Powerless efficient energy-saving improved AO sewage treatment process

Abstract

An unpowered, efficient and energy-saving improved AO sewage treatment process relates to the technical field of sewage treatment, and comprises: a selection zone for directly receiving return sludge and return nitrification liquid; the pre-anoxic zone is used for directly receiving inlet water, returned sludge and returned nitrification liquid; the anoxic zone is used for carrying out denitrification reaction under an anoxic condition and directly receiving inlet water; the anaerobic zone is used for directly receiving inlet water, returned sludge and returned nitrification liquid; the low-oxygen zone is used for carrying out short-cut nitrification and denitrification reaction under a controlled anoxic condition; the aerobic zone is used for completing organic matter degradation, ammonia nitrogen nitration and excessive phosphorus uptake of phosphorus-accumulating bacteria; the settling zone is used for mud-water separation; wherein nitrification liquid backflow and sludge backflow among the areas are realized through an air stripping device which takes air as a power source. Based on an aeration system in the prior art, the air blower is used as a power source, so that the system energy consumption, the equipment investment and the operation and maintenance cost are remarkably reduced.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a non-powered, highly efficient, and energy-saving improved A²O wastewater treatment process. Background Technology

[0002] Effective removal of organic pollutants, nitrogen, and phosphorus from wastewater is a core issue that has long been a challenge for urban wastewater treatment plants and industrial wastewater treatment systems. Traditional activated sludge processes and their derivatives are widely used in various wastewater treatment projects due to their mature operation and broad applicability. Among them, the A²O (Anaerobic–Anoxic–Oxic) process (also known as the "AAO process") achieves simultaneous biological phosphorus and nitrogen removal by sequentially setting up anaerobic, anoxic, and aerobic zones within the same biological system, making it one of the most widely used nitrogen and phosphorus removal processes currently.

[0003] However, in actual engineering operations, the traditional A²O process and its improved forms still have many shortcomings.

[0004] First, the traditional A²O process typically relies on a variety of underwater mechanical power equipment, such as submersible mixers, submersible propellers, nitrification liquor return pumps, sludge return pumps, and sludge scrapers, to achieve mixing, propulsion, and return. This not only involves a large number of devices and complex structures, but also high energy consumption, high failure rate, and high maintenance and repair costs. In particular, when the system needs to be shut down for maintenance, it will have an adverse impact on the continuous and stable operation of the wastewater treatment system.

[0005] Secondly, in traditional A²O processes, nitrification liquor recirculation and sludge recirculation are mostly carried out using mechanical pumping. The recirculation ratio is limited by equipment capacity, making it difficult to achieve a high recirculation ratio. When the influent water quality fluctuates significantly or the shock load is high, the pollutant concentration gradient in the reaction tank is obvious. Microorganisms are easily inhibited by high concentrations of organic matter, ammonia nitrogen, or toxic and harmful substances, which leads to insufficient system resistance to shock loads and large fluctuations in nitrogen and phosphorus removal efficiency and effect.

[0006] Furthermore, in traditional A²O processes, the anoxic and anaerobic zones are easily affected by dissolved oxygen carried by the nitrified liquor returned from the aerobic zone, leading to the inhibition of anaerobic phosphorus release and anoxic denitrification reactions. To eliminate dissolved oxygen in the returned liquor, it is usually necessary to set up a large deoxygenation tank or rely on a long water retention time, further increasing the footprint and engineering investment of the wastewater treatment system.

[0007] Furthermore, with increasingly stringent wastewater treatment and discharge standards and a growing proportion of wastewater with low carbon sources (low C / N ratio), the traditional A²O process faces greater challenges in achieving deep total nitrogen removal. To ensure effective denitrification, external carbon sources are often required, leading to significantly higher operating costs and increased operational management complexity.

[0008] In summary, existing A²O and its improved processes still have significant shortcomings in terms of equipment integration, energy consumption, reflux methods, shock resistance, adaptability to low carbon sources, and operation at high sludge concentrations. There is an urgent need for an improved A²O wastewater treatment process and device that has a simpler structure, more stable operation, lower energy consumption, higher nitrogen and phosphorus removal efficiency, and is suitable for new construction and in-situ upgrading. Summary of the Invention

[0009] The purpose of this invention is to provide a non-powered, high-efficiency, energy-saving improved A²O wastewater treatment process. By setting a pre-anoxic zone at the front end of the biological system and adopting a non-traditional zone sequence arrangement of "pre-anoxic zone - anoxic zone - anaerobic zone", combined with a pneumatically driven airlift device, the system can reduce energy consumption and equipment complexity while improving nitrogen and phosphorus removal efficiency, carbon source utilization rate and system shock resistance.

