AOA wastewater treatment process and wastewater treatment system based on circulating clarifier

Abstract

This invention provides an AOA wastewater treatment process and system based on a circulating clarifier, relating to the field of wastewater treatment. The treatment process includes the following steps: sequentially setting up an anaerobic zone, an aerobic zone, and an anoxic zone, and inoculating the three zones with sludge; fixing at least one circulating clarifier on the upper part of the anoxic zone, with an auxiliary circulating component on the outside of the circulating clarifier; allowing the wastewater to be treated to pass through the anaerobic zone and the aerobic zone sequentially, forming a sludge-water mixture; generating an airlift effect on both sides of the circulating clarifier in the upper part of the anoxic zone through the auxiliary circulating component, thereby forming a circulation to promote biochemical reactions and sludge-water separation, and achieving a nitrogen stripping effect; generating a stirring effect in the lower part of the anoxic zone, thereby promoting the biochemical reaction of the sludge-water mixture; the sludge-water mixture that has undergone biochemical reactions enters the circulating clarifier for sludge-water separation, discharging the separated supernatant, and the separated sludge falling back to the lower part of the anoxic zone; and returning the sludge from the lower part of the anoxic zone to the anaerobic zone.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment, specifically to an AOA wastewater treatment process and system based on a circulating clarifier. Background Technology

[0002] The A2O (anaerobic-anoxic-aerobic) process is the most common process in existing municipal wastewater treatment plants that utilizes activated sludge to treat wastewater. This process completes both nitrogen and phosphorus removal in a single sludge system, and is simple to operate and has mature technology. However, the A2O system suffers from the conflict between carbon source competition between denitrifying bacteria and polyphosphate-accumulating bacteria, and the conflict between maintaining nitrogen removal efficiency through reflux of nitrifying liquor and disrupting the anoxic denitrification environment. This leads to problems such as low simultaneous nitrogen and phosphorus removal efficiency, high operating energy consumption, and large carbon source dosage. The AOA (anaerobic-aerobic-anoxic) process breaks through the traditional A2O process flow by placing the aerobic stage upstream, enabling deep nitrogen and phosphorus removal from domestic wastewater with low C / N ratios without the need for external carbon sources. Therefore, the AOA process has become a hot research topic in the current wastewater treatment field.

[0003] The operating principle of the AOA process is as follows: Wastewater flows sequentially through three biological treatment units: anaerobic, aerobic, and anoxic. In the anaerobic stage, microorganisms utilize the organic matter in the wastewater to convert it into an internal carbon source and undergo phosphorus release. In the aerobic stage, aerobic nitrification and phosphorus uptake occur. In the anoxic stage, microorganisms utilize the internal carbon source stored in the anaerobic stage for endogenous denitrification, achieving deep nitrogen removal. Finally, the treated wastewater enters the secondary sedimentation tank, and the settled sludge is returned to the anaerobic and anoxic stages through a return system to maintain the sludge concentration in the system. Therefore, on the one hand, the existing AOA process directly sends the effluent from the anoxic stage into the secondary sedimentation tank. However, the sludge in the anoxic stage has poor settling performance, easily carrying nitrogen microbubbles generated by denitrification, and easily creating an anaerobic environment in the secondary sedimentation tank, inducing sludge floating in the tank, resulting in a high concentration of suspended solids in the effluent and unstable effluent quality. On the other hand, existing AOA processes typically employ a dual sludge recirculation mode. Studies have shown that increasing the sludge recirculation ratio increases the influent velocity to the secondary sedimentation tank, causing the vortex region to shift upwards and affecting the sludge-water separation efficiency. Furthermore, the secondary sedimentation tank in biological treatment processes occupies a large area, resulting in high infrastructure investment costs. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an AOA wastewater treatment process and system based on a circulating clarifier, which reduces the concentration of suspended solids in the water, improves the efficiency of biochemical reactions, and eliminates the need for a secondary sedimentation tank, thus solving the problems of sludge runoff, large footprint, and high investment costs associated with secondary sedimentation tanks in existing technologies.

[0005] This invention provides an AOA wastewater treatment process based on a circulating clarifier, the wastewater treatment process comprising the following steps:

[0006] Step S1: Sequentially set up an anaerobic zone, an aerobic zone, and an anoxic zone, and inoculate sludge into the anaerobic zone, the aerobic zone, and the anoxic zone. Fix at least one circulating clarifier on the upper part of the anoxic zone, and provide an auxiliary circulating component on the outside of the circulating clarifier.

[0007] Step S2: The wastewater to be treated is passed sequentially through the anaerobic zone and the aerobic zone to form a mud-water mixture;

[0008] Step S3: The mud-water mixture enters the anoxic zone and undergoes the following process in the anoxic zone:

[0009] Step S3-1: The auxiliary circulation component generates an air-lift effect on both sides of the circulation clarifier in the upper part of the anoxic zone, thereby driving the mud-water mixture to form a circulation, thus promoting biochemical reaction and mud-water separation, and achieving nitrogen stripping effect through the air-lift effect; a stirring effect is generated in the lower part of the anoxic zone, thereby promoting the biochemical reaction of the mud-water mixture;

[0010] Step S3-2: The mud-water mixture that has undergone biochemical reaction enters the circulating clarifier, where mud-water separation occurs. The supernatant after separation is discharged, and the separated sludge falls back to the lower part of the anoxic zone.

