Application of improved UCT phosphorus and nitrogen removal system with segmented water inlet and multi-stage A / O coupling

Abstract

The present invention provides a segmented water inlet multi-stage A / O coupled improved UCT phosphorus removal and nitrogen removal system and its application, which relates to the field of sewage treatment. It comprises an anaerobic zone, multi-stage A / O units and a secondary sedimentation tank arranged in sequence. Each A / O unit comprises an anoxic zone and an aerobic zone connected in series, and the aerobic zone of the last A / O unit is connected to the secondary sedimentation tank. The water inlet pipe of the anaerobic zone is connected to the water inlet main pipe, and the water outlet pipe of the anaerobic zone is respectively connected to the water inlet pipe of the anoxic zone of each A / O unit. The sewage to be treated first enters the anaerobic zone to release phosphorus, and then enters each anoxic zone in sections for denitrification, thereby improving the denitrification and phosphorus removal efficiency of the system. The residual sludge in the secondary sedimentation tank is returned to the anoxic zone of the first A / O unit through the sludge return pipe to first remove nitrate nitrogen, and then enters the anaerobic zone through the first internal return pipe connecting the anoxic zone of the first A / O unit and the anaerobic zone for anaerobic phosphorus release. Since there is no interference of nitrate nitrogen in the reflux liquid, the phosphorus removal effect of the system is further improved.

Description

Technical Field

[0001] The present invention relates to the field of sewage treatment, and in particular to a segmented water inlet multi-stage A / O coupling improved UCT phosphorus and nitrogen removal system and its application. Background Art

[0002] The segmented inlet multi-stage A / O process consists of multiple anoxic and aerobic zones connected in series, alternating in series. Wastewater enters each anoxic zone and is treated in sequence, ultimately achieving denitrification. This process, a post-denitrification process that requires no internal recirculation, features high denitrification efficiency, small tank volumes, high carbon source utilization, and low energy consumption. It has been increasingly used in engineering projects in recent years.

[0003] The segmented water inlet multi-stage A / O process has achieved positive results in practice. In recent years, many large domestic sewage treatment plants have adopted and borrowed the design ideas of this process to varying degrees. However, the traditional multi-stage A / O process still has some problems in its application, which are mainly reflected in the following aspects: First, the traditional multi-stage A / O process is mainly used for denitrification. In situations where denitrification and phosphorus removal are required, the traditional multi-stage AO process requires additional anaerobic zones to improve the phosphorus removal effect. At present, the anaerobic zone is generally set before or after the first anoxic zone. Although this setting improves the phosphorus removal effect of the traditional A / O process, practice has shown that it is still not as good as the traditional A 2 Secondly, because traditional multi-stage A / O processes generally do not have internal recirculation, according to traditional multi-stage A / O design theory, when the total nitrogen removal rate of sewage needs to be met, it is necessary to increase the number of stages to improve the total nitrogen removal rate of sewage. Increasing the number of stages increases the complexity of system operation, making it inconvenient to operate and apply. Moreover, increasing the number of stages does not continuously improve the removal rate, so it has poor adaptability to water quality. In actual design, there is often a certain amount of waste to meet the removal rate requirements.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a segmented water inlet multi-stage A / O coupled improved UCT phosphorus removal and nitrogen removal system and application, which can improve the phosphorus removal effect and total nitrogen removal rate of the traditional multi-stage A / O process.

[0006] The embodiments of the present invention are implemented in the following ways:

[0007] In a first aspect, the present invention provides a segmented water inlet multi-stage A / O coupled improved UCT phosphorus and nitrogen removal system, comprising an anaerobic zone, multi-stage A / O units and a secondary sedimentation tank arranged in sequence.

[0008] Each A / O unit consists of anoxic and aerobic zones connected in series. Therefore, when multiple A / O units are combined, an alternating structure of anoxic and aerobic zones is formed. The aerobic zone of the last A / O unit is connected to the secondary sedimentation tank.

[0009] The anaerobic zone's inlet pipe connects to the main inlet pipe, receiving the wastewater to be treated. The anaerobic zone's outlet pipe is connected to the inlet pipe of each anoxic zone in each A / O unit. This ensures that the wastewater first enters the anaerobic zone for treatment, fully releasing phosphorus, and then flows out of the anaerobic zone into the anoxic zone of each A / O unit for denitrification. This sufficient phosphorus release at the front end allows for sufficient phosphorus absorption in the aerobic zones of the multi-stage A / O units, improving the system's phosphorus removal efficiency.

[0010] The sludge outlet of the secondary sedimentation tank is connected to the anoxic zone of the first A / O unit through a sludge return pipe. Since the external return sludge comes from the aerobic zone of the last A / O unit and contains a large amount of nitrate nitrogen, if it is directly returned to the anaerobic zone, the anaerobic environment of the anaerobic zone will be destroyed, and the phosphorus removal effect will be reduced. Therefore, the present invention first passes the external return sludge into the anoxic zone of the first A / O unit, removes nitrate nitrogen in the anoxic zone, and then returns the treated external return sludge to the anaerobic zone through the first internal return pipe connecting the anoxic zone of the first A / O unit with the anaerobic zone, thereby ensuring the anaerobic environment of the anaerobic zone and further improving the phosphorus removal effect.

[0011] In a second aspect, the present invention provides an application of a system according to any one of the aforementioned embodiments in the field of sewage treatment.

