A combined aerobic biological calcium removal system for papermaking wastewater

Abstract

This utility model relates to the field of wastewater treatment, and more particularly to an aerobic biological calcium removal co-treatment system for papermaking wastewater, comprising: a zoned aerobic tank, a monitoring module, a PLC controller, and actuator components; the zoned aerobic tank is divided into a front-end main degradation zone and a rear-end crystal nucleus growth zone by a retaining wall; the front-end main degradation zone is equipped with several first aeration devices, and the rear-end crystal nucleus growth zone is equipped with several second aeration devices; the monitoring module includes an online calcium ion monitor and a DO sensor located in the front-end main degradation zone, and an online pH meter, a DO sensor, and an alkalinity analyzer located in the rear-end crystal nucleus growth zone; the actuator components include a NaOH dosing pump, a Na2CO3 dosing pump, and a variable frequency aeration fan; the PLC controller is connected to the monitoring module and the actuator components via signal transmission lines. The overall system solves the problem of low sedimentation efficiency caused by homogeneous aeration through a physical zoning structure, and simultaneously addresses the problem of the lack of a dedicated calcium ion monitoring structure by introducing an embedded layout of the monitoring module.

Description

Technical Field

[0001] This utility model relates to the field of wastewater treatment, and more particularly to an aerobic biological calcium removal and co-treatment system for papermaking wastewater. Background Technology

[0002] Wastewater from the paper industry generally contains high concentrations of calcium ions (Ca). 2+ Concentrations ≥200mg / L can easily lead to pipe scaling, aeration device blockage, and sludge calcification, severely hindering the stable operation of the treatment system. Current mainstream technologies suffer from three structural defects:

[0003] 1. Chemical precipitation method relies on high reagent input: Traditional processes require the addition of large amounts of Na2CO3 / NaOH to induce precipitation, which not only accounts for more than 40% of the total treatment cost, but also leads to a surge in sludge volume of 30%-50%, significantly increasing the burden of subsequent sludge dewatering and disposal;

[0004] 2. The biological treatment unit lacks a dedicated structure for calcium removal: Conventional aerobic tanks use a homogeneous aeration design, resulting in strong fluid turbulence, making it difficult for calcium carbonate crystals to grow and precipitate, with a natural precipitation efficiency of only 30%-50%. More importantly, existing systems do not have a zoned control structure designed to meet the physical environmental requirements for calcium ion precipitation, leading to a persistently low calcium ion removal rate.

[0005] 3. Fragmented multi-parameter control leads to system instability: Calcium ion precipitation and organic matter degradation compete for alkalinity resources, but existing monitoring equipment only focuses on a single parameter (such as DO or pH) and has not established a pH-alkalinity-DO linkage control mechanism. When influent calcium ion levels fluctuate, the system cannot dynamically coordinate the process requirements of degradation and precipitation, frequently resulting in a chain of failures such as pH oscillations and decreased sludge activity. Summary of the Invention

[0006] To address the aforementioned issues, this invention provides an aerobic biological calcium removal co-treatment system for papermaking wastewater. It directly solves the problem of low sedimentation efficiency caused by homogeneous aeration through a physical partitioning structure, while simultaneously addressing the issue of the lack of a dedicated calcium ion monitoring structure by introducing an embedded layout of the monitoring module.

[0007] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0008] A papermaking wastewater aerobic biological calcium removal co-treatment system includes: a zoned aerobic tank, a monitoring module, a PLC controller, and actuator components;

[0009] The zoned aerobic tank is divided into a front main degradation zone and a rear crystal nucleus growth zone by a retaining wall; the front main degradation zone is equipped with several first aeration devices, and the rear crystal nucleus growth zone is equipped with several second aeration devices.

[0010] The monitoring module includes an online calcium ion monitor and a DO sensor located in the front main degradation zone, and an online pH meter, a DO sensor, and an alkalinity analyzer located in the rear crystal nucleation zone.

[0011] The actuator assembly includes a NaOH dosing pump connected to the upstream main degradation zone, a Na2CO3 dosing pump connected to the upstream main degradation zone, and variable frequency aeration blowers connected to the first aeration device and the second aeration device respectively; the PLC controller is connected to the monitoring module and the actuator assembly through signal transmission lines.

