Pre-anoxic modified sequencing batch intermittent reaction sewage treatment system and operation method

Abstract

This invention belongs to the field of wastewater treatment technology and provides a pre-anaerobic modified sequencing batch reactor (SBR) wastewater treatment system. The system comprises an anoxic tank, a biological treatment tank, and a sedimentation tank connected in sequence. The biological treatment tank includes a first MSBR tank and a second MSBR tank connected at the bottom. A first nitrification liquor return pipeline connects the second MSBR tank to the anoxic tank, and a second nitrification liquor return pipeline connects the second MSBR tank to the first MSBR tank, respectively, for returning the generated nitrification liquor to the anoxic tank and the first MSBR tank. A first sludge return pipeline connects the sedimentation tank to the anoxic tank, and a second sludge return pipeline connects the sedimentation tank to the first MSBR tank, respectively, for returning the generated sludge to the anoxic tank and the first MSBR tank. This invention combines the advantages of both AAO and SBR systems. The dual biological treatment tanks connected in series create two different biological reaction environments, resulting in better pollutant removal, convenient operation and management, low energy consumption, and strong shock resistance.

Description

Technical Field

[0001] This invention belongs to the technical field of wastewater treatment, specifically relating to a pre-anaerobic modified sequencing batch reactor wastewater treatment system and its operation method. Background Technology

[0002] Existing rural sewage treatment processes are essentially scaled-down versions of urban sewage treatment plant processes, or simply scaled-down versions of urban processes with an additional shell to create so-called integrated treatment equipment. These are unsuitable for rural areas where water quality and quantity are unstable, funding is insufficient, and management and maintenance technologies are limited. Unlike cities, rural domestic sewage is dispersed, difficult to collect uniformly, and its volume is small, fluctuates greatly seasonally, and exhibits significant regional differences in water quality and quantity. Therefore, sewage treatment cannot simply apply the same methods as urban sewage treatment, nor can it be a one-size-fits-all approach. However, most rural areas implement measures once the population exceeds twenty households, applying the urban "connection + centralized treatment + standard discharge" model. This results in high construction costs, heavy operation and maintenance burdens, and poor operational efficiency. In some cases, sewage treatment plants are even shut down due to long-term lack of water intake or neglect of management and maintenance, leading to resource waste and hindering long-term improvement of the local ecological environment.

[0003] To address the numerous challenges faced by rural wastewater treatment, such as incompatibility with existing urban wastewater treatment plant processes, limited investment funds, immature management and maintenance technologies, high energy consumption, limited site area, and unstable treatment effects, this invention aims to provide a relatively inexpensive, locally adaptable, highly integrated, convenient and efficient management and maintenance process that offers stable treatment results and energy savings. This process will meet the wastewater treatment needs of rural areas, maintain the long-term stable operation of rural wastewater treatment plants, and achieve environmental protection and sustainable development goals. Summary of the Invention

[0004] A brief overview of the invention is given below to provide a basic understanding of certain aspects of it. It should be understood that this overview is not an exhaustive summary of the invention. It is not intended to identify key or essential parts of the invention, nor is it intended to limit the scope of the invention. Its purpose is merely to present certain concepts in a simplified form as a prelude to the more detailed description that follows.

[0005] In view of the aforementioned deficiencies in the prior art, the purpose of this invention is to provide a pre-anaerobic modified sequencing batch reactor (SBR) wastewater treatment system and method, to at least solve many problems in current rural township wastewater treatment, such as incompatibility with existing urban wastewater treatment plant processes, limited investment funds, immature management and maintenance technologies, high energy consumption, limited site area, and unstable treatment effects. This process is a relatively inexpensive, adaptable to local conditions and variations in water quality and quantity, highly integrated, easy to manage and maintain, efficient, provides stable treatment results, and is energy-saving. It can meet the wastewater treatment needs of rural areas, maintain the long-term stable operation of township wastewater treatment plants, and meet the requirements of environmental protection and sustainable development.

[0006] According to a first aspect of the present invention, a pre-anaerobic modified sequencing batch reactor (MSBR) wastewater treatment system is provided, comprising: an anoxic tank, a biological treatment tank, and a sedimentation tank connected in sequence, wherein the biological treatment tank includes a first MSBR tank and a second MSBR tank connected at the bottom; wherein, A first nitrification liquor return pipeline is provided between the second MSBR tank and the anoxic tank to return the nitrification liquor generated in the second MSBR tank to the anoxic tank; a second nitrification liquor return pipeline is provided between the second MSBR tank and the first MSBR tank to return the nitrification liquor generated in the second MSBR tank to the first MSBR tank. A first sludge return pipeline is provided between the sedimentation tank and the anoxic tank to return the sludge generated in the sedimentation tank to the anoxic tank; a second sludge return pipeline is provided between the sedimentation tank and the first MSBR tank to return the sludge generated in the sedimentation tank to the first MSBR tank.

[0007] In a preferred embodiment of the above-mentioned pre-anaerobic modified sequencing batch reactor (MSBR) wastewater treatment system, the inlet of the anoxic tank is connected to the first inlet pipe, the first nitrification liquid return pipe, and the first sludge return pipe, respectively, to receive wastewater transported from the wastewater lift pump, nitrification liquid generated in the second MSBR tank, and sludge generated in the sedimentation tank; the outlet of the anoxic tank is connected to the first MSBR tank through a pipe. Preferably, the inlet of the anoxic tank is located at the bottom of one side, and the outlet is located at the top of the opposite side. Preferably, the anoxic tank is equipped with a push-flow aerator, which is connected to an external blower. Further, the push-flow aerator is a circumferential three-dimensional push-flow aerator, and the blower is a ring blower.

[0008] In a preferred embodiment of the above-mentioned pre-anaerobic modified sequencing batch reactor wastewater treatment system, the inlet end of the first MSBR tank is connected to the second inlet pipe, the second nitrification liquid return pipe, and the second sludge return pipe, respectively, to receive the effluent from the anoxic tank, the nitrification liquid generated in the second MSBR tank, and the sludge generated in the sedimentation tank. Preferably, the second water inlet pipe is a horizontal straight pipe with multiple water outlet holes evenly opened on it; Furthermore, the outlet sections of the second nitrification liquid return pipe and the second sludge return pipe are arranged along the direction of the second inlet pipe and are raised at an angle of 40-50° to the water surface.

[0009] In a preferred embodiment of the above-mentioned pre-anaerobic modified sequencing batch reactor (MSBR) wastewater treatment system, an effluent collection pipe is provided above the effluent side of the second MSBR tank. Preferably, the water collection pipe is a horizontal straight pipe with multiple water inlet holes evenly opened on one side and water outlet holes provided on the other side, which is connected to the water inlet pipe of the sedimentation tank.

[0010] In a preferred embodiment of the above-mentioned pre-anaerobic modified sequencing batch reactor (MSBR) wastewater treatment system, both the first MSBR tank and the second MSBR tank are equipped with aeration devices at the bottom to provide dissolved oxygen and agitate the mixed liquor within the tanks. Preferably, the aeration device is a microporous aeration device, including microporous aeration discs evenly distributed on the bottom of the pool and an air pipe connected thereto, with the other end of the air pipe connected to a blower; further, the blower is a Roots blower.

[0011] The aforementioned pre-anaerobic modified sequencing batch reactor wastewater treatment system, as a preferred embodiment, further includes: an automatic control system, which is connected to the auxiliary equipment of the anoxic tank, the biological tank, and the sedimentation tank respectively, and controls their operation.

[0012] According to a second aspect of the present invention, an operating method for the above-mentioned pre-anaerobic modified sequencing batch reactor wastewater treatment system is provided, comprising: the biological tank operating in a cyclical manner, each cycle comprising: an aeration stage, a stagnation stage, and an influent / effluent stage. During the aeration stage, the wastewater treatment system stops influent and effluent, and aeration occurs in the biological treatment tank, while the nitrified liquid in the second MSBR tank is returned. During the stagnation phase, the wastewater treatment system stops influent and effluent, aeration ceases in the biological treatment tank, and nitrification liquid in the second MSBR tank is no longer returned. During the influent and effluent stages, the wastewater treatment system receives and effluent, the sludge from the sedimentation tank is returned, aeration ceases in the biological treatment tank, and the nitrified liquid in the second MSBR tank is no longer returned. Preferably, the cycle is one hour, with each stage accounting for 50%, 8.3%, and 41.7% of the time, respectively.

[0013] In the above-mentioned operation method of the pre-anaerobic modified sequencing batch reactor wastewater treatment system, as a preferred embodiment, the dissolved oxygen in the anoxic tank is maintained at 0.2-0.5 mg / L.