[0012] The beneficial effects of the embodiments of the present invention are:

[0013] The present invention provides a segmented water inlet multi-stage A / O coupled improved UCT phosphorus removal and nitrogen removal system. By setting an anaerobic zone before the multi-stage A / O unit, the influent first undergoes an anaerobic process and then enters the downstream multi-stage A / O unit, thereby overcoming the problem of the traditional multi-stage A / O process in which only a portion of the sewage passes through the anaerobic zone to release phosphorus. Through the above improvements, this system retains the excellent denitrification performance of the multi-stage A / O process while further improving its phosphorus removal effect. In addition, the present invention macroscopically combines the upstream anaerobic unit with the downstream multi-stage A / O unit to form an improved UCT phosphorus removal and nitrogen removal process. By returning the sludge in the secondary sedimentation tank to the anoxic zone of the first-stage A / O unit and then returning it from the anoxic zone of the first-stage A / O unit to the anaerobic zone, the nitrate nitrogen in the returned sludge is effectively eliminated. Through the above design, the present invention combines the advantages of the multi-stage A / O process and the improved UCT process, and further improves the denitrification and phosphorus removal effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0015] Figure 1 This is a structural schematic diagram of the segmented water inlet multi-stage A / O coupling improved UCT phosphorus and nitrogen removal system provided by the first embodiment of the present invention.

[0016] Icons: 100-Segmented water inlet multi-stage A / O coupling improved UCT phosphorus removal and nitrogen removal system; 110-Second sedimentation tank; 111-Sludge outlet; 112-Water outlet; 121-First anoxic zone; 122-First aerobic zone; 123-Second anoxic zone; 124-Second aerobic zone; 125-Third anoxic zone; 126-Third aerobic zone; 127-Fourth anoxic zone; 128-Fourth aerobic zone; 129-Anaerobic zone; 130-Water inlet main pipe; 131-First valve; 132-Regulating valve; 141-Sludge return pipe; 142-First internal return pipe; 143-Second internal return pipe; 151-Aeration and oxygenation device; 152-Aeration branch pipe; 153-Aeration main pipe; 154-Air conditioning device. DETAILED DESCRIPTION

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0018] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0019] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0020] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" and the like indicate positions or locations based on the positions shown in the accompanying drawings, or the positions or locations in which the inventive product is typically placed when in use. These terms are intended solely to facilitate the description of the present invention and to simplify the description, and are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third," etc., are used solely to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0021] Furthermore, terms such as "horizontal" and "vertical" do not necessarily mean that a component must be absolutely horizontal or overhanging, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but rather that it can be slightly tilted.

[0022] In the description of the present invention, it should also be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0023] In a first aspect, the present invention provides a staged water inlet multi-stage A / O coupled improved UCT phosphorus and nitrogen removal system 100, comprising an anaerobic zone 129, multi-stage A / O units and a secondary sedimentation tank 110 arranged in sequence.

[0024] Each A / O unit includes an anoxic zone and an aerobic zone connected in series. Therefore, when multiple A / O units are combined, a structure is formed in which anoxic zones and aerobic zones are arranged alternately. The aerobic zone of the last A / O unit is connected to the secondary sedimentation tank 110.

[0025] The traditional multi-stage AO process requires additional anaerobic zones to improve the phosphorus removal effect. Currently, the anaerobic zone is generally set before or after the first anoxic zone. Although this setting improves the phosphorus removal effect of the traditional A / O process, it is still not as good as the traditional A / O process. 2 / O process. The reason is that when the anaerobic zone is set before or after the first anoxic zone, only the first section of the influent undergoes the anaerobic process, and the rest of the sewage does not undergo the anaerobic process. The water distribution ratio of the first section is generally small, so it is difficult to achieve a good phosphorus removal effect. Therefore, the inventor proposed that the water inlet pipe of the anaerobic zone 129 be connected to the water inlet main 130 for the introduction of the sewage to be treated, and the outlet pipe of the anaerobic zone 129 be connected to the water inlet pipe of the anoxic zone of each section of the A / O unit. Therefore, the sewage to be treated first enters the anaerobic zone 129 for treatment, fully releases phosphorus, and then flows out of the anaerobic zone 129 and enters the anoxic zone of each section of the A / O unit for denitrification.

[0026] The sludge outlet 111 of the secondary sedimentation tank 110 is connected to the anoxic zone of the first A / O unit through the sludge return pipe 141. Since the external return sludge comes from the aerobic zone of the last A / O unit and contains rich nitrate nitrogen, if it is directly returned to the anaerobic zone 129, the phosphorus removal effect will be reduced. Therefore, the present invention first passes the external return sludge into the anoxic zone of the first A / O unit, removes nitrate nitrogen in the anoxic zone, and then returns the treated external return sludge to the anaerobic zone 129 through the first internal return pipe 142 connecting the anoxic zone of the first A / O unit and the anaerobic zone 129, thereby further improving the phosphorus removal effect.

