A water collecting well phosphorus removal dosing mixing system and a design method thereof

Abstract

The application discloses a water collecting well phosphorus removal and medicine adding mixing system and a design method thereof, relates to the field of water collecting wells, and aims to solve the problem that in the prior art, it is difficult to realize efficient utilization of medicine under high discharge standards. The technical scheme is that a collaborative optimization water collecting well phosphorus removal and medicine adding mixing system and an optimization design method of "model construction-state evaluation-rule optimization-comprehensive decision" are established. Through hydraulic model simulation and a multi-dimensional evaluation matrix, an accurate coupling architecture of "asymmetric flow guide+eccentric stirring+layered flow field cutting+specific opening" is established, efficient reconstruction of a flow field, deep elimination of dead water zones and accurate control of a velocity gradient (G>500s ‑1 ) are realized, so that the goals of significantly reducing medicine consumption, improving chemical phosphorus removal efficiency and saving energy and reducing consumption in water plant operation are achieved.

Description

Technical Field

[0001] This invention relates to the field of water collection well technology, specifically to a phosphorus removal and chemical dosing mixing system for water collection wells and its design method. Background Technology

[0002] With increasingly stringent national and local standards for total phosphorus (TP) emissions from wastewater treatment plants, biological phosphorus removal alone is often insufficient to meet the requirements. Therefore, chemical phosphorus removal must be used in conjunction with biological phosphorus removal to ensure that the effluent TP consistently meets the standards. Typically, chemical phosphorus removal agents are added at the end of the biological reactor or at the collection well, and the phosphorus is removed by sedimentation in the secondary sedimentation tank.

[0003] In the secondary biological treatment process of wastewater treatment plants, the collection well is usually located between the biological treatment tank and the secondary sedimentation tank. Specifically, after the effluent from the two series of biological treatment tanks flows down, it is piped into the collection well, where it merges. The effluent from the collection well then flows into the distribution well and finally enters the secondary sedimentation tank for sludge-water separation.

[0004] Currently, chemical phosphorus removal agents are typically added directly to the cascade at the end of the biological treatment tank, utilizing the local turbulence generated by the cascade for mixing. However, due to the highly uneven energy release and extremely short mixing time generated by the cascade, the mixing effect is poor, resulting in the agent not being able to fully diffuse in the water. In actual operation, it is often necessary to add a dosage far exceeding the theoretical value, but the phosphorus removal effect is still unsatisfactory. The molar ratio of actual agent consumption to phosphorus removal is seriously mismatched, resulting in huge agent waste and increased operating costs.

[0005] To improve mixing, some wastewater treatment plants have added agitators to their collection wells based on engineering experience. However, the location and angle of the inlet and outlet pipes of the collection well, as well as fluctuations in water volume, have a significant impact on the flow field. Simply adding agitators based on experience often fails to fundamentally solve the problem. Due to a lack of scientific flow field design, severe "short-circuiting" can easily occur inside the collection well, causing chemicals to flow directly to the outlet with the mainstream water flow.

[0006] In summary, existing methods for phosphorus removal dosing in water collection wells lack a systematic design approach based on hydraulic optimization, making it difficult to achieve efficient chemical utilization under high emission standards. Therefore, there is an urgent need for an optimized design method and system for the dosing and mixing system that can scientifically reconstruct the flow field by considering the specific dimensions of the water collection well and inlet / outlet pipes. Summary of the Invention

[0007] This invention aims to solve the technical problems existing in the phosphorus removal chemical dosing process of water collection wells, such as uneven mixing, high proportion of dead water zone, severe short-flow, and low chemical utilization. It proposes a phosphorus removal chemical dosing mixing system for water collection wells and its design method based on collaborative optimization of "model construction—state evaluation—rule optimization—comprehensive decision-making." Through hydraulic model simulation and multi-dimensional evaluation matrices, a precise coupling architecture of "asymmetric flow guidance + eccentric stirring + layered flow field cutting + specific openings" is established, achieving efficient flow field reconstruction, deep elimination of dead water zone, and reduction of velocity gradient (G > 500 s). -1 Precise control is needed to achieve the goals of significantly reducing chemical consumption, improving chemical phosphorus removal efficiency, and saving energy and reducing consumption in water plant operations.

