A method for in-situ conversion of an MBR system into an AGS system

Abstract

This invention relates to a method for in-situ conversion of an MBR system into an AGS system, comprising the following steps: S1, setting the HRT of the aerobic granular sludge system based on the available area and water treatment capacity of the original biological treatment tank in the MBR system, and redistributing the tank volume of the original biological treatment tank in the MBR system; S2, removing the original biological treatment tank partitions, guide walls, and their internal equipment according to the required tank volume, sealing the original inlet / outlet and return pipe holes, and adding new partitions to form a predetermined number of aerobic granular sludge tanks; S3, converting the original MBR membrane tanks in the MBR system into interconnected high-efficiency sedimentation tanks and filter cloth filters according to the treatment scale and variation coefficient of the aerobic granular sludge tanks; S4, installing online instruments and process equipment, and reprogramming the wastewater treatment plant control system to achieve process control. Its beneficial effect is that the system can be successfully transformed with minimal modifications to the original structures, greatly saving conversion costs.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a method for in-situ conversion of an MBR system into an AGS system. Background Technology

[0002] MBR (Membrane Bioreactor) process systems are widely used due to their small footprint and high effluent quality, especially in underground wastewater treatment plants. Currently, large-scale municipal wastewater treatment plants primarily utilize MBR processes in combination with biological treatment processes such as AO, A2O, and SBR, along with MBR membrane tanks. Nitrogen and phosphorus removal are achieved in the biological treatment tank, while rapid sludge-water separation is achieved in the MBR membrane tank. Although MBR processes reduce the footprint and improve treatment load and effluent quality compared to traditional processes like AO, A2O, and SBR, they also have drawbacks: high membrane costs, susceptibility to membrane fouling requiring regular replacement of membrane modules, inconvenience in operation and management, and high energy consumption. This is mainly due to the need to maintain a certain membrane driving pressure, high aeration intensity, and the need to flush the membrane surface during the sludge-water separation process. Additionally, the biological treatment stage involves high chemical consumption.

[0003] AGS (Aerobic Granular Sludge) technology is hailed as a next-generation wastewater treatment technology. Aerobic granular sludge has a high particle density, exhibiting shock resistance and rapid settling. The settling effect of aerobic granular sludge in 5 minutes is essentially equivalent to that of traditional flocculent sludge in 30 minutes. Furthermore, the granular, layered structure enables simultaneous nitrogen and phosphorus removal, resulting in stronger treatment capacity and better effluent quality. Therefore, aerobic granular sludge technology represents a major trend in the future of water treatment.

[0004] Currently, for existing and operational MBR (Membrane Bioreactor) systems, due to the aforementioned systemic problems, upgrading the MBR process to other processes to achieve energy conservation and emission reduction requires dismantling and rebuilding the original system. This inevitably leads to a significant increase in civil engineering costs, land acquisition costs, and other investment expenses. While aerobic granular sludge technology can avoid these problems, there is still a lack of effective methods for upgrading MBR systems to aerobic granular sludge systems in situ, especially when there is no new land available around the wastewater treatment plant. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a method for in-situ conversion of an MBR system into an AGS system, which solves the technical problems of high operating costs such as high energy consumption and high chemical consumption of existing MBR systems, as well as the difficulty and high cost of in-situ upgrade and conversion of MBR systems.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0009] In a first aspect, embodiments of the present invention provide a method for in-situ conversion of an MBR system into an AGS system, comprising the following steps: S1, redistribution of tank volume: based on the available area and water treatment capacity of the original biological tank in the MBR system, the HRT of the aerobic granular sludge system is set, and the tank volume of the original biological tank in the MBR system is redistributed; S2, according to the required tank volume, the original biological tank partition walls, guide walls and their internal equipment are removed, the original inlet and outlet and return pipe holes are sealed, and new partition walls are added to form a predetermined number of aerobic granular sludge tanks; S3, according to the treatment scale and variation coefficient of the aerobic granular sludge tanks, the original MBR membrane tanks in the MBR system are converted into interconnected high-efficiency sedimentation tanks and filter cloth tanks, and the effluent from the aerobic granular sludge tanks flows sequentially through the high-efficiency sedimentation tanks and filter cloth tanks; S4, online instruments and process equipment are installed in the civil engineering system after the conversion in steps S2 and S3, and the wastewater treatment plant control system is reprogrammed to realize process control.