[0027] Wastewater treatment is a complex process, requiring a treatment method tailored to influent and effluent quality standards to ensure that the wastewater entering the system meets effluent quality standards for discharge. Therefore, varying influent quality leads to varying treatment methods. A common goal in this field is to rapidly design a cost-effective method that meets effluent standards based on influent quality. Common parameters in multi-stage A / O processes generally include the number of stages, influent flow rate, sludge return ratio, internal recirculation ratio, and total nitrogen removal rate. Once the influent and effluent quality are determined, optimal design parameters must be selected to achieve the goal of cost-effective wastewater treatment. Currently, the design of multi-stage A / O systems primarily relies on calculations based on the Japan Sewerage Corporation and the German ATV specifications. However, both of these methods are designed for single-stage treatment processes, presenting numerous challenges when applied to multi-stage A / O systems. Applying these methods to engineering designs can lead to inconsistent results and failure to meet effluent quality requirements. To solve the above problems, designers often need to rely on experience to make multiple adjustments and trial calculations to the design methods or parameters, which reduces the efficiency and accuracy of the design work. At the same time, the above process requires a high level of experience from designers, and there are often large deviations between different designers. This is not only not conducive to energy conservation and consumption reduction during operation, but also brings huge risks to project implementation and the stability of sewage treatment effects.

[0028] In order to solve this technical problem, the inventors, through long-term research, discovered the relationship between parameters such as the number of segments, water flow rate, sludge return ratio, internal return ratio, and total nitrogen removal rate. Based on the segmented water inlet multi-stage A / O coupling improved UCT phosphorus removal and denitrification system 100, a method for confirming various parameters of sewage treatment is provided, which provides a basis for the design steps of sewage treatment. The parameters confirmed by the following formulas, combined with the system of the present invention, can achieve better sewage treatment effects while reducing equipment cost investment. The quality of the treated effluent can be significantly purified, avoiding the deviations caused by the current calculations based on Japanese and German standards and the different experiences of designers, which is conducive to the standardization and stability of the design and operation work.

[0029] In an optional embodiment, the water inlet flow rates of the multiple anoxic zones are in a geometric progression according to the arrangement order of the anoxic zones.

[0030] Preferably, the water flow distribution coefficient of the anoxic zone of the last A / O unit is calculated according to the following formula:

[0031]

[0032] Among them, r n - represents the water flow distribution coefficient of the anoxic zone of the last A / O unit, q- represents the common ratio of the geometric progression, n- represents the total number of A / O units, and n is a positive integer greater than 0.

[0033] The above formula shows that the inlet flow distribution coefficient for the anoxic zone of the final A / O unit is related to the total number of A / O unit sections, n, and the common ratio, q, of the geometric progression. Once n and q are known, the inlet flow distribution coefficient, rn, for the anoxic zone of the final A / O unit can be determined. Since the inlet flows of multiple anoxic zones follow a geometric progression in their order, knowing rn and q allows the inlet flow distribution coefficients for all anoxic zones to be determined, thereby determining the water inlet plan for each anoxic zone in the system.

[0034] It should be noted that the water flow distribution coefficient mentioned in the present invention is numerically equal to the ratio of the water flow of the anoxic zone to the total water flow. Therefore, after the water flow distribution coefficient is calculated, the water flow value of each anoxic zone can be obtained according to the total water flow. For example, the water flow distribution coefficient of the anoxic zone of the last A / O unit described above is r n It is numerically equal to the ratio of the water inlet flow rate of the anoxic zone of the nth section, i.e. the last section of the A / O unit in the present invention, to the total water inlet flow rate.

[0035] In order to further calculate the water flow distribution coefficient of the anoxic zone of the last section of the A / O unit, the inventors, after long-term research, concluded that the common ratio of the geometric series is the ratio of the water flow distribution coefficients of two adjacent anoxic zones, and calculated it using the following formula:

[0036]

[0037] Among them, r i - represents the water flow distribution coefficient of the i-th section; r i-1 - represents the distribution coefficient of the influent flow rate of the i-1th section; i is an integer ≥ 2; K- represents the ratio of the mass of BOD5 to total Kjeldahl nitrogen (TKN) in the influent, which can be expressed as kg BOD5 / kgTKN; α- represents the removal of unit mass of nitrate nitrogen (NO3 - The mass of BOD5 consumed by nitrogen (-N), that is, the theoretical carbon-nitrogen ratio, can be expressed as g BOD5 / gNO3 - -N.

[0038] In the above formula, the common ratio of the geometric series is related to K and α, where K depends on the influent water quality. Therefore, the influent flow rate of each anoxic zone can be designed according to different water qualities, which is beneficial to improving the sewage treatment effect and efficiency. α is the theoretical carbon-nitrogen ratio. For biological denitrification reactions, the larger α is, the greater the denitrification rate is, and the higher the carbon-nitrogen ratio required in the anoxic tank is. When the carbon-nitrogen ratio K in the influent is small, in order to obtain a higher total nitrogen removal rate, it is necessary to reduce the α value to reduce q, which will reduce the denitrification rate and increase the capacity of the anoxic tank. However, the α value cannot be reduced indefinitely. Theoretically, 2.86g COD is required to remove 1g of nitrate nitrogen by denitrification, and the actual reaction is much higher than this value. According to the "Outdoor Drainage Design Standard" GB50014-2021, the influent carbon-nitrogen ratio should be greater than 4 during biological denitrification. When the q value design requirements cannot be met by reducing the α value, it is necessary to add a carbon source to increase the K value. Therefore, when designing the sewage treatment method, the adjusted α / K value should be used as the design q value to obtain better sewage treatment effects.