[0014] In the above-mentioned pre-anaerobic modified sequencing batch reactor wastewater treatment system, as a preferred embodiment, in the anoxic tank, the plug-flow aerator is turned on for 50-55 minutes, then stopped for 5-10 minutes, and then turned on again, and so on; the blower is turned on for 5-10 minutes, then stopped for 50-55 minutes, and then turned on again, and so on.

[0015] In the above-mentioned operation method of the pre-anoxic modified sequencing batch reactor wastewater treatment system, as a preferred embodiment, the nitrification liquor recirculation ratio is 200%-300% during the aeration stage; preferably, the ratio of the nitrification liquor recirculation rate in the anoxic tank to the nitrification liquor recirculation rate in the first MSBR tank is 2:1.

[0016] During the influent and effluent stages, the sludge return ratio is 100%-150%; preferably, the ratio of sludge return flow in the anoxic tank to sludge return flow in the first MSBR tank is 2:1.

[0017] This invention, through reasonable improvements to the structure and operation of traditional sequencing batch reactors (SBRs), avoids the irrational use of time and space in traditional SBRs. It connects two modified SBR tanks (a first MSBR tank and a second MSBR tank) in series. Through a special structure and different influent methods, the wastewater in the first MSBR tank flows downwards while the wastewater in the second MSBR tank flows upwards, creating two different biochemical environments. An anoxic tank is set up at the front end, using a circumferential three-dimensional push-flow aerator and a ring blower to provide stirring and a micro-oxygen environment, constructing a pre-anoxic modified sequencing batch reactor (AMSBR) process. Under time-logic control via PLC, this process operates stably for a long time in a mode where aeration occurs without water inflow and water inflow occurs without aeration, efficiently treating rural wastewater and removing pollutants such as organic matter, nitrogen, and phosphorus.

[0018] Compared with the prior art, the beneficial effects of the present invention are: (1) The pre-anoxic tank enables the process to cope with the high concentration of wastewater in some rural areas without affecting the subsequent biochemical section. It plays a certain buffering role in the system and improves the process's resistance to shock. The anoxic tank can decompose large organic molecules in wastewater into small molecules, which is more conducive to the removal of pollutants. At the same time, when dealing with smelly wastewater, the anoxic tank can also play a deodorizing role, ensuring the air quality in the plant area.

[0019] (2) By making reasonable improvements to the structure and operation of the traditional sequencing batch activated sludge process, while retaining the intermittent water intake method, the decanting and stirring structures are eliminated, so that the biological treatment section can operate continuously with full water and constant water, avoiding the idle time of the tank in the traditional method. The utilization rate of the tank space of the biological treatment section is improved, the water treatment volume per unit time is higher, and the stirring effect is provided for the system while aeration, avoiding the energy consumption of setting up a separate stirrer.

[0020] (3) By adopting the operation mode of aeration without water intake and water intake without aeration, the aeration stage time in the biological tank can be adjusted according to the daily water treatment volume and effluent status, avoiding the occurrence of equipment operation during unnecessary operating periods, saving energy consumed by aeration to a certain extent, and also increasing the operability of the process.

[0021] (4) The two biological treatment tanks are connected in series and the two tanks are connected by openings at the bottom of the partition, so that the sewage in the tank can flow forward in a push flow manner, and the sludge concentration in the two tanks is different, thus creating two different biological reaction environments, and the pollutant removal effect is more significant.

[0022] (5) The present invention has the advantages of simple structure, convenient operation and management, low energy consumption and strong impact resistance, which significantly improves the treatment efficiency, energy consumption and treatment effect stability compared with traditional sewage treatment processes. At the same time, the process can also adapt to the special environmental and water quality conditions in rural areas and can be flexibly adjusted according to specific needs. Attached Figure Description

[0023] The present invention can be better understood by referring to the description given below in conjunction with the accompanying drawings, in which the same or similar reference numerals are used throughout the drawings to denote the same or similar parts. These drawings, together with the following detailed description, are incorporated in and form part of this specification, and are used to further illustrate preferred embodiments of the invention and explain the principles and advantages of the invention. Wherein: Figure 1 This is a schematic diagram of the pre-anoxic modified sequencing batch reactor according to an embodiment of the present invention; The reference numerals in the figure are as follows: 1-Anoxic tank; 11-First nitrification liquid return pipe; 12-First sludge return pipe; 13-First inlet pipe; 14-Inlet control valve; 15-Flow meter; 16-Circular three-dimensional push flow aerator; 17-Circular blower; 18-Outlet; 2-Biological treatment tank; 201-First modified sequencing batch activated sludge reactor (hereinafter referred to as the first MSBR tank); 202-Second modified sequencing batch activated sludge reactor (hereinafter referred to as the second MSBR tank); 21-Second inlet pipe; 22-Second nitrification liquor return pipe; 23-Second sludge return pipe; 24-Second sludge return control valve; 25-Second nitrification liquor return control valve; 26-First nitrification liquor return control valve; 27-First sludge return control valve; 28-First air valve; 29-Sludge venting valve; 210 - Microporous aeration disc; 211 - Through hole; 212 - Water collection pipe; 213 - Air pipe; 214 - Second air pipe valve; 215 - Nitrification liquid return pump; 3-Sedimentation tank; 31-Sludge return pump; 32-Overflow weir; 33-Guide cylinder; 34-Outlet pipe.

[0024] Those skilled in the art should understand that the same reference numerals represent the same components or components with equivalent functions. All drawings are merely for the purpose of explaining the technical content of the present invention. The numbers used in the preferred embodiments, the positions of components, the relationships between components, and the dimensions of components, etc., do not constitute a limitation on the technical solution itself, but should be extended to the entire field covered by this technical field. The elements and components in the drawings are shown only for simplicity and clarity, and are not necessarily drawn to scale; for example, the dimensions of some elements and components in the drawings may be enlarged relative to other elements and components to help improve the understanding of the embodiments of the present invention. Detailed Implementation

[0025] Exemplary embodiments of the invention will be described below with reference to the accompanying drawings. For clarity and brevity, not all features of actual implementations are described in the specification. However, it should be understood that many implementation-specific decisions must be made in the development of any such actual embodiment to achieve the developer’s specific goals, such as complying with those constraints related to the apparatus and business, and these constraints may vary from implementation to implementation. Furthermore, it should be understood that while development work can be very complex and time-consuming, such development work is merely a routine task for those skilled in the art who benefit from the content of this invention.

[0026] It should also be noted that, in order to avoid obscuring the invention with unnecessary details, only the device structure and / or processing steps closely related to the solution of the invention are shown in the accompanying drawings, while other details that are not closely related to the invention are omitted.

[0027] It should be noted that, in this invention, "A and / or B" should be interpreted as any one of the following three parallel cases: A; B; A and B. For example, "first air valve and / or second air valve" should be interpreted as any one of the following three parallel cases: first air valve; second air valve; first air valve and second air valve.

[0028] The first aspect of this invention provides a pre-anaerobic modified sequencing batch reactor (SBR) wastewater treatment system, see [link to relevant documentation]. Figure 1 An example structure of the above-described treatment system is shown, comprising an anoxic tank 1, a biological treatment tank 2, and a sedimentation tank 3 connected in sequence. The biological treatment tank 2 includes a first modified sequencing batch reactor (MSBR) 201 and a second modified MSBR 202 connected at the bottom. The various facilities and their connections are further described below.

[0029] 1. Anoxic pool 1 The primary function of the anoxic tank 1 is to detoxify, denitrify, decompose macromolecules, and remove odors from wastewater. If the influent contains macromolecular organic matter that aerobic microorganisms cannot directly utilize, the anaerobic reaction process of some facultative anaerobic microorganisms in the anoxic tank, through a hydrolysis and acidification stage, transforms these macromolecular organic matter, which is unfavorable to subsequent aerobic microorganisms, into a smaller molecular state that can be directly used by aerobic microorganisms, thus improving the biodegradability of the wastewater. Since domestic wastewater generally does not contain toxic substances, the detoxification process also involves transforming substances unfavorable to subsequent aerobic microorganisms into various reactions that facilitate subsequent treatment, thereby improving the biochemical performance of the wastewater. Furthermore, during the collection of domestic wastewater, anaerobic fermentation inevitably occurs in sewage pipes and collection wells, producing gases with unpleasant odors such as hydrogen sulfide and methanethiol. Long-term anaerobic processes can cause the wastewater in the collection wells to become foul-smelling. The anoxic tank contains various microbial communities, some of which have the ability to degrade sulfides and other odor-producing substances. These microorganisms regulate the generation and release of odor substances through interaction and competition. Some anaerobic bacteria can use odorous substances such as hydrogen sulfide as electron acceptors for respiration, converting them into odorless substances such as sulfates. Furthermore, in anoxic ponds, some chemical reactions also participate in the deodorization process. For example, hydrogen sulfide can react with metal ions to form insoluble metal sulfide precipitates, reducing the concentration and odor of hydrogen sulfide to some extent. Denitrification under anoxic conditions can achieve nitrogen removal.