[0012] Furthermore, the front-end main degradation zone accounts for 65%-75% of the total volume of the partitioned aerobic tank, and the rear-end crystal nucleus growth zone accounts for 25%-35% of the total volume of the partitioned aerobic tank.

[0013] Furthermore, the aeration intensity of the first aeration device in the main degradation zone is an air volume of 6-10.8 m³ / s. 3 / (m 2 (·h), DO value controlled at 2.5-3.0 mg / L, the aeration intensity of the second aeration device in the downstream crystal nucleation zone is 2.4-4.8 m³ / h. 3 / (m 2 (·h), DO value controlled at 1.5-2.0mg / L.

[0014] Furthermore, the front main degradation zone is divided into several sub-regions by a retaining wall, and adjacent sub-regions are connected end to end by a reserved channel at the end of the retaining wall.

[0015] Furthermore, the sub-region located at the tail end is connected to the subsequent crystal nucleus growth region through a reserved channel at the end of the retaining wall.

[0016] Furthermore, the aspect ratio of each corridor in the sub-region and the subsequent crystal nucleus growth region is >5:1.

[0017] Furthermore, the variable frequency aeration blower is connected to the first aeration device and the second aeration device respectively through a suspended pipe or a pipe at the bottom of the pool.

[0018] The beneficial effects of this utility model are as follows:

[0019] 1. The physical partitioning structure (separating the main degradation zone at the front and the crystal growth zone at the rear by a retaining wall) directly solves the problem of low sedimentation efficiency caused by homogeneous aeration. The dense aeration device at the front (the first aeration device) generates strong turbulence, efficiently degrading organic matter and releasing CO2 to dissolve into HCO3. -This provides an ionic basis for calcium ion precipitation; the downstream sparse aeration device (second aeration device) significantly reduces fluid shear force, allowing wastewater to smoothly transition from a high-disturbance state to a low-disturbance state, providing a physical environment for CaCO3 crystal nuclei growth—this structure replaces the traditional single tank, fundamentally avoiding the environmental conflict between degradation and precipitation.

[0020] 2. The embedded layout of the monitoring module simultaneously addresses the issue of "lack of a dedicated calcium ion monitoring structure." The front-end online calcium ion monitor directly tracks Ca... 2+ Concentration changes (rather than relying on indirect parameters) are monitored, and the pH meter and alkalinity analyzer are installed close to the precipitation area to ensure that the data reflects the microenvironment for crystal growth in real time. When the monitoring data is sent to the PLC controller via the signal transmission line, the system immediately activates the actuator components: the NaOH dosing pump quickly injects the reagent to adjust the pH, the Na2CO3 dosing pump specifically replenishes the alkalinity, and the variable frequency aeration fan dynamically adjusts the aeration intensity of the front and rear sections (the fan of the first aeration device maintains high DO in the front section, and the fan of the second aeration device suppresses disturbances in the rear section).

[0021] 3. The PLC acts as the central control unit, integrating discrete parameters such as calcium ion concentration, pH, alkalinity, and dissolved oxygen (DO) into a unified control signal, instructing the actuators to respond in a coordinated manner within seconds. For example, when the pH in the downstream section decreases due to fluctuations in the influent, the pH meter signal triggers the PLC to start the dosing pump, while the aeration fan in the second aeration device gradually reduces the aeration volume to simultaneously lower the DO, preventing over-aeration from eroding sediment. The entire process requires no manual intervention; the PLC programmable controller automatically adjusts based on the detected data and possesses anti-interference capabilities. Attached Figure Description

[0022] Figure 1 This is a plan view of the aerobic tank layout in Embodiment 1 of this utility model.

[0023] Figure 2 This is a system module diagram of this utility model.

[0024] Figure 3 This is a plan view of the aerobic tank layout in Embodiment 2 of this utility model.