[0039] In an optional embodiment, the main inlet pipe 130 is further connected to the outlet pipe of the anaerobic zone 129 via a bypass pipe equipped with a first valve 131. Therefore, the present invention also provides an alternative sewage treatment path, namely, sewage can enter the various anoxic zones through the anaerobic zone 129, or it can directly enter the various inlet pipes through the main inlet pipe 130 and then enter the various anoxic zones. Because the treatment effect is better when sewage enters the anaerobic zone 129 first, it is preferred to enter the anaerobic zone 129 first and then the anoxic zone. However, in actual operation, if an anaerobic zone malfunctions or a small amount of additional water flow is required for one or more anoxic zones, it can also be directly passed into the anoxic zone through the main inlet pipe 130.

[0040] In an optional embodiment, the water inlet main 130 is connected to a water distribution well or a water distribution channel to provide water to the system.

[0041] In an optional embodiment, a regulating valve 132 is provided on the water inlet pipe of the anaerobic zone 129 and the water inlet pipe of the anoxic zone of each A / O unit. The regulating valve 132 can control the water inlet flow rate of the anaerobic zone 129 and each anoxic zone. For example, the water inlet flow rate of each anoxic zone can be controlled according to the aforementioned formula.

[0042] In an optional embodiment, the aerobic zone of the last A / O unit is also connected to the anoxic zone of the last A / O unit through the second internal reflux pipe 143. This fully retains the advantages of the post-denitrification of the upstream multi-stage A / O unit, and at the same time, the nitrate nitrogen in the reflux liquid can fully utilize the carbon source in the anoxic zone, thereby improving the operational flexibility and total nitrogen removal effect.

[0043] In an optional embodiment, the second internal reflux ratio of the internal reflux between the aerobic zone and the anoxic zone of the last A / O unit is calculated by the following formula:

[0044]

[0045] Among them, R 内,n - represents the second internal recirculation ratio between the aerobic zone and the anoxic zone of the last A / O unit, r n - represents the inlet flow distribution coefficient of the anoxic zone of the last A / O unit, η- represents the total nitrogen removal rate, R- represents the sludge return ratio, that is, the ratio of the external return sludge flow to the total inlet flow, n- represents the total number of A / O units, and n is a positive integer greater than 0.

[0046] The second internal reflow ratio calculated based on the inlet flow distribution coefficient, total nitrogen removal rate and sludge reflow ratio of the anoxic zone of the last A / O unit can accurately control the amount of nitrate from the aerobic zone returning to the anoxic zone of the last A / O unit, thereby improving the denitrification effect of the system.

[0047] According to the above formula, in the design process of sewage treatment, the inventors first discovered the relationship between parameters such as the number of segments, water flow rate, sludge return ratio, internal return ratio and total nitrogen removal rate, and then obtained the corresponding calculation formula through deduction. It was found based on the data feedback of the embodiment that the design of the sewage treatment method using the formula provided by the present invention can improve the sewage treatment efficiency while reducing costs, and ensure that the effluent water quality is stable and meets the standards, which provides a basis for sewage treatment design.

[0048] Preferably, the second internal reflux pipe 143 is also provided with a valve for controlling the connection of the second internal reflux pipe 143 and a reflux pump for lifting the nitrification liquid in the aerobic zone to the anoxic zone. The provision of the reflux pump and the valve can better control the reflux of the nitrification liquid in the aerobic zone or not to reflux to the anoxic zone of the last section A / O unit.

[0049] In an optional embodiment, the calculation formula of the total nitrogen removal rate η is as follows:

[0050]

[0051] Among them, η represents the total nitrogen removal rate, R represents the sludge return ratio, that is, the ratio of the external return sludge flow to the total inlet flow, q represents the common ratio of the geometric progression, n represents the total number of A / O units, and n is a positive integer greater than 0.

[0052] The total nitrogen removal rate is related to the nitrogen concentration of the inlet and outlet water, which is the ratio of the total nitrogen concentration of the outlet water to the total nitrogen concentration of the inlet water. Therefore, the total nitrogen removal rate η that needs to be achieved theoretically can be calculated based on the inlet and outlet water qualities. 理 In the actual treatment process, the actual total nitrogen removal rate η value will change according to the system structure or water distribution changes. Therefore, in the process of designing the sewage treatment method, the total nitrogen removal rate of the biochemical pool system can be determined according to the designed n, q and R values, so that the total nitrogen removal rate η is greater than η 理 , from which the relevant n, q, and R values ​​can be determined. The system provided by the present invention can effectively improve the accuracy and efficiency of the design and operation of a multi-stage A / O process, reduce the workload and design deviation in the process design, and can also provide a reference for actual sewage plant operation, which is conducive to improving sewage treatment efficiency.

[0053] In an optional embodiment, each A / O unit's anoxic zone is equipped with a carbon source injection point. Due to varying influent water quality, achieving a high total nitrogen removal rate is difficult when the influent carbon content is low. Therefore, additional carbon source can be added to the carbon source injection point to improve the total nitrogen removal rate. The carbon source injection point should be located as close as possible to the entrance of the anoxic zone to maximize carbon source utilization.

[0054] In an optional embodiment, a dissolved oxygen concentration meter, a sludge concentration meter and an oxidation-reduction potential meter are provided in the anoxic zone of each A / O unit, and the positions of the dissolved oxygen concentration meter, the sludge concentration meter and the oxidation-reduction potential meter can be conventionally set as needed.