[0008] To achieve the above objectives, this invention discloses a phosphorus removal and chemical mixing system for a water collection well and its design method. The technical solution adopted is as follows: during the design of the water collection well, a three-dimensional hydraulic numerical model is constructed and the flow field is simulated. Key flow field characteristic parameters of the mixing effect of the water collection well are extracted, and an evaluation matrix is ​​constructed. The flow field state is judged through the evaluation matrix, and a mapping relationship between structural parameter changes and flow field response laws is established. Combined with a comprehensive evaluation function, synergistic optimization is performed by maximizing positive indicators and minimizing negative indicators. Through optimization using the comprehensive evaluation function, the flow field can be optimized.

[0009] As a preferred embodiment of the present invention, the key flow field characteristic parameters of the mixing effect of the water collection well include the proportion of dead water zone V. dead Active region ratio V active ΔHRT (deviation between actual and theoretical residence time) and C (uniformity coefficient of reagent concentration) u The uniform intensity E of the circulating flow field throughout the pool b Energy consumption for mixing (E), risk index of retaining wall blockage (R) b Structural safety factor F s .

[0010] As a preferred technical solution of the present invention, the flow field state includes short-flow-dominant type, dead zone-dominant type, vertical stratification type, insufficient reagent diffusion type, high energy consumption type, blockage risk type and structural risk type. According to different flow field states, the structural parameters of the water collection well are adjusted, which brings about changes in the flow field response law.

[0011] As a preferred embodiment of the present invention, the comprehensive evaluation function is: F = W1×V active – W2×V dead – W3×ΔHRT + W4×C u + W5×E b – W6×E – W7×R b + W8×F s Among them, W1 to W8 are the corresponding indicator weight coefficients; When the structural parameters of the water collection well are adjusted, the change in the flow field response law leads to the change in the flow field characteristic parameters, which in turn causes the F value to change. When the F value is the maximum, the structural parameters of the water collection well are output.

[0012] This invention further discloses a phosphorus removal and chemical dosing mixing system for a water collection well, which is obtained by the optimization design method described above. The system includes a water collection well with an inlet pipe and an outlet pipe connected to it, the outlet pipe being connected to the bottom of the water collection well. The water collection well has a baffle wall, and a stirring mechanism is located in the inner cavity of the water collection well on the side of the baffle wall directly connected to the inlet pipe. The stirring mechanism is eccentrically positioned, and the upper and lower parts of the baffle wall have water passage holes. Above the water collection well is a phosphorus removal chemical dosing device, the dosing point of which ensures that the added chemical can directly enter the main circulating flow field formed by the stirring mechanism. The structural parameters of the water collection well are obtained by optimization using the comprehensive evaluation function. In this scheme, the stirring mechanism not only promotes mixing and the baffle wall increases the residence time of water in the collection well, but also effectively breaks the original axisymmetric vortex structure of the collection well by setting the stirring mechanism eccentrically, avoiding the formation of closed vortex zones, so that the water forms a directional flow path under the action of the baffle wall, thereby extending the actual flow path of the fluid in the collection well, and coupling the action of the stirring mechanism and the baffle wall to further optimize the mixing effect.

[0013] As a preferred embodiment of the present invention, the stirring mechanism is a paddle type. When H / D≤2, a single-layer stirring blade is used; when 2<H / D≤3, a double-layer stirring blade is used; when 3<H / D≤4, a triple-layer stirring blade is used; and when H / D>4, a four-layer or higher stirring blade is used.

[0014] As a preferred embodiment of the present invention, when 2 < H / D, the axial vertical distance between two adjacent layers of stirring blades is 0.5 to 1.2 times the blade diameter, and the stirring blades of two adjacent layers are staggered at 90° in circumferential phase.

