside the circulation clarifier in the anoxic zone, and adjusts its gas flow rate and height according to the actual effluent conditions during operation, thereby controlling the air lift circulation flow rate and achieving triple effects: first, it provides an air lift circulation stirring effect, which promotes the full mixing of sewage and sludge in the anoxic zone and improves the mass transfer efficiency of the biochemical reaction; second, it provides efficient circulation power, which can enhance the mud-water separation effect and avoid the effluent sludge leakage caused by poor circulation; finally, it provides effective disturbance power to promote the stripping of nitrogen during the anoxic denitrification reaction, improve the sludge sedimentation performance of the anoxic zone, reduce the sludge floating and effluent sludge leakage caused by nitrogen entrainment in the traditional AOA process, and ultimately improve the effluent effect.

[0018] (3) The present invention achieves two functions by installing a specially selected stirring device at the bottom of the anoxic zone and adjusting the stirring intensity according to the sludge concentration during operation, thereby controlling the stirring range in the lower part of the anoxic zone: on the one hand, it promotes the full mixing of sewage and sludge in the lower part of the anoxic zone, thereby enhancing the efficiency of the biochemical reaction; on the other hand, it realizes that the sludge concentration in the lower part of the anoxic zone (the return sludge concentration) is higher than the sludge concentration in the upper part. The higher return sludge concentration can increase the sludge concentration in each reaction zone of the system, thereby improving the sewage treatment effect. At the same time, the lower upper sludge concentration reduces the solid load of the upper circulation clarifier, enhances the solid-liquid separation effect of the circulation clarifier, and further optimizes the effluent water quality.

[0019] (4) By adding the anaerobic / aerobic switching zone and the aerobic / anoxic switching zone, the present invention can flexibly adjust the status of each functional zone according to the influent water quality and water quantity, so that the system can adapt to various fluctuations in water quality and water quantity and ensure the stability of the effluent.

[0020] Compared to traditional AOA systems, this system can improve sludge settling performance in the anoxic zone while reducing footprint through auxiliary circulation, nitrogen stripping, and sludge concentration stratification. This reduces sludge solids loading, thereby enhancing mud-water separation and stabilizing effluent suspended solids concentration at a low level. Furthermore, sludge concentration stratification increases return sludge concentration, enhancing wastewater treatment efficiency and reducing energy consumption during the wastewater treatment process. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Flow chart of an AOA sewage treatment process based on a loop clarifier according to a first embodiment of the present invention; Figure 2 Flow chart of an AOA sewage treatment process based on a loop clarifier according to a second embodiment of the present invention; Figure 3 Schematic diagram of an AOA sewage treatment system based on a loop clarifier according to the present invention.

[0022] Figure 4 is a schematic diagram of a loop clarifier according to the present invention.

[0023] Figure numbers: 1- anaerobic zone; 2- aerobic zone; 3- anoxic zone; 4- water inlet pipe; 41- water inlet pump; 42- water inlet flow control valve; 5- water outlet pipe; 6- first sludge return pipe; 7- second sludge return pipe; 8- aeration assembly; 81- second air inlet pipe; 82- aeration plate; 83- air supply system; 9- stirring facility; 10- stirring device; 11- circulation clarifier; 111- shell; 1111- side plate; 1112- bottom plate; 1113- vertical plate; 112- sedimentation chamber; 113- guide channel; 114- overflow weir; 115- auxiliary circulation assembly; 1151- first air inlet pipe; 1152- auxiliary circulation pipe; 1153- pipeline fixing device; 116- cover plate; 117- sludge outlet. DETAILED DESCRIPTION

[0024] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments. The principles and features of the present invention will be described below in conjunction with the accompanying drawings. It should be noted that the embodiments and features of the embodiments in this application may be combined with each other unless there is a conflict. The embodiments cited are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0025] Example 1 The first aspect of the present invention provides an AOA sewage treatment process based on a loop clarifier, such as Figure 1 As shown, the sewage treatment process of the present invention comprises the following steps: Step S1: An anaerobic zone, an aerobic zone, and an anoxic zone are sequentially arranged and inoculated with sludge. At least one recirculation clarifier is fixedly installed above the anoxic zone, and an auxiliary recirculation assembly is provided outside the recirculation clarifier. Specifically, the anaerobic zone, the aerobic zone, and the anoxic zone can each be provided with one or more tanks. The specific configuration can be determined based on site conditions and is not particularly limited by the present invention. In some embodiments, the initial sludge inoculation concentration in these three zones can be, for example, 3 g / L to 7 g / L.