[0055] In an optional embodiment, a stirring and plugging device is provided in the anoxic zone of each A / O unit to promote the mass transfer effect in the anoxic zone and improve the denitrification capacity of the anoxic zone.

[0056] In an optional embodiment, the sludge outlet 111 of the secondary clarifier 110 is connected to the front end of the anoxic zone of the first A / O unit via a sludge return line 141. The rear end of the anoxic zone of the first A / O unit is also connected to the front end of the anaerobic zone 129 via a first internal return line 142. Therefore, the sludge returned from the secondary clarifier 110 can undergo a complete denitrification process in the anoxic zone of the first A / O unit before recirculating from the rear end of the anoxic zone of the first A / O unit to the front end of the anaerobic zone 129 via an internal return line. This ensures the sludge concentration in the anaerobic zone while preventing interference from nitrate nitrogen, thereby improving phosphorus removal efficiency. The sludge returned from the first internal return line 142 has a first internal return ratio, which, based on design experience, is typically 100% to 200%.

[0057] In an optional embodiment, in order to ensure sufficient oxygen in the aerobic zone, an aerobic zone of each A / O unit is further provided with an aeration and oxygenation device 151. Each aeration and oxygenation device 151 is connected to an aeration main pipe 153 through a one-to-one corresponding aeration branch pipe 152 extending from the aerobic zone. Each aeration branch pipe 152 is provided with an air conditioning device 154. The air conditioning device 154 can be an air regulating valve and an air flow meter for detecting and adjusting the amount of air introduced into the aerobic zone.

[0058] In an optional embodiment, the number of segments of the A / O unit is not limited and can be set according to actual needs, for example, it can be 2 segments, 3 segments, 4 segments, 5 segments or 6 segments.

[0059] In an optional embodiment, the secondary sedimentation tank 110 further includes a water outlet 112 . After the sewage entering the secondary sedimentation tank 110 is allowed to settle, the sludge is discharged from the sludge outlet 111 and the sewage is discharged from the water outlet 112 .

[0060] In a second aspect, the present invention provides an application of a system according to any one of the aforementioned embodiments in the field of sewage treatment.

[0061] First embodiment

[0062] Please refer to Figure 1 This embodiment provides a staged water inlet multi-stage A / O coupled improved UCT phosphorus and nitrogen removal system 100, which includes an anaerobic zone 129, four A / O units and a secondary sedimentation tank 110 arranged in sequence.

[0063] Each A / O unit segment includes an anoxic zone and an aerobic zone connected in series. Therefore, when four A / O units are sequentially combined, a structure is formed in which anoxic and aerobic zones are alternately arranged. For ease of description, the anoxic and aerobic zones alternately arranged in series from the first to the fourth A / O unit segments are designated as first anoxic zone 121, first aerobic zone 122, second anoxic zone 123, second aerobic zone 124, third anoxic zone 125, third aerobic zone 126, fourth anoxic zone 127, and fourth aerobic zone 128.

[0064] The inlet pipe of the anaerobic zone 129 is connected to the main inlet pipe 130 for receiving the treated sewage. The outlet pipe of the anaerobic zone 129 is connected to the inlet pipes of the first anoxic zone 121, the second anoxic zone 123, the third anoxic zone 125, and the fourth anoxic zone 127, respectively. This ensures that the treated sewage first enters the anaerobic zone 129 for treatment, fully releasing phosphorus, and then flows out of the anaerobic zone 129 and enters each anoxic zone for denitrification. This sufficient phosphorus release at the front end allows for sufficient phosphorus absorption in the aerobic zones of the multi-stage A / O units, improving the system's phosphorus removal efficiency.

[0065] The fourth aerobic zone 128 is connected to the secondary sedimentation tank 110 and is used to precipitate and discharge the sewage after being treated by the four-stage A / O units.

[0066] The sludge outlet 111 of the secondary sedimentation tank 110 is connected to the front end of the first anoxic zone 121 through the sludge return pipe 141. Since the external return sludge comes from the fourth aerobic zone 128 and contains rich nitrate nitrogen, if it is directly returned to the anaerobic zone 129, the phosphorus removal effect will be reduced. Therefore, in this embodiment, the external return sludge is first passed into the first anoxic zone 121, and the nitrate nitrogen is first removed in the first anoxic zone 121. Since the external return sludge directly enters the front end of the first anoxic zone 121, the external return sludge undergoes a complete denitrification process in the first anoxic zone 121, and then enters the front end of the anaerobic zone 129 from the rear end of the first anoxic zone 121 through the first internal return pipe 142. This not only ensures the sludge concentration in the anaerobic zone, but also avoids the influence of nitrate nitrogen in the return liquid on phosphorus removal.

[0067] In this embodiment, the water inlet main pipe 130 is also connected to the outlet pipe of the anaerobic zone 129 through a bypass pipe provided with a first valve 131. The first valve 131 can be controlled to control whether the treated sewage in the water inlet main pipe 130 is directly passed into the first anoxic zone 121, the second anoxic zone 123, the third anoxic zone 125 and the fourth anoxic zone 127.