[0015] Compared with existing technologies, the beneficial effects of this invention are as follows: By constructing an evaluation matrix, this invention establishes a correlation between the geometric structure of the water collection well and the internal flow field response. By establishing a comprehensive evaluation function to evaluate the flow field, it can achieve synergistic optimization of various geometric parameters of the water collection well. Furthermore, by eccentrically setting the stirring mechanism and installing baffles within the water collection well, the water retention time can be increased. Simultaneously, the eccentric stirring mechanism and baffles couple the fluid, extending the actual flow path of the fluid within the water collection well and reducing dead zones, thereby improving reagent uniformity and achieving optimal phosphorus removal efficiency with minimal reagent usage. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of the AA cross-sectional structure of the present invention; Figure 3 This is a schematic diagram of the retaining wall structure of the present invention; Figure 4 This is a plan view of the water collection well before optimization in Embodiment 1 of the present invention; Figure 5 This is an optimized layout diagram of the stirring mechanism in Embodiment 1 of the present invention; Figure 6 This is a diagram showing the optimized hydraulic retention time of the water collection well in Embodiment 1 of the present invention. Figure 7 This is a diagram showing the proportion of the active zone in the water collection well after optimization in Embodiment 1 of the present invention; Figure 8 This is a vector diagram of the flow field at different heights within the water collection well after optimization in Embodiment 1 of the present invention; Figure 9 This is a field diagram of phosphorus removal agent concentration in the water collection well after optimization in Example 1 of the present invention.

[0017] In the diagram: 1. Water collection well; 2. Inlet pipe; 3. Outlet pipe; 4. Agitator; 5. Retaining wall; 501. First water passage hole; 502. Second water passage hole; 6. Wall support. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 are within the scope of protection of the present invention.

[0019] Example 1 like Figure 1 , Figure 2 As shown, in response to the short-flow phenomenon, vortex structure and bottom deposition problems that are prone to occur in the water collection well 1, this embodiment adopts an asymmetric porous flow guide wall system with functional partitions to actively reconstruct the macroscopic flow field inside the water collection well 1.

[0020] (1) Asymmetric spatial layout The retaining wall 5 is not symmetrically arranged along the center line of the water collection well 1, but is asymmetrically offset according to the orientation of the water inlet pipe 2, the direction of the water inlet kinetic energy and the mainstream path.

[0021] This method effectively breaks the original axisymmetric vortex structure of the water collection well 1, avoids the formation of closed vortex zones, and allows the water to form a directional flow path under the action of the retaining wall 5, thereby extending the actual flow path of the fluid in the water collection well 1.

[0022] (2) Differentiated porous design like Figure 3 As shown, retaining wall 5 has a differentiated porous structure along its height: First water passage 501: It is set as a large-area opening. Its main function is to control the main flow path in the water collection well 1 and significantly improve the average hydraulic residence time by extending the bypass distance. Second water passage 502: Multiple small-area openings are set at the lower part of the retaining wall 5. The local pressure difference formed before and after the retaining wall 5 generates a jet effect, which is used to break the dead zone of bottom backflow, induce vertical hydraulic exchange, and prevent the deposition of chemicals and sludge in the bottom area.

[0023] By constraining the opening area, the total area of ​​the upper opening is made significantly larger than that of the lower opening, while maintaining a sufficient flow velocity gradient (G > 500 s). -1 At the same time, the flow field covers the entire area of ​​the water collection well 1.

[0024] To complement the reconstruction of the macroscopic flow field by the baffle system, this invention optimizes the micro-dynamics of the stirring device and proposes an eccentric multi-layer cross-flow field cutting mechanism to enhance the instantaneous mixing effect of the chemical phosphorus removal agent.

[0025] (1) Asymmetric eccentric vortex breaking mechanism The stirring mechanism 4 adopts an eccentric arrangement logic, and its axis installation position forms a preset spatial misalignment with the retaining wall 5. By utilizing the unbalanced inertial torque generated by the eccentric rotation, the axisymmetric flow field of the conventional stirrer is forcibly broken, and the formation of central vortex and local dead water zone in the well is completely suppressed.

[0026] (2) Multi-layer 90° cross-shear dynamics The stirring mechanism 4 employs double-layer or multi-layer propeller blades, with adjacent layers of blades staggered at 90° in circumferential phase. This geometry creates a periodic "asynchronous flow field cutting" effect in the vertical direction, inducing a composite flow pattern where spiral upward flow and central downward swirling flow are coupled. This design allows the phosphorus removal agent to undergo instantaneous micro-mixing within the well before entering the secondary settling tank.

[0027] The initial diffusion path of the phosphorus removal agent after entering the collection well has a significant impact on the final mixing effect. If the agent is added off-center from the core area of ​​the main circulation flow field, local high-concentration areas may form or the agent utilization efficiency may decrease. Therefore, the agent addition point is preferably located in the core area of ​​the main circulation flow field around the main shaft of the agitator.

