A sludge concentration method applied to MBR membrane tank

Abstract

The present application realizes sludge concentration operation by adding a concentrated liquid reflux system in the MBR sewage treatment membrane tank, carries out sludge concentration while normal water production, can replace another sludge concentration facility, reduces investment and operation cost, and reduces the land occupation of the sludge concentration facility. The method comprises adding a sludge concentration pipeline (603) at the front end of the membrane tank corridor (102), discharging concentrated liquid to other areas of the membrane tank by the sludge concentration pipeline (603) through the action of a concentrated liquid pump (503), frequency control of the concentrated liquid pump (503), pipeline setting of a concentrated liquid flow meter (703) for monitoring the concentrated liquid flow, setting of a sludge discharge sludge concentration meter (203) on the sludge discharge pipeline side for monitoring the sludge concentration on the sludge discharge side. The operation of the water inlet gate (301), the water production pump (501) and the concentrated liquid pump (503) is controlled by a PLC industrial computer. The method can stabilize the sludge concentration of the sludge discharge system and make the sludge discharge system run efficiently.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment, and in particular relates to a method for thickening sludge and increasing sludge concentration using a membrane tank. Background Technology

[0002] In common activated sludge wastewater treatment systems, sludge needs to be periodically removed to maintain the activity of microorganisms and prevent sludge aging. The removed excess sludge is then processed by a desludge system to reduce its moisture content and volume, facilitating subsequent treatment.

[0003] In common MBR wastewater treatment processes, sludge thickening tanks or thickeners are typically used to concentrate sludge and increase the influent sludge concentration in the dewatering system, ensuring the stability and efficiency of the sludge removal system. However, sludge thickening tanks require a large area, and their thickening effect is affected by factors such as temperature, retention time, and sludge activity in the biological system, resulting in unstable thickening performance. Thickeners require additional supporting equipment and facilities, increasing investment and processing costs, and their thickening effect is also affected by sludge activity and thickening system operating parameters, leading to unstable results.

[0004] Sludge thickening tanks are a common structure used for sludge thickening, typically employing a vertical flow or radial flow design. They can be categorized into intermittent and continuous operation types. Intermittent operation is primarily used in small wastewater treatment plants or industrial wastewater treatment plants, while continuous operation is used in large and medium-sized wastewater treatment plants. The drawbacks of this process include: large footprint; extensive auxiliary equipment; and inconsistent thickening efficiency due to factors such as sludge retention time, temperature, and sludge settling properties. Summary of the Invention

[0005] To address the shortcomings of existing sludge thickening methods in MBR processes, this invention provides a sludge thickening method applied to MBR membrane tanks. By improving the existing MBR wastewater treatment process, a concentrate return system is added to the MBR wastewater treatment membrane tank to achieve sludge thickening operations. Sludge thickening is performed simultaneously with normal water production, replacing a separate dedicated sludge thickening facility, thus reducing investment and operating costs, and also reducing the footprint of the sludge thickening facility. The method includes adding a sludge thickening pipeline (603) at the front end of the membrane tank corridor (102). The sludge thickening pipeline (603) discharges concentrate to other areas of the membrane tank via a concentrate pump (503). The concentrate pump (503) is frequency-controlled, and a concentrate flow meter (703) is installed on the pipeline to monitor the concentrate flow rate. A sludge concentration meter (203) is installed on the sludge discharge pipeline side to monitor the sludge concentration on the discharge side. A PLC industrial control computer is used to control the operation of the inlet gate (301), the permeate pump (501), and the concentrate pump (503). This method can stabilize the sludge concentration in the sludge discharge system, thereby enabling the sludge discharge system to operate efficiently.