[0026] The circulating clarifier fixedly installed above the anoxic zone can be installed, for example, by means of a support frame extending from the bottom and / or side, or a metal frame suspended from above, as long as the stability of the circulating clarifier can be ensured.

[0027] Step S2: The sewage to be treated passes through the anaerobic zone and the aerobic zone in sequence to form a mud-water mixture. Further, step S2 may also include: Step S2-1: The untreated sewage enters the anaerobic zone and reacts with the sludge returned from the anoxic zone to form a sewage-sludge mixture. The untreated sewage enters the anaerobic zone through the water inlet pipe. The anaerobic zone primarily undergoes anaerobic phosphorus release and organic matter removal. Glucose-accumulating bacteria and phosphate-accumulating bacteria utilize organic matter stored in the sewage as an internal carbon source, while phosphate-accumulating bacteria also release phosphate. In some embodiments, during operation of the anaerobic zone, the dissolved oxygen concentration should be controlled below 0.2 mg / L.

[0028] Step S2-2: The sewage and sludge mixture formed in the anaerobic zone enters the aerobic zone, where it reacts with oxygen to form the mud-water mixture. The effluent from the anaerobic zone (i.e., the sewage and sludge mixture) enters the aerobic zone. Under aeration, the sewage and sludge are fully contacted and mixed with oxygen. The aerobic zone primarily undergoes aerobic nitrification and aerobic phosphorus uptake. Nitrifying bacteria convert ammonia nitrogen into nitrate nitrogen and nitrite nitrogen, while phosphate-accumulating bacteria utilize their internal carbon source to absorb extracellular phosphate, achieving phosphorus removal. During operation in the aerobic zone, the dissolved oxygen concentration in the aerobic zone is controlled at 0.5-4 mg / L by regulating the aeration intensity, ensuring that the aerobic zone can effectively achieve nitrification while avoiding consumption of the internal carbon source and energy waste caused by excessive aeration.

[0029] Step S3: The mud-water mixture enters the anoxic zone, and the following processes are performed in the anoxic zone: Step S3-1, generating an air lift effect on both sides of the circulation clarifier at the upper part of the anoxic zone through the auxiliary circulation component, thereby driving the mud-water mixture to form a circulation, thereby promoting biochemical reaction and mud-water separation, and achieving a nitrogen stripping effect through the air lift effect; generating a stirring effect at the lower part of the anoxic zone, thereby promoting the biochemical reaction of the mud-water mixture; Step S3-2, the mud-water mixture that has undergone biochemical reaction enters the interior of the circulation clarifier, mud-water separation occurs inside the circulation clarifier, the supernatant after separation is discharged, and the separated sludge falls back to the lower part of the anoxic zone.

[0030] In the above-mentioned step S3, after the effluent from the aerobic zone (i.e., the mud-water mixture) enters the anoxic zone, biochemical reactions occur in the upper and lower parts of the anoxic zone. An auxiliary circulation component is provided on the outside of the circulation clarifier. The auxiliary circulation component can produce an air lift effect. The air lift effect can drive the mud-water mixture to form a circulation, promote mass transfer between sludge and sewage, and thus promote biochemical reactions. Furthermore, the nitrogen generated by the biochemical reaction may entrain a certain amount of sludge during the floating process, and floating sludge will be generated on the water surface, affecting the effluent water quality. The present invention realizes nitrogen stripping through the above-mentioned air lift effect, thereby avoiding the nitrogen from entraining too much sludge during the rising process, and realizes nitrogen stripping while promoting biochemical reactions.

[0031] Furthermore, in some embodiments, the circulation effect generated by the gas lift effect above the anoxic zone, i.e., the gas lift circulation flow rate, can be regulated by adjusting the gas flow rate of the auxiliary circulation assembly. The gas flow rate of the auxiliary circulation assembly is set at 20-80 m 3 / h; and / or in some alternative embodiments, the circulation effect generated by the air lift is regulated by adjusting the installation height of the auxiliary circulation component, and the adjustable range of the installation height of the auxiliary circulation component is set between the middle position and the bottom position of the outer side of the circulation clarifier.

[0032] The height of the auxiliary circulation assembly is set within a range between the middle position outside the circulation clarifier and the bottom position of the circulation clarifier, thereby effectively controlling the airlift circulation flow rate, preventing excessive circulation from causing excessive sludge at the bottom to be lifted to the upper part of the anoxic zone, and ensuring that the sludge in the anoxic zone gradually decreases vertically from bottom to top, thereby ensuring that the average sludge concentration in the lower part of the anoxic zone is higher than that in the upper part of the anoxic zone. In some preferred embodiments, the height adjustment of the auxiliary circulation assembly can be automatic, for example, adjusting the height based on changes in the airlift circulation flow rate or sludge concentration.