[0011] Step S4: Return the sludge from the lower part of the anoxic zone to the anaerobic zone.

[0012] Furthermore, the circulation effect generated by the airlift action is controlled by adjusting the gas flow rate of the auxiliary circulation component, with the gas flow rate set at 20~80 m³ / h; and / or

[0013] The circulation effect generated by the air-lift action is controlled by adjusting the installation height of the auxiliary circulation component, which is set between the middle and bottom positions on the outer side of the circulation clarifier.

[0014] Furthermore, a stirring device is provided at the lower part of the anoxic zone, and the stirring effect is controlled at the lower part of the anoxic zone by controlling the stirring rate of the stirring device.

[0015] Furthermore, the sludge concentration in the upper part of the anoxic zone and the lower part of the anoxic zone are stratified, with the sludge concentration in the upper part of the anoxic zone being 3g / L~6g / L and the sludge concentration in the lower part of the anoxic zone being 5g / L~10g / L.

[0016] Furthermore, in step S4, the sludge return ratio in the lower part of the anoxic zone is controlled at 50%~300%.

[0017] Furthermore, step S4 also includes returning the sludge from the lower part of the anoxic zone to the front end of the anoxic zone.

[0018] Furthermore, step S1 may also include:

[0019] An anaerobic / aerobic switching zone is provided between the anaerobic zone and the aerobic zone; and / or

[0020] An aerobic / hypoxic switching zone is set between the aerobic zone and the hypoxic zone.

[0021] According to a second aspect of the present invention, an AOA wastewater treatment system based on a circulating clarifier is provided, the wastewater treatment system comprising, in sequence, an anaerobic zone, an aerobic zone, and an anoxic zone, characterized in that at least one circulating clarifier is fixedly installed on the upper part of the anoxic zone, an auxiliary circulating component is provided on the outer side of the circulating clarifier, and a stirring device and a reflux facility are provided on the lower part of the anoxic zone.

[0022] Furthermore, the circulating clarifier includes:

[0023] The shell has an auxiliary circulation assembly installed on its outer side, and a sludge outlet is formed at the bottom of the shell, which is connected to the lower part of the anoxic zone.

[0024] A settling chamber, formed inside the shell, is surrounded by two vertical plates arranged along the front-rear direction of the shell and the front and rear side plates of the shell. An overflow weir is installed at the upper part of the settling chamber; and

[0025] A flow channel is formed between the shell and the settling chamber.

[0026] Furthermore, 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 at any height range from the middle of the outer side of the housing to the outer side of the sludge outlet via the pipe fixing device.

[0027] Furthermore, the wastewater treatment system also includes:

[0028] An anaerobic / aerobic switching zone, located at the rear end of the anaerobic zone, has a volume of 25% to 50% of the anaerobic zone; and

[0029] The aerobic / hypoxic switching zone is located at the rear of the aerobic zone and has a volume of 25-50% of that of the aerobic zone.

[0030] The AOA wastewater treatment process based on a circulating clarifier of the present invention has the following advantages:

[0031] (1) This invention develops a circulating clarifier for use in anoxic zones, which integrates reaction and precipitation in anoxic zones. This achieves an effective combination of the circulating clarifier and the AOA process. Compared with the traditional AOA process, the secondary sedimentation tank is eliminated, saving at least 30% of the floor space.

[0032] (2) This invention achieves three effects by installing an auxiliary circulation pipe on the outside of the circulation clarifier in the anoxic zone and adjusting its gas flow rate and height according to the actual effluent conditions during operation: First, it provides the stirring effect of air lifting circulation, which promotes the full mixing of sewage and sludge in the anoxic zone and improves the mass transfer efficiency of biochemical reaction; Second, it provides efficient circulation power, which can enhance the sludge-water separation effect and avoid the phenomenon of sludge running out of effluent due to poor circulation; Finally, it provides effective disturbance power, which promotes the stripping of nitrogen during the anoxic denitrification reaction, improves the sludge settling performance in the anoxic zone, reduces the phenomenon of sludge floating and sludge running out of effluent caused by nitrogen entrainment in the traditional AOA process, and ultimately improves the effluent effect.

[0033] (3) This invention achieves two effects by installing a specially selected stirring device in the lower part 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 and enhances the efficiency of biochemical reaction; on the other hand, it achieves a higher sludge concentration (return sludge concentration) in the lower part of the anoxic zone than 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 circulating clarifier, enhances the solid-liquid separation effect of the circulating clarifier, and further optimizes the effluent quality.

[0034] (4) By adding anaerobic / aerobic switching zone and aerobic / anoxic switching zone, the present invention can flexibly adjust the state of each functional zone according to the influent water quality and quantity, so that the system can adapt to various water quality and quantity fluctuations and ensure the stability of the effluent.