[0010] To achieve the above-mentioned objectives, the present invention adopts the following technical solution.

[0011] A non-powered, high-efficiency, energy-saving modified A²O wastewater treatment device includes a selection zone, a pre-anoxic zone, an anoxic zone, an anaerobic zone, a hypoxic zone, an aerobic zone, and a sedimentation zone arranged sequentially, wherein:

[0012] The selection zone is used to directly receive the returned sludge and returned nitrified liquor, and to consume the dissolved oxygen entrained in the returned sludge or returned nitrified liquor.

[0013] The pre-anoxic zone is used to directly receive influent, return sludge and return nitrification liquid, and to carry out deoxygenation and pre-denitrification under anoxic conditions.

[0014] The anoxic zone is used to carry out denitrification under anoxic conditions and directly receives the influent.

[0015] The anaerobic zone is used to directly receive influent, returned sludge and returned nitrification liquid, and to carry out biological phosphorus release reaction under conditions without free oxygen.

[0016] The low-oxygen zone is used for short-cut nitrification and denitrification reactions under controlled anoxic conditions.

[0017] The aerobic zone is used to complete the degradation of organic matter, nitrification of ammonia nitrogen, and excessive phosphorus uptake by polyphosphate-accumulating bacteria.

[0018] The sedimentation zone is used for sludge-water separation and the sludge is returned to the selection zone, pre-anoxic zone and anaerobic zone by the output sludge.

[0019] The nitrification liquid recirculation and sludge recirculation between the various regions are both achieved through an air-powered airlift device.

[0020] As a preferred embodiment, the air-lift device includes:

[0021] An inverted cone is surrounded by a swirling air inlet pipe. The swirling air inlet pipe can inject airflow from the aeration line into the interior of the inverted cone along the tangential direction of the inner wall of the inverted cone, thereby forming a swirling flow inside the inverted cone. At the same time, the airflow is injected into the inverted cone at an upward angle, thereby causing the swirling flow to flow upward.

[0022] A conical cap, the large end of which is fixedly connected to the upper end of an inverted cone, has guide vanes evenly distributed along the circumference of the conical cap, and the conical cap is connected inside and outside at the guide vanes, so that the swirling flow inside the inverted cone can flow to the top of the conical cap under the guidance of the guide vanes.

[0023] The lower end of the drainage tube is fixedly connected to the center of the conical cap and communicates with the space below the conical cap. The upper end of the drainage tube extends laterally. The drainage tube includes a vertical section connected to the conical cap. A drainage air inlet pipe is provided on the side of the vertical section. The outlet end of the drainage air inlet pipe is inserted laterally into the vertical section of the drainage tube and bent upward.

[0024] As a preferred embodiment, the low-oxygen zone is equipped with an online dissolved oxygen monitoring device, which is linked to the blower for control. The low-oxygen zone can switch between three operating modes with different dissolved oxygen levels, namely, low-oxygen operation mode, anoxic operation mode, or aerobic operation mode, according to the influent water quality conditions.

[0025] As a preferred embodiment, the anoxic zone is set before the anaerobic zone, so that the nitrate nitrogen in the reflux nitrification liquid is preferentially removed by denitrification before entering the anaerobic zone, thereby avoiding the inhibition of the anaerobic phosphorus release process by nitrate nitrogen.

[0026] As a preferred embodiment, the air-lifting device is provided at the end of the aerobic zone to achieve cyclic dilution between the aerobic zone and the hypoxic zone.

[0027] As a preferred embodiment, no sludge scraper or sludge return pump is installed in the sedimentation zone, and the settled sludge is returned without power through the air-lift device.

[0028] The present invention also provides a wastewater treatment method based on the above-mentioned non-powered, high-efficiency, energy-saving improved A²O wastewater treatment device, comprising the following steps:

[0029] 1) The mixture of wastewater, returned nitrified liquid, and returned sludge enters the pre-anoxic zone for deoxygenation and pre-denitrification;

[0030] 2) The mixed liquor in the pre-anoxic zone enters the anoxic zone for denitrification and nitrogen removal;

[0031] 3) The mixed solution in the anoxic zone enters the anaerobic zone for anaerobic phosphorus release by polyphosphate-accumulating bacteria;

[0032] 4) The mixed liquor in the anoxic and anaerobic zones can be transferred into the low-oxygen zone by airlift and then flow into the aerobic zone to complete denitrification, phosphorus removal and organic matter degradation; at the same time, the mixed liquor in the aerobic zone can also be transferred into the low-oxygen zone by airlift to achieve cyclic dilution between the aerobic and low-oxygen zones.