[0025] Reference numerals: 10. PLC controller; 11. Sub-region; 12. Rear crystal growth zone; 111. First aeration device; 121. Second aeration device; 13. Retaining wall; 110. Reserved channel; 21. Calcium ion online monitor; 22. DO sensor; 23. Online pH meter; 24. Alkalinity analyzer; 31. NaOH dosing pump; 32. Na2CO3 dosing pump; 33. Aeration fan of the first aeration device; 34. Aeration fan of the second aeration device. Detailed Implementation

[0026] Implementation method 1:

[0027] Please see Figure 1-2 As shown, this utility model relates to a large paper mill (daily processing capacity of 15,000 m³ / day). 3 In this system, high-calcium wastewater is treated efficiently through innovative physical structure. (See attached diagram.) Figure 2 As shown, the main degradation zone at the front of the push-flow corridor is divided into three serial sub-regions 11 (A1→A2→A3) by a retaining wall 13. Adjacent sub-regions 11 are connected end-to-end through reserved channels 110 at their ends. Sub-region 11A3 is directly connected to the subsequent nucleus growth zone 12 (zone B) through a channel of the same specification. (The length-to-width ratio of each corridor in the sub-regions and the subsequent nucleus growth zone is 6:1). Adjacent sub-regions 11 are connected end-to-end through reserved channels 110 at the ends of the retaining wall 13, and the sub-region 11 at the tail end is connected to the subsequent nucleus growth zone 12 through reserved channels 110 at the ends of the retaining wall 13. Therefore, in Example 1, the main degradation zone at the front occupies 75% of the total volume of the partitioned aerobic tank, and the subsequent nucleus growth zone occupies 25% of the total volume of the partitioned aerobic tank.

[0028] All sub-areas 11 in the front section are equipped with a first aeration device 111. In this example, a double swirl aerator is used, with an aeration intensity of 9 m³ / h. 3 / (m 2 (h) The DO is maintained at 2.8 ± 0.2 mg / L by the aeration fan 33 of the first aeration device. In this embodiment, the aeration fan 33 of the first aeration device is connected to multiple first aeration devices 111 through a suspended first pipe; the second aeration device 121 in the subsequent section B is provided in this example, which is a double swirl aerator with an aeration intensity of 3.6 m³ / h. 3 / (m 2 ·h), controlled by the aeration blower 34 of the second aeration device, DO = 1.6 ± 0.1 mg / L. In this embodiment, the aeration blower 34 of the second aeration device is connected to multiple second aeration devices 121 through a suspended second pipe.

[0029] Monitoring module layout: An online calcium ion monitor 21 (range 0-500 mg / L) and a DO sensor 22 (range 0-5 mg / L) are embedded in the side wall of the connecting channel between A1 and A2 to capture key parameters of the transition flow state in real time. Downstream of the connection point between A3 and B, a DO sensor 22, an online pH meter 23 (accuracy ±0.1), and an alkalinity analyzer 24 (microfiltration membrane anti-clogging design) are centrally deployed to simultaneously monitor the initial precipitation environment. All sensors transmit data to the PLC controller 10 via the Modbus protocol. When the online pH meter 23 in the A3-B zone detects a pH value lower than the dynamic threshold of 7.5 + 0.01 × (Ca... 2+When the alkalinity is -200, the PLC starts the NaOH dosing pump 31 to inject the drug into the inlet of zone A3-B within 2 seconds; when the alkalinity analyzer 24 shows alkalinity <150mg / L, the Na2CO3 dosing pump 32 (at the same position as the NaOH dosing pump 31) is immediately triggered to replenish the alkalinity.

[0030] Its advantages are: 1) Homogeneous aeration throughout the entire front stage (aeration intensity is 9m³ / h air volume) 3 / (m 2 • h) Eliminates the degradation blind zone of traditional gradient design, stabilizing the COD removal rate at over 92%; 2) Monitoring points in the A1-A2 connecting channel provide early warning of degradation anomalies (such as a sudden drop in DO indicating a decrease in microbial activity), enabling the PLC controller to respond 3 minutes earlier; 3) Multi-parameter linkage in the A3-B zone achieves "zero-time-difference" control of the sedimentation environment (pH fluctuation < ±0.3). Operational data shows: Influent Ca 2+ At a concentration of 325±38 mg / L, the effluent concentration was stable at 42±4 mg / L (removal rate of 87.1%), the cost of the reagent per ton of water was 0.41 yuan, and the aeration device operated continuously for 200 days without scaling or clogging (traditional systems require cleaning on average every 90 days), verifying the reliability and stability of this structure for efficient removal of calcium ions.

[0031] Each sub-region 11 (such as A1 / A2 / A3 in Example 1) is equipped with a first aeration device 111 (a dual-swirl aerator with an aeration intensity of 6-10.8 m³ / h). 3 / (m 2 These devices are connected to the first aeration device aeration fan 33, with the fan frequency dynamically adjusted (25-50Hz) in response to real-time data from the DO sensor 22.