[0035] Compared to traditional AOA systems, this invention, while reducing floor space, specifically improves sludge settling performance in anoxic zones through auxiliary circulating nitrogen stripping and sludge concentration stratification, thereby reducing sludge solids load and enhancing sludge-water separation. This results in a stable effluent suspended solids concentration at a low level. Furthermore, sludge concentration stratification increases the return sludge concentration, enhancing wastewater treatment efficiency and reducing energy consumption during the treatment process. Attached Figure Description

[0036] Figure 1 A flowchart of an AOA wastewater treatment process based on a circulating clarifier according to a first embodiment of the present invention;

[0037] Figure 2 A flowchart of an AOA wastewater treatment process based on a circulating clarifier according to a second embodiment of the present invention;

[0038] Figure 3 This is a schematic diagram of an AOA wastewater treatment system based on a circulating clarifier according to the present invention.

[0039] Figure 4 This is a schematic diagram of the circulating clarifier according to the present invention.

[0040] Diagram labels: 1-Anaerobic zone; 2-Aerobic zone; 3-Anoxic zone; 4-Inlet pipe; 41-Inlet pump; 42-Inlet flow control valve; 5-Outlet pipe; 6-First sludge return pipe; 7-Second sludge return pipe; 8-Aeration assembly; 81-Second air inlet pipe; 82-Aeration disc; 83-Air supply system; 9-Mixing equipment; 10-Mixing device; 11-Circulating clarifier; 111-Shell; 1111-Side plate; 1112-Bottom plate; 1113-Vertical plate; 112-Settling chamber; 113-Flow guide channel; 114-Overflow weir; 115-Auxiliary circulating assembly; 1151-First air inlet pipe; 1152-Auxiliary circulating pipe; 1153-Pipe fixing device; 116-Cover plate; 117-Sludge outlet. Detailed Implementation

[0041] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. The principles and features of the present invention are described below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The embodiments given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0042] Example 1

[0043] The first aspect of the present invention provides an AOA wastewater treatment process based on a circulating clarifier, such as... Figure 1 As shown, the wastewater treatment process of the present invention includes the following steps:

[0044] Step S1: Sequentially set up an anaerobic zone, an aerobic zone, and an anoxic zone, and inoculate sludge into each zone. At least one circulating clarifier is fixedly installed on the upper part of the anoxic zone, with an auxiliary circulating component on its outer side. Specifically, one or more tanks can be set up for each of the anaerobic, aerobic, and anoxic zones; the specific configuration can be determined based on site conditions, and this invention does not impose any particular limitation. In some embodiments, the initial sludge inoculation concentration in the above three zones can be, for example, 3 g / L to 7 g / L.

[0045] The circulating clarifier, which is fixedly installed at the top of the anoxic zone, can be installed by means of a support frame extending from the bottom and / or the side, or by a metal frame suspended from above, as long as the stability of the circulating clarifier can be ensured.

[0046] Step S2: The wastewater to be treated is passed sequentially through an anaerobic zone and an aerobic zone to form a sludge-water mixture. Further, step S2 may also include:

[0047] Step S2-1: The wastewater to be treated is introduced into the anaerobic zone and mixed with the sludge returned from the anoxic zone to form a mixture of wastewater and sludge. The wastewater to be treated enters the anaerobic zone through the inlet pipe. The anaerobic zone mainly involves anaerobic phosphorus release and organic matter removal. Polyphosphate-accumulating bacteria utilize the organic matter in the wastewater as an internal carbon source, while polyphosphate-accumulating bacteria simultaneously release phosphates. In some embodiments, the dissolved oxygen concentration should be controlled below 0.2 mg / L during operation in the anaerobic zone.

[0048] Step S2-2: The mixture of wastewater and sludge formed in the anaerobic zone is introduced into the aerobic zone. The mixture reacts with oxygen to form a sludge-water mixture. The effluent from the anaerobic zone (i.e., the mixture of wastewater and sludge) enters the aerobic zone, where, under aeration, the wastewater and sludge fully mix with oxygen. The aerobic zone primarily involves aerobic nitrification and aerobic phosphorus uptake. Nitrifying bacteria convert ammonia nitrogen into nitrate and nitrite nitrogen, while polyphosphate-accumulating bacteria utilize their internal carbon sources to absorb extracellular phosphate, thus removing phosphorus. During operation in the aerobic zone, the dissolved oxygen concentration is controlled between 0.5-4 mg / L by adjusting the aeration intensity. This ensures effective nitrification while avoiding excessive aeration that would consume internal carbon sources and waste energy.

[0049] Step S3: The mud-water mixture enters the anoxic zone, where the following process is carried out:

[0050] Step S3-1: The auxiliary circulation component generates an air-lift effect on both sides of the circulation clarifier in the upper part of the anoxic zone, thereby driving the mud-water mixture to form a circulation, thus promoting biochemical reaction and mud-water separation, and achieving nitrogen stripping effect through the air-lift effect; a stirring effect is generated in 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, where mud-water separation occurs, the supernatant after separation is discharged, and the separated sludge falls back to the lower part of the anoxic zone.