[0033] 5) The mixed liquor in the aerobic zone enters the sedimentation zone for mud-water separation and the sludge is returned.

[0034] Compared with the prior art, the present invention has at least the following beneficial effects:

[0035] 1. An aeration system consisting of a blower, aeration pipeline, and aeration device is an essential component of existing wastewater treatment processes. Based on existing aeration systems, this invention uses a blower as a power source to eliminate (or partially eliminate) underwater mechanical equipment used in traditional technologies, such as submersible mixers, flow promoters, return pumps, and sludge scrapers, thereby significantly reducing system energy consumption, equipment investment, and operation and maintenance costs.

[0036] 2. By setting up a special air-lift device with both stirring and air-lifting functions, the integrated operation of aeration, mixing, flow propulsion and internal and external reflux is realized. The reflux ratio is large and the flow pattern is uniform, which effectively improves the efficiency of nitrogen and phosphorus removal reaction.

[0037] 3. By setting up a switchable low-oxygen zone, short-cut nitrification and denitrification can be achieved, maintaining high nitrogen removal efficiency under low carbon source conditions and reducing the amount of external carbon source added.

[0038] 4. The pre-anoxic zone set in this invention is a functional zone with short residence time, high reflux load, and mainly for denitrification and deoxygenation. Structurally, it is not a simple enlarged version of the deoxygenation tank in the traditional A²O process, but a front-end adjustment and buffer unit that works in coordination with the subsequent reaction zones.

[0039] By setting up a pre-anoxic zone and placing it before the anaerobic zone, nitrate nitrogen is fully removed before entering the anaerobic zone, preventing it from competing with polyphosphate-accumulating bacteria for carbon sources as an electron acceptor. This mechanistically ensures the completeness of the anaerobic phosphorus release reaction. Furthermore, high-quality influent carbon sources are preferentially used for denitrification in both the pre-anoxic and anoxic zones, improving the nitrogen removal efficiency per unit carbon source and significantly reducing the amount of external carbon source required.

[0040] 5. Through integrated structural design, the number of pools and floor space are reduced, making it suitable for in-situ upgrading, capacity expansion and energy-saving renovation of newly built sewage treatment plants and existing sewage treatment facilities. Attached Figure Description

[0041] Figure 1 This is a plan view of the wastewater treatment device described in this invention.

[0042] Figure 2Is with Figure 1 The corresponding wireframe diagram.

[0043] Figure 3 This is a schematic diagram of the air-lift device.

[0044] Figure 4 yes Figure 3 Arrangement diagram of the vortex inlet pipe around the inverted cone.

[0045] In the diagram, 1 is an inverted cone; 2 is a swirl inlet pipe; 3 is a conical cap; 4 is a guide vane; 5 is a drain pipe; and 6 is a drain inlet pipe. Detailed Implementation

[0046] The following section provides a further, complete, and detailed explanation of the specific implementation methods and working principles of the present invention, taking into account the specific structural composition of the device and the flow paths of sewage and sludge in each functional area.

[0047] I. Overall Structure and Flow Organization

[0048] like Figure 1 As shown in this embodiment, the non-powered, high-efficiency, energy-saving modified A²O wastewater treatment process adopts an integrated structure with a single tank and multiple functional zones. The tank is divided into a selection zone, a pre-anoxic zone, anoxic zone, anaerobic zone, hypoxic zone, aerobic zone, and sedimentation zone by partition walls.

[0049] Specifically, the functional areas are interconnected through common methods such as bottom connecting holes, lateral inlets, or overflow weirs, thus forming a continuous hydraulic flow. Bottom connecting holes, lateral inlets, and overflow weirs are all existing conventional technologies and will not be described in detail here.

[0050] like Figure 1 and 2 As shown, in this embodiment, wastewater flows sequentially through each functional zone in a predetermined direction under the impetus of gravity, airflow, and return liquid; sludge undergoes sludge-water separation in the sedimentation zone and is then returned to the front end of the system via an airlift device, realizing the recycling of sludge within the system. In the entire system, the main wastewater flow and the sludge return flow are coupled together and form a stable and continuous plug-circulation composite flow pattern through pneumatic drive.