[0006] The sludge thickening method applied to an MBR membrane tank according to the present invention involves an MBR membrane tank comprising three interconnected membrane tank inlet zones (101), a membrane tank corridor (102), and a membrane tank return zone (103). Inlet gates (301) and return gates (302) are respectively installed at both ends of the membrane tank corridor (102). An MBR reactor (401) is installed in the membrane tank corridor (102), and a permeate pump (501) and a permeate flow meter (701) are installed on the permeate pipeline (601) connected to it. The membrane tank inlet... A sludge concentration meter (201) is installed in the inlet area (101), and a sludge concentration meter (202) is installed in the return area (103) of the membrane tank. A sludge discharge pipeline (602) is connected to the front end of the membrane tank corridor (102), and a sludge discharge pump (502) and a sludge discharge flow meter (702) are installed on the pipeline. The MBR reactor (401) produces treated water through the product water pipeline (601) under the suction action of the product water pump (501), and the sludge discharge pump (502) pumps the sludge to the sludge treatment system through the sludge discharge pipeline (602).

[0007] A concentrate return system is added to the MBR wastewater treatment membrane tank. The system consists of a sludge thickening pipeline (603), a concentrate pump (503), and a concentrate flow meter (703). The sludge thickening pipeline (603) is located near the sludge discharge pipeline (602) at the front end of the membrane tank corridor (102) and is connected to the membrane tank corridor (102). A concentrate pump (503) and a concentrate flow meter (703) are installed on it. The concentrate pump (503) pumps the concentrate to other areas of the membrane tank through the sludge thickening pipeline (603). The concentrate flow meter (703) is used to monitor the concentrate flow in real time. A sludge concentration meter (203) for monitoring the sludge concentration on the sludge discharge side is also added near the sludge discharge pipeline (602).

[0008] The operation control terminal of the MBR membrane tank is equipped with a PLC industrial control computer. The data acquisition terminals of the sludge concentration meter (201) in the influent zone, the sludge concentration meter (202) in the return zone, the sludge concentration meter (203) in the discharge zone, the permeate flow meter (701), the discharge flow meter (702), and the concentrate flow meter (703) are connected to the data input terminal of the PLC industrial control computer. The control signal output terminal of the PLC industrial control computer is connected to the control terminal of the influent gate (301), the permeate pump (501), and the concentrate pump (503).

[0009] The sludge thickening method includes the following steps:

[0010] S1. The control valve values ​​are determined in the PLC industrial control computer based on the parameters of sludge concentration, water production flow, sludge discharge flow and concentrate flow collected by the corresponding data acquisition terminal, and the control parameters of the inlet gate (301) and the concentrate pump (503) are preset.

[0011] S2. Close the inlet gate (301). When the membrane tank is operating normally and producing water, the inlet water of the membrane tank corridor (102) comes from the membrane tank return zone (103). When the inlet water flow rate is Q1, the inlet water concentration, which is the sludge concentration in the return zone, is MLSS (202). The product water flow rate is Q (701), the product water concentration is 0, the sludge discharge flow rate is Q (702), and the concentrate flow rate is Q (703). The sludge discharge and concentrate return concentrations are the same, which is MLSS (203). Through the conservation of water volume and the conservation of dry solids, we can obtain:

[0012] Q1=Q(701)+Q(702)+Q(703)

[0013] MLSS(203)×[Q(702)+Q(703)]=Q1×MLSS(202)

[0014] Conclusion:

[0015] MLSS(203)=MLSS(202)×[Q(701)+Q(702)+Q(703)]÷[Q(702)+Q(703)]

[0016] Substituting the concentration control threshold of the sludge concentration MLSS (203) set in the PLC industrial control computer into the above formula, the sludge concentration MLSS (202), sludge discharge flow rate Q (702), and product water flow rate Q (701) in the return zone are obtained from the data collected in real time by the PLC industrial control computer, and the corresponding concentrate flow rate Q (703) can be calculated.

[0017] S3. Based on the calculated concentrate flow rate Q (703), adjust the concentrate pump (503) in real time.

[0018] The operating frequency is adjusted to ensure that the actual flow rate equals the calculated flow rate; the data in step S2 change in real time and are calculated based on the average operating value to reduce the frequency of frequency conversion adjustment.