[0051] In step S3 above, the effluent from the aerobic zone (i.e., the sludge-water mixture) enters the anoxic zone, where biochemical reactions occur in the upper and lower parts of the anoxic zone respectively. An auxiliary circulation component is provided on the outside of the circulating clarifier. This component generates an airlift effect, which drives the sludge-water mixture to form a circulation, promoting mass transfer between sludge and wastewater, thereby promoting the biochemical reaction. Furthermore, the nitrogen gas produced during the biochemical reaction may carry a certain amount of sludge during its ascent, resulting in floating sludge on the water surface and affecting the effluent quality. This invention achieves nitrogen stripping through the aforementioned airlift effect, thereby preventing excessive sludge entrainment during nitrogen ascent and achieving nitrogen stripping while promoting the biochemical reaction.

[0052] Furthermore, in some embodiments, the circulation effect generated by the airlift in the upper part of the anoxic zone can be controlled by adjusting the gas flow rate of the auxiliary circulation component, i.e., the airlift circulation flow rate. The gas flow rate of the auxiliary circulation component is set at 20~80m³ / h. 3 / h; and / or in some alternative embodiments, the circulation effect generated by the airlift action is controlled by adjusting the installation height of the auxiliary circulation assembly, the adjustable range of which is set between the middle position and the bottom position of the outer side of the circulation clarifier.

[0053] The height of the auxiliary circulation component is set between the middle position on the outer side of the circulation clarifier and the bottom position of the circulation clarifier. This effectively controls the air-lift circulation flow rate, preventing excessive circulation that would cause excessive sludge from the bottom to rise to the upper part of the anoxic zone. It ensures that the sludge in the anoxic zone gradually decreases vertically from bottom to top, thus making the average sludge concentration in the lower part of the anoxic zone higher than that in the upper part. In some preferred embodiments, the height of the auxiliary circulation component can be automatically adjusted, for example, based on changes in air-lift circulation flow rate or sludge concentration.

[0054] Therefore, the circulation generated by the airlift not only promotes the thorough mixing of sludge and wastewater on both sides of the circulating clarifier, thus facilitating the biochemical reaction, but also allows the reacted wastewater and sludge to enter the interior of the circulating clarifier. The circulation generated by the airlift further promotes the separation of mud and water inside the circulating clarifier, promotes sludge settling, and also promotes nitrogen stripping, preventing sludge from being carried upwards by nitrogen during its ascent, which would result in a large amount of floating sludge on the surface of the circulating clarifier. This achieves multiple benefits.

[0055] A stirring device is installed at the bottom of the anoxic zone. By controlling the stirring rate of the stirring device, the stirring effect is limited to the bottom of the anoxic zone. This ensures that the sludge in the bottom of the anoxic zone is mixed evenly while avoiding excessive influence of the stirring effect on the circulation in the top of the anoxic zone (i.e., both sides of the circulating clarifier). This ensures that the sludge in the anoxic zone gradually decreases from bottom to top in the vertical direction, so that the average concentration of the sludge in the bottom of the anoxic zone is higher than that in the top of the anoxic zone.

[0056] Furthermore, circulating clarifiers typically have an overflow weir at the top, which connects to the drainage system. The separated supernatant flows upward and is discharged from the system via the overflow weir. The lower part of the circulating clarifier is usually open, allowing it to connect with the lower part of the anoxic zone. The sludge after sludge-water separation falls from the opening of the circulating clarifier into the lower part of the anoxic zone.

[0057] Because of the aforementioned auxiliary circulation components and stirring device, the airlift circulation generated by the auxiliary circulation components mainly acts on the upper region of the anoxic zone, while the mixing generated by the stirring device mainly acts on the lower region of the anoxic zone. This ensures that the sludge in the anoxic zone can be mixed from top to bottom while exhibiting a gradual decrease in concentration from bottom to top vertically, resulting in a higher average sludge concentration in the lower part of the anoxic zone compared to the upper part. Under these conditions, the sludge concentration in the upper part of the anoxic zone is 3 g / L to 6 g / L, and the sludge concentration in the lower part of the anoxic zone is 5 g / L to 10 g / L.

[0058] Step S4: The sludge from the lower part of the anoxic zone is returned to the anaerobic zone. In the lower part of the anoxic zone, the falling sludge and the original sewage sludge from the anoxic tank are fully mixed under the stirring action, ensuring the mass transfer efficiency of the biochemical reaction between sewage and microorganisms. Then, the high-concentration sludge is returned to the anaerobic zone through a return device, mixing with the sludge in the anaerobic zone for further reaction. The high sludge concentration in the lower part of the anoxic zone in this invention increases the sludge concentration in both the anaerobic and aerobic zones, thereby improving the sewage treatment effect. Simultaneously, the lower upper sludge concentration reduces the solid load on the upper circulating clarifier, enhancing the solid-liquid separation effect and further optimizing the effluent quality. The sludge from the return zone in the lower part of the anoxic zone is returned to the anaerobic zone. To ensure sufficient sludge concentration in the anaerobic zone, the return ratio can be controlled between 50% and 300% (the sludge return ratio is equal to the ratio of the sludge return flow rate to the influent flow rate). Furthermore, it should be noted that after the process of the present invention is started, the reflux process is also started simultaneously. When the wastewater to be treated enters the anaerobic zone, it will not only mix with the original sludge in the anaerobic zone, but also with the sludge refluxed from the anoxic zone.