[0051] II. Structure and Working Principle of the Selection Area

[0052] The selector zone, located at the very front of the unit, directly receives returned sludge and returned nitrified liquor, consuming the dissolved oxygen carried in the returned sludge or returned nitrified liquor to prevent dissolved oxygen from damaging the anaerobic environment. The selector zone minimizes the dissolved oxygen in its internal mixed liquor, allowing it to fully utilize the organic matter in the influent after mixing with it in the subsequent reaction zone, resulting in better anaerobic phosphorus release and anoxic denitrification, reducing the need for external carbon sources and saving operating costs.

[0053] The main substances present in the selector zone include: returned sludge, nitrified liquid produced during the biochemical reaction, and dissolved oxygen. Since the returned sludge and nitrified liquid inevitably carry a certain amount of dissolved oxygen, directly introducing them into the subsequent reaction zone would inhibit the subsequent reactions. Therefore, the primary function of the selector zone is to consume and dilute the dissolved oxygen carried in the returned liquid. Through thorough mixing of the returned sludge and the returned nitrified liquid, the dissolved oxygen in the nitrified liquid is rapidly reduced.

[0054] III. Structure and Working Principle of the Pre-Hypoxia Zone

[0055] The pre-anoxic zone is used to directly receive influent, returned sludge and returned nitrified liquid, and to carry out deoxygenation and pre-denitrification under anoxic conditions.

[0056] 1. Substances entering the pre-hypoxic zone include:

[0057] Soluble organic matter (COD, VFAs) in fresh influent;

[0058] Return sludge from the sedimentation zone;

[0059] Refluxed nitrified liquid from the low-oxygen zone, the aerobic zone, or the junction of the two;

[0060] A small amount of dissolved oxygen was carried along;

[0061] 2. Microbial composition:

[0062] Denitrifying bacteria and some facultative anaerobic microorganisms.

[0063] 3. The main reactions that occur

[0064] In environments with low dissolved oxygen:

[0065] Denitrifying bacteria preferentially consume dissolved oxygen;

[0066] The organic matter in the influent is used to reduce nitrate nitrogen and nitrite nitrogen into nitrogen gas.

[0067] It significantly reduces the NO3⁻ concentration and dissolved oxygen level in the mixture.

[0068] 4. The function of the pre-hypoxic zone:

[0069] 1) Consume the dissolved oxygen carried by the reflux to create a truly indeterminate anoxic / anaerobic environment, prevent the subsequent anaerobic phosphorus release reaction from being inhibited, and improve the stability and reliability of the operating environment in the subsequent anoxic and anaerobic zones.

[0070] 2) Pre-denitrification reduces the nitrate nitrogen concentration before entering the anoxic zone, thereby reducing the denitrification load in the anoxic zone and decreasing the system's dependence on external carbon sources.

[0071] 3) High-quality carbon sources should be prioritized for denitrification to improve carbon source utilization efficiency.

[0072] By placing the pre-anoxic zone at the front end of the influent, the high-quality organic matter in the influent is preferentially utilized by denitrifying bacteria, rather than being rapidly consumed by aerobic heterotrophic bacteria in the aerobic zone. This forms a "carbon source priority service for denitrification" allocation mechanism, which can effectively improve the denitrification efficiency corresponding to the removal of chemical oxygen demand (COD) and significantly reduce the amount of external carbon source added.

[0073] 4) Buffer water quality and quantity shocks to improve the system's shock resistance.

[0074] When the quality or quantity of the influent fluctuates, the nitrifying liquid returned to the pre-anoxic zone can dilute the influent, reduce the instantaneous concentration of organic matter, ammonia nitrogen and other substances, prevent the anoxic and anaerobic zones from being impacted, improve the stability of the microbial community, and extend the safe operating range of the system under high load.

[0075] 5) Effects on subsequent hypoxic and anaerobic zones:

[0076] First, it provides stable influent conditions with low dissolved oxygen and low nitrate nitrogen for the anoxic zone;

[0077] Second, it prevents nitrate nitrogen from entering the anaerobic zone and inhibiting phosphorus release by polyphosphate-accumulating bacteria;

[0078] Third, construct a truly anaerobic environment.