[0030] Typically, the anoxic tank 1 can be square or cylindrical, but this invention does not limit it to this shape. Under appropriate conditions, other cross-sectional shapes can also be used, as long as they do not excessively affect the flow pattern of the internal wastewater. The anoxic tank 11 is connected to the first inlet pipe 13, the first nitrification liquid return pipe 11, and the first sludge return pipe 12, respectively. Wastewater can be introduced into the anoxic tank 1 through the first inlet pipe 13. The anoxic tank 11 is connected to the second MSBR tank 202 through the first nitrification liquid return pipe 11, and can receive the nitrification liquid generated and returned by the second MSBR tank 202. The anoxic tank 11 is connected to the sedimentation tank 3 through the first sludge return pipe 12, and can receive the sludge generated and returned from the bottom of the sedimentation tank 3. The anoxic tank 11 is also equipped with a push-flow aerator connected to a blower. The outlet 18 of the anoxic tank 11 is connected to the first MSBR tank 201 through a pipe.

[0031] In this embodiment of the invention, the anoxic tank 1 mainly consists of a circumferential three-dimensional propulsion aerator 16 and a ring blower 17. The circumferential three-dimensional propulsion aerator 16 generates a vortex effect through the rotation of its bottom blades, causing the sludge deposited at the bottom of the tank to agitate and suspend in the tank. The ring blower 17 intermittently aerates the tank, breaking larger air bubbles into smaller ones under the action of the blades of the circumferential three-dimensional propulsion aerator 16, providing dissolved oxygen (DO) to the sludge in the tank, thereby better maintaining the anoxic state with low DO in the tank. Preferably, both the circumferential three-dimensional propulsion aerator 16 and the ring blower 17 are connected to an automatic control system, which controls their operating modes. For example, in a preferred embodiment of the invention, the circumferential three-dimensional propulsion aerator 16 operates for 55 minutes, then stops for 5 minutes, and then starts again, repeating this cycle; while the ring blower 17 operates for 5 minutes, then stops for 55 minutes, and then starts again, repeating this cycle. The anoxic tank 1 is equipped with a first inlet pipe 13, a first nitrification liquid return pipe 11, and a first sludge return pipe 12, which respectively realize the inflow of sewage, the return of nitrification liquid from the second MSBR tank 202, and the return of sludge from the sedimentation tank 12. The first inlet pipe 13 is equipped with an inlet control valve 14 (such as a manual butterfly valve with a one-way valve) and a flow meter 15 (such as a rotor flow meter), and is connected to a sewage lift pump, that is, it is connected to the collection well storing the sewage to be treated through the sewage lift pump. The timing and amount of sewage inflow can be controlled by the sewage lift pump, the inlet control valve 14, and the flow meter 15.

[0032] The first nitrification liquor return pipe 11 is connected to the nitrification liquor return pipe of the second MSBR tank 202, forming the first nitrification liquor return pipeline. The first nitrification liquor return pipe 11 is equipped with a first nitrification liquor return control valve 26, such as a ball valve or other valve that can control the return flow. The start, stop and return flow of the nitrification liquor return process to the anoxic tank 1 are controlled by the power provided by the nitrification liquor return pump 215 installed on the return pipeline and the first nitrification liquor return control valve 26.

[0033] The first sludge return pipe 12 is connected to the sludge return pipe of the sedimentation tank 3, forming the first sludge return pipeline. The first sludge return pipe 12 is equipped with a first sludge return control valve 27, such as a ball valve or other valve that can control the return flow. The start, stop and return flow of the sludge return process to the anoxic tank 1 are controlled by the power provided by the sludge return pump 31 installed on the return pipeline and the first sludge return control valve 27.

[0034] Preferably, the outlets of the three water pipes, namely the inlet pipe 1, the first nitrification liquid return pipe 11, and the first sludge return pipe 12, are all arranged at the bottom of the opposite side of the outlet 18 of the anoxic tank 1. This maximizes the path of the incoming liquid to the outlet 18 and ensures thorough and uniform mixing with the raw water, avoiding the situation where the liquid enters and exits directly without treatment due to insufficient residence time in the anoxic tank 1.

[0035] 2. Biochemical Pool 2 The process method of this invention is a modified sequencing batch reactor (MSBR). Correspondingly, the biological treatment tank 2 of this invention also employs two modified MSBR reactors connected in series, eliminating the stirring device commonly found in traditional MSBR reactors and instead using aeration to agitate the mixed liquor within the tank. In embodiments of this invention, the biological treatment tank 2 includes a first modified MSBR reactor (first MSBR tank) 201 and a second modified MSBR reactor (second MSBR tank) 202, with their bottoms connected. The effluent from the first MSBR tank 201 flows through this second MSBR tank 202.

[0036] The main functions of biological tank 2 are: 1) to carry out aerobic nitrification, using the organic carbon source in the influent to convert ammonia nitrogen into nitrite nitrogen and nitrate nitrogen, which is convenient for subsequent return to anoxic tank 1 for denitrification; 2) to remove organic matter and reduce the COD of the effluent; 3) to remove phosphorus biologically, as polyphosphate-accumulating bacteria will take up phosphorus from the outside during the aerobic process and store it in the sludge in a polymerized form, ensuring that the phosphorus content in the effluent is low.

[0037] 2.1 First MSBR Pool 201 The first MSBR tank 201 is connected to a second inlet pipe 21, a second nitrification liquid return pipe 22, and a second sludge return pipe 23. The second inlet pipe 21 is connected to the outlet 18 of the anoxic tank 1 to receive the effluent from the anoxic tank 1. The second nitrification liquid return pipe 22 is connected to the second MSBR tank 202 to receive the nitrified liquid produced in the second MSBR tank 202. The second sludge return pipe 23 is connected to the sedimentation tank 3 to receive the sludge produced at the bottom of the sedimentation tank 3. The wastewater in the first MSBR tank 201 is circulated by the inlet water driving the movement of the raw water within the tank, making full use of gravity. The water flow direction is from top to bottom and from left to right (see [reference]). Figure 1 ).

[0038] Specifically, the second inlet pipe 21 of the first MSBR tank 201 is a horizontal inlet pipe. For example, a horizontally arranged UPVC straight pipe is provided on the first MSBR tank, and multiple small holes with a diameter of 35mm are evenly opened on the pipe so that the water is evenly distributed on the surface of the first MSBR tank 201. The second inlet pipe 21 is generally set above one side (inlet side) of the first MSBR tank 201. To ensure that the nitrified liquid and sludge returned to the first MSBR tank 201 are mixed evenly with the influent, the outlet sections of the second nitrified liquid return pipe 22 and the second sludge return pipe 23 can be set along the direction of the second influent pipe 21 (i.e., parallel to the second influent pipe 21) and raised at a 45° angle to the water surface. This ensures that the outlet direction of the returned nitrified liquid and sludge is perpendicular to the influent direction of the biological treatment tank 1. This design avoids the drawbacks of excessively high local pollutant concentrations and uneven mixing caused by the outlet direction of the returned nitrified liquid and sludge being basically consistent with the influent direction of the biological treatment tank 1.

[0039] The outlet of the first MSBR tank 201 is a through hole 211 located at the bottom of the other side of the tank body, which communicates with the second MSBR tank 202. (See also...) Figure 1 The influent to the first MSBR tank 201 is evenly distributed on the left side surface of the tank. The influent propels the movement of the raw water within the tank, fully utilizing gravity. The water flows from top to bottom and from left to right, passing through the bottom through-hole 211 and entering the second MSBR tank 202. Therefore, the first MSBR tank 201 is a downflow reactor.