[0059] Furthermore, it should be noted that the biochemical reactions occurring on both sides of the circulating clarifier and in the lower part of the anoxic zone are essentially the same: both involve the anoxic denitrification and denitrification phosphorus removal of the mud-water mixture within the anoxic zone. During this process, denitrifying polysaccharide bacteria and denitrifying phosphorus-accumulating bacteria utilize their internal carbon sources to convert nitrate or nitrite nitrogen into nitrogen gas, while simultaneously undergoing partial phosphorus uptake, achieving deep removal of nitrogen and phosphorus. During operation in the anoxic zone, the dissolved oxygen concentration is controlled below 0.2 mg / L.

[0060] Furthermore, in some embodiments of the present invention, step S4 further includes returning the sludge from the lower part 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 lower part of the anoxic zone enter the front end of the anoxic zone together, and the reactions of steps S3 and S4 continue to occur in the anoxic zone.

[0061] The AOA wastewater treatment process based on a circulating clarifier provided by this invention controls the circulation effect generated by airlift by adjusting the gas flow rate and height of the auxiliary circulating components on both sides of the circulating clarifier in the upper part of the anoxic zone during operation. Specifically, the airlift circulation flow rate ensures effective airlift circulation stirring, allowing sludge and wastewater to fully contact and undergo mass transfer, thus promoting biochemical reactions. Furthermore, it provides efficient circulation power, enabling the sludge-water mixture to fully enter the circulating clarifier for sludge-water separation. The separated sludge flows smoothly out from the bottom, avoiding sludge runoff in the effluent due to poor circulation. Finally, aeration increases external disturbance to the circulating clarifier, allowing nitrogen gas produced by denitrification to be released and blown out, improving the settling performance of sludge in the anoxic zone and reducing floating sludge in the effluent from the circulating clarifier – achieving three benefits in one step.

[0062] Furthermore, by adjusting the stirring intensity of the agitator according to actual conditions, and controlling the stirring range to be in the lower part of the anoxic zone, the sludge concentration in the lower part of the anoxic zone is made higher than that in the upper part, 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 overall sludge concentration in all functional areas of the system, which is beneficial to enhancing the removal efficiency of process pollutants. On the other hand, the lower sludge concentration in the upper part of the anoxic zone reduces the solids load of the circulating clarifier, which is beneficial to improving sedimentation efficiency and reducing effluent sludge problems. In summary, by comprehensively adjusting the circulation flow rate of the auxiliary circulation component of the circulating clarifier and / or the stirring intensity in the lower part of the anoxic zone, the sludge settling performance can be improved and the sludge concentration can be stratified, ultimately enhancing the system's effluent quality.

[0063] Example 2

[0064] See Figure 2The difference between this wastewater treatment process and that of Example 1 is that, in this example, an anaerobic / aerobic switching zone is set between the anaerobic and aerobic zones, and / or an aerobic / anoxic switching zone can be set between the aerobic and anoxic zones 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.

[0065] It should be noted that in the wastewater treatment process of this embodiment, the anaerobic / aerobic switching zone is allowed to flexibly switch between anaerobic and aerobic states, adjusting the optimal anaerobic hydraulic retention time to ensure effective storage of internal carbon sources. The aerobic / anoxic switching zone is also allowed to flexibly switch between aerobic and anoxic states, adjusting the optimal aerobic hydraulic retention time to avoid insufficient aerobic nitrification or excessive aeration consuming internal carbon sources.

[0066] Example 3

[0067] According to a second aspect of the present invention, an AOA wastewater treatment system based on a circulating clarifier is provided, see [link to relevant documentation]. Figure 3 and Figure 4 The wastewater treatment system sequentially includes an anaerobic zone 1, an aerobic zone 2, and an anoxic zone 3. Each of these three zones can have at least one tank. At least one circulating clarifier 11 is fixedly installed on the upper part of the anoxic zone 3. This circulating clarifier 11 can typically be fixed using methods such as suspension or support; this is not particularly limited in this invention. For example, the at least one circulating clarifier can be arranged side-by-side above the anoxic zone, or symmetrically arranged above the anoxic zone; the specific arrangement is not particularly limited in this application. An auxiliary circulating assembly 115 is provided on the outer side of the circulating clarifier 11. Furthermore, the wastewater treatment system of this invention can also be provided with an inlet pipe 4 and an outlet pipe 5, used for feeding water into the anaerobic zone 1 and discharging the supernatant separated by the circulating clarifier 11 in the upper part of the anoxic zone 3, respectively. Further, a stirring device 10 and a reflux facility are provided at the lower part of the anoxic zone 3.

[0068] Specifically, the aforementioned stirring device 10 can be, for example, a stirrer, such as a submersible propeller or a submersible mixer, thereby limiting the stirring action to the lower part of the anoxic zone, preventing disturbance to the upper part of the anoxic zone (both sides of the circulating clarifier), and enabling the sludge in the lower part of the anoxic zone to remain in a homogeneous state.

[0069] The sludge return facility is used to return the sludge from the anoxic zone 3 to the anaerobic zone 1. Specifically, the sludge 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.