[0079] IV. Structure and Working Principle of the Hypoxic Zone

[0080] The anoxic zone is used to carry out denitrification under anoxic conditions and directly accepts the influent.

[0081] The anoxic zone is set after the pre-anoxic zone, and no aeration is carried out inside it either, with the dissolved oxygen concentration controlled below 0.5 mg / L.

[0082] In the anoxic zone, under conditions of no free oxygen but with combined oxygen, denitrifying bacteria utilize organic matter in the influent as electron donors and nitrate or nitrite nitrogen in the reflux nitrification solution as electron acceptors, reducing nitrate or nitrite nitrogen to nitrogen gas. When the carbon-to-nitrogen ratio in the influent is low, an external carbon source is added to provide electron donors for denitrification, further reducing total nitrogen.

[0083] The mixture in the anoxic zone is lifted to the front of the hypoxic zone (e.g., by airlift) Figure 1 As shown in the figure, the mixed liquor in the anoxic zone is subjected to an air-lift device to achieve the complete mixing effect required for anoxic denitrification.

[0084] In the anoxic zone, the main substances present in the nitrifying liquid include organic matter, nitrates or nitrites, activated sludge, and a small amount of dissolved oxygen. The dominant functional bacteria in this zone are denitrifying bacteria. Denitrifying bacteria use organic matter as an electron donor and nitrates or nitrites as electron acceptors, reducing them stepwise to nitrogen gas, which is then released into the water.

[0085] By refluxing nitrification liquid and sludge at the same point, the sludge concentration distribution in the anoxic zone is more uniform, and the contact between nitrate and organic matter is more sufficient. This avoids the problem of reduced denitrification efficiency caused by traditional partial reflux, thereby significantly improving the removal effect of total nitrogen.

[0086] V. Structure and Working Principle of the Anaerobic Zone

[0087] The anaerobic zone is used to directly receive influent, returned sludge, and returned nitrification liquid, and to carry out biological phosphorus release reactions under conditions without free oxygen.

[0088] In the absence of free oxygen and with low levels of combined oxygen, polyphosphate-accumulating bacteria in the sludge returned to the anaerobic zone utilize volatile fatty acids (VFAs) or other easily degradable organic matter in the influent to decompose polyphosphates and obtain energy. The phosphates are released into the water and are then excessively absorbed after entering the aerobic zone, thereby removing phosphates from the wastewater.

[0089] The sludge returned from the anaerobic zone is returned through the air-lift device in the sedimentation zone.

[0090] The anaerobic zone is located downstream of the anoxic zone. No air is introduced into the anaerobic zone, and no mechanical stirring devices are installed. Mixing within the anaerobic zone is mainly achieved by the propulsion of the upstream reflux liquid and the overall flow pattern formed by the airlift device.

[0091] Within the anaerobic zone, the nitrifying liquor contains virtually no free dissolved oxygen, and the concentration of combined oxygen is extremely low, creating a strictly anaerobic environment. At this stage, the dominant microbial community in the sludge is polyphosphate-accumulating bacteria (PAOs). Under anaerobic conditions, PAOs utilize readily degradable organic matter such as VFAs in the wastewater as a carbon source, obtaining energy by decomposing the polyphosphates stored within their cells, thereby releasing phosphates into the water as orthophosphates. This process facilitates the transfer of phosphorus from the sludge to the aqueous phase, creating conditions for excessive phosphorus uptake in the subsequent aerobic zone. Simultaneously, some denitrifying bacteria in the anaerobic zone perform preliminary denitrification of residual nitrates under low combined oxygen conditions, helping to reduce the nitrate nitrogen load within the system.

[0092] VI. Structure and Working Principle of the Hypoxic Zone

[0093] The low-oxygen zone is used for short-cut nitrification and denitrification reactions under controlled anoxic conditions.

[0094] In this embodiment, the low-oxygen zone refers to the reaction zone with dissolved oxygen <0.5 mg / L and redox potential around +100mV, where short-range nitrification and denitrification reactions mainly occur.

[0095] In this embodiment, the low-oxygen zone offers high flexibility. It can not only operate according to the designed low-oxygen zone mode, but also flexibly adjust to aerobic or anoxic operation based on the influent water quality. Furthermore, the duration of aerobic or anoxic operation can be automatically controlled, maximizing effluent water quality while minimizing power and chemical consumption, and enhancing the system's flexibility and stability. The main removal targets in this zone are organic matter, ammonia nitrogen, and total nitrogen. Continuous and stable operation is achieved through the linkage of the automatic control system with the dissolved oxygen meter and blower.