[0040] The first MSBR tank 201 is equipped with an aeration device at the bottom to provide dissolved oxygen and to agitate the mixed liquor within the tank through aeration disturbance, eliminating the need for a traditional stirring device. More specifically, the aeration device is a microporous aeration device to provide microbubbles, such as a tubular microporous aerator or a disc microporous aerator. Preferably, the aeration device includes microporous aeration discs 210 evenly distributed at the bottom of the tank and an air pipe 213 connected to them. A first air pipe valve 28 is installed on the air pipe 213, and the other end of the air pipe 213 is connected to a blower. In a specific example, air branch pipes can be laid at the bottom of the first MSBR tank 201 and connected to several microporous aeration discs 210 (such as 260-type microporous aeration discs with a hole diameter of Φ260mm). Based on the tank size, blower power and other basic parameters, the required number of microporous aeration discs 210 can be reasonably set and evenly distributed at the bottom of the tank. The air branch pipes are connected to the air pipes 213 and indirectly connected to the blower (such as a Roots blower). The aeration timing and aeration volume can be adjusted by the first air pipe valve 28 (such as a cast iron butterfly valve) set on the air pipe 213.

[0041] The second nitrification liquor return pipe 22 is connected to the digestion return pipe of the second MSBR tank 202, and can receive the nitrified liquor generated and returned by the second MSBR tank 202. The second nitrification liquor return pipe 22 is equipped with a second nitrification liquor return control valve 25, such as a ball valve or other valve that can control the return flow. The start, termination and return flow of the nitrification liquor return process to the first MSBR tank 201 are controlled by the power provided by the nitrification liquor return pump 215 installed on the return pipe and the second nitrification liquor return control valve 25.

[0042] The second sludge return pipe 23 is connected to the sludge return pipe of the sedimentation tank 3, and can receive the concentrated sludge generated and returned from the bottom of the sedimentation tank 3. The second sludge return pipe 23 is equipped with a second sludge return control valve 24, such as a ball valve or other valve that can control the return flow. The start, termination and return flow of the concentrated sludge return process to the first MSBR tank 201 are controlled by the power provided by the sludge return pump 31 installed on the return pipe and the second sludge return control valve 24.

[0043] 2.2, Second MSBR Pool 202 The bottom of the second MSBR tank 202 is connected to the bottom of the first MSBR tank 201, through which wastewater in the first MSBR tank 201 flows to the second MSBR tank 202. That is, the inlet of the second MSBR tank 202 is located at the bottom of the tank. Typically, the first MSBR tank 201 and the second MSBR tank 202 are two structures of basically the same size, arranged side by side. In specific examples, they can be separated by a partition, with a through hole 211 at the bottom of the partition to connect the two tanks.

[0044] An effluent collection pipe 212 is provided above the other side (effluent side) of the second MSBR tank 202. Preferably, the effluent collection pipe 212 can be a horizontal pipe structure, placed horizontally on the second MSBR tank. In a specific example, a horizontal UPVC pipe can be provided on the second MSBR tank 202, with small holes evenly distributed on the pipe to collect the effluent, facilitating its transport to the subsequent sedimentation tank 3 for further treatment. See [link to relevant documentation] Figure 1 The effluent from the first MSBR tank 201 enters the second MSBR tank 202 through the through hole 211 at the bottom of the tank, pushing the raw water in the tank to the right and upward. Therefore, the second MSBR tank 202 is an upflow reactor.

[0045] The second MSBR tank 202 is also equipped with an aeration device at the bottom to provide dissolved oxygen and agitate the mixed liquor through aeration, eliminating the need for a traditional stirring device. More specifically, the aeration device is a microporous aeration device to provide microbubbles, such as a tubular microporous aerator or a disc microporous aerator. Preferably, the aeration device includes microporous aeration discs 210 evenly distributed at the bottom of the tank, connected to air pipes 213, with a second air pipe valve 214 installed on the air pipes 213, and a blower connected to the other end of the air pipes 213. In a specific example, air branch pipes can be laid at the bottom of the pool and connected to several microporous aeration discs 210 (such as the 260-type microporous aeration disc, whose aperture is Φ260mm, hence the name 260-type microporous aeration disc, which is a commercially available product). Based on the basic parameters such as the size of the pool and the power of the blower, the required number of microporous aeration discs 210 can be reasonably set and evenly distributed. The air branch pipes are connected to the air pipes 213 and indirectly connected to the blower (Roots blower). The aeration timing and aeration volume can be adjusted by the second air pipe valve 214 (such as a cast iron butterfly valve) set on the air pipe 213.

[0046] The second MSBR tank is equipped with a nitrification liquid return pipe, with its inlet end located near the bottom of the tank and its outlet end connected to the first nitrification liquid return pipe 11 and the second nitrification liquid return pipe 22 respectively. The nitrification liquid return pipe is equipped with a nitrification liquid return pump 215, which can provide power to supply the nitrification liquid generated by the second MSBR tank 202 to the anoxic tank 1 and the first MSBR tank 201.

[0047] 3. Sedimentation tank 3 The function of sedimentation tank 3 is to receive the effluent from biological treatment tank 2, separate the sludge from the water, clarify the mixed liquor, concentrate the sludge, and return the separated sludge. A conventional secondary sedimentation tank can be used. In one embodiment of the invention, sedimentation tank 3 is a conventional vertical flow sedimentation tank; a sludge hopper is provided at the bottom of the tank for sludge concentration; an overflow weir 32 is provided at the top of the tank, through which the settled clear water is collected and discharged via an outlet pipe 34; a guide tube 33 is provided in the middle of the tank, which is connected to the outlet of biological treatment tank 2. Specifically, the effluent from the second MSBR tank 202 can be introduced into sedimentation tank 3 through a pipeline connecting the effluent collection pipe 212 of the second MSBR tank 202 and the guide tube 33 of sedimentation tank 3. The sedimentation tank 3 is equipped with a sludge return pipe. Its inlet end is located near the bottom of the tank, and its outlet end is connected to the first sludge return pipe 12 and the second sludge return pipe 23 respectively. The sludge return pipe is equipped with a sludge return pump 31, which can provide concentrated sludge produced by the sedimentation tank 3 to the anoxic tank 1 and the first MSBR tank 201.

[0048] 4. Automatic control system In embodiments of the present invention, an automatic control system is used to control the operation of the anoxic tank 1, the biological treatment tank 2, and the sedimentation tank 3. Specifically, the present invention can use a PLC automatic control module to achieve full-area control of the entire wastewater treatment plant, including but not limited to controlling the start and stop of the bar screen system, wastewater lift pump, dosing system, the annular three-dimensional push-flow aerator 16 and the annular blower 17 in the anoxic tank 1, the Roots blower and the nitrification liquid return pump 215 in the biological treatment tank 2, the sludge return pump 31 in the sedimentation tank 3, and the sludge pump and submersible pump in the clear water tank.

[0049] The automatic control system of this invention possesses a strict time logic based on a pre-set program. Its core principle is to completely separate the aeration and influent stages in the biological treatment tank 2. For example, it operates on an hourly cycle, which consists of three main processes: the aeration stage, the stagnation stage, and the influent / effluent stage, sequentially occurring within the biological treatment tank 2. These three stages account for 50%, 8.3%, and 41.7% of the total time, respectively. Furthermore, the actual operating time of each stage can be appropriately adjusted based on the daily treated water volume and effluent quality, demonstrating good operability and avoiding energy waste caused by operating during unnecessary stages.

[0050] During the aeration stage, the automatic control system controls the Roots blower and nitrification liquor return pump 215 to operate, while the wastewater lift pump does not operate (i.e., the entire system stops both introducing and discharging wastewater). Simultaneously, the nitrified liquor produced in the second MSBR tank 202 is returned to the anoxic tank 1 and the first MSBR tank 201 respectively (the nitrification liquor return ratio is calculated based on the daily treatment volume (Q) and the tank volume, and is generally (2-3)). Q). Since the primary purpose of nitrifying liquor recirculation is for denitrification, the proportion of nitrifying liquor recirculated to anoxic tank 1 is relatively large, accounting for about 2 / 3 of the total recirculation flow. The purpose of recirculating to the first MSBR tank 201 is to agitate the water and prevent sludge buildup. Simultaneously, the two biological treatment tanks ensure more thorough pollutant removal; therefore, the proportion of nitrifying liquor recirculated to the first MSBR tank 201 does not need to be too high, about 1 / 3 of the total recirculation flow. In practical engineering, the ratio of recirculated liquor to anoxic tank 1 and the first MSBR tank 201 can be adjusted reasonably based on the denitrification effect of the biological treatment tank effluent. In one application example, the nitrifying liquor recirculation ratio at this stage is 300%, with the recirculation ratio of nitrifying liquor in anoxic tank 1 being 200% and the recirculation ratio of nitrifying liquor in the first MSBR tank 201 being 100%.