[0033] Therefore, the circulation generated by the air lift effect can not only promote the full mixing of sludge and sewage on both sides of the circulation clarifier to promote biochemical reactions, but also the air lift effect can promote the sewage and sludge after the reaction to enter the circulation clarifier. The circulation generated by the air lift effect can further promote the separation of mud and water inside the circulation clarifier, promote sludge sedimentation, and promote nitrogen stripping to avoid carrying sludge up during the rising process of nitrogen, resulting in a large amount of floating sludge on the surface of the circulation clarifier, achieving multiple goals at one stroke.

[0034] A stirring device is provided at the lower part of the anoxic zone. By controlling the stirring rate of the stirring device, the stirring range is controlled within the lower part of the anoxic zone, ensuring uniform mixing of the sludge in the lower part of the anoxic zone while avoiding excessive influence of the stirring on the circulation in the upper part of the anoxic zone (i.e., on both sides of the circulation clarifier), thereby ensuring that the sludge in the anoxic zone shows a trend of gradually decreasing from bottom to top in the vertical direction, so that the average concentration of the sludge in the lower part of the anoxic zone is higher than that in the upper part of the anoxic zone.

[0035] Furthermore, the upper portion of the loop clarifier is typically equipped with an overflow weir, which connects to the drainage system. The separated supernatant flows upward through the overflow weir and is discharged from the drainage system. The lower portion of the loop clarifier is typically open, allowing it to communicate with the lower portion of the anoxic zone. The sludge, after separation, falls through the opening of the loop clarifier into the lower portion of the anoxic zone.

[0036] Due to the installation of the auxiliary circulation assembly and stirring device, the air stripping circulation generated by the auxiliary circulation assembly can be mainly applied to the upper area of ​​the anoxic zone, while the stirring and mixing generated by the stirring device can be mainly applied to the lower area of ​​the anoxic zone. This ensures that the sludge in the anoxic zone can be mixed at the same time, while showing a gradual decrease in vertical concentration from bottom to top, so that the average sludge concentration in the lower anoxic zone is higher than that in the upper anoxic zone. In this case, the sludge concentration in the upper anoxic zone is 3g / L to 6g / L, and the sludge concentration in the lower anoxic zone is 5g / L to 10g / L.

[0037] Step S4, returning the sludge in the lower part of the anoxic zone to the anaerobic zone. In the lower part of the anoxic zone, the falling sludge and the original sewage sludge in the anoxic tank are fully contacted and mixed under the stirring action of the lower part of the anoxic zone, thereby ensuring the mass transfer efficiency of the biochemical reaction between sewage and microorganisms. Subsequently, the high-concentration sludge is returned to the anaerobic zone through the reflux device, mixed with the sludge in the anaerobic zone and continued to react. The sludge concentration in the lower part of the anoxic zone of the present invention is high, and the higher return sludge concentration can increase the sludge concentration in the anaerobic and aerobic zones of the system, thereby improving the sewage treatment effect. At the same time, the lower upper sludge concentration reduces the solid load of the upper circulation clarifier, enhances the solid-liquid separation effect of the circulation clarifier, and further optimizes the effluent water quality. The sludge in the reflux zone at the bottom of the anoxic zone tank body is returned to the anaerobic zone. In order to ensure sufficient sludge concentration in the anaerobic zone, the reflux ratio can be controlled at 50%~300% (the sludge return ratio is equal to the ratio of the sludge return flow rate to the inlet flow rate). In addition, it should be noted that after the process of the present invention is started, the return process is also started simultaneously. When the sewage to be treated enters the anaerobic zone, it will not only mix with the original sludge in the anaerobic zone, but also mix with the sludge returned from the anoxic zone.

[0038] It should also be noted that the biochemical reactions occurring on both sides of the circulation clarifier and in the lower anoxic zone are essentially the same: anoxic denitrification and denitrification for phosphorus removal within the mud-water mixture. During this biochemical reaction, denitrifying sugar-accumulating bacteria and denitrifying phosphorus-accumulating bacteria utilize their internal carbon sources to convert nitrate or nitrite nitrogen into nitrogen gas, while also partially absorbing phosphorus, achieving deep nitrogen and phosphorus removal. During operation in the anoxic zone, the dissolved oxygen concentration is controlled below 0.2 mg / L.

[0039] Furthermore, in some embodiments of the present invention, the above-mentioned step S4 also includes returning the sludge at the bottom of the anoxic zone to the front end of the anoxic zone. At this time, the mud-water mixture discharged from the aerobic zone and part of the sludge returned from the bottom of the anoxic zone enter the front end of the anoxic zone together, and the reactions of the above-mentioned steps S3 and S4 continue to occur in the anoxic zone.