[0070] In some embodiments, the reflux facility of the present invention may further include a second sludge reflux pipeline 7 connecting the lower part of the anoxic zone and the front end of the anoxic zone 3, which is used to reflux the sludge below the anoxic zone 3 to the front end of the anoxic zone 3. Both the first sludge reflux pipeline 6 and the second sludge reflux pipeline 7 are equipped with a reflux flow control valve and a reflux pump. In some embodiments, only a reflux pump capable of adjusting the reflux flow rate may be required.

[0071] Further, the circulating clarifier 11 of the present invention includes: a shell 111, a settling chamber 112, and a flow guiding channel 113. An auxiliary circulating assembly 115 is installed on the outer side of the shell 111, and a sludge outlet 117 is formed below the shell 111. The sludge outlet 117 communicates with the lower part of the anoxic zone 3. The sludge after sludge-water separation in the circulating clarifier 11 falls back into the anoxic zone 3 below through the sludge outlet 117. The settling chamber 112 is formed inside the shell 111 and is surrounded by two vertical plates 1113 arranged along the front and rear direction of the shell 111 and the front and rear side plates 1111 of the shell 111. An overflow weir 114 is installed on the upper part of the settling chamber 112. The flow guiding channel 113 is formed between the shell 111 and the settling chamber 112.

[0072] Specifically, when the sludge-water mixture from the aerobic zone 2 enters the anoxic zone 3, due to the auxiliary circulation component 115 installed on the outside of the circulating clarifier 11, the sludge-water mixture generates a circulation effect under the airlift action of the auxiliary circulation component 115, resulting in a circulating biochemical reaction outside the circulating clarifier 11. Simultaneously, due to this airlift action, the sludge-water mixture enters the circulating clarifier 11 and enters the settling chamber 112 through the guide channel 113 of the circulating clarifier 11. In the settling chamber 112, the sludge-water mixture undergoes sludge-water separation. The less dense supernatant flows upward and is discharged outside the system through the overflow weir 114 outlet. In some embodiments, the wastewater treatment system is equipped with an effluent pipe 5 connected to the overflow weir 114 outlet, thereby discharging the supernatant through the overflow weir 114. The denser sludge flows downward and returns to the lower part of the anoxic zone 3 through the sludge outlet 117 at the bottom of the circulating clarifier 11. In the lower part of the anoxic zone 3, wastewater and sludge are thoroughly mixed under stirring to ensure efficient mass transfer in the biochemical reactions between wastewater and microorganisms. Subsequently, the sludge is returned to the front end of anaerobic zone 1 and anoxic zone 3 via the first and second sludge return pipes, respectively.

[0073] Therefore, this invention integrates the circulating clarifier 11 into the anoxic zone 3 of the AOA wastewater treatment system, eliminating the need for a separate secondary sedimentation tank, reducing the system's footprint, and decreasing energy consumption during the treatment process. Simultaneously, it improves wastewater treatment efficiency and reduces sludge runoff in the effluent.

[0074] 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 fixing device 1153. The auxiliary circulation pipe 1152 is installed to the outside of the housing 111 of the circulation clarifier 11 via the pipe fixing device 1153. The first air inlet pipe 1151 is connected to 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 is not particularly limited in the present invention. A gas flow regulating valve is provided on the first air inlet pipe 1151 to regulate the air inlet flow rate, thereby controlling the auxiliary circulation flow rate.

[0075] In some embodiments of the present invention, the auxiliary circulation pipe 1152 of the present invention can be installed by the pipe fixing device 1153 to any height range from the middle of the outer side of the housing 111 of the circulation clarifier 11 to the outer side of the sludge outlet 117, such as... Figure 4 As shown. The pipe fixing device 1153 can be, for example, a fixing device with a fixing rod provided with pipe clamps, U-shaped clamps and U-shaped clamp baffles, etc. The fixing device is installed on the outside of the circulating clarifier. The first air inlet pipe 1151 is connected to the fixing device through pipe clamps, and the auxiliary circulating pipe 1152 is connected to the fixing device through U-shaped clamps and U-shaped clamp baffles. The pipe fixing device 1153 of the present invention is not particularly limited.

[0076] Therefore, the aforementioned auxiliary circulation device can, on the one hand, ensure an effective airlift circulation flow rate, allowing the mud-water mixture to enter the circulation clarifier 11; on the other hand, by increasing external disturbances to the circulation clarifier 11 through aeration and oxygenation, the nitrogen gas produced by the denitrification reaction in its anoxic zone 3 can be released and blown out, improving the settling performance of the sludge in the anoxic zone 3 and reducing the occurrence of floating sludge in the effluent of the circulation clarifier 11.

[0077] In other embodiments of the present invention, the housing 111 of the circulating clarifier 11 may further include the following structure: a side plate 1111 and a bottom plate 1112, such as... Figure 4 As shown, the side plates 1111 are connected end to end to form a through-body structure, that is, the side plates include front and rear side plates and left and right side plates. The bottom plate 1112 extends downward and inward from the lower edge of the side plates 1111, thus enclosing a conical structure. The lower edge of the bottom plate 1112, which extends downward and inward, is not closed, thus reserving a sludge outlet 117. In other words, the open opening at the lower edge forms the aforementioned sludge outlet 117. In some embodiments, the side plates 1111 and the bottom plate 1112 of the circulating clarifier 11 can be integrally formed, or they can be connected by welding, as long as the connection can be sealed.