[0051] In addition, a short settling period is set after the aeration stage. This settling period is designed to allow the biological treatment tank 2 to settle for a period of time, facilitating sludge sedimentation and preventing excessive sludge contamination in the effluent. It also allows microorganisms to continue utilizing the remaining dissolved oxygen to further remove pollutants. During the settling period, the automatic control system stops the Roots blower and nitrification liquid return pump 215, ceasing aeration in the biological treatment tank 2 and stopping the return of nitrification liquid. The entire system remains in a state of neither inflow nor outflow, and sludge from the sedimentation tank 3 is not returned.

[0052] During the influent and effluent stages, the automatic control system activates the sludge return pump 31 and the wastewater lift pump, achieving a dual function of sludge return and influent / effluent discharge. Specifically, it achieves: 2) returning the concentrated sludge from the bottom of sedimentation tank 2 to anoxic tank 1 and biological treatment tank 2 respectively; 1) introducing wastewater into anoxic tank 1, while simultaneously feeding water into the first MSBR tank 201 from anoxic tank 1, and propelling the raw water in biological treatment tank 2 forward into sedimentation tank 3, from which sedimentation tank 3 discharges effluent. In one application example, this stage causes sludge generated in sedimentation tank 3 to be returned to anoxic tank 1 and the first MSBR tank 201 at a return ratio of 150%, where the sludge return ratio in anoxic tank 1 is 100%, and the sludge return ratio in the first MSBR tank 201 is 50%.

[0053] In addition, this wastewater treatment system is equipped with a chemical dosing system to address situations where the water quality and quantity do not meet biochemical requirements. Based on the influent and effluent water quality, the automatic control system can automatically control the addition of carbon sources, alkali solutions, and phosphorus removal agents, achieving full automation of the process. Other auxiliary subsystems, such as a bar screen system, a clear water tank sludge pump, and a submersible pump, are also included in this wastewater treatment system. These are connected to and controlled by the automatic control system to function when necessary, and will not be described in detail here.

[0054] The above are some preferred structural options of the present invention. Other structures are also possible for each of the aforementioned components. Each of the preferred structures can be used individually or in combination, provided they do not conflict with each other; combined use will yield better results.

[0055] A second aspect of the present invention also provides an operating method for the above-mentioned pre-anaerobic modified sequencing batch reactor wastewater treatment system, comprising: the biological treatment tank 2 operating in a cyclical manner, each cycle including: an aeration stage, a stagnation stage, and an influent / effluent stage, preferably with the time percentages of each stage being 50%, 8.3%, and 41.7%, respectively; During the aeration stage, the entire system stops influent and effluent, and aeration occurs in the biological treatment tank 2. The nitrified liquid in the second MSBR tank 202 is returned. That is, during this stage, the blower and the nitrified liquid return pump 215 are working while the sewage lift pump is not working. In this application, it is only required that the nitrified liquid return is carried out during the aeration stage and that the preset return flow rate is reached. It is not required that the start and stop times of the nitrified liquid return pump 215 and the blower are completely consistent. The nitrified liquid return pump 215 and the blower can adjust their respective operating times according to the treatment effect.

[0056] During the stagnation phase, the entire system stops inflowing and outflowing water, and aeration ceases in the biological tank 2. The nitrified liquid in the second MSBR tank 202 is no longer returned. That is, during this phase, the wastewater lift pump, the auxiliary equipment of the biological tank 2 including the blower, the nitrified liquid return pump 215, and the auxiliary equipment of the secondary sedimentation tank 3, the sludge return pump 31, are all not working. During the influent and effluent stages, the entire system influents and effluents, sludge is returned from sedimentation tank 3, aeration ceases in biological treatment tank 2, and nitrification liquid is no longer returned from the second MSBR tank 202. That is, during this stage, the blower and nitrification liquid return pump 215 are not operating, while the wastewater lift pump and sludge return pump 31 are operating. In this application, it is sufficient that sludge return occurs during the influent and effluent stages and reaches the preset return flow rate; it is not required that the start and stop times of the sludge return pump 31 be completely synchronized with those of the wastewater lift pump. The wastewater lift pump and sludge return pump 31 can adjust their respective operating times according to the actual treatment capacity.

[0057] In terms of operation, the wastewater treatment system of this invention operates entirely under the control of an intelligent control system that sequentially controls the start and stop of each device according to a time-based logic. For biological treatment tank 2, the main operating logic is "no water intake during aeration, and no aeration during water intake," which corresponds to the cyclical execution of three processes: aerobic, anoxic, and anaerobic. For example, the entire process is based on an hourly cycle, with the 30th minute as the dividing line within a cycle. The first 30 minutes are the aeration stage, which serves an aerobic function. During this stage, the sewage lift pump does not work (neither water enters nor exits). After aeration, the equipment in biological tank 2 is completely stopped for 5 minutes, which is the stagnation stage. The purpose is to allow biological tank 2 to stand still for a period of time to allow the sludge to settle, avoiding excessive sludge in the effluent. It is also to allow microorganisms to continue to use the remaining dissolved oxygen to further remove pollutants. From the 36th minute onwards, it is the influent and effluent stage. During this stage, the Roots blower attached to biological tank 2 does not work (no aeration). The sewage from anoxic tank 1 continues to utilize the dissolved oxygen that was not consumed in the aerobic stage in biological tank 2 until it is completely consumed. This stage involves a transition from anoxic to anaerobic processes.

[0058] Nitrification liquor recirculation is completed during the aeration stage, while sludge recirculation is completed during the influent and effluent stages. This design logic can prevent the sludge recirculation during aeration from causing the mixed liquor extracted from sedimentation tank 3 to be greater than the water entering from the second MSBR tank 202. Simultaneous activation of internal and external recirculation (i.e., simultaneous activation of nitrification liquor recirculation and sludge recirculation) would result in excessive water entering the first MSBR tank 201. Under the driving force of the water flow, wastewater from anoxic tank 1 would be mixed evenly in biological treatment tank 2 but before the pollutants were fully removed by microorganisms, and would then carry sludge into sedimentation tank 3. Sludge recirculation during the influent and effluent stages would not cause the above situation. If the nitrification liquid return pump 215 is turned on during the influent and effluent stages, there are the following disadvantages: (1) The sewage that has just entered the biological treatment tank 2 is returned to the anoxic tank 1 before it has been treated, which wastes energy and has no practical effect on sewage treatment; (2) The sludge is in a settling state during the influent and effluent stages. If the nitrification liquid return pump 215 is turned on at this time, it will cause a large loss of sludge in the second MSBR tank 202. Based on the above two disadvantages, the operation mode of synchronous influent and effluent and nitrification liquid return is not adopted.

[0059] Furthermore, within each operational phase, the operating time can be adjusted according to the actual wastewater treatment situation. Specifically, during the aeration phase, the aeration time can be adjusted based on the effluent indicators of sedimentation tank 3. For example, if the ammonia nitrogen content or COD in the effluent is too high, it indicates insufficient dissolved oxygen. This can be resolved by increasing the aeration time, adjusting the blower frequency, or adjusting the opening size of the first air valve 28 and / or the second air valve 214 (such as a manual butterfly valve). Conversely, the aeration time should be appropriately reduced. During the influent and effluent phases, the influent time should be reasonably adjusted according to the daily wastewater treatment volume and the wastewater lift pump flow rate. It is worth mentioning that, regardless of whether it is the aeration stage or the influent and effluent stage, the adjustment of the running time within the stage will not change the original stage setting logic. That is, the first 30 minutes of the one-hour running cycle is the aeration stage, the 5-minute pause is the stagnation stage, and the last 25 minutes is the influent and effluent stage. The so-called time adjustment is only carried out in the corresponding running stage. For example, in the set aeration stage of 30 minutes, the actual aeration time is adjusted within 30 minutes, such as 10 minutes, 20 minutes, 25 minutes, 30 minutes, etc. This has the following advantages: (1) The program setting can be reasonably adjusted according to the actual operating conditions of the sewage treatment plant, and the operation and management are convenient and simple; (2) The running time is adjusted according to the treatment volume and treatment effect, avoiding the occurrence of equipment operation in unnecessary running stages, and keeping the entire process cycle within one hour, which saves energy consumption to a certain extent; (3) A short stagnation stage is set after the aeration stage. In other words, in the work of one cycle, at least 5 minutes of settling time is reserved after aeration treatment, which avoids excessive loss of sludge in the biological tank and also increases the pollutant removal time, making the effluent clearer.

[0060] In the above operating method, as a preferred embodiment, the dissolved oxygen in the anoxic tank 1 is maintained at 0.2-0.5 mg / L.

[0061] More preferably, in the anoxic tank 1, the circumferential three-dimensional push-flow aerator 16 is turned on for 50-55 minutes and then stopped for 5-10 minutes, and then turned on again, and so on; the annular blower 17 is turned on for 5-10 minutes and then stopped for 50-55 minutes, and then turned on again, and so on.