[0028] Based on the above design concept, this invention discloses a phosphorus removal and chemical dosing mixing system for a water collection well. The technical solution adopted is as follows: It includes a water collection well 1, within which a retaining wall 5 is installed via a wall support 6. The retaining wall 5 divides the water collection well 1 into a first water collection zone and a second water collection zone. The wall support 6 is located in the second water collection zone. Figure 3 As shown, a first water passage hole 501 is opened at the top of the retaining wall 5, and a second water passage hole 502 is opened at the two corners below. The first water collection area and the second water collection area are connected to the top of the retaining wall 5 through the first water passage hole 501, the second water passage hole 502, and the water collection well 1 is also connected to the inlet pipe 2 and the outlet pipe 3. The inlet pipe 2 is connected to the middle of the first water collection area, and the outlet pipe 3 is connected to the bottom of the second water collection area. A stirring mechanism 4 is installed in the first water collection area. The stirring mechanism 4 is eccentrically set and is a double-layer or multi-layer propulsion paddle agitator driven by a motor. The adjacent two layers of paddles are staggered and cross-installed at 90° in the circumferential phase. A phosphorus removal dosing device is installed above the water collection well 1. The dosing point of the phosphorus removal dosing device is located above the uppermost stirring blade and close to the main shaft of the stirring mechanism 4, so that the added agent can directly enter the main circulation flow field formed by the stirring mechanism 4, avoiding the agent from entering the dead water area or forming a short flow path, and improving the agent diffusion speed and utilization efficiency.

[0029] This embodiment also discloses a design method for the above-mentioned phosphorus removal and chemical dosing system in the water collection well, in order to optimize its geometric parameters. The technical solution adopted includes the following steps: Step 1: Obtain the geometric boundary parameters of the collection well 1, including but not limited to well diameter D, well depth H, pipe diameter of inlet pipe 2 and outlet pipe 3, spatial height, azimuth angle and water intake method; at the same time, introduce the water volume parameters of the sewage treatment plant under normal operating conditions and the most unfavorable operating conditions (such as high reflux ratio, summer peak flow rate superimposed with backwash wastewater flow rate), and use CFD software to perform hydraulic simulation of the collection well 1 to obtain the initial geometric parameters; Step 2, based on the hydraulic simulation results, extract the key flow field characteristic parameters that affect the mixing effect of the water collection well, including: 1) the proportion of dead water zone V dead ;2) Active region percentage V active 3) Deviation between actual residence time and theoretical residence time ΔHRT; 4) Uniformity coefficient of reagent concentration C u ;5) Uniform intensity E of the circulating flow field throughout the pool b ;6) Stirring energy consumption E;7) Blockage risk index of retaining wall 5 R b ;8) Structural safety factor F s ; Step 3: Construct a flow field reconstruction evaluation matrix based on the above feature parameters, and identify and classify the flow field state of water collection well 1. For different flow field states, automatically match the corresponding optimization strategy. The corresponding optimization strategy is as follows: Based on 120 sets of hydraulic simulation results under different working conditions and engineering operation verification data, establish an association rule base of "structural parameters - flow field response - optimization parameters", as detailed below:

[0030] The simulation variables for 120 different working conditions include, but are not limited to: the location of the retaining wall 5 (distance relative to the center of the collection well 1), the height of the retaining wall 5, the number, location, size and shape of the openings in the retaining wall 5, the type of agitator blades, the installation height and eccentric position of the agitator, the number and structure of the agitator blades, and the agitator rotation speed. Among these, the horizontal deflection angle of a single blade is used as one of the flow field control parameters. By changing the ratio of the axial thrust component to the radial diffusion component generated by the blades, the main circulation flow field morphology, the agent diffusion path and the mixing uniformity are adjusted, thereby affecting the overall circulation intensity and agent capture efficiency.