[0068] In this embodiment, the water inlet pipe of the anaerobic zone 129 and the water inlet pipes of the four anoxic zones are provided with regulating valves 132 . The regulating valves 132 can control the water inlet flow rate of the anaerobic zone 129 and each anoxic zone.

[0069] In this embodiment, the fourth aerobic zone 128 is also connected to the fourth anoxic zone 127 through the second internal recirculation pipe 143, without destroying the structure of the previous three-stage A / O unit. It fully utilizes the advantages of the post-denitrification of the multi-stage A / O unit. At the same time, the nitrate nitrogen in the second internal recirculation can fully utilize the carbon source in the fourth anoxic zone 127, thereby improving the total nitrogen removal rate of the sewage and improving the flexibility of the system operation.

[0070] In this embodiment, in order to ensure sufficient oxygen in the aerobic zone, an aeration and oxygenation device 151 is further provided in the first aerobic zone 122, the second aerobic zone 124, the third aerobic zone 126 and the fourth aerobic zone 128. Each aeration and oxygenation device 151 is connected to the aeration main pipe 153 through a corresponding aeration branch pipe 152 extending from the aerobic zone.

[0071] Furthermore, each aeration branch pipe 152 is provided with an air conditioning device 154 , including an air regulating valve and an air flow meter, for adjusting the amount of oxygen added into the aerobic zone.

[0072] In this embodiment, stirring and propelling flow devices are provided in the first anoxic zone 121 , the second anoxic zone 123 , the third anoxic zone 125 and the fourth anoxic zone 127 to promote the reaction in the anoxic zone and improve the denitrification capacity of the anoxic zone.

[0073] In the embodiment, carbon source addition points are provided in the first anoxic zone 121, the second anoxic zone 123, the third anoxic zone 125 and the fourth anoxic zone 127. Due to the different influent water quality conditions, when the influent carbon content is low, it is difficult to achieve a higher total nitrogen removal rate. Therefore, additional carbon source can be added from the carbon source addition point to improve the total nitrogen removal rate of the sewage.

[0074] In this embodiment, a dissolved oxygen concentration meter, a sludge concentration meter and an oxidation-reduction potential meter are provided in the first anoxic zone 121 , the second anoxic zone 123 , the third anoxic zone 125 and the fourth anoxic zone 127 .

[0075] In this embodiment, the secondary sedimentation tank 110 further includes a water outlet 112 . After the sewage entering the secondary sedimentation tank 110 is allowed to settle, the sludge is discharged from the sludge outlet 111 and the sewage is discharged from the water outlet 112 .

[0076] This embodiment provides a segmented water inlet multi-stage A / O coupling improved UCT phosphorus removal and nitrogen removal system 100, the operation process of which is as follows:

[0077] The first valve 131 is closed, and the regulating valve 132 of the anaerobic zone 129 is opened. The sewage to be treated enters the anaerobic zone 129 from the water inlet main pipe 130 through the regulating valve 132 for phosphorus release. The sewage treated in the anaerobic zone 129 flows out from the outlet pipe of the anaerobic zone 129. The regulating valves 132 of the four anoxic zones are opened, and the sewage treated in the anaerobic zone 129 enters the four anoxic zones in turn for denitrification treatment. After treatment in the first anoxic zone 121, the wastewater flows to the first aerobic zone 122, and then from the first aerobic zone 122 to the second anoxic zone 123. The wastewater in the second anoxic zone 123 undergoes denitrification again before entering the second aerobic zone 124. This process continues in this manner, and after undergoing alternating treatment in the four A / O units, the wastewater enters the fourth aerobic zone 128. After treatment in the fourth aerobic zone 128, the wastewater flows to the secondary sedimentation tank 110 for settling. The upper layer of clear water is directly discharged from the secondary sedimentation tank 110, while the lower layer of sludge is partially discharged from the system through a pipeline, while the remaining portion returns to the first anoxic zone 121. The sludge returned to the first anoxic zone 121 undergoes denitrification again before returning to the anaerobic zone 129 through the first internal return pipe 142, ensuring the sludge concentration in the anaerobic zone.

[0078] It is understandable that while the sewage in the first anoxic zone 121 is being treated, the sewage in the second anoxic zone 123 , the third anoxic zone 125 and the fourth anoxic zone 127 are also being treated simultaneously. For the treatment method, please refer to the sewage treatment process in the first anoxic zone 121 .

[0079] In addition, the sludge in the fourth aerobic zone 128 can also be returned to the fourth anoxic zone 127 through the second internal return pipe 143, and the nitrate produced in the aerobic process can be converted into nitrogen gas again and separated, thereby improving the denitrification capacity of the sewage.

[0080] During the above treatment process, in order to ensure the oxygen content in the aerobic zone, the amount of air added can be adjusted by the air conditioning device 154.

[0081] Test Example 1

[0082] Based on the system of Example 1, a sewage treatment scheme is designed, as follows:

[0083] The designed water volume of a biological pool in a certain project is 2000m 3 / d. Influent water quality: CODcr = 400 mg / L, BOD5 = 220 mg / L, NH3-N = 55 mg / L, TN = 70 mg / L; effluent water quality: CODcr = 50 mg / L, BOD5 = 6 mg / L, NH3-N = 1.5 mg / L, TN = 10 mg / L.

[0084] 1) Calculate the total nitrogen removal rate η to meet the effluent water quality requirements 理

[0085]

[0086] Therefore, the actual total nitrogen removal rate η of the designed system when treating the sewage is s It should be greater than the theoretical total nitrogen removal rate of 85.7%.