[0040] The AOA sewage treatment process based on a circulation clarifier provided by the present invention controls the circulation effect generated by the gas lift action, that is, the gas lift circulation flow rate, by regulating the gas flow rate and height of the auxiliary circulation components on both sides of the upper circulation clarifier of the anoxic zone during operation in the anoxic zone. On the one hand, it can ensure that an effective gas lift circulation stirring effect is provided so that the sludge and sewage are fully in contact with each other to cause mass transfer, thereby promoting biochemical reactions; on the other hand, it provides efficient circulation power, so that the mud-water mixture can fully enter the interior of the circulation clarifier to cause mud-water separation, and the separated sludge flows out smoothly from the bottom, avoiding the phenomenon of mud running out of the effluent due to poor circulation; on the other hand, aeration and oxygenation are used to increase the disturbance outside the circulation clarifier, so that the nitrogen generated by the denitrification reaction is released and blown out, thereby improving the sedimentation performance of the sludge in the anoxic zone and reducing the occurrence of floating mud in the effluent of the circulation clarifier, thus achieving three goals at one stroke.

[0041] In addition, by adjusting the stirring intensity of the stirring device according to actual conditions and controlling the stirring range of the stirring device to the lower part of the anoxic zone, the sludge concentration in the lower part of the anoxic zone is increased to be higher than that in the upper part of the anoxic zone, thereby achieving a sludge concentration difference between the upper and lower parts of the anoxic zone. On the one hand, the higher return sludge concentration (sludge concentration in the lower part of the anoxic zone) increases the sludge concentration in all functional areas of the system as a whole, which is beneficial to enhancing the process pollutant removal efficiency. On the other hand, the lower sludge concentration in the upper part of the anoxic zone reduces the settled solids load of the circulation clarifier, which is beneficial to improving sedimentation efficiency and reducing the problem of floating sludge in the effluent. In summary, by comprehensively adjusting the circulation flow rate of the auxiliary circulation component of the circulation clarifier and / or the stirring intensity in the lower part of the anoxic zone, it is possible to improve sludge settling performance and stratify sludge concentration, ultimately enhancing the effluent effect of the system.

[0042] Example 2 See also Figure 2 The difference between this embodiment and the sewage treatment process of Example 1 is that an anaerobic / aerobic switching zone is provided between the anaerobic zone and the aerobic zone, and / or an aerobic / anoxic switching zone can be provided between the aerobic zone and the anoxic zone as needed. The volume of the anaerobic / aerobic switching zone is 25%-50% of that of the anaerobic zone, and the volume of the aerobic / anoxic switching zone is 25%-50% of that of the aerobic zone.

[0043] It should be noted that in the sewage treatment process of this embodiment, the anaerobic / aerobic switching zone is allowed to flexibly switch between anaerobic or aerobic conditions, and the optimal anaerobic hydraulic retention time is adjusted to ensure effective storage of the internal carbon source. The aerobic / anoxic switching zone is allowed to flexibly switch between aerobic or anoxic conditions, and the optimal aerobic hydraulic retention time is adjusted to avoid insufficient aerobic nitrification or excessive aeration that consumes the internal carbon source.

[0044] Example 3 According to a second aspect of the present invention, an AOA sewage treatment system based on a loop clarifier is provided. Figure 3 and Figure 4, the sewage treatment system includes in sequence: an anaerobic zone 1, an aerobic zone 2 and an anoxic zone 3. The above-mentioned anaerobic zone 1, aerobic zone 2 and anoxic zone 3 can be provided with at least one tank body respectively. At least one circulation clarifier 11 is fixedly installed on the upper part of the anoxic zone 3. Usually, the circulation clarifier 11 can be fixed by hanging, supporting and the like, which is not particularly limited by the present invention. The at least one circulation clarifier can, for example, be arranged in parallel above the anoxic zone, or can be arranged symmetrically above the anoxic zone. The specific arrangement method is not particularly limited in this application. An auxiliary circulation component 115 is provided on the outside of the circulation clarifier 11. In addition, the sewage treatment system of the present invention can also be provided with an inlet pipe 4 and an outlet pipe 5, which are respectively used to supply water to the anaerobic zone 1 and discharge the supernatant separated by the circulation clarifier 11 on the upper part of the anoxic zone 3. Furthermore, a stirring device 10 and a reflux facility are provided at the lower part of the anoxic zone 3.