[0010] The modification involves directly redistributing the volume of the existing biological treatment tanks in the MBR system, converting them into a predetermined number of aerobic granular sludge tanks. The existing MBR membrane tanks are then transformed into high-efficiency sedimentation tanks and cloth filter tanks. The main civil engineering components of the original MBR system (ground and perimeter walls, etc.) remain unchanged. Furthermore, other upstream and downstream water treatment units remain unchanged, significantly reducing modification costs. A new AGS water treatment system is formed in situ based on the MBR system, requiring no additional land, demonstrating strong engineering adaptability. Simultaneously, the modified AGS system offers higher water treatment capacity, significantly reduced energy and chemical consumption, and better effluent quality, achieving multiple benefits.

[0011] In a preferred embodiment of the present invention, in S2 of the method described, after modification, an inlet buffer tank and a sludge buffer tank are provided inside or outside the aerobic granular sludge tank area; the inlet buffer tank can supply water to be treated to the aerobic granular sludge tank; the sludge to be discharged from the aerobic granular sludge tank can flow to the sludge buffer tank.

[0012] In cases where the existing MBR system's distribution well is small or there is no reserved land, a portion of the original biological treatment tank area needs to be used as an influent buffer tank and a sludge buffer tank. If there is reserved land, it is possible to construct separate influent and sludge buffer tanks, using the entire original biological treatment tank area of ​​the MBR system for aerobic granular sludge tanks. This allows for flexible configuration of the influent and sludge buffer tanks as needed, offering high flexibility in the design.

[0013] In a preferred embodiment of the present invention, in the method described in S2, the volume ratio of the influent buffer tank to the individual aerobic granular sludge tank is 1:20-1:5, and the volume ratio of the sludge buffer tank to the individual aerobic granular sludge tank is 1:50-1:20; the influent buffer tank is located close to the inlet of the aerobic granular sludge system. According to the aforementioned volume ratio, the existing limited space of the system can be fully utilized, further improving the hydraulic efficiency and treatment effect of the system, and reducing energy consumption.

[0014] In a preferred embodiment of the present invention, in the method described in S2, there are multiple aerobic granular sludge tanks, and each aerobic granular sludge tank has an equal volume; the length-to-width ratio of a single aerobic granular sludge tank is ≤2; the aerobic granular sludge tanks are operated in a sequential batch manner, and the preset number of aerobic granular sludge tanks is ≥2; wherein, when the preset number of aerobic granular sludge tanks is ≥3, continuous influent and effluent operation can be achieved.

[0015] The equal volume of each aerobic granular sludge tank ensures balanced system operation and prevents significant differences in water treatment between tanks due to large volume variations, which would hinder system control. The low aspect ratio design improves the operational efficiency of aeration and water distribution equipment within the tanks, while also enhancing sludge settling performance. Using a sequencing batch reactor (SBR) operation for the aerobic granular sludge tanks further enhances the system's flexibility and adaptability.

[0016] In a preferred embodiment of the present invention, in the method described in S2, when the preset number of aerobic granular sludge tanks is greater than 4, the tanks are operated in groups; the aerobic granular sludge tanks in each group and the individual aerobic granular sludge tanks in each group are operated in parallel.

[0017] For situations involving more than one aerobic granular sludge tank, adopting a grouped parallel operation method can achieve more precise operation control and improve the stability and efficiency of the system.

[0018] In a preferred embodiment of the present invention, in the method described in S3, each aerobic granular sludge tank is equipped with an effluent overflow weir, and the overflow weir is connected to the high-efficiency sedimentation tank.