[0019] S4. The sludge concentration meter (203) reaches the preset maximum threshold, and the PLC industrial control computer issues a stop production order.

[0020] Water command: The permeate pump (501) is shut down to prevent damage to the membrane module due to excessive concentration.

[0021] S5. When the sludge concentration meter (203) reaches the preset minimum threshold, the PLC industrial control computer issues a stop sludge discharge command, and the sludge discharge pump (502) is shut down to prevent low-concentration sludge from entering the dewatering process and causing malfunctions.

[0022] Compared with existing sludge thickening technologies, the present invention has the following advantages:

[0023] By using PLC for real-time calculation and adjustment, the sludge concentration can be kept constant with an error within ±500mg / L, thereby stabilizing the subsequent sludge desludge system and achieving quality improvement and efficiency enhancement.

[0024] Adding a concentrate return system to the MBR wastewater treatment membrane tank enables sludge thickening without the need for additional thickening systems or thickening tanks. Sludge thickening is carried out simultaneously with normal water production, saving costs and reducing the footprint.

[0025] The PLC industrial control computer was used to realize real-time monitoring of water production and sludge discharge operations, and sludge concentration was achieved without affecting the normal operation of the water production system and the sludge discharge system.

[0026] It effectively avoids membrane module damage and dewatering process failures, reduces operating costs, and improves production efficiency. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the sludge thickening process structure of the MBR membrane tank of the present invention.

[0029] Figure 2 This is a schematic diagram of the PLC industrial control computer control logic of the present invention.

[0030] Legend: 101-Membrane tank inlet area, 102-Membrane tank corridor, 103-Membrane tank return area, 201-Inlet sludge concentration meter, 202-Return area sludge concentration meter, 203-Sludge discharge sludge concentration meter, 301-Inlet gate, 302-Return gate, 401-MBR reactor, 501-Permeate pump, 601-Permeate pipeline, 701-Permeate flow meter, 602-Sludge discharge pipeline, 502-Sludge discharge pump, 702-Sludge discharge flow meter, 603-Sludge thickening pipeline, 503-Concentrate pump, 703-Concentrate flow meter. Detailed Implementation

[0031] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0032] like Figure 1 As shown, this invention improves the existing MBR wastewater treatment process by adding a concentrate return system to the MBR wastewater treatment membrane tank to achieve sludge thickening. Sludge thickening occurs simultaneously with normal water production, replacing a separate dedicated sludge thickening facility, thus reducing investment and operating costs, and also reducing the floor space required for sludge thickening facilities. The sludge thickening method applied to an MBR membrane tank according to this invention involves an MBR membrane tank comprising three interconnected membrane tank inlet zones 101, a membrane tank corridor 102, and a membrane tank return zone 103. Inlet gates 301 and return gates 302 are respectively installed at both ends of the membrane tank corridor 102. An MBR reactor 401 is installed in the membrane tank corridor 102, and a permeate pump 501 and a permeate flow meter 701 are installed on the permeate pipeline 601 connected to it. An inlet sludge concentration meter 201 is installed in the membrane tank inlet zone 101, and a return zone sludge concentration meter 202 is installed in the membrane tank return zone 103. A sludge discharge pipeline 602 is connected to the front end of the membrane tank corridor 102, and a sludge discharge pump 502 and a sludge discharge flow meter 702 are installed on the pipeline. The MBR reactor 401 produces treated water through the product water pipeline 601 under the suction action of the product water pump 501, and the sludge discharge pump 502 pumps the sludge to the sludge treatment system through the sludge discharge pipeline 602.