[0045] Specifically, the above-mentioned stirring device 10 can be, for example, a stirrer, such as a submersible flow propeller or a submersible stirrer, so that the stirring action is limited to the lower part of the anoxic zone, does not cause disturbance to the upper part of the anoxic zone (on both sides of the circulation clarifier), and can keep the sludge in the lower part of the anoxic zone in a homogeneous state.

[0046] The return facility is used to return the sludge in the anoxic zone 3 to the anaerobic zone 1. Specifically, the return facility may include: a first sludge return pipeline 6 connecting the lower part of the anoxic zone and the anaerobic zone, which is used to return the sludge below the anoxic zone 3 to the anaerobic zone 1.

[0047] In some embodiments, the reflow facility of the present invention may further include a second sludge reflow pipeline 7 connecting the lower portion of the anoxic zone with the front end of the anoxic zone 3, which is used to reflow the sludge below the anoxic zone 3 to the front end of the anoxic zone 3. The first sludge reflow pipeline 6 and the second sludge reflow pipeline 7 are both provided with a reflow flow control valve and a reflow pump. In some embodiments, only a reflow pump capable of adjusting the reflow flow may be provided.

[0048] Furthermore, the circulating clarifier 11 of the present invention includes: a shell 111, a sedimentation chamber 112, and a diversion channel 113. An auxiliary circulating assembly 115 is installed on the outside of the shell 111, and a sludge outlet 117 is formed below the shell 111. The sludge outlet 117 is connected to the lower part of the anoxic zone 3. After the mud and water are separated in the circulating clarifier 11, the sludge falls back into the anoxic zone 3 below through the sludge outlet 117. The sedimentation chamber 112 is formed inside the shell 111 and is surrounded by two vertical plates 1113 arranged along the front and rear directions of the shell 111 and the side plates 1111 at the front and rear of the shell 111. An overflow weir 114 is installed on the upper part of the sedimentation chamber 112. The diversion channel 113 is formed between the shell 111 and the sedimentation chamber 112.

[0049] Specifically, after the mud-water mixture passes through the aerobic zone 2 and enters the anoxic zone 3, the auxiliary circulation assembly 115 provided on the outside of the circulation clarifier 11 generates a circulation effect due to the air lift effect of the auxiliary circulation assembly 115, and a circulation biochemical reaction occurs outside the circulation clarifier 11. At the same time, due to this air lift effect, the mud-water mixture enters the circulation clarifier 11 and enters the sedimentation chamber 112 through the guide channel 113 of the circulation clarifier 11. The mud-water mixture undergoes mud-water separation in the sedimentation chamber 112, and the supernatant with low density flows upward and is discharged outside the system through the overflow weir 114 outlet. In some embodiments, the sewage treatment system is provided with an outlet pipe 5 connected to the overflow weir 114 outlet, thereby discharging the supernatant through the overflow weir 114. The sludge with higher density flows downward and returns to the lower part of the tank body of the anoxic zone 3 through the sludge outlet 117 at the bottom of the circulation clarifier 11. In the lower part of the anoxic zone 3, the sewage and sludge are fully mixed and contacted by agitation, ensuring efficient biochemical reactions and mass transfer between the sewage and microorganisms. The sludge then flows back to the front of the anaerobic zone 1 and anoxic zone 3 through the first and second sludge return pipes, respectively.

[0050] Thus, the present invention integrates the loop clarifier 11 into the anoxic zone 3 of the AOA sewage treatment system, eliminating the need for a separate secondary sedimentation tank. This reduces the system's footprint and energy consumption during the treatment process. Furthermore, it improves sewage treatment efficiency and reduces sludge buildup in the effluent.

[0051] Furthermore, the auxiliary circulation assembly 115 of the present invention includes a first air inlet pipe 1151, an auxiliary circulation pipe 1152, and a pipe fixture 1153. The auxiliary circulation pipe 1152 is mounted to the outside of the housing 111 of the circulation clarifier 11 via the pipe fixture 1153, and the first air inlet pipe 1151 is in communication with the auxiliary circulation pipe 1152. The other end of the first air inlet pipe 1151 can be connected to an external air supply device, the specific air supply device of which is not particularly limited in the present invention. The first air inlet pipe 1151 is provided with a gas flow control valve to adjust the flow rate of the intake air, thereby regulating the auxiliary circulation flow rate.