[0019] In a preferred embodiment of the present invention, in S2, an inlet device, a drain device, an aeration device, a water distribution device, and a sludge discharge device are installed in each aerobic granular sludge tank; magnetic levitation fans are added according to the number of aerobic granular sludge tank groups, and the magnetic levitation fans are connected to the aeration devices separately or together with the original fans of the MBR system.

[0020] If the existing blower of the MBR system can be utilized, a small number of magnetic levitation blowers can be added for air volume adjustment in the aerobic granular sludge tank, which saves the cost of replacing the blower.

[0021] In a preferred embodiment of the present invention, in step S4 of the method, the installation of online instruments includes: installing a dissolved oxygen sensor, an ORP sensor, an ammonia nitrogen sensor, a nitrate sensor, a phosphate sensor, a level gauge, and a sludge concentration meter in the aerobic granular sludge tank; installing level gauges in the influent buffer tank and the sludge buffer tank respectively; installing a phosphate sensor and a level gauge in the high-efficiency sedimentation tank; and installing a level gauge and an SS measuring instrument in the filter cloth filter tank.

[0022] Under the condition that the requirements of use are met, existing instruments and sensors can be used, which further saves on the cost of modification.

[0023] In a preferred embodiment of the present invention, the method described in step S4, reprogramming the wastewater treatment plant control system, includes: redesigning the process UI interface; setting up operation control programs for the aerobic granular sludge tank, high-efficiency sedimentation tank, filter cloth filter, influent buffer tank, and sludge buffer tank; and connecting and debugging the control programs with the process equipment and online instruments in the aerobic granular sludge tank, high-efficiency sedimentation tank, filter cloth filter, influent buffer tank, and sludge buffer tank to enable the aerobic granular sludge tank, high-efficiency sedimentation tank, filter cloth filter, influent buffer tank, and sludge buffer tank to operate according to the set control programs.

[0024] As a preferred embodiment of the present invention, the method is modified when the water treatment load of the MBR system is low, and the MBR system is modified in groups.

[0025] Choosing a time when the MBR system's water treatment load is relatively low and implementing the retrofit in groups can minimize the impact on the existing water treatment process, ensure a smooth transition during the retrofit process, and reduce retrofit costs and risks.

[0026] (III) Beneficial Effects

[0027] The beneficial effects of this invention are as follows: This invention provides a method for in-situ conversion of an MBR system into an AGS system. By directly reclassifying the original biological treatment tank in the MBR system into a predetermined number of aerobic granular sludge tanks, and then transforming the original MBR membrane tanks into interconnected high-efficiency sedimentation tanks and cloth filter tanks, the effluent from the aerobic granular sludge tanks flows sequentially through these tanks. Other upstream and downstream water treatment units remain unchanged, thus forming a new AGS water treatment system in situ within the MBR system. Compared to existing technologies, the modified system can fully leverage the advantages of AGS water treatment, such as high efficiency and low consumption. Furthermore, it eliminates the need to increase the footprint of the original MBR system, achieving a smooth transition from an MBR system to an AGS system with minimal modifications to the existing structures, significantly reducing conversion costs.

[0028] Adding an influent buffer tank and a sludge buffer tank can stabilize the influent water quality and flow rate, avoid the impact of shock loads on the aerobic granular sludge tank, and provide buffer space for sludge treatment, thereby enhancing the stability and flexibility of the system.

[0029] The volume ratio of the influent buffer tank to the individual aerobic granular sludge tank is 1:20-1:5, and the volume ratio of the sludge buffer tank to the individual aerobic granular sludge tank is 1:50-1:20. This can make full use of the limited space, further improve the hydraulic efficiency and treatment effect of the system, and reduce energy consumption.

[0030] The equal volume of each aerobic granular sludge tank ensures balanced system operation, while the low aspect ratio design improves the performance of aeration and water distribution equipment within the tanks, and enhances sludge settling properties. Sequencing-batch operation of the aerobic granular sludge tanks increases system flexibility and adaptability. For systems with more than one aerobic granular sludge tank, parallel operation in groups allows for more precise operational control, improving system stability and efficiency.