[0033] The traditional sludge removal process for MBR membrane tanks is as follows:

[0034] During normal operation of the MBR membrane tank, the inlet gate 301 and return gate 302 of the membrane tank corridor are normally open. Wastewater treated by the upstream processes sequentially enters the membrane tank inlet zone 101, the membrane tank corridor 102, and the membrane tank return zone 103. The MBR reactor 401, under the suction of the permeate pump 501, produces treated water through the permeate pipeline 601. Wastewater flows from the membrane tank inlet zone 101 through the membrane tank corridor 102 to the membrane tank return zone 103. Simultaneously, the sludge concentration gradually increases as treated water is produced. The sludge discharge pipeline 602 is equipped with a sludge discharge pump 502 and a sludge discharge flow meter 702. The sludge is discharged by the sludge discharge pump 502 into a thickener or other sludge thickening equipment and facilities. After chemical dosing and physical sedimentation to increase the sludge concentration, it then enters the subsequent sludge dewatering system.

[0035] This invention adds a concentrate return system to the membrane tank of an MBR wastewater treatment plant. This system consists of a sludge thickening pipeline 603, a concentrate pump 503, and a concentrate flow meter 703. The sludge thickening pipeline 603 is located near the sludge discharge pipeline 602 at the front end of the membrane tank corridor 102 and connects to the corridor 102. The concentrate pump 503 and the concentrate flow meter 703 are installed on the pipeline. The concentrate pump 503 pumps the concentrate to other areas of the membrane tank through the sludge thickening pipeline 603, and the concentrate flow meter 703 monitors the concentrate flow rate in real time. A sludge concentration meter 203 is also added near the sludge discharge pipeline 602 to monitor the sludge concentration on the sludge discharge side. In the above facilities, the sludge thickening pipeline 603 is preferably a DN350 stainless steel pipe, and the concentrate pump 503 can preferably have a maximum flow rate of 270 m³ / h. 3 / h, variable frequency water pump, concentrate flow meter 703 preferably has a range of 0-50000 mg / L.

[0036] like Figure 2 As shown, in order to control the permeate and sludge thickening operations in real time, a PLC industrial control computer is set up at the operation control terminal of the MBR membrane tank. The data acquisition terminals of the sludge concentration meter 201 in the influent zone, the sludge concentration meter 202 in the return zone, the sludge concentration meter 203 in the discharge zone, the permeate flow meter 701, the discharge flow meter 702, and the concentrate flow meter 703 are connected to the data input terminals of the PLC industrial control computer. The control signal output terminals of the PLC industrial control computer are connected to the control terminals of the influent gate 301, the permeate pump 501, and the concentrate pump 503.

[0037] The sludge thickening method includes the following steps:

[0038] S1. The control valve values ​​are determined in the PLC industrial control computer based on the parameters of sludge concentration, water production flow, sludge discharge flow and concentrate flow collected by the corresponding data acquisition terminal, and the control parameters of the inlet gate 301 and the concentrate pump 503 are preset.

[0039] S2. When the inlet gate 301 is closed and the membrane tank is operating normally, the inlet water to the membrane tank corridor 102 comes from the membrane tank return zone 103. When the inlet flow rate is Q1, the inlet concentration, i.e., the sludge concentration in the return zone, is MLSS202. The product water flow rate is Q701, the product water concentration is 0, the sludge discharge flow rate is Q702, and the concentrate flow rate is Q703. The sludge discharge and concentrate return concentrations are the same, which is MLSS203. Through the conservation of water volume and the conservation of oven-dry solids, we can obtain:

[0040] Q1 = Q701 + Q702 + Q703

[0041] MLSS203×[Q702+Q703]=Q1×MLSS202

[0042] Conclusion:

[0043] MLSS203=MLSS202×[Q701+Q702+Q703]÷[Q702+Q703]

[0044] Substituting the concentration control threshold of sludge concentration MLSS203 set in the PLC industrial control computer into the above formula, the sludge concentration MLSS202 in the return zone, sludge discharge flow rate Q702, and product water flow rate Q701 are obtained from the data collected in real time by the PLC industrial control computer, and the corresponding concentrate flow rate Q703 can be calculated.

[0045] S3. Based on the calculated concentrate flow rate of Q703, adjust the operating frequency of concentrate pump 503 in real time.

[0046] The rate is adjusted so that the actual flow rate equals the calculated flow rate; the data in step S2 change in real time and are calculated based on the average operating value to reduce the frequency of frequency conversion adjustment.