[0078] In this case, the auxiliary circulation pipe 1152 can be installed at any height between the junction of the side plate 1111 and the base plate 1112 and the outer bottom edge of the base plate 1112 of the circulation clarifier 11. Preferably, the auxiliary circulation pipe 1152 can be installed at any height between the junction of the left and right side plates 1111 and the base plate 1112 and the outer bottom edge of the base plate 1112 of the circulation clarifier 11.

[0079] In some embodiments of the present invention, the auxiliary circulation assembly can be configured as a lifting mode (not shown in the figures). In this case, the pipeline fixing device may include a lifting frame and a fixing member. The lifting frame can be installed vertically along the bottom plate of the circulation clarifier, and the fixing member is used to connect the lifting frame and 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, a circulation flow rate monitor can be set up to automatically control the height of the auxiliary circulation assembly according to the circulation flow rate. A transmission device can be set up to achieve automatic adjustment.

[0080] Further, see Figure 3 A settling chamber 112 is formed inside the shell 111, and is surrounded by two vertical plates 1113 arranged along the front-rear direction of the shell 11 and side plates 1111 at the front and rear of the shell. The upper edge of the vertical plate 1113 is higher than the height of the upper edge of the side plate 1111 relative to the bottom of the pool, and the lower edge of the vertical plate 1113 is also higher than the height of the lower edge of the side plate 1111 relative to the bottom of the pool. Figure 3 As shown, there is a certain distance between the two vertical plates 1113 and the side plates 1111 on both sides, thus forming a channel between the side plates 1111 and the vertical plates, which is the flow guide channel 113. That is to say, the flow guide channel 113 is formed between the shell 111 and the settling chamber 112. When the mud-water mixture enters the circulating clarifier 11 from the anoxic tank, it will not directly enter the settling chamber 112, but will enter the settling chamber 112 through the flow guide channel 113.

[0081] 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 may also be provided with a cover plate 116, which is installed on the top of the settling chamber 112. For example, it may be a push-pull type or a sliding type, that is, it can be easy to open. The specific form is not particularly limited by the present invention.

[0082] Furthermore, to flexibly adjust the state of each functional zone, the wastewater 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 anaerobic zone 1, and its volume is 25% to 50% of that of anaerobic zone 1. The aerobic / anoxic switching zone is located at the rear end of aerobic zone 2, and its volume is 25% to 50% of that of aerobic zone 2. By setting up the anaerobic / aerobic switching zone and the aerobic / anoxic switching zone, the state of each functional zone can be adjusted according to the influent water quality and quantity, thereby enabling the system to adapt to various fluctuations in water quality and quantity and ensuring the stability of the effluent.

[0083] Furthermore, to achieve the reaction in each zone, stirring devices 9 are installed in the anaerobic zone 1, the anaerobic / aerobic switching zone, and the aerobic / anoxic switching zone of the present invention. These stirring devices 9 can be, for example, conventional flow promoters. It should be noted that the stirring height range of the stirrer in the anoxic zone 3 is smaller than the stirring height range of the stirrers in the anaerobic zone 1, the anaerobic / aerobic switching zone, and the aerobic / anoxic switching zone. Aeration components 8 are installed in the aerobic zone 2, the anaerobic / aerobic switching zone, and the aerobic / anoxic switching zone of the present invention. Specifically, the aeration component 8 includes a second air inlet pipe 81, an aeration disc 82, and an air supply system 83. The second air inlet pipe 81 is connected to the aeration disc 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 component 8 and the air supply device in the auxiliary circulation component 115 can be the same or separate, and the present invention does not impose any particular limitation on this. Furthermore, the air supply system and air supply device can be, for example, an air delivery device such as a blower.

[0084] Furthermore, in some embodiments, the anaerobic zone 1 of the present invention is connected to the inlet pipe 4, and the inlet pipe 4 further includes an inlet pump 41 and an inlet flow control valve 42. The inlet pump 41 can pump the sewage to be treated into the anaerobic zone 1, and the inlet flow control valve 42 can control the inlet water volume.

[0085] In addition, a sludge concentration sensor may be provided at the lower part of the anoxic zone 3 of the present invention to sense the sludge concentration, thereby changing the auxiliary circulation flow rate of the auxiliary circulation component 115 and controlling the stirring degree of the stirring device 10 according to the sludge concentration.

[0086] Furthermore, in some embodiments of the present invention, the wastewater treatment system of the present invention may be equipped with a controller, and sensor devices such as sludge sensors and wastewater flow sensors, which are wirelessly connected to the controller, are installed in each zone. At the same time, the aforementioned solenoid valves and other devices can also be wirelessly connected to the controller, thereby regulating the operating status of each zone.