[0031] Adding magnetic levitation fans as needed can ensure the adjustability of the aeration process in the aerobic granular sludge tank, while retaining the original fans to the greatest extent possible, thus saving on renovation costs.

[0032] Choosing a time when the MBR system's water treatment load is relatively low and implementing the retrofit in groups can minimize the impact on the existing water treatment process, ensure a smooth transition during the retrofit process, and reduce retrofit costs and risks. Attached Figure Description

[0033] Figure 1 This is a layout diagram of the MBR system before modification in Embodiment 1 of the method for in-situ conversion of an MBR system into an AGS system according to the present invention;

[0034] Figure 2 for Figure 1 Layout diagram of the MBR system being upgraded to an AGS system. Detailed Implementation

[0035] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] This invention provides a method for in-situ conversion of an MBR system into an AGS system. It addresses the high energy and chemical consumption issues of existing MBR systems, as well as the difficulties and high costs of in-situ upgrades. The method involves directly reclassifying the original biological treatment tanks in the MBR system into a predetermined number of aerobic granular sludge tanks. Then, the original MBR membrane tanks are transformed into interconnected high-efficiency sedimentation tanks and filter cloth tanks. The effluent from the aerobic granular sludge tanks flows sequentially through these tanks, while other upstream and downstream water treatment units remain unchanged. This creates a new AGS water treatment system in situ within the MBR system. Compared to existing technologies, the converted system fully leverages the high efficiency and low consumption advantages of AGS water treatment. Furthermore, it eliminates the need to increase the footprint of the existing MBR system, achieving a smooth transition from MBR to AGS with minimal modifications to the existing structures, thus significantly reducing conversion costs.

[0037] To better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present invention can be understood more clearly and thoroughly, and that the scope of the present invention can be fully conveyed to those skilled in the art.

[0038] Example 1

[0039] This embodiment provides a method for in-situ conversion of an MBR system into an AGS system, specifically taking wastewater treatment plant A as an example. Figure 1 As shown, the wastewater treatment plant originally used the A2O+MBR process, with a designed treatment capacity of 50,000 tons / day. It was constructed of rectangular reinforced concrete and divided into two groups. The anaerobic tank had a HRT of 1.5h, the anoxic tank 4.5h, the aerobic tank 6h, and the facultative tank 1.1h, for a total HRT of 13.1h. The effective water depth was 6m, and the tank depth was 6.5m. The membrane tank had an HRT of 1.06h, a tank depth of 5m, and an effective water depth of 3.6m, divided into 10 compartments. The influent water quality for the A2O+MBR process is shown in Table 1.

[0040] Table 1

[0041]

[0042] The following are the specific steps for the renovation of Wastewater Treatment Plant A:

[0043] (1) Design and implementation of aerobic granular sludge tanks, high-efficiency sedimentation tanks, and cloth filter tanks: such as Figure 1 and Figure 2As shown, based on the water treatment scale of Wastewater Treatment Plant A and the treatment capacity of the AGS system, eight identical aerobic granular sludge tanks (AGS), one influent buffer tank, and one sludge buffer tank are designed. The existing equipment, pipes, and instruments in the original A2O biological treatment tank are removed, and the holes in the external wall of the A2O tank are sealed. The internal partitions are removed, and the internal volume of the A2O biological treatment tank is redistributed according to the above design using newly constructed partition walls. A space of at least 1.5m can be reserved between adjacent walls as a pipe gallery area for the external pipe layout of the AGS tanks.

[0044] Then, the auxiliary equipment inside the MBR membrane tank is removed, and the internal space is transformed into a high-efficiency sedimentation tank and a filter cloth filter. The volume ratio of the influent buffer tank to the individual aerobic granular sludge tank is 1:20-1:5, and the volume ratio of the sludge buffer tank to the individual aerobic granular sludge tank is 1:50-1:20.

[0045] The original MBR system's inlet is first connected to an inlet buffer tank, which is used to regulate the inlet flow rate and water quality to ensure the stability of the subsequent treatment process. The effluent from the inlet buffer tank then enters the AGS tank for nitrogen and phosphorus removal. The effluent from the upper part of the AGS tank then enters the high-efficiency sedimentation tank and the filter cloth filter in sequence. The high-efficiency sedimentation tank further removes total phosphorus and suspended solids (SS) contained in the effluent, and the filter cloth filter further removes suspended solids in the water.