[0047] S4. The sludge concentration meter 203 has reached the preset maximum threshold, and the PLC industrial control computer issues a stop production order.

[0048] Water command: Product water pump 501 shuts down to prevent damage to the membrane module due to excessive concentration.

[0049] S5. When the sludge concentration meter 203 reaches the preset minimum threshold, the PLC industrial control computer issues a stop sludge discharge command, and the sludge discharge pump 502 is shut down to prevent low-concentration sludge from entering the dewatering process and causing malfunctions.

[0050] The present invention, in conjunction with specific implementation examples, provides the following embodiment:

[0051] S1. The control valve values ​​are determined in the PLC industrial control computer based on the parameters of sludge concentration, water production flow, sludge discharge flow and concentrate flow collected by the corresponding data acquisition terminal, and the control parameters of the inlet gate 301 and the concentrate pump 503 are preset.

[0052] S2. Close the inlet gate 301. During normal operation of the membrane tank, the inlet water to the membrane tank corridor 102 comes from the membrane tank return zone 103. When the inlet flow rate is Q1, the inlet concentration, i.e., the sludge concentration MLSS202 in the return zone, is 8000 mg / L, and the product water flow rate Q701 is 220 m³ / L. 3 / h, permeate concentration is 0, sludge discharge flow rate Q702 is 50m³ / h, effluent concentration is 0, sludge discharge flow rate is 50m³ / h. 3 / h, the concentrate flow rate is Q703, the sludge discharge concentration MLSS203 is consistent with the concentrate return concentration, which is 16000 mg / L. Through water conservation and dry solids conservation, we can obtain:

[0053] MLSS203=MLSS202×[Q701+Q702+Q703]÷[Q702+Q703]

[0054] Substituting the control threshold of 16000 mg / L for the sludge concentration MLSS203 set in the PLC industrial control computer into the above formula, and using the data collected in real time by the PLC industrial control computer, it is determined that the sludge concentration MLSS202 in the return zone is 8000 mg / L, and the sludge discharge flow rate Q702 is 50 m³ / L. 3 / h, the product water flow rate Q701 is 220m³ / h. 3 / h, the corresponding concentrate flow rate Q703 is calculated to be 170m³. 3 / h.

[0055] S3. The calculated concentrate flow rate Q703 is 170m³. 3 / h, adjust the operating frequency of the concentrate pump 503 in real time to achieve the actual flow rate equal to the calculated flow rate; the data in the formula of step S2 change in real time and are calculated based on the average operating value to reduce the frequency of frequency conversion adjustment.

[0056] S4. The sludge concentration MLSS203 has reached the preset maximum threshold, and the PLC industrial control computer issues a stop production order.

[0057] Water command: Product water pump 501 shuts down to prevent damage to the membrane module due to excessive concentration.

[0058] S5. When the sludge concentration MLSS203 reaches the preset minimum threshold, the PLC industrial control computer issues a stop sludge discharge command, and the sludge discharge pump 502 is shut down to prevent low-concentration sludge from entering the dewatering process and causing malfunctions.