[0087] Therefore, the wastewater treatment system of this invention effectively combines the circulating clarifier 11 with the AOA process, eliminating the need for a separate secondary sedimentation tank, saving floor space and reducing energy consumption during treatment. The auxiliary circulating component 115, with its flow rate adjusted according to the actual effluent conditions, promotes the removal of nitrogen generated during the anoxic denitrification reaction, improves the sludge settling performance in the anoxic zone 3, reduces sludge floating caused by nitrogen entrainment, and minimizes sludge runoff in the effluent, thus improving effluent quality. By controlling 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 that in the upper part, achieving a sludge concentration difference between the upper and lower parts of the anoxic zone. The higher return sludge concentration (lower sludge concentration in the anoxic zone) increases the sludge concentration in both the anaerobic zone 1 and the aerobic zone 2, thereby improving wastewater treatment efficiency. Simultaneously, it reduces the upper sludge concentration, thus lowering the solids load on the circulating clarifier 11, enhancing the solid-liquid separation effect within the circulating clarifier 11, and further optimizing the effluent quality. Setting up anaerobic / aerobic switching zones and aerobic / anoxic switching zones allows for the adjustment of the state of each functional zone according to water quality and quantity, thus enabling application to various fluctuations in water quality and quantity and ensuring the stability of the effluent.

[0088] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions 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 suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

Claims

1. An AOA wastewater treatment process based on a circulating clarifier, characterized in that, The wastewater treatment process includes the following steps: Step S1: Sequentially set up an anaerobic zone, an aerobic zone, and an anoxic zone, and inoculate sludge into the anaerobic zone, the aerobic zone, and the 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; wherein... The circulating clarifier includes: The shell has an auxiliary circulation assembly installed on its outer side, and a sludge outlet is formed at the bottom of the shell, which is connected to the lower part of the anoxic zone. A settling chamber, formed inside the shell, is surrounded by two vertical plates arranged along the front-rear direction of the shell and the front and rear side plates of the shell. An overflow weir is installed at the upper part of the settling chamber; and A flow channel is formed between the housing and the settling chamber, and wherein... 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 at any height range from the middle of the outer side of the housing to the outer side of the sludge outlet via the pipe fixing device. Step S2: The wastewater to be treated is passed sequentially through the anaerobic zone and the aerobic zone to form a mud-water mixture; Step S3: The mud-water mixture enters the anoxic zone and undergoes the following process in the anoxic zone: Step S3-1: The auxiliary circulation component generates an air-lift effect on both sides of the circulation clarifier in the upper part of the anoxic zone, thereby driving the mud-water mixture to form a circulation, thus promoting biochemical reaction and mud-water separation, and achieving nitrogen stripping effect through the air-lift effect; a stirring effect is generated in 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 circulating clarifier, where mud-water separation occurs. The supernatant after separation is discharged, and the separated sludge falls back to the lower part of the anoxic zone. Step S4: Return the sludge from the lower part of the anoxic zone to the anaerobic zone; The circulation effect generated by the airlift action is controlled by adjusting the gas flow rate of the auxiliary circulation component, with the gas flow rate set between 20 and 80 m³. 3 / h; and / or The circulation effect generated by the air lifting action is controlled by adjusting the installation height of the auxiliary circulation component. The installation height of the auxiliary circulation component is set between the middle and bottom positions on the outer side of the circulation clarifier. A stirring device is provided at the lower part of the anoxic zone. The stirring range is controlled at the lower part of the anoxic zone by controlling the stirring rate of the stirring device.

2. The AOA wastewater treatment process based on a circulating clarifier according to claim 1, characterized in that, The sludge concentration in the upper and lower parts of the anoxic zone is stratified, with the sludge concentration in the upper part of the anoxic zone being 3 g / L to 6 g / L and the sludge concentration in the lower part of the anoxic zone being 5 g / L to 10 g / L.

3. The AOA wastewater treatment process based on a circulating 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%~300%.

4. The AOA wastewater treatment process based on a circulating clarifier according to claim 1, characterized in that, Step S4 further includes returning the sludge from the lower part of the anoxic zone to the front of the anoxic zone.

5. The AOA wastewater treatment process based on a circulating clarifier according to claim 1, characterized in that, Step S1 further includes: An anaerobic / aerobic switching zone is provided between the anaerobic zone and the aerobic zone; and / or An aerobic / hypoxic switching zone is set between the aerobic zone and the hypoxic zone.

6. An AOA wastewater treatment system based on a circulating clarifier, wherein the wastewater treatment system uses the AOA wastewater treatment process based on a circulating clarifier according to any one of claims 1 to 5 for wastewater treatment, characterized in that, The wastewater treatment system comprises, in sequence, an anaerobic zone, an aerobic zone, and an anoxic zone. The anoxic zone is characterized by having at least one circulating clarifier fixedly installed at its upper part, an auxiliary circulating component on the outer side of the circulating clarifier, and a stirring device and a reflux facility at its lower part.

7. The AOA wastewater treatment system based on a circulating clarifier according to claim 6, characterized in that, The wastewater treatment system also includes: An anaerobic / aerobic switching zone, located at the rear end of the anaerobic zone, has a volume of 25% to 50% of the anaerobic zone; and The aerobic / hypoxic switching zone is located at the rear of the aerobic zone and has a volume of 25-50% of that of the aerobic zone.

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