[0096] During operation in the low-oxygen zone, dissolved oxygen is precisely controlled within the range of 0.1–0.5 mg / L. Under these conditions, nitrifying and denitrifying bacteria coexist within the system, enabling short-cut nitrification and denitrification reactions. Specifically, ammonia nitrogen is preferentially oxidized to nitrite and then reduced to nitrogen gas by denitrifying bacteria within the same area. Compared to the traditional complete nitrification-denitrification pathway, this process significantly reduces oxygen and organic carbon requirements, making it particularly suitable for operating conditions with low influent carbon-to-nitrogen ratios.

[0097] VII. Structure and Working Principle of the Aerobic Zone

[0098] The aerobic zone is used to complete the degradation of organic matter, nitrification of ammonia nitrogen, and excessive phosphorus uptake by polyphosphate-accumulating bacteria.

[0099] The aerobic zone is located at the end of all reaction zones (before the sedimentation zone). Its main function is to thoroughly eliminate organic matter and ammonia nitrogen in the wastewater, reducing them to a minimum. It is also the primary area for polyphosphate-accumulating bacteria to carry out polyphosphate reactions, ensuring sufficient phosphorus uptake by the sludge. An airlift device is installed at the end of this zone; high-proportion circulating dilution achieves complete mixing between the aerobic and hypoxic zones, creating a long-term low-matter operating environment for the microorganisms in the aerobic system. This reduces the toxic and inhibitory effects of high-concentration pollutants on microorganisms, improving the biological system's resistance to shock loads and its removal efficiency.

[0100] The aerobic zone, located after the hypoxic zone, is the final enhanced treatment unit of the biochemical reaction system. Within the aerobic zone, oxygen is continuously supplied to the nitrifying liquid through aeration devices, maintaining dissolved oxygen levels within the range of 2–4 mg / L.

[0101] Within the aerobic zone, the dominant bacterial communities include nitrifying bacteria, heterotrophic bacteria, and polyphosphate-accumulating bacteria. Heterotrophic bacteria perform deep oxidation and decomposition of organic matter in wastewater; nitrifying bacteria further oxidize ammonia nitrogen into nitrates; and polyphosphate-accumulating bacteria, under sufficient dissolved oxygen conditions, excessively absorb phosphorus, reabsorbing the phosphorus released from the anaerobic zone and storing it within their cells as polyphosphates.

[0102] At the end of the aerobic zone, a large proportion of nitrified liquid is circulated back through an airlift device, creating a near-completely mixed composite flow between the aerobic and hypoxic zones. This reduces the adverse effects of localized high loads on microorganisms and improves the overall system's resistance to shocks.

[0103] VIII. Structure and Working Principle of the Sedimentation Zone

[0104] The sedimentation zone is used for sludge-water separation and to return sludge to the selection zone, pre-anoxic zone and anaerobic zone by outputting sludge.

[0105] The sedimentation zone is located at the end of the aerobic zone and can achieve sludge-water separation using a conventional inclined tube sedimentation structure. After entering the sedimentation zone, the flow velocity of the nitrified liquor decreases significantly, and the activated sludge slides down the surface of the inclined tube under gravity and accumulates at the bottom of the sedimentation zone.

[0106] The supernatant in the sedimentation zone is discharged through a water collection device as the final effluent; part of the settled sludge is discharged outside the system, while the other part of the settled sludge is returned to other reaction zones through an air-lift device under pneumatic drive, completing the closed-loop circulation of sludge within the system.

[0107] Through the synergistic effect of the above-mentioned functional zones, this invention achieves the efficient removal of organic matter, ammonia nitrogen, total nitrogen and total phosphorus from wastewater, ultimately achieving the goal of stable and compliant discharge.

[0108] IX. Working Principle of the Air Lifting Device

[0109] The air-lift device in this embodiment is a novel air-lift device with an innovative design. Unlike conventional air-lift devices in the prior art, the air-lift device in this embodiment has both stirring and air-lifting functions. When applied to various reaction zones, it can help achieve multiple functions such as aeration, mixing, flow propulsion, and internal and external reflux.