[0032] For example, when DO is below 2.5 mg / L, the PLC controller 10 instructs the fan to increase its frequency to the upper limit of 50 Hz to increase the aeration intensity; when DO approaches 3.0 mg / L, the frequency is reduced to 30 Hz to prevent over-aeration. In Example 1, this design stabilizes the initial DO at 2.8 ± 0.2 mg / L, ensuring efficient degradation of organic matter by microorganisms. A second aeration device 121 (a dual-vortex aerator with an aeration intensity of 2.4-4.8 m³ / L) is deployed in the downstream section. 3 / (m 2 ·h)) is connected to the second aeration device aeration blower 34. The PLC controller 10 monitors in real time through the downstream DO sensor 22 (range 0-3mg / L). If the DO is higher than 2.0mg / L, the blower frequency is immediately triggered to suppress disturbance; if it is lower than 1.5mg / L, the frequency is slightly increased to prevent sedimentation stagnation.

[0033] DO sensor 22 (the front end is located in the connecting channel of sub-region 11, and the rear end is located at the entrance of the crystal nucleus growth area) sends real-time data to PLC controller 10 every 10 seconds. The front DO sensor 22 (range 0-5mg / L) captures the inflection point of degradation efficiency, and the rear DO sensor 22 (range 0-3mg / L) monitors the stability of the precipitation environment.

[0034] Example 2

[0035] See Figure 3 With a daily processing capacity of 2700m³ 3 In a medium-sized paper mill, this system achieves efficient treatment of high-calcium wastewater through a compact structural design. The main degradation zone at the front of the plug-flow corridor (with an aspect ratio of 6:1, consistent with Example 1) is divided into two series sub-regions 11 (C1→C2) by a retaining wall 13. Adjacent sub-regions 11 are connected by reserved channels 110 at their ends, while sub-region 11C2 is directly connected to the subsequent crystal nucleus growth zone 12 (D zone) via a channel of the same specifications. Therefore, in Example 2, the main degradation zone occupies 2 / 3 of the total volume of the aerobic tank, and the subsequent crystal nucleus growth zone occupies 1 / 3 of the total volume of the aerobic tank.

[0036] This layout maximizes flow channel efficiency within a limited space. All sub-regions 11 in the front section are equipped with a first aeration device 111 (a dual-swirl aerator with an aeration intensity of 7.2 m³ / h) of uniform density. 3 / (m 2 The DO concentration is maintained at 2.7 ± 0.2 mg / L by the aeration fan 33 of the first aeration device. In this embodiment, the aeration fan 33 of the first aeration device is connected to multiple first aeration devices 111 via a suspended first pipe; a second aeration device 121 (double swirl aerator, with an aeration intensity of 3.0 m³ / h) is installed in the downstream section D area. 3 / (m 2 The DO concentration is controlled by the aeration fan 34 of the second aeration device, which is set to 1.7 ± 0.1 mg / L. In this embodiment, the aeration fan 34 of the second aeration device is connected to multiple second aeration devices 121 via a suspended second pipe.

[0037] In this embodiment 2, the monitoring module adopts a compact layout: an online calcium ion monitor 21 (range 0-500 mg / L) and a DO sensor 22 (range 0-5 mg / L) are centrally installed on the side wall of the connecting channel between C1 and C2 to capture the changes in key parameters of the flow transition zone in real time; downstream of the connection point between C2 and D, a DO sensor 22, an online pH meter 23 (accuracy ±0.1), and an alkalinity analyzer 24 (anti-clogging microchannel design) are simultaneously deployed to accurately control the initial sedimentation environment. All sensors transmit data to the PLC controller 10 in real time via the Modbus protocol. The system adds a low flow rate adaptation algorithm—when the influent flow rate is <100 m³ / h. 3When the flow rate is 0.8L / min, the pulse frequency of the dosing pump is automatically reduced (NaOH pump 0.8L / min → 0.5L / min) to avoid local oversaturation of the agent under low to medium flow conditions.