[0031] For short-flow-dominated flow fields, where the hydraulic residence time is too short, the vertical position of the main opening of the baffle wall should be adjusted first. This can be achieved by increasing the opening height of the first water passage 501 and / or decreasing its opening ratio to extend the main circulation path, increase the volume of the first water collection area, and extend the hydraulic residence time. If ΔHRT continues to increase, the height of the baffle wall 5 should be increased. For dead-zone-dominated flow fields, where the proportion of dead water is too large, the opening height of some of the second water passages 502 should be reduced first, and / or the number of second water passages 502 should be increased to enhance the bottom fluid exchange capacity and reduce the proportion of dead water. The eccentricity of the stirring mechanism 4 should be increased, and the opening area of ​​the second water passages 502 should be increased to enhance the bottom exchange capacity and reduce the proportion of dead water. For vertically stratified flow fields, where the exchange intensity between the upper and lower layers of water is insufficient, the installation height of the stirrer should be adjusted first. If E bTo further reduce the flow rate, increase the number of impeller layers and decrease the spacing between adjacent impeller layers to increase the number of flow control zones. For flow fields with insufficient reagent diffusion, where reagent mixing uniformity is insufficient, prioritize moving the reagent addition point closer to the impeller and main shaft to bring the reagent closer to the center of the main circulation flow field, and change the stirring direction to increase mixing uniformity. If mixing uniformity is still insufficient, further increase the number of impeller layers and the stirring motor speed. For high-energy-consumption flow fields, where the stirring motor consumes too much energy, increase the number of impeller layers while reducing the speed to ensure mixing uniformity and vertical flow control. While increasing the exchange intensity of the flow layer, energy consumption is reduced. For flow fields with a risk of clogging, the first and second water passages 501 and 502 are prone to clogging. Therefore, the water passages are rounded to reduce the blind zone of water flow scouring and increase the opening area to increase the scouring water flow rate. For flow fields with structural risks, the opening area of ​​the water passages is too large, which leads to a decrease in the strength of the retaining wall. Therefore, the opening area of ​​the second water passage 502 is reduced. For flow fields with insufficient exchange at the bottom, the installation height of the agitator is reduced. For flow fields with excessively high local flow velocities at the bottom, the installation height is increased, thereby achieving optimized reconstruction of the vertical circulation flow field.

[0032] For complex flow fields, iterative calculations are performed using a collaborative optimization approach for the parameters of the retaining wall and the agitator. Through flow field state identification and optimization strategy matching, collaborative optimization of the structural parameters of the retaining wall and the agitator is achieved. Furthermore, considering the vertical momentum decay characteristics of water collection well 1, a flow field cutting model based on the H / D ratio is constructed: according to the height-to-diameter ratio (H / D), influent kinetic energy and water volume of water collection well 1, the water collection well is divided into several "flow field control zones" along the water depth direction. When there are vertical velocity decay regions or flow isolation regions in the calculated and predicted flow field, the system automatically increases the number of control zones to ensure that each control zone corresponds to at least one layer of stirring blades, and the gradient transfer of energy and matter is realized through the flow field overlap area of ​​adjacent control zones. This invention establishes a recommended correspondence between the height-to-diameter ratio (H / D) and the number of stirring layers: H / D≤2 single layer 2 < H / D ≤ 3 Double layer 3 < H / D ≤ 4 Three floors H / D > 4 Fourth floor and above