[0062] In the above operating method, as a preferred embodiment, for the biological tank 2, during the aeration stage, the nitrification liquor recirculation ratio is 200%-300%; more preferably, the ratio of the nitrification liquor recirculation rate in the anoxic tank 1 to the nitrification liquor recirculation rate in the first MSBR tank 201 is 2:1.

[0063] In the above operating method, as a preferred embodiment, for the biological treatment tank 2, the sludge return ratio is 100%-150% during the influent and effluent stages; more preferably, the ratio of the sludge return flow rate in the anoxic tank 1 to the sludge return flow rate in the first MSBR tank 201 is 2:1.

[0064] Example 1 The pre-anaerobic modified sequencing batch reactor wastewater treatment system of this embodiment includes: 1. Anoxic Pool 1: The main equipment consists of a circumferential three-dimensional propulsion aerator 16 and a ring blower 17. The circumferential three-dimensional propulsion aerator 16 generates a vortex effect through the rotation of its bottom blades, which agitates the sludge deposited at the bottom of the tank, suspending it in the tank. The ring blower 17 intermittently blows air into the tank, and the blades of the circumferential three-dimensional propulsion aerator 16 break larger bubbles into smaller bubbles, providing dissolved oxygen to the sludge in the tank, thereby maintaining a low DO (dissolved oxygen) anoxic state in the tank. Both the circumferential three-dimensional propulsion aerator 16 and the ring blower 17 are connected to an automatic control system, and their operating modes are controlled as follows: aerator on for 55 minutes, off for 5 minutes; ring blower on for 5 minutes, off for 55 minutes. The anoxic tank 1 is connected to the first inlet pipe 13, the first nitrification liquid return pipe 11, and the first sludge return pipe 12. The wastewater inlet pipe 13 is connected to a wastewater lift pump to introduce wastewater into the anoxic tank 1. The first nitrification liquid return pipe 11 is used to supply the nitrification liquid produced by the second MSBR tank 202. The first sludge return pipe 12 is used for the sludge produced at the bottom of the sedimentation tank 3. The outlets of the three inlet pipes (the aforementioned first inlet pipe 13, first nitrification liquid return pipe 11, and first sludge return pipe 12) are all arranged at the bottom of the diagonal side of the outlet of the anoxic tank 1. This maximizes the path of the incoming liquid to the outlet 18 and ensures thorough and uniform mixing, preventing the liquid from entering and exiting the anoxic tank 1 without treatment due to insufficient residence time.

[0065] 2. Biochemical Pool 2: Biological treatment tank 2 consists of two modified sequencing batch reactors (MSBRs) of essentially the same size and structure: the first MSBR tank 201 and the second MSBR tank 202. The first MSBR tank 201 and the second MSBR tank 202 are separated by a partition, with a through-hole 211 at the bottom of the partition connecting the two tanks. The influent to biological treatment tank 2 is gravity-flowed. A second influent pipe 21 (horizontally positioned UPVC pipe) is installed above the influent side of the first MSBR tank 201, with several 35mm holes evenly distributed on the pipe. The effluent from biological treatment tank 2 is collected by an effluent collection pipe 212 with the same structure as the influent pipe, horizontally positioned above the effluent side of the second MSBR tank 202, and finally connected to the guide tube 33 of sedimentation tank 3.

[0066] When the sewage lift pump is turned on, the influent will stay in the anoxic tank 1 for a period of time, undergoing denitrification, deodorization, and detoxification processes, and then be pushed to the inlet of MSBR tank #1 201. The influent is evenly distributed on the surface of the first MSBR tank 201 by the second inlet pipe 21. Under the driving force of the influent, the sewage after aeration treatment in the anoxic tank 1 will push the raw water in the first MSBR tank 201 from the top to the bottom, and then transition to the second MSBR tank 202 through the through holes 211 on the baffle. The influent at the bottom inlet of the second MSBR tank 202 will push the raw water upward to the effluent collection pipe 212, and finally enter the sedimentation tank 3 through the guide tube 33.

[0067] In this embodiment, the first MSBR tank 201 is a downflow reactor, while the second MSBR tank 202 is an upflow reactor. Wastewater travels the longest path from the inlet through the biological treatment tank 2 to the outlet. The different flow patterns in the two tanks also result in more thorough removal of pollutants. Simultaneously, the plug flow motion also causes a difference in sludge concentration between the two tanks. Due to the pushing action of the influent wastewater and the return of nitrifying liquid and sludge, the sludge deposited at the bottom of the first MSBR tank 201 enters the second MSBR tank 202 through the bottom openings 211. This results in a much higher sludge concentration in the second MSBR tank 202 than in the first MSBR tank 201, creating two different biological environments in the two tanks. In the first MSBR tank 201, due to the low sludge concentration, the number and activity of microorganisms are limited, resulting in a relatively low pollutant treatment capacity. However, the lower sludge concentration also reduces the resistance of the first MSBR tank 201, increasing water flow and providing greater contact opportunities between microorganisms and pollutants, indirectly enhancing the microbial degradation capacity. In the second MSBR tank 202, the higher sludge concentration provides a greater number and activity of microorganisms, enhancing the biodegradation capacity of pollutants. Furthermore, the high-concentration sludge contains a large amount of biofilm and extracellular polymers, which can better adsorb and immobilize pollutants, improving pollutant removal efficiency. Simultaneously, the increased sludge concentration also increases the flow resistance of wastewater within the tank, reducing water flow and allowing more time for pollutant removal. In addition, a nitrification liquid return pipe is installed in the second MSBR tank 202. Its inlet end is relatively close to the bottom of the tank. Its function is to return the nitrification liquid (i.e., the wastewater with greatly reduced organic matter content after aeration treatment and ammonia nitrogen oxidized into nitrate nitrogen and nitrite nitrogen through the nitrification process) to the pre-anoxic tank 1 and the first MSBR tank 201 respectively. The total return ratio is calculated based on the daily treated water volume (Q) and the volume of the biological treatment tank, and is generally (2-3). Q is 2-3 times the daily water treatment volume (Q). Among them, the return of nitrified liquid to the pre-anoxic tank 1 can play three roles: (1) reducing the influent load, (2) improving the process's resistance to shock, maintaining the sludge concentration in the anoxic tank 1 to a certain extent, and (3) through the artificially controlled anoxic environment, reducing the nitrate nitrogen and nitrite nitrogen contained in the return liquid to nitrogen gas through the denitrification process, thus achieving biological denitrification. In addition, the return of nitrification liquid to the first MSBR tank 201 can also reduce the load of wastewater entering the biological treatment tank 2, avoid the impact of excessively high instantaneous concentration on the microbial living environment, and improve the operational stability of the biological treatment tank 2. The return allows the wastewater to pass through the two reaction tanks again, and the pollutants are removed to a greater extent. At the same time, the return carries some sludge from the second MSBR tank, which also maintains a relatively constant sludge concentration in the biological treatment tank 2, and prevents the sludge concentration (MLSS) in the first MSBR tank 201 from being too low due to excessive sludge entering the second MSBR tank 202 under the action of water flow.

[0068] 3. Sedimentation tank 3: Sedimentation tank 3 is a vertical flow secondary sedimentation tank. A guide tube 33 is installed in the middle of the tank, which is connected to the effluent collection pipe 212 of the second MSBR tank 202 through a pipeline, thereby guiding the effluent of the second MSBR tank 202 into sedimentation tank 3. An overflow weir 32 is provided at the top of the tank, through which the clear water after sedimentation is discharged. A sludge hopper for thickening sludge is provided at the bottom of the tank; a sludge return pipe is also provided, with its inlet end located near the bottom of the tank, and its outlet end connected to the first sludge return pipe 12 and the second sludge return pipe 23 respectively, and thickened sludge is supplied to the anoxic tank 1 and the first MSBR tank 201 respectively through the sludge return pump 31.

[0069] 4. Automatic Control System: The automatic control system adopts a PLC automatic control module, which is connected to the corresponding equipment to realize the overall control of the entire sewage treatment plant, including the start and stop control of equipment such as the influent lift pump, the annular three-dimensional push flow aerator 16 and the ring blower 17 attached to the anoxic tank 1, the Roots blower and nitrification liquid return pump 215 attached to the biological treatment tank 3, and the sludge return pump 31 attached to the vertical flow secondary sedimentation tank.