[0038] When the pH value detected by the online pH meter 23 in zone C2-D is lower than the dynamic threshold of 7.5 + 0.01 × (Ca 2+ When the alkalinity is -200°C, the PLC starts the NaOH dosing pump 31 to inject NaOH into the C1 inlet within 1.5 seconds; when the alkalinity analyzer 24 shows alkalinity <150 mg / L, the Na2CO3 dosing pump 32 is immediately triggered to replenish alkalinity. This control strategy, combined with the compact structure, produces significant benefits: 1) The C1-C2 channel monitoring point provides an early warning of process abnormalities 2 minutes in advance (e.g., when calcium ions suddenly increase by 20%, the PLC prioritizes reducing the downstream DO to suppress crystal erosion); 2) The direct-connection channel in the C2-D zone (flow rate 0.18 m / s) ensures crystal growth time of up to 35 minutes; 3) Homogeneous aeration throughout the entire front section (aeration intensity of 7.2 m³ / s airflow). 3 / (m 2 •h)) keeps the COD removal rate stable at over 90%.

[0039] Inlet Ca 2+ At a concentration of 280±30 mg / L, the effluent concentration stabilized at 43±5 mg / L (removal rate 84.6%), with a reagent cost of 0.44 yuan per ton of water. The aeration device operated continuously for 180 days without scaling or clogging. This was particularly effective during low-load periods at night (flow rate 80 m³ / h). 3 The low-flow algorithm accurately controls the addition of chemicals with an error rate of <2.5%, solving the common problem of chemical waste in small and medium-sized plants.

[0040] The above embodiments are merely preferred embodiments of the present utility model and are not intended to limit the scope of the present utility model. Various modifications and improvements made to the technical solutions of the present utility model by those skilled in the art without departing from the spirit of the present utility model should fall within the protection scope defined by the claims of the present utility model.

Claims

1. A synergistic aerobic biological calcium removal system for papermaking wastewater, characterized in that: include: Zoning aerobic tank, monitoring module, PLC controller, actuator components; The zoned aerobic tank is divided into a front-end main degradation zone and a rear-end crystal nucleation zone by a retaining wall. The front main degradation zone is equipped with several first aeration devices, and the rear crystal nucleus growth zone is equipped with several second aeration devices. The monitoring module includes an online calcium ion monitor and a DO sensor located in the front main degradation zone, and an online pH meter, a DO sensor, and an alkalinity analyzer located in the rear crystal nucleation zone. The actuator assembly includes a NaOH dosing pump connected to the upstream main degradation zone, a Na2CO3 dosing pump connected to the upstream main degradation zone, and variable frequency aeration blowers connected to the first aeration device and the second aeration device respectively; the PLC controller is connected to the monitoring module and the actuator assembly through signal transmission lines.

2. The aerobic biological calcium removal and co-treatment system for papermaking wastewater according to claim 1, characterized in that: The front-end main degradation zone accounts for 65%-75% of the total volume of the aerobic tank, while the rear-end crystal nucleus growth zone accounts for 25%-35% of the total volume of the aerobic tank.

3. The aerobic biological calcium removal and co-treatment system for papermaking wastewater according to claim 2, characterized in that: The first aeration device has an aeration intensity of 6-10.8 m 3 (m 2 ·h) in the front main degradation zone, and a DO value of 2.5-3.0 mg / L is controlled. The second aeration device has an aeration intensity of 2.4-4.8 m 3 (m 2 ·h) in the rear crystal nucleus growth zone, and a DO value of 1.5-2.0 mg / L is controlled.

4. The aerobic biological calcium removal and co-treatment system for papermaking wastewater according to claim 2, characterized in that: The main degradation zone at the front end is divided into several sub-regions by a retaining wall, and adjacent sub-regions are connected end to end by a reserved channel at the end of the retaining wall.

5. The aerobic biological calcium removal and co-treatment system for papermaking wastewater according to claim 4, characterized in that: The sub-region located at the tail end is connected to the subsequent crystal nucleus growth region through a reserved channel at the end of the retaining wall.

6. The aerobic biological calcium removal and co-treatment system for papermaking wastewater according to claim 5, characterized in that: The aspect ratio of each corridor in the sub-region and the subsequent nucleus growth region is >5:

1.

7. The aerobic biological calcium removal and co-treatment system for papermaking wastewater according to claim 1, characterized in that: The variable frequency aeration blower is connected to the first aeration device and the second aeration device through a suspended pipe or a pipe at the bottom of the pool, respectively.

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