[0110] The air-lift device includes:

[0111] An inverted cone 1 is surrounded by swirling air inlet pipes 2. The swirling air inlet pipes 2 can inject airflow from the aeration pipeline into the interior of the inverted cone 1 along the tangential direction of the inner wall of the inverted cone 1, thereby forming a swirling flow inside the inverted cone 1. At the same time, the airflow is injected into the inverted cone 1 at an upward angle, thereby causing the swirling flow to flow upward. In this embodiment, there are three swirling air inlet pipes 2, which are evenly distributed along the circumference.

[0112] The conical cap 3 has its large end fixedly connected to the upper end of the inverted cone 1. Guide vanes 4 are evenly distributed along the circumference of the conical cap 3. The conical cap 3 is connected inside and outside at the guide vanes 4. The swirling flow inside the inverted cone 1 can flow to the top of the conical cap 3 under the guidance of the guide vanes 4.

[0113] The lower end of the drainage tube 5 is fixedly connected to the center of the conical cap 3 and communicates with the space below the conical cap 3. The upper end of the drainage tube 5 extends laterally. The drainage tube 5 includes a vertical section connected to the conical cap 3. A drainage air inlet pipe 6 is provided on the side of the vertical section. The outlet end of the drainage air inlet pipe 6 is inserted laterally into the vertical section of the drainage tube 5 and bent upward.

[0114] In use, the airflow from the swirl inlet pipe 2 enters the inverted cone 1, forming a gas-liquid mixed jet, which then forms an upward swirling flow within the inverted cone 1. The upward swirling flow passes through the gaps between the guide vanes 4 and, guided by the guide vanes 4, maintains its original rotation direction and flows upward toward the conical cap 3 (the tilt angle of the guide vanes 4 is consistent with the rotation direction of the swirling flow reaching the guide vanes 4), thereby allowing the swirling flow to continue to disperse within the region, achieving stirring throughout the entire region.

[0115] Some air bubbles trapped in the swirling flow within the inverted cone 1 enter the guide pipe 5 along with the liquid flow, achieving the air lifting function. Simultaneously, the guide air inlet pipe 6 blows air upwards within the guide pipe 5, significantly improving air lifting efficiency. By controlling the airflow (pressure, flow rate, air intake rhythm (e.g., intermittent air intake, large bubble air intake)) within the swirling air inlet pipe 2 and the guide air inlet pipe 6 respectively, the intensity and efficiency of stirring and air lifting can be precisely controlled.

[0116] To increase dissolved oxygen levels, the inverted cone 1 can be configured as a sandwich structure for aeration. Densely packed air holes are machined into the outer wall of the sandwich, and the sandwich is connected to the aeration pipeline to form a highly efficient oxygenation and aeration device.

[0117] In addition to the airlift device with aeration and stirring functions, this invention can also simultaneously employ conventional oxygenation and agitation aeration devices:

[0118] Oxygenation aeration aims to increase dissolved oxygen concentration, and conventional microporous aeration discs can be used as aeration devices.

[0119] Stirring aeration aims to stir the nitrified liquid. During aeration, conventional methods such as directional airflow guidance, air-water mixed jet aeration, intermittent air supply, large bubbles, and low air volume can be used to reduce the amount of oxygen dissolved in the nitrified liquid during the aeration process, so as to meet the requirements of low dissolved oxygen in areas such as selective zones, anoxic zones, anaerobic zones, and low-oxygen zones.

[0120] Although the stirring aeration in this invention can meet the requirements for oxygen deficiency in most working conditions, mechanical stirring mechanisms can still be partially used in working conditions with extremely high oxygen deficiency requirements to improve the adaptability of this invention to different working conditions.

[0121] The above embodiments are only used to illustrate the technical solutions of the present invention. Those skilled in the art can make various equivalent substitutions and improvements to the present invention without departing from the spirit and scope of protection of the present invention, and all such substitutions and improvements should fall within the scope of protection of the present invention.