[0033] Establish a layer-linked mapping logic: when H / D≤2, use a single-layer stirring blade; when 2<H / D≤3, use a double-layer stirring blade; when 3<H / D≤4, use a triple-layer stirring blade; when H / D>4, use a four-layer or higher stirring blade. The mixing shaft adopts a standard modular design, with several standard mounting flange positions pre-installed at equal intervals along the axial direction. Based on the calculation results of the flow field control zone, the number of mixing blade layers can be increased or decreased through flange connections. Unused interfaces are sealed with closed flange covers to ensure the strong versatility of the mixing shaft for water collection wells of different sizes. To ensure effective connection of the flow field in each layer control zone, the axial vertical spacing of adjacent blades is determined according to the flow field control zone, generally taking 0.5 to 1.2 times the blade diameter, to ensure the formation of a continuous three-dimensional main circulation flow field in the vertical direction. During the design process, based on the geometric dimensions, operating conditions, and target flow field state of the water collection well 1, the corresponding parameter combinations are automatically selected by calling the above rule base and verified in conjunction with the flow field evaluation matrix, thereby forming an optimized design scheme suitable for the target water collection well. Step 4, establish the proportion of dead water areas V dead Minimize the proportion of effective active area V active The comprehensive evaluation function, with the core objective of maximizing the actual hydraulic residence time to be close to the theoretical residence time, assigns weight coefficients to each evaluation index according to engineering design requirements and incorporates flow field continuity as a constraint. The final comprehensive evaluation function is as follows: F = W1×V active – W2×V dead – W3×ΔHRT + W4×C u + W5×E b – W6×E – W7×R b + W8×F s Wherein: W1~W8 are the corresponding index weight coefficients; the weight coefficients W1~W8 are not fixed values, but are dynamically determined according to the flow field state identification results of the water collection well; when identified as a short-flow dominant flow field, the weight corresponding to the actual residence time deviation ΔHRT is increased by W3; when identified as a dead zone dominant flow field, the active zone ratio V is increased. active Corresponding weight W1 and dead water area proportion V dead The corresponding weight W2 makes the evaluation function focus on the degree of flow field activation and the effect of dead zone reduction (by enhancing V). active The positive contribution to the overall evaluation value F, and the enhancement of V dead The negative impact on the comprehensive evaluation value F guides the optimization of the retaining wall structure parameters and stirring mechanism parameters towards a direction that favors the formation of a main circulation flow field throughout the pool, expands the active flow area, and reduces the proportion of dead water, thereby achieving flow field reconstruction in the collection well. When the flow field is identified as insufficient reagent diffusion, the reagent concentration uniformity coefficient C is increased. u The corresponding weight is W4; when the flow field is identified as structurally risky, the structural safety factor F is increased. sThe corresponding weight is W8. The adjustment range of the weight is related to the degree to which the corresponding evaluation indicator deviates from the target value. When an evaluation indicator deviates from the target value, the corresponding weight coefficient is dynamically adjusted according to the degree of deviation. Preferably, the adjustment amount per cycle is 5% to 20% of the current weight value; the greater the deviation, the higher the corresponding weight adjustment ratio; the smaller the deviation, the lower the corresponding weight adjustment ratio. After each round of adjustment, all weight coefficients are normalized to ensure that each weight coefficient satisfies ΣW. i =1, enabling the evaluation function to adaptively optimize for different engineering scenarios.

[0034] By iteratively calculating the evaluation function values ​​corresponding to different combinations of parameters of the retaining wall 5 and the stirring mechanism 4, when the evaluation function F reaches its maximum value, the corresponding optimized design parameters are output, including: 1) the installation position of the retaining wall (volume of the first water collection area); 2) the installation height of the retaining wall; 3) the opening ratio of the retaining wall; 4) the opening size of the retaining wall; 5) the opening position of the retaining wall; 6) the eccentric distance of the stirrer; 7) the installation height of the stirrer; 8) the number of stirring blade layers; 9) the structure of the stirring blade; 10) the running direction and speed of the stirrer; finally, the optimal combination of structural parameters adapted to the specific water collection well structure and operating conditions is output.

[0035] The above optimization design method and system will be further explained below based on a specific example: The plan view of the collection well 1 of a sewage treatment plant before optimization is shown below. Figure 4 As shown, hydraulic simulation of the water collection well 1 revealed the following significant quantitative bottlenecks in the mixing of phosphorus removal agents in the water collection well 1: (1) There are a large number of dynamic dead zones in the current water collection well 1, with the dead water area accounting for as much as 40%, resulting in low effective volume utilization; (2) The average actual hydraulic residence time is only 22.62s, which is only 40% of the theoretical hydraulic residence time. The water flow field is uneven, which cannot provide stable spatiotemporal conditions for the full reaction of the agent and the sewage; (3) The agent diffusion is limited, resulting in excessively high local concentrations and insufficient overall reaction, which directly affects the phosphorus removal efficiency of the subsequent secondary sedimentation tank and the stability of the effluent compliance.

[0036] The collection well 1 of the sewage treatment plant was optimized and improved. The collection well 1 of the sewage treatment plant has a circular structure with a diameter of 3m and a depth of 7.8m. The current water depth is 7.25m. The collection well 1 is equipped with two DN1200 inlet pipes and one DN1400 outlet pipe.

[0037] The water collection well 1 is responsible for mixing the phosphorus removal agent after it has been added. Under the original operating conditions, the flow field in the water collection well 1 was uneven, the hydraulic efficiency was low, and there were obvious short-flow and local dead water zones. The phosphorus removal agent had insufficient diffusion and the mixing effect was not ideal.

[0038] Based on the above-mentioned structure and operating conditions of the water collection well, a three-dimensional hydraulic numerical model of water collection well 1 was constructed. The finite volume method was used to perform discrete calculations on the governing equations, and simulation analysis was conducted on different combinations of retaining walls and agitators.