[0046] (2) Installation of new equipment and pipelines: The 8 AGS tanks are divided into 2 groups. Each AGS tank is equipped with a water distribution device, an aeration device, a sludge removal device and a water outlet device. The external pipelines of the AGS tanks can be laid out in the pipe gallery area. When connecting with the pipelines for water inlet, drainage, sludge removal and aeration in the tank, holes can be reserved in the wall and then sealed after connection.

[0047] The inlet buffer tank is connected to the external water supply network (existing equipment) and is equipped with 5 inlet pumps, four in operation and one on standby. Two pumps are used for the inlet of one group of AGS tanks, and the other two are used for the other group of AGS tanks. Each group of AGS tanks can share a main pipeline, which is divided into four branch pipes within the pipe gallery area for water supply. Each branch pipe is equipped with an electric valve for control and is connected to the water distribution device in the AGS tank.

[0048] An overflow weir is installed at the top of the AGS tank as a drainage device, which can increase the effective depth of the AGS tank to about 6.3m. The drainage device is connected to the high-efficiency sedimentation tank.

[0049] Each of the eight AGS tanks is equipped with a sludge discharge device, which is connected to external pipelines. The sludge enters a sludge buffer tank through a pipe gallery. The sludge buffer tank is equipped with a sludge pump, which discharges substandard sludge to the existing sludge treatment unit. Here, some usable sludge particles can be recovered from the sludge buffer tank and reused in the AGS tanks.

[0050] If the existing blower can be utilized, only one new magnetic levitation blower needs to be added for air volume regulation within the AGS tank. A main aeration pipeline is led out from the blower room, splitting into two branch pipelines near the AGS tank. A pressure transmitter and a gas flow meter are installed on each branch pipeline. As the branch pipeline approaches the AGS tank, it splits into four branch pipelines, each connecting to one of the four internal aeration devices within the AGS tank. Regulating valves are installed on the branch pipelines to control the aeration volume within the AGS tank. The aeration pipelines are arranged at the top of the AGS tank and connected to the internal aeration devices.

[0051] (3) Instrument installation and automatic control system design:

[0052] Level gauges, as well as meters for dissolved oxygen, ammonia nitrogen, nitrate, and phosphate, were installed in all AGS tanks. The automation system for the AGS tank process was redesigned, referring to... Figure 2 The AGS tanks 1-4 are controlled as one group, while AGS tanks 5-8 are controlled as another group. All device and online instrument signals from the AGS tanks, high-efficiency sedimentation tanks, filter cloth filters, influent buffer tanks, and sludge buffer tanks are integrated into the automatic control system. An automatic control program is written to control the aeration, sludge discharge, influent, and effluent of the AGS tanks, achieving minimal human intervention.

[0053] Results of the retrofit: Before the retrofit, the MBR system had a treatment capacity of 50,000 tons / day, an HRT of 13.1 hours, and effluent COD, ammonia nitrogen, total nitrogen, and total phosphorus levels of ≤30, ≤1, ≤13.1, and ≤0.3 mg / L, respectively. The energy consumption per ton of water was approximately 0.35 kWh / m³. 3 After the AGS system was upgraded, its treatment capacity remained at 50,000 tons / day, with a HRT of 11.1 hours. The average values ​​of effluent COD, ammonia nitrogen, total nitrogen, and total phosphorus were ≤30, ≤1, ≤12.5, and ≤0.3 mg / L, respectively, and the energy consumption per ton of water was approximately 0.25 kWh / m³. 3 After the renovation, energy consumption per ton of water decreased by 28.6%, and overall drug consumption decreased by 21%.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for in-situ conversion of an MBR system into an AGS system, characterized in that, Includes the following steps: S1. Tank volume reallocation: Based on the available area and water treatment capacity of the original biological tank in the MBR system, set the HRT of the aerobic granular sludge system and reallocate the tank volume of the original biological tank in the MBR system. S2. According to the required tank volume, remove the original biological treatment tank partition wall, guide wall and its internal equipment, seal the original inlet and outlet and return pipe holes, and add new partition walls to form a preset number of aerobic granular sludge tanks. S3: Based on the treatment scale and variation coefficient of the aerobic granular sludge tank, the original MBR membrane tank in the MBR system is transformed into a high-efficiency sedimentation tank and a filter cloth filter that are interconnected. The effluent from the aerobic granular sludge tank flows through the high-efficiency sedimentation tank and the filter cloth filter in sequence. S4: Install online instruments and process equipment in the civil engineering system after the modifications in steps S2 and S3, and reprogram the wastewater treatment plant control system to achieve process control.