[0059] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1.A sludge concentration method applied to an MBR membrane tank, the MBR membrane tank comprising three mutually connected membrane tank water inlet areas (101), a membrane tank gallery (102), and membrane tank reflux areas (103), a water inlet gate (301) and a reflux gate (302) being respectively arranged at both ends of the membrane tank gallery (102); an MBR reactor (401) being arranged in the membrane tank gallery (102), a water production pump (501) and a water production flowmeter (701) being arranged on a water production pipeline (601) connected to the MBR reactor (401); a water inlet area sludge concentration meter (201) being arranged in the membrane tank water inlet area (101), and a reflux area sludge concentration meter (202) being arranged in the membrane tank reflux area (103); a sludge discharge pipeline (602) being connected to the front end of the membrane tank gallery (102), and a sludge discharge pump (502) and a sludge discharge flowmeter (702) being arranged on the sludge discharge pipeline (602); the MBR reactor (401) produces treated water through the water production pipeline (601) under the suction of the water production pump (501), and the sludge discharge pump (502) discharges sludge to a sludge treatment system through the sludge discharge pipeline (602); characterized in that: a concentrated liquid reflux system is additionally arranged in the MBR wastewater treatment membrane tank, the system comprising a sludge concentration pipeline (603), a concentrated liquid pump (503), and a concentrated liquid flowmeter (703), the sludge concentration pipeline (603) being arranged at a position close to the sludge discharge pipeline (602) at the front end of the membrane tank gallery (102) and being connected to the membrane tank gallery (102), the concentrated liquid pump (503) and the concentrated liquid flowmeter (703) being arranged on the sludge concentration pipeline (603), the concentrated liquid pump (503) discharging concentrated liquid to other areas of the membrane tank through the sludge concentration pipeline (603), and the concentrated liquid flowmeter (703) being used to monitor the flow of the concentrated liquid in real time; a sludge discharge sludge concentration meter (203) is additionally arranged at a position close to the sludge discharge pipeline (602) to monitor the sludge concentration on the sludge discharge side; a PLC industrial computer is arranged at the operation control end of the MBR membrane tank, and the data acquisition ends of the water inlet area sludge concentration meter (201), the reflux area sludge concentration meter (202), the sludge discharge sludge concentration meter (203), the water production flowmeter (701), the sludge discharge flowmeter (702), and the concentrated liquid flowmeter (703) are correspondingly connected to the data input end of the PLC industrial computer; the control signal output end of the PLC industrial computer is correspondingly connected to the control ends of the water inlet gate (301), the water production pump (501), and the concentrated liquid pump (503); the sludge concentration method comprises the following steps: S1.determining the control valve value of the water inlet gate (301) and the concentrated liquid pump (503) according to the control valve value of the sludge concentration, the water production flow, the sludge discharge flow, and the concentrated liquid flow acquired by the corresponding data acquisition end in the PLC industrial computer. ​ S2. Close the inlet sluice (301), when the membrane tank is running normally, the water inlet of the membrane tank corridor (102) comes from the membrane tank backflow area (103), when the water inlet quantity is Q1, the water inlet concentration is the sludge concentration of the backflow area MLSS (202), the water production flow is Q (701), the water production concentration is 0, the sludge discharge flow is Q (702), the concentrated liquid flow is Q (703), the sludge discharge and concentrated liquid backflow concentration are consistent, which is MLSS (203), through water conservation and absolute dry solid conservation, the following can be obtained: Q1=Q (701) +Q (702) +Q (703) MLSS (203) ×[Q (702) +Q (703)]=Q1×MLSS(202) Obtain: MLSS(203)=MLSS(202)×[Q(701)+Q(702)+Q(703)]÷[Q(702)+Q(703)] The sludge concentration MLSS (203) set in the PLC industrial computer is substituted into the above formula, the sludge concentration MLSS (202) of the backflow area, the sludge discharge flow Q (702) and the water production flow Q (701) are obtained by real-time acquisition of data through the PLC industrial computer, and the corresponding concentrated liquid flow Q (703) can be calculated; S3. According to the calculated corresponding concentrated liquid flow Q (703), the operating frequency of the concentrated liquid pump (503) is adjusted in real time to achieve that the actual flow is equal to the calculated flow; The data in step S2 formula changes in real time, and the calculation is made according to the running average, so as to reduce the frequency of frequency adjustment; S4. When the sludge concentration meter (203) reaches the preset maximum threshold, the PLC industrial computer sends a stop water production instruction, and the water production pump (501) is closed to prevent damage of the membrane group caused by excessive concentration; S5. When the sludge concentration meter (203) reaches the preset minimum threshold, the PLC industrial computer sends a stop sludge discharge instruction, and the sludge discharge pump (502) is closed to prevent low-concentration sludge from entering the dewatering process and causing failure.

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