[0087] 2) Determine the number of segments n and the common ratio q

[0088] Based on the theoretical carbon-nitrogen ratio α=4, the calculation formula of q is as follows:

[0089]

[0090] Assuming the sludge return ratio R = 100%, when n = 3, q ​​= 1.27, the calculation formula for the total nitrogen removal rate η is as follows:

[0091]

[0092] Assuming the sludge return ratio R = 100%, when n = 4, q = 1.27, the calculation formula for the total nitrogen removal rate η is as follows:

[0093]

[0094] Since η 计 <η 理 Therefore, further adjustments to the values ​​of n, R, or q are necessary. Increasing the number of segments, implementing internal recirculation, and adding a carbon source are all options for improving the total nitrogen removal rate. However, too many segments increase operational complexity, and given the low flow rate in this case, too many segments would reduce the volume of each anoxic and aerobic zone, making construction inconvenient. Therefore, in this example, the number of segments is set at 3, and internal recirculation and the addition of a carbon source are used to improve the total nitrogen removal rate.

[0095] 3) Calculate the water flow distribution coefficient of each anoxic zone

[0096]

[0097]

[0098]

[0099] Wherein, r1 is the water inlet flow distribution coefficient of the first anoxic zone 121 , r2 is the water inlet flow distribution coefficient of the second anoxic zone 123 , and r3 is the water inlet flow distribution coefficient of the third anoxic zone 125 .

[0100] 4) Internal reflux

[0101]

[0102] 5) Add carbon source

[0103] When setting up a reflux at the end of the process, a carbon source must be added to the anoxic zone of the inflow section to remove nitrate nitrogen from the reflux. The amount of carbon source added can be calculated based on the mass of nitrate nitrogen in the reflux.

[0104] The nitrate nitrogen concentration in the effluent without considering the backflow is:

[0105]

[0106] The amount of carbon source to be added daily is:

[0107] BOD 5,投 =2000×90.2%×14.5×4=104kg / d

[0108] The type and quality of the added carbon source can be calculated based on existing technology.

[0109] Based on the system of Example 1, by distributing according to the above water flow distribution coefficient, and ensuring R = 100%, n = 3, and the second internal reflux ratio is 90.2%, the actual total nitrogen removal rate η can be achieved. s =85.7%, which meets the theoretical total nitrogen removal rate requirement and the effluent meets the standard. The tank capacity of the anaerobic zone and various levels of anoxic and aerobic zones can be calculated according to relevant specifications.

[0110] The calculation method is based on the "Outdoor Drainage Design Standard", where the water temperature is 15℃ and the safety factor S is F =2.0, denitrification reaction rate K de =0.05kgNO3 - -N / kgMLSS·d, sludge yield coefficient = 0.45kgMLVSS / kgBOD5, total sludge yield coefficient = 1.0kgMLSS / kgBOD5. The parameters and results of the calculation process are detailed in Table 1.

[0111] Table 1 Sewage treatment design results

[0112]

[0113]

[0114] Test Example 2

[0115] Based on the system of Example 1, a sewage treatment scheme is designed, as follows:

[0116] The designed water volume of a biological pool in a certain project is 30,000m 3 / d. Influent water quality: CODcr = 300 mg / L, BOD5 = 194 mg / L, NH3-N = 55 mg / L, TN = 70 mg / L; effluent water quality: CODcr = 50 mg / L, BOD5 = 6 mg / L, NH3-N = 1.5 mg / L, TN = 12 mg / L.

[0117] 1) Calculate the total nitrogen removal rate η to meet the effluent water quality requirements 理

[0118]

[0119] Therefore, the actual total nitrogen removal rate η of the designed system when treating the sewage is s It should be greater than the theoretical total nitrogen removal rate of 82.86%.

[0120] 2) Determine the number of segments n and the common ratio q

[0121] Based on the theoretical carbon-nitrogen ratio α=4, the calculation formula of q is as follows:

[0122]

[0123] Assuming the sludge return ratio R = 100%, when q = 1.44 and n = 4, the calculation formula for the total nitrogen removal rate η is as follows:

[0124]

[0125] Assuming the sludge return ratio R = 100%, when q = 1.44 and n = 4, the calculation formula for the total nitrogen removal rate η is as follows:

[0126]

[0127] Since η 计 <η 理 , so it is necessary to further adjust the values ​​of n, R or q.

[0128] Increasing the number of sections, setting up internal recirculation, and adding a carbon source are all options for improving the total nitrogen removal rate. Increasing the number of sections can improve the total nitrogen removal rate, but in engineering, the number of sections is generally not greater than 5. Therefore, in this example, the number of sections is 4, and adding a carbon source is used to further improve the total nitrogen removal rate.

[0129] After calculation, when n=4, R=100%, q=1.186, and the total nitrogen removal rate is 84.14%, which can meet the total nitrogen removal rate requirements calculated in the first step, and η, n, R and q also satisfy the corresponding relationship. Therefore, the next step of design is carried out based on q=1.186.

[0130] 3) Add carbon source

[0131] According to the Outdoor Drainage Design Standard, when q = 1.186, the influent BOD5 = 236 mg / L. However, in this solution, the influent BOD5 = 194 mg / L. Therefore, a carbon source must be added to increase the BOD5 content. The type and quality of the added carbon source can be calculated using existing techniques.