2. The method as described in claim 1, characterized in that, In S2, after the modification An inlet buffer tank and a sludge buffer tank are also provided inside or outside the aerobic granular sludge tank area. The inlet buffer tank can supply water to be treated to the aerobic granular sludge tank; The sludge awaiting discharge in the aerobic granular sludge tank can flow to the sludge buffer tank.

3. The method as described in claim 2, characterized in that, In S2, the volume ratio of the influent buffer tank to the individual aerobic granular sludge tank is 1:20-1:5, and the volume ratio of the sludge buffer tank to the individual aerobic granular sludge tank is 1:50-1:

20. The inlet buffer tank is located near the inlet of the aerobic granular sludge system.

4. The method as described in claim 1, characterized in that, In S2, there are multiple aerobic granular sludge tanks, and each aerobic granular sludge tank has the same volume. The aspect ratio of a single aerobic granular sludge tank is ≤2; The aerobic granular sludge tank adopts a sequencing batch operation, and the preset number of aerobic granular sludge tanks is ≥2. When the preset number of aerobic granular sludge tanks is ≥3, continuous influent and effluent operation can be achieved.

5. The method as described in claim 4, characterized in that, In S2, when the preset number of aerobic granular sludge tanks is greater than 4, the tanks will be operated in groups. The aerobic granular sludge tanks in each group, as well as the individual aerobic granular sludge tanks in each group, operate in parallel.

6. The method as described in claim 1, characterized in that, In S3, each aerobic granular sludge tank is equipped with an effluent overflow weir, which is connected to the high-efficiency sedimentation tank.

7. The method as described in claim 5, characterized in that, In S2, each aerobic granular sludge tank is equipped with an inlet device, a drain device, an aeration device, a water distribution device, and a sludge discharge device. Add magnetic levitation fans according to the number of aerobic granular sludge tank groups. The magnetic levitation fans can be connected to the aeration devices separately or together with the existing fans of the MBR system.

8. The method as described in claim 2, characterized in that, In S4, the online instruments to be installed include: a dissolved oxygen sensor, an ORP sensor, an ammonia nitrogen sensor, a nitrate sensor, a phosphate sensor, a level gauge, and a sludge concentration meter installed in the aerobic granular sludge tank. Level gauges were installed in the influent buffer tank and the sludge buffer tank, respectively. Install phosphate sensors and level gauges in the high-efficiency sedimentation tank; Install level gauges and SS measuring instruments in the filter cloth filter tank.

9. The method as described in claim 2, characterized in that, In S4, the redesign of the wastewater treatment plant control system includes: redesigning the process UI interface; Set up the operation control program for the aerobic granular sludge tank, high-efficiency sedimentation tank, filter cloth filter, influent buffer tank and sludge buffer tank; The control program is connected and debugged with the process equipment and online instruments in the aerobic granular sludge, high-efficiency sedimentation tank, filter cloth filter, influent buffer tank and sludge buffer tank to enable the aerobic granular sludge, high-efficiency sedimentation tank, filter cloth filter, influent buffer tank and sludge buffer tank to operate according to the set control program.

10. The method as described in claim 1, characterized in that, The timing for the upgrade is during seasons when the water treatment load of the MBR system is relatively low, and the MBR system is upgraded in groups.

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