[0052] In some embodiments of the present invention, the auxiliary circulation pipe 1152 of the present invention can be installed to any height range from the middle of the outer side of the shell 111 of the circulation clarifier 11 to the outer side of the sludge outlet 117 through the pipe fixing device 1153, such as Figure 4 The pipe fixing device 1153 can be, for example, a fixing rod equipped with a pipe clamp, a U-shaped clamp, and a U-shaped clamp baffle. The fixing device is installed on the outside of the circulation clarifier. The first air inlet pipe 1151 is connected to the fixing device via a pipe clamp, and the auxiliary circulation pipe 1152 is connected to the fixing device via a U-shaped clamp and a U-shaped clamp baffle. The pipe fixing device 1153 of the present invention is not particularly limited.

[0053] Therefore, the auxiliary circulation device can, on the one hand, ensure an effective airlift circulation flow rate so that the mud-water mixture can enter the interior of the circulation clarifier 11; on the other hand, it increases the external disturbance of the circulation clarifier 11 by means of aeration and oxygenation, so that the nitrogen generated by the denitrification reaction in the anoxic zone 3 can be released and blown out, thereby improving the sedimentation performance of the sludge in the anoxic zone 3 and reducing the occurrence of floating sludge in the effluent of the circulation clarifier 11.

[0054] In some other embodiments of the present invention, the housing 111 of the circulating clarifier 11 of the present invention may further include the following structures: side plates 1111 and bottom plates 1112, such as Figure 4 As shown, the side panels 1111 are connected end to end to form a vertically penetrating box body, that is, the side panels include front and rear side panels and left and right side panels. The bottom panel 1112 extends downward and inward from the lower edge of the side panels 1111, thereby forming a conical structure. The lower edge of the bottom panel 1112 extending downward and inward is not closed, thus reserving the sludge outlet 117. In other words, the opening at the lower edge that is not closed forms the aforementioned sludge outlet 117. In some embodiments, the side panels 1111 and bottom panel 1112 of the circulating clarifier 11 can be integrally formed or connected by welding, as long as the connection can be ensured to be sealed.

[0055] In this case, the auxiliary circulation pipe 1152 can be installed at any height range between the junction of the side plate 1111 and the bottom plate 1112 and the outer edge of the bottom of the bottom plate 1112 of the circulating clarifier 11. Preferably, the auxiliary circulation pipe 1152 can be installed at any height range between the junction of the left and right side plates 1111 and the bottom plate 1112 and the outer edge of the bottom of the bottom plate 1112 of the circulating clarifier 11.

[0056] In other embodiments of the present invention, the auxiliary circulation assembly can be configured to operate in a lifting mode (not shown). In this case, the pipe fixing device can include, for example, a lifting frame and a fixing member. The lifting frame can be installed in the vertical direction of the bottom plate of the circulation clarifier, and the fixing member is used to connect the lifting frame to the auxiliary circulation pipe. The height of the auxiliary circulation assembly can be controlled by an external controller. In this embodiment, the lifting mode can be automatically adjusted, for example, based on the circulation flow rate of the circulation clarifier. In this case, for example, a circulation flow rate monitor of the circulation clarifier can be provided to automatically control the height of the auxiliary circulation assembly based on the circulation flow rate. A transmission device can also be provided to achieve automatic adjustment.

[0057] Further, see Figure 3The sedimentation chamber 112 is formed inside the shell 111 and is surrounded by two vertical plates 1113 arranged along the front and rear directions of the shell 11 and the front and rear side plates 1111 of the shell. The height of the upper edge of the vertical plate 1113 relative to the pool bottom is higher than the height of the upper edge of the side plate 1111 relative to the pool bottom, and the height of the lower edge of the vertical plate 1113 relative to the pool bottom is also higher than the height of the lower edge of the side plate 1111 relative to the pool bottom. Figure 3 As shown, there is a certain distance between the two vertical plates 1113 and the side plates 1111 on either side. As a result, a channel, namely the diversion channel 113, is formed between the side plates 1111 and the vertical plates. In other words, the diversion channel 113 is formed between the shell 111 and the settling chamber 112. When the mud-water mixture enters the circulation clarifier 11 from the anoxic tank, it does not directly enter the settling chamber 112. Instead, it enters the settling chamber 112 through the diversion channel 113.

[0058] In some embodiments, the system of the present invention can be used outdoors or in other harsh environments. In this case, the circulating clarifier 11 of the present invention can also be provided with a cover 116, which is installed on the top of the sedimentation chamber 112. For example, the cover 116 can be push-pull type, or slidable type, that is, it can be easy to open. The specific form is not particularly limited by the present invention.