[0070] The operation method of the pre-anaerobic modified sequencing batch reactor wastewater treatment system in this embodiment is as follows: The entire system operates in a cyclical manner, with each cycle lasting one hour. Each cycle includes an aeration phase (30 minutes), a stagnation phase (5 minutes), and an influent / effluent phase (25 minutes). During the aeration stage, the entire system stops inflow and outflow, aeration occurs in biological tank 2, and nitrification liquid is returned in the second MSBR tank 202. That is, during this stage, the blower and nitrification liquid return pump 215 work while the sewage lift pump does not work. During the stagnation phase, the entire system neither receives nor discharges water, and aeration ceases in biological tank 2. The nitrified liquid in the second MSBR tank 202 is no longer returned. That is, during this phase, the wastewater lift pump, the auxiliary equipment of biological tank 2 including the blower and nitrified liquid return pump 215, and the auxiliary equipment of secondary sedimentation tank 3, the sludge return pump 31, are all not working. During the influent and effluent stages, the entire system simultaneously receives and effluent, the sludge in sedimentation tank 3 is returned, and there is no longer aeration or nitrification liquid return in biological treatment tank 2. That is, during this stage, the blower and nitrification liquid return pump 215 do not work, while the sewage lift pump and sludge return pump 31 work.

[0071] In anoxic tank 1, the circumferential three-dimensional plug-flow aerator 16 operates for 50-55 minutes, then stops for 5-10 minutes, and then restarts, repeating this cycle. Similarly, the annular blower 17 operates for 5-10 minutes, then stops for 50-55 minutes, and then restarts, repeating this cycle. This maintains the dissolved oxygen in anoxic tank 1 at 0.2-0.5 mg / L. The operation of the circumferential three-dimensional plug-flow aerator 16 and the annular blower 17 in anoxic tank 1 is not directly related to the operation of the auxiliary equipment in biological tank 2; it is only necessary to maintain the dissolved oxygen in anoxic tank 1 at the aforementioned level.

[0072] For biological tank 2, during the aeration stage, the nitrification liquor return ratio is 200%-300%, and the ratio of the nitrification liquor return flow rate in anoxic tank 1 to that in the first MSBR tank 201 is 2:1; during the influent and effluent stages, the sludge return ratio is 100%-150%, and the ratio of the sludge return flow rate in anoxic tank 1 to that in the first MSBR tank 201 is 2:1.

[0073] After the wastewater treatment system in this embodiment was built, it underwent a one-week commissioning test, followed by a normal operation test. During the two months of normal operation, influent and effluent samples were repeatedly tested. The results are shown in Table 1. It can be seen that the effluent meets the design requirements of Class A of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB 18918-2002), and even far exceeds the design effluent standards. In subsequent actual operation, it also demonstrated excellent stability and removal performance. The effluent concentration of ammonia nitrogen was consistently less than 0.5 mg / L, total nitrogen less than 1 mg / L, total phosphorus less than 0.1 mg / L, and COD less than 15 mg / L, with removal rates all maintained above 85%.

[0074] Table 1. Test results of influent and effluent samples taken during two months of normal operation experiment.

[0075] In principle, the pre-anaerobic modified sequencing batch reactor (AMSBR) process of this invention combines the advantages of A... 2The MSBR system combines the advantages of both O and SBR systems. It exhibits different dissolved oxygen environments at different times, combining anoxic and anaerobic phases during influent and effluent flow, aerobic phase during aeration, and anoxic phase for a period after aeration stagnation. This system primarily degrades and removes pollutants during the aeration, stagnation, and influent / effluent flow stages. Phosphorus removal in the system relies on two methods: biological phosphorus removal by polyphosphate-accumulating bacteria in biological tank 2, and the addition of a phosphorus removal agent via a dosing pipe located near the effluent collection pipe 212 in the second MSBR tank 202. Wastewater after phosphorus removal agent addition enters sedimentation tank 3 for mixing and reaction, producing chemical sludge. Phosphorus removal is achieved by discharging the phosphorus-rich sludge from sedimentation tank 3. Nitrifying bacteria convert ammonia nitrogen to nitrate nitrogen under aerobic conditions. The digestate is then returned to anoxic tank 1 where denitrifying bacteria, under anoxic conditions, denitrify with a carbon source. Organic matter removal mainly relies on the absorption by polyphosphate-accumulating bacteria in the anoxic zone, the denitrification consumption by denitrifying bacteria, and the decomposition of organic matter by aerobic heterotrophic bacteria and polyphosphate-accumulating bacteria in the aeration zone. In terms of operation, the MSBR system strictly adheres to a system of aeration without water inflow and water inflow without aeration, and divides the operation into different time periods. Within the same cycle, different operating modes are used in different time periods to achieve different treatment objectives. Specifically, the MSBR system operates intermittently in a cyclical manner. One cycle includes three stages: aeration, stagnation, and influent / effluent. The fluid within the tank exhibits different movement patterns in different stages: During the aeration stage, due to the aeration and stirring effect, the MSBR tank operates in a completely mixed mode. At this time, the wastewater and flocculent sludge are in full contact, and microorganisms utilize the organic carbon source in the wastewater to perform nitrification to remove ammonia nitrogen and adsorb phosphorus. In the influent / effluent stage, since there is no aeration or stirring effect, the wastewater entering the MSBR tank from the second influent pipe 21 pushes the raw water that has been stationary for a period of time forward. At this time, the fluid movement pattern within the MSBR tank is plug flow, and under the action of this plug force... Most of the activated sludge in the first MSBR tank 201 will be pushed into the second MSBR tank 202 through the through holes 211 of the partition plate between the two tanks, thus forming two biochemical environments with different biomass. At the same time, due to the different influent and effluent methods in the two tanks of the biochemical tank 2 (influent at the surface and effluent at the bottom of the first MSBR tank 201; influent at the bottom and effluent at the surface of the second MSBR tank 202), the fluid in the first MSBR tank 201 will exhibit a descending flow, while the fluid in the second MSBR tank 202 will exhibit an upflow. The different fluid movement modes of descending and upflow will make the wastewater have the longest movement path when passing through the biochemical tank 2, which can provide sufficient hydraulic retention time for microorganisms to decompose and consume the pollutants in the influent.

[0076] Based on the above analysis, the pre-anaerobic modified sequencing batch reactor (AMSBR) process of the present invention has the following advantages: (1) Flexible operation and simple maintenance. The MSBR system adopts a sequencing batch cycle operation mode, and one cycle includes three stages: aeration, stagnation and influent / effluent stages, which correspond to aerobic, anoxic, anoxic and anaerobic processes, respectively. The time ratio of each stage in the operation cycle can be adjusted at any time according to the influent water quality characteristics and effluent requirements, and the system can be designed and operated with different configurations to achieve different treatment purposes. At the same time, the system maintains the operation mode of no water intake during the aeration stage and no aeration during the influent stage. (2) Due to the different influent and effluent positions in the two tanks of the MSBR system, the fluid in the first MSBR tank moves in a descending flow pattern, while the fluid in the second MSBR tank moves in an ascending flow pattern. Furthermore, due to the thrust force during influent, two biochemical environments with significant differences in biomass are formed, and a higher sludge concentration is maintained in the second MSBR tank. The unique fluid movement pattern of the two tanks results in the longest path that the wastewater travels through the tanks, ensuring that the system has sufficient hydraulic retention time for microbial metabolism, thus achieving a higher pollutant removal effect. (3) The reaction rate of wastewater biochemical treatment is directly proportional to the concentration of reactants. During the reaction process in the biochemical tank 2 of the entire AMSBR system, mixed liquor recirculation is carried out. Before the sludge enters the anoxic tank 1, there is a concentration and pre-denitrification process in the sedimentation tank 3. The concentration process ensures that there is sufficient sludge concentration in the anoxic tank 1 with a small sludge recirculation flow rate, increasing the actual hydraulic retention time of the anoxic tank 1, while reducing the dilution of the influent, which is equivalent to increasing the concentration of reactants, thereby increasing the reaction rate. (4) When the biological treatment tank 2 is in the sedimentation stage (stagnation stage and influent / effluent stage), due to the lack of aeration and agitation and the stagnation period, the sludge in the biological treatment tank 2 settles to the bottom of the tank, forming a sludge layer. The sludge layer before and after the baffle (i.e., the partition between the MSBR#1 tank and the MSBR#2 tank) can act as a sludge filter to intercept and filter suspended particles in the sewage, which plays an important role in improving the effluent quality and denitrification caused by anoxic endogenous respiration. (5) Traditional SBR and its modified processes use decanters for drainage, and the system does not operate at a high water level for a considerable period of time, resulting in a reduction in the volume utilization rate of the reaction tank. However, the AMSBR system of the present invention always maintains a full water level and constant water level, making full use of the reaction tank volume and effectively increasing the treatment capacity per unit time. At the same time, the AMSBR system of the present invention retains the sequencing batch treatment method of the traditional SBR process, which is suitable for sewage treatment in rural areas with small water volume and complex composition (the cycle running time can be determined according to the water volume and influent composition).