[0039] During the simulation, the proportion of the active zone and the hydraulic residence time distribution characteristics within the water collection well 1 were used as the main evaluation indicators. A total of 120 different working conditions were set up for comparative analysis, focusing on the structural parameters of the retaining wall 5 and the parameters of the stirring mechanism 4. Through optimization using a comprehensive evaluation function, the following structural parameters for the retaining wall 5 were obtained: the retaining wall 5 is located 0.75m from the center of the water collection well 1, and its height is 6.9m. The retaining wall 5 adopts an asymmetric porous structure, specifically including: a first water passage 501 at the upper part of the retaining wall with one opening, the opening size being 1.0m × 1.5m; and a second water passage 502 at the lower part of the retaining wall with two openings, each opening size being 0.4m × 0.2m.

[0040] The retaining wall structure forms an effective flow channel within the water collection well, extending the water flow path and activating water flow in the lower and bottom areas of the retaining wall.

[0041] Based on the aforementioned retaining wall structure, the four parameters of the mixing mechanism were further optimized. The mixer uses a propeller-type mixing blade, which draws water downwards during rotation; the mixer's motor power is 15kW, using frequency conversion control; the mixer speed is 101rpm; the mixing blade diameter is 1.45m; the mixing blade is configured with a two-layer structure: the lower blade is approximately 4.25m above the bottom of the collection well; the upper blade is approximately 5.25m above the bottom of the collection well; the two layers of mixing blades are installed at a 90° angle in the plane. The stirring mechanism 4 is eccentrically arranged within the water collection well, with its planar center coordinates approximately (0.30m, 0.30m). Figure 5 As shown.

[0042] The reagent dosing point is set approximately 0.5m from the main agitator shaft and about 0.5m above the agitator blades. After entering the water, the reagent can directly enter the main circulating flow field induced by the agitator, avoiding stagnant water zones or short-circuit paths, thus improving the reagent diffusion rate and utilization efficiency.

[0043] After optimization, a stable overall circulating flow field is formed inside the water collection well 1, with the main circulation connecting different water depths; such as Figure 6 , Figure 7 As shown, the hydraulic dead zone inside the collection well is significantly reduced, the proportion of active zone increases to 96.7%, and the proportion of dead zone is only about 3.3%; the actual hydraulic residence time of collection well 1 is basically consistent with the theoretical residence time, and the short-flow phenomenon is significantly weakened.

[0044] like Figure 8As shown, after optimization, a stable full-pool circulating flow field is formed inside the water collection well 1. The main circulation runs through different water depths, and the vertical flow is significant, which effectively promotes the exchange and mixing of the upper and lower water bodies and eliminates dead zones in the flow.

[0045] like Figure 9 As shown, after the phosphorus removal agent enters the water collection well from the dosing point, it can quickly diffuse to the entire water space. The agent concentration is evenly distributed in different heights and different vertical profiles, and there are no obvious agent retention areas or mixing blind areas. This avoids local over- or under-dosing of the agent, and the mixing and mass transfer performance of water collection well 1 is good.

[0046] The wastewater treatment plant's location requires that the total phosphorus concentration in the wastewater discharge not exceed 0.1 mg / L. To meet this requirement, the phosphate concentration in the secondary sedimentation tank effluent must not exceed 0.3 mg / L. Before the modification, the average phosphate concentration in the biological treatment tank effluent was 0.45 mg / L, and the dosage of polyferric sulfate was 30.5 mg / L. The average phosphate concentration in the secondary sedimentation tank effluent was 0.3 mg / L. After optimization using Example 1, while ensuring the effluent quality consistently reaches below 0.3 mg / L, the dosage of polyferric sulfate was reduced to an average of 12 mg / L, resulting in a reduction of approximately 61% in reagent consumption compared to before the modification. By using Example 1 for optimization, the mixing effect of the phosphorus removal reagent in the collection well was significantly improved, and the utilization efficiency of the phosphorus removal reagent was significantly increased while ensuring the stability of the effluent total phosphorus compliance.