[0059] Furthermore, in order to flexibly adjust the status of each functional zone, the sewage treatment system of the present invention may also include an anaerobic / aerobic switching zone and an aerobic / anoxic switching zone. The anaerobic / aerobic switching zone is located at the rear end of the anaerobic zone 1, and its volume is 25% to 50% of the anaerobic zone 1. The aerobic / anoxic switching zone is located at the rear end of the aerobic zone 2, and its volume is 25% to 50% of the aerobic zone 2. By providing the anaerobic / aerobic switching zone and the aerobic / anoxic switching zone, the status of each functional zone can be adjusted according to the influent water quality and water quantity, thereby making the system adaptable to various fluctuations in water quality and water quantity, ensuring the stability of the effluent.

[0060] Furthermore, in order to achieve the reaction in each zone, a stirring device 9 is installed in the anaerobic zone 1, the anaerobic / aerobic switching zone, and the aerobic / anoxic switching zone of the present invention. The stirring device 9 can be, for example, a conventional flow propeller. It should be noted that the stirring disturbance height range of the stirrer in the anoxic zone 3 is smaller than the stirring height range of the stirrer in the anaerobic zone 1, the anaerobic / aerobic switching zone, and the aerobic / anoxic switching zone. An aeration assembly 8 is installed in the aerobic zone 2, the anaerobic / aerobic switching zone, and the aerobic / anoxic switching zone of the present invention. Specifically, the aeration assembly 8 includes a second air inlet pipe 81, an aeration disk 82, and an air supply system 83. The second air inlet pipe 81 is connected to the aeration disk 82. The gas outlet of the air supply system 83 is connected to the inlet of the second air inlet pipe 81, and / or the gas outlet of the air supply system 83 is connected to the inlet of the first air inlet pipe 1151. The first air inlet pipe 1151 is connected to the auxiliary circulation pipe 1152. The air supply system 83 of the aeration assembly 8 and the air supply device in the auxiliary circulation assembly 115 can be the same or separate, which is not particularly limited by the present invention. In addition, the air supply system and air supply device can be, for example, an air supply device such as a blower.

[0061] Furthermore, in some embodiments, the anaerobic zone 1 of the present invention is connected to the water inlet pipe 4, which also includes an inlet pump 41 and an inlet flow control valve 42. The sewage to be treated can be pumped into the anaerobic zone 1 through the inlet pump 41, and the inlet water volume is controlled by the inlet flow control valve 42.

[0062] In addition, a sludge concentration sensor may be provided at the bottom of the anoxic zone 3 of the present invention for sensing the sludge concentration, thereby changing the auxiliary circulation flow of the auxiliary circulation component 115 and controlling the stirring degree of the stirring device 10 according to the sludge concentration.

[0063] Furthermore, in some embodiments of the present invention, the sewage treatment system of the present invention may be provided with a controller, and sensor devices including but not limited to sludge sensors, sewage flow sensors, etc. wirelessly connected to the controller may be provided in each zone. At the same time, the above-mentioned solenoid valves and other devices may also be wirelessly connected to the controller, thereby regulating the operating status of each area.

[0064] Thus, the sewage treatment system of the present invention effectively combines the circulation clarifier 11 with the AOA process, eliminating the need for a separate secondary sedimentation tank, saving floor space while reducing energy consumption during the treatment process. Providing an auxiliary circulation assembly 115 and adjusting the circulation flow rate according to the actual effluent conditions can promote the stripping of nitrogen generated during the anoxic denitrification reaction, improve the sludge settling performance of the anoxic zone 3, reduce sludge floating caused by nitrogen entrainment, and reduce the phenomenon of effluent sludge running, thereby improving the effluent effect. By regulating the stirring intensity in the lower part of the anoxic zone 3, the sludge concentration in the lower part of the anoxic zone is made higher than the sludge concentration in the upper part of the anoxic zone, achieving a sludge concentration difference between the upper and lower parts of the anoxic zone. The higher return sludge concentration (sludge concentration in the lower part of the anoxic zone) can increase the sludge concentration in the anaerobic zone 1 and aerobic zone 2 of the system, thereby improving the sewage treatment effect. At the same time, the upper sludge concentration is reduced, thereby reducing the solid load of the circulation clarifier 11, enhancing the solid-liquid separation effect within the circulation clarifier 11, and further optimizing the effluent water quality. Setting up anaerobic / aerobic switching zones and aerobic / anoxic switching zones can adjust the status of each functional zone according to water quality and water quantity, so as to be applicable to fluctuations in various water quality and water quantity and ensure water outlet stability.

[0065] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. The specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification and features of different embodiments or examples, unless they are mutually inconsistent.