[0077] Finally, it should be noted that, where applicable, relational terms such as left and right, first and second, etc., are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0078] Although the invention has been disclosed above through the description of specific embodiments, it should be understood that those skilled in the art can design various modifications, improvements, or equivalents to the invention within the spirit and scope of the appended embodiments. These modifications, improvements, or equivalents should also be considered to be included within the scope of protection claimed by the invention.

Claims

1. A pre-anaerobic modified sequencing batch reactor (SBR) wastewater treatment system, characterized in that, It includes an anoxic tank (1), a biological treatment tank (2), and a sedimentation tank (3) connected in sequence, wherein the biological treatment tank (2) includes a first MSBR tank (201) and a second MSBR tank (202) connected at the bottom; wherein, A first nitrification liquid return pipeline is provided between the second MSBR tank (202) and the anoxic tank (1) for returning the nitrification liquid generated in the second MSBR tank (202) to the anoxic tank (1); a second nitrification liquid return pipeline is provided between the second MSBR tank (202) and the first MSBR tank (201) for returning the nitrification liquid generated in the second MSBR tank (202) to the first MSBR tank (201); A first sludge return pipeline is provided between the sedimentation tank (3) and the anoxic tank (1) for returning the sludge generated in the sedimentation tank (3) to the anoxic tank (1); a second sludge return pipeline is provided between the sedimentation tank (3) and the first MSBR tank (201) for returning the sludge generated in the sedimentation tank (3) to the first MSBR tank (201). The first MSBR tank (201) is a downflow reactor, and the second MSBR tank (202) is an upflow reactor. The outlet of the first MSBR tank (201) is a through hole (211) located at the bottom of the other side of the tank. The water inlet of the first MSBR tank (201) is evenly distributed on the left side surface of the first MSBR tank. The water inlet pushes the movement of the raw water in the tank, making full use of gravity. The water flows from top to bottom and from left to right, through the through hole (211), into the second MSBR tank (202), and continues to push the raw water in the tank to move to the right and upward. It also includes: an automatic control system, which is connected to the auxiliary equipment of the anoxic tank (1), the biological tank (2) and the sedimentation tank (3) respectively, and controls their operation; The biological tank (2) operates in a cycle, and each cycle includes: aeration stage, stagnation stage, and water inlet and outlet stage. During the aeration stage, the wastewater treatment system stops influent and effluent, and aeration is carried out in the biological tank (2), while the nitrified liquid in the second MSBR tank (202) is returned. During the stagnation phase, the wastewater treatment system stops influent and effluent, and aeration ceases in the biological treatment tank (2), while the nitrified liquid in the second MSBR tank (202) no longer flows back. During the influent and effluent stages, the wastewater treatment system receives and effluent, and the sludge in the sedimentation tank (3) is returned, and the biological treatment tank (2) is no longer aerated, and the nitrified liquid in the second MSBR tank (202) is no longer returned.

2. The pre-anaerobic modified sequencing batch reactor wastewater treatment system according to claim 1, characterized in that, The inlet of the anoxic tank (1) is connected to the first inlet pipe (13), the first nitrification liquid return pipe (11) and the first sludge return pipe (12) respectively, and receives sewage transported from the sewage lift pump, nitrification liquid generated in the second MSBR tank (202) and sludge generated in the sedimentation tank (3); the outlet of the anoxic tank (1) is connected to the first MSBR tank (201) through a pipe.

3. The pre-anaerobic modified sequencing batch reactor wastewater treatment system according to claim 2, characterized in that, The inlet of the anoxic pool (1) is located at the bottom of one side, and the outlet is located at the top of the opposite side.

4. The pre-anaerobic modified sequencing batch reactor wastewater treatment system according to claim 2 or 3, characterized in that, The anoxic pool (1) is equipped with a push-flow aerator, which is connected to an external blower.

5. The pre-anaerobic modified sequencing batch reactor wastewater treatment system according to claim 4, characterized in that, The aerator is a circumferential three-dimensional aerator, and the blower is a ring blower.

6. The pre-anaerobic modified sequencing batch reactor wastewater treatment system according to claim 1, characterized in that, The first MSBR tank (201) is connected above the inlet end to the second inlet pipe (21), the second nitrification liquid return pipe (22), and the second sludge return pipe (23), respectively, to receive the effluent from the anoxic tank (1), the nitrification liquid generated in the second MSBR tank (202), and the sludge generated in the sedimentation tank (3).

7. The pre-anaerobic modified sequencing batch reactor wastewater treatment system according to claim 6, characterized in that, The second water inlet pipe (21) is a horizontal straight pipe with multiple water outlet holes evenly opened on it.

8. The pre-anaerobic modified sequencing batch reactor wastewater treatment system according to claim 7, characterized in that, The outlet sections of the second nitrification liquid return pipe (22) and the second sludge return pipe (23) are set along the direction of the second inlet pipe (21) and are raised at an angle of 40-50° to the water surface.

9. The pre-anaerobic modified sequencing batch reactor wastewater treatment system according to claim 1, characterized in that, An effluent collection pipe (212) is provided above the effluent side of the second MSBR tank (202).

10. The pre-anaerobic modified sequencing batch reactor wastewater treatment system according to claim 9, characterized in that, The water collection pipe (212) is a horizontal straight pipe with multiple water inlet holes evenly opened on one side and water outlet holes on the other side, which is connected to the water inlet pipe of the sedimentation tank (3).

11. The pre-anaerobic modified sequencing batch reactor wastewater treatment system according to any one of claims 6-10, characterized in that, Both the first MSBR tank (201) and the second MSBR tank (202) are equipped with aeration devices at the bottom to provide dissolved oxygen and agitate the mixed liquid in the tank.

12. The pre-anaerobic modified sequencing batch reactor wastewater treatment system according to claim 11, characterized in that, The aeration device is a microporous aeration device, including microporous aeration discs (210) evenly distributed on the bottom of the pool and air pipes (213) connected thereto, with the other end of the air pipes (213) connected to a blower.

13. The pre-anaerobic modified sequencing batch reactor wastewater treatment system according to claim 12, characterized in that, The blower is a Roots blower.

14. The method of operating the pre-anaerobic modified sequencing batch reactor wastewater treatment system as described in any one of claims 1-13, characterized in that, include: The biological tank (2) operates in a cycle, and each cycle includes: aeration stage, stagnation stage, and water inlet and outlet stage. During the aeration stage, the wastewater treatment system stops influent and effluent, and aeration is carried out in the biological tank (2), while the nitrified liquid in the second MSBR tank (202) is returned. During the stagnation phase, the wastewater treatment system stops influent and effluent, and aeration ceases in the biological treatment tank (2), while the nitrified liquid in the second MSBR tank (202) no longer flows back. During the influent and effluent stages, the wastewater treatment system receives and effluent, and the sludge in the sedimentation tank (3) is returned, and the biological treatment tank (2) is no longer aerated, and the nitrified liquid in the second MSBR tank (202) is no longer returned.

15. The operating method as described in claim 14, characterized in that, The cycle is one hour, with each stage accounting for 50%, 8.3%, and 41.7% of the time, respectively.

16. The operating method according to claim 14 or 15, characterized in that, The dissolved oxygen in the anoxic pool (1) is maintained at 0.2-0.5 mg / L.

17. The operating method according to claim 16, characterized in that, In the anoxic pool (1), the push-flow aerator is turned on for 50-55 minutes and then stopped for 5-10 minutes, and then turned on again, and so on; the blower is turned on for 5-10 minutes and then stopped for 50-55 minutes, and then turned on again, and so on.

18. The operating method according to claim 16, characterized in that, During the aeration stage, the nitrification liquor reflux ratio is 200%-300%.

19. The operating method according to claim 18, characterized in that, During the aeration stage, the ratio of the nitrification liquor return flow rate in the anoxic tank (1) to the nitrification liquor return flow rate in the first MSBR tank (201) is 2:

1.

20. The operating method according to claim 18 or 19, characterized in that, During the influent and effluent stages, the sludge return ratio is 100%-150%.

21. The operating method according to claim 20, characterized in that, During the influent and effluent stages, the ratio of sludge return flow in the anoxic tank (1) to sludge return flow in the first MSBR tank (201) is 2:1.

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