Claims

1. A non-powered, high-efficiency, energy-saving improved A²O wastewater treatment device, characterized in that: This includes a selection zone, a pre-anoxic zone, anoxic zone, anaerobic zone, hypoxic zone, aerobic zone, and sedimentation zone, which are sequentially connected, wherein: The selection zone is used to directly receive the returned sludge and returned nitrified liquor, and to consume the dissolved oxygen entrained in the returned sludge or returned nitrified liquor. The pre-anoxic zone is used to directly receive influent, return sludge and return nitrification liquid, and to carry out deoxygenation and pre-denitrification under anoxic conditions. The anoxic zone is used to carry out denitrification under anoxic conditions and directly receives the influent. The anaerobic zone is used to directly receive influent, returned sludge and returned nitrification liquid, and to carry out biological phosphorus release reaction under conditions without free oxygen. The low-oxygen zone is used for short-cut nitrification and denitrification reactions under controlled anoxic conditions. The aerobic zone is used to complete the degradation of organic matter, nitrification of ammonia nitrogen, and excessive phosphorus uptake by polyphosphate-accumulating bacteria. The sedimentation zone is used for sludge-water separation and the sludge is returned to the selection zone, pre-anoxic zone and anaerobic zone by the output sludge. The nitrification liquid recirculation and sludge recirculation between the various regions are both achieved through an air-powered airlift device.

2. The non-powered, high-efficiency, energy-saving, improved A²O wastewater treatment device according to claim 1, characterized in that, The air-lift device includes: An inverted cone (1) is surrounded by a swirling air inlet pipe (2). The swirling air inlet pipe (2) can inject airflow from the aeration pipeline into the interior of the inverted cone (1) along the tangential direction of the inner wall of the inverted cone (1), thereby forming a swirling flow inside the inverted cone (1). At the same time, the airflow is injected into the inverted cone (1) at an upward angle, thereby causing the swirling flow to flow upward. Conical cap (3), the large end of conical cap (3) is fixedly connected to the upper end of inverted cone (1), and guide vanes (4) are evenly distributed along the circumference of conical cap (3). Conical cap (3) is connected inside and outside at guide vanes (4), and the swirling flow in inverted cone (1) can flow to the top of conical cap (3) under the guidance of guide vanes (4). The lower end of the drainage tube (5) is fixedly connected to the center of the conical cap (3) and communicates with the space below the conical cap (3). The upper end of the drainage tube (5) extends laterally. The drainage tube (5) includes a vertical section connected to the conical cap (3). A drainage inlet pipe (6) is provided on the side of the vertical section. The outlet end of the drainage inlet pipe (6) is inserted laterally into the vertical section of the drainage tube (5) and bent upward.

3. The non-powered, high-efficiency, energy-saving, improved A²O wastewater treatment device according to claim 1, characterized in that: The low-oxygen zone is equipped with an online dissolved oxygen monitoring device, which is linked to the blower for control. The low-oxygen zone can switch between three operating modes with different dissolved oxygen levels, namely low-oxygen operation mode, anoxic operation mode, or aerobic operation mode, depending on the influent water quality conditions.

4. The non-powered, high-efficiency, energy-saving, improved A²O wastewater treatment device according to claim 3, characterized in that: The anoxic zone is set before the anaerobic zone so that nitrate nitrogen in the reflux nitrification liquid is preferentially removed by denitrification before entering the anaerobic zone, thereby avoiding the inhibition of nitrate nitrogen on the anaerobic phosphorus release process.

5. The non-powered, high-efficiency, energy-saving, improved A²O wastewater treatment device according to claim 1, characterized in that: The air-lift device is installed at the end of the aerobic zone to achieve cyclic dilution between the aerobic zone and the hypoxic zone.

6. The non-powered, high-efficiency, energy-saving, improved A²O wastewater treatment device according to claim 1, characterized in that: No sludge scraper or sludge return pump is installed in the sedimentation zone; the settled sludge is returned without power through the air-lift device.

7. A method for treating wastewater using the non-powered, high-efficiency, energy-saving modified A²O wastewater treatment device according to any one of claims 1 to 6, characterized in that, Includes the following steps: 1) The mixture of wastewater, returned nitrified liquid, and returned sludge enters the pre-anoxic zone for deoxygenation and pre-denitrification; 2) The mixed liquor in the pre-anoxic zone enters the anoxic zone for denitrification and nitrogen removal; 3) The mixed solution in the anoxic zone enters the anaerobic zone for anaerobic phosphorus release by polyphosphate-accumulating bacteria; 4) The mixed liquor in the anoxic and anaerobic zones can be transferred into the low-oxygen zone by airlift and then flow into the aerobic zone to complete denitrification, phosphorus removal and organic matter degradation; at the same time, the mixed liquor in the aerobic zone can also be transferred into the low-oxygen zone by airlift to achieve cyclic dilution between the aerobic and low-oxygen zones. 5) The mixed liquor in the aerobic zone enters the sedimentation zone for mud-water separation and the sludge is returned.

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