Claims

1. An AOA sewage treatment process based on a loop clarifier, characterized in that: The sewage treatment process comprises the following steps: Step S1, sequentially setting up an anaerobic zone, an aerobic zone, and an anoxic zone, and inoculating sludge into the anaerobic zone, the aerobic zone, and the anoxic zone, and fixing at least one circulation clarifier on the upper portion of the anoxic zone, with an auxiliary circulation assembly provided on the outer side of the circulation clarifier; Step S2, allowing the sewage to be treated to pass through the anaerobic zone and the aerobic zone in sequence to form a mud-water mixture; Step S3: The mud-water mixture enters the anoxic zone and performs the following processes in the anoxic zone: Step S3-1, generating an air stripping effect on both sides of the circulation clarifier in the upper part of the anoxic zone by the auxiliary circulation component, thereby driving the mud-water mixture to form a circulation, thereby promoting biochemical reaction and mud-water separation, and achieving a nitrogen stripping effect through the air stripping effect; generating a stirring effect in the lower part of the anoxic zone, thereby promoting the biochemical reaction of the mud-water mixture; Step S3-2: The sludge-water mixture that has undergone biochemical reaction enters the circulation clarifier, where sludge and water are separated, and the supernatant is discharged. The separated sludge falls back to the lower part of the anoxic zone; Step S4: returning the sludge in the lower part of the anoxic zone to the anaerobic zone.

2. The AOA sewage treatment process based on a loop clarifier according to claim 1, characterized in that: The circulation effect produced by the gas lift is regulated by adjusting the gas flow of the auxiliary circulation component. The gas flow is set at 20~80m 3 / h; and / or The circulation effect generated by the air lift action is regulated by adjusting the installation height of the auxiliary circulation assembly, and the installation height of the auxiliary circulation assembly is set between the middle position and the bottom position of the outer side of the circulation clarifier.

3. The AOA sewage treatment process based on a loop clarifier according to claim 1, characterized in that: A stirring device is provided at the lower part of the anoxic zone, and the range of the stirring effect is controlled at the lower part of the anoxic zone by controlling the stirring rate of the stirring device.

4. The AOA sewage treatment process based on a loop clarifier according to claim 2 or 3, characterized in that: The sludge concentration in the upper part of the anoxic zone and the lower part of the anoxic zone are stratified. The sludge concentration in the upper part of the anoxic zone is 3g / L-6g / L, and the sludge concentration in the lower part of the anoxic zone is 5g / L-10g / L.

5. The AOA sewage treatment process based on a loop clarifier according to claim 1, characterized in that: In step S4, the sludge return ratio in the lower part of the anoxic zone is controlled at 50% to 300%.

6. The AOA sewage treatment process based on a loop clarifier according to claim 5, characterized in that: The step S4 further includes returning the sludge at the bottom of the anoxic zone to the front end of the anoxic zone.

7. The AOA sewage treatment process based on a loop clarifier according to claim 1, characterized in that: The step S1 may further include: providing an anaerobic / aerobic switching zone between the anaerobic zone and the aerobic zone; and / or An aerobic / anoxic switching zone is provided between the aerobic zone and the anoxic zone.

8. An AOA sewage treatment system based on a loop clarifier, characterized in that: The sewage treatment system includes in sequence: an anaerobic zone, an aerobic zone and an anoxic zone. At least one circulating clarifier is fixedly installed on the upper part of the anoxic zone, and an auxiliary circulating component is provided on the outer side of the circulating clarifier. A stirring device and a reflux facility are provided at the lower part of the anoxic zone.

9. The AOA sewage treatment system based on a loop clarifier according to claim 8, characterized in that: The circulating clarifier comprises: A shell, an auxiliary circulation assembly is installed on the outside of the shell, a sludge outlet is formed below the shell, and the sludge outlet is communicated with the lower part of the anoxic zone; A sedimentation chamber is formed inside the shell and is surrounded by two vertical plates arranged along the front-to-rear direction of the shell and the front and rear side plates of the shell, and an overflow weir is installed on the upper part of the sedimentation chamber; and A flow guide channel is formed between the shell and the sedimentation chamber.

10. The AOA sewage treatment system based on a loop clarifier according to claim 9, characterized in that: The auxiliary circulation assembly includes a first air inlet pipe, an auxiliary circulation pipe and a pipe fixing device. The auxiliary circulation pipe is installed to any height range from the middle of the outer side of the shell to the outer side of the sludge outlet through the pipe fixing device.

11. The AOA sewage treatment system based on a loop clarifier according to any one of claims 8 to 10, characterized in that: The sewage treatment system further comprises: an anaerobic / aerobic switching zone, located at the rear end of the anaerobic zone, with a volume of 25% to 50% of the anaerobic zone; and The aerobic / anoxic switching zone is located at the rear end of the aerobic zone, and its volume is 25-50% of that of the aerobic zone.

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