[0132] 4) Calculate the water flow distribution coefficient of each anoxic zone

[0133]

[0134]

[0135]

[0136]

[0137] Among them, r1 is the water inlet flow distribution coefficient of the first anoxic zone 121, r2 is the water inlet flow distribution coefficient of the second anoxic zone 123, r3 is the water inlet flow distribution coefficient of the third anoxic zone 125, and r4 is the water inlet flow distribution coefficient of the fourth anoxic zone 127.

[0138] Based on the system of Example 1, by distributing according to the above water flow distribution coefficient and ensuring R = 100%, the actual total nitrogen removal rate η can be achieved. s =84.14%, exceeding the theoretical total nitrogen removal rate of 82.86%, and the effluent meets the standard. The tank capacity of the anaerobic zone and each level of anoxic and aerobic zones can be calculated according to relevant specifications. The calculation parameters are the same as those in Experiment 1. The parameters and results of the calculation process are detailed in Table 2.

[0139] Table 2 Sewage treatment design results

[0140]

[0141] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A staged water inlet multi-stage A / O coupling improved UCT phosphorus and nitrogen removal process, characterized in that: It includes anaerobic zone, multi-stage A / O unit and secondary sedimentation tank arranged in sequence; Each section of the A / O unit comprises an anoxic zone and an aerobic zone connected in series, and the aerobic zone of the last section of the A / O unit is connected to the secondary sedimentation tank; The water inlet pipe of the anaerobic zone is connected to the main water inlet pipe for transporting the sewage to be treated, and the water outlet pipe of the anaerobic zone is respectively connected to the water inlet pipe of the anoxic zone of each section of the A / O unit; The sludge outlet of the secondary sedimentation tank is connected to the anoxic zone of the first section of the A / O unit through a sludge return pipe, and the anoxic zone of the first section of the multi-stage A / O unit is also connected to the anaerobic zone through a first internal return pipe; The water inlet flow rates of the plurality of anoxic zones are in geometric progression according to the arrangement order of the anoxic zones; The inlet flow distribution coefficient of the anoxic zone of the A / O unit described in the last paragraph is calculated according to the following formula: Among them, r n - represents the water flow distribution coefficient of the anoxic zone of the last section of the A / O unit, q- represents the common ratio of the geometric progression, n- represents the total number of sections of the A / O unit, and n is a positive integer greater than 0; The common ratio q of the geometric progression is the ratio of the water flow distribution coefficients of two adjacent anoxic zones, which is calculated by the following formula: Among them, r i - represents the water flow distribution coefficient of the i-th section; r i-1 - represents the influent flow distribution coefficient of the i-1th section; i is an integer ≥ 2; K - represents the ratio of the mass of BOD5 to the total Kjeldahl nitrogen in the influent; α - represents the mass of BOD5 consumed to remove unit mass of nitrate nitrogen in the anoxic zone; The aerobic zone of the A / O unit of the last section is also connected to the anoxic zone of the A / O unit of the last section through a second internal reflux pipe; The second internal reflux ratio of the internal reflux between the aerobic zone and the anoxic zone of the A / O unit in the last section is calculated by the following formula: Among them, R 内 , n- represents the second internal reflux ratio between the aerobic zone and the anoxic zone of the A / O unit in the last section, r n - represents the water flow distribution coefficient of the anoxic zone of the A / O unit in the last paragraph, η- represents the total nitrogen removal rate, and R- represents the sludge return, that is, the ratio of the sludge flow to the total water flow; The calculation formula of total nitrogen removal rate η is as follows: Among them, η represents the total nitrogen removal rate, R represents the ratio of the external return sludge flow rate to the total influent flow rate, q represents the common ratio of the geometric series, and n represents the total number of A / O units.

2. The process according to claim 1, characterized in that The water inlet main pipe is communicated with the water outlet pipe of the anaerobic zone through an overpass pipe provided with a first valve.

3. The process according to claim 2, characterized in that The water inlet pipe of the anaerobic zone and the water inlet pipe of the anoxic zone of each section of the A / O unit are both provided with regulating valves.

4. The process according to claim 1, characterized in that The sludge outlet of the secondary sedimentation tank is connected to the front end of the anoxic zone of the first section A / O unit through a sludge return pipe, and the rear end of the anoxic zone of the first section A / O unit is also connected to the front end of the anaerobic zone through a first internal return pipe.

5. The process according to claim 1, characterized in that An aeration and oxygenation device is also provided in the aerobic zone of each section of the A / O unit. Each of the aeration and oxygenation devices is connected to the aeration main pipe through a corresponding aeration branch pipe extending from the aerobic zone. Each of the aeration branch pipes is provided with an air regulating valve and an air flow meter.

6. The process according to claim 5, characterized in that A stirring and flow-pushing device is provided in the anoxic zone of each section of the A / O unit.

7. The process according to claim 5, characterized in that The anoxic zone of each section of the A / O unit is provided with a carbon source addition point.

8. The process according to claim 7, characterized in that The anoxic zone of each section of the A / O unit is provided with a dissolved oxygen concentration meter, a sludge concentration meter and an oxidation-reduction potential meter.

9. Use of the process according to any one of claims 1 to 8 in the field of sewage treatment.

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