[0047] As can be seen from the above-described modifications, the optimized design method of the present invention has the following advantages: (1) Realize the transformation from experience-driven to model-driven design patterns Example 1 constructs an integrated optimization design system based on "flow field reconstruction evaluation matrix, parameter association rule base, and comprehensive evaluation decision," completely changing the traditional design model of water collection wells that relies on engineering experience. By establishing a multi-dimensional evaluation matrix covering the proportion of dead water zones, reagent uniformity, hydraulic efficiency, and operating energy consumption, a comprehensive quantitative evaluation of the mixing system's performance is achieved. Based on a large amount of simulation data, the parameter association rule base deeply maps the well height-to-diameter ratio, inlet and outlet water arrangement, and key parameters of the retaining walls and agitators, enabling intelligent matching and recommendation of optimization parameters under complex operating conditions.

[0048] This design method not only achieves multi-objective collaborative optimization of the retaining wall diversion system and the mixing system, but also upgrades the customized design of projects into a rule-driven standardized model. Compared with traditional design, this invention significantly reduces the reliance on human experience, greatly shortens the solution development cycle, and while ensuring the reliability of design parameters, greatly enhances the replicability and technological promotion value of mixing solutions in different wastewater treatment scenarios.

[0049] (2) By breaking the axisymmetric flow state, the three-dimensional mixing capacity inside the water collection well is enhanced. Example 1 adopts an eccentrically arranged multi-layer stirring blade structure, and through the cross installation angle design between adjacent blades, it disrupts the original axisymmetric flow pattern inside the water collection well 1, avoiding the formation of a closed flow state dominated by a single rotating plane.

[0050] Under the action of this structure, a three-dimensional main circulation flow field is induced inside the water collection well 1, which is connected vertically, so that the water body generates effective flow in both horizontal and vertical directions, significantly enhancing the exchange capacity between different water layers.

[0051] This three-dimensional mixing mechanism improves the mixing conditions within the water collection well 1 from the perspective of fluid structure, overcoming the problem that traditional single-layer or symmetrically arranged mixing methods cannot eliminate local vortices and quiet zones.

[0052] (3) Achieve synergistic optimization between the retaining wall and the agitator, significantly reducing the proportion of dead water zone in the water collection well. Example 1 constructs a three-dimensional hydraulic numerical model based on the structural conditions of the well diameter, well depth, and the position and angle of the inlet and outlet pipes of the water collection well 1. By performing multi-dimensional coupling optimization on key parameters such as the installation position, height and opening form of the retaining wall 5, as well as the installation position, number of blades, number of layers and blade angle of the agitator, the guiding effect of the retaining wall 5 and the flow induced by the agitator 4 form a synergistic effect in space.

[0053] Compared with the traditional method of relying solely on mechanical stirring or experience to set up retaining walls, Example 1 actively reconstructs the flow field structure to form a stable and continuous overall circulating flow field within the water collection well 1, effectively weakening the local closed backflow zone and low-speed stagnation zone.

[0054] Numerical simulations have verified that, under the actual operating conditions of the collection well in a wastewater treatment plant, the optimized structural scheme of Example 1 significantly increases the proportion of the effective active zone in the collection well from approximately 40% in the initial state to 96.7%, while reducing the proportion of the dead water zone to approximately 3.3%. This is significantly better than the traditional structural layout and fully demonstrates the technical advantages of the synergistic optimization of the retaining wall and the agitator.

[0055] (4) Improve the effective volume utilization rate of the sump well so that the actual hydraulic retention behavior is close to the theoretical design state. Through the scientifically designed opening of the asymmetric guide wall and the three-dimensional swirling effect formed by the eccentrically arranged agitator, Example 1 effectively avoids short-flow phenomenon and the generation of ineffective volume inside the water collection well, so that the water body obtains a more uniform and reasonable residence time distribution in the water collection well 1.

[0056] Numerical simulation results show that after adopting the technical solution of Example 1, the actual average hydraulic residence time of the water collection well 1 is highly consistent with the theoretical residence time, the short-flow ratio is significantly reduced, and the long-term retention volume is effectively controlled.

[0057] Thus, Example 1 improves the effective volume utilization rate and overall hydraulic efficiency without increasing the volume of the water collection well 1, providing a stable and controllable hydraulic environment for the subsequent phosphorus removal process.

[0058] (5) Significantly improves the diffusion rate and spatial uniformity of phosphorus removal agents, avoiding local over- or under-application of agents. Under the structural and parameter combination conditions described in Example 1, after the phosphorus removal agent enters the water collection well 1 from the dosing point, it can be quickly captured by the main circulating flow field formed by the baffle wall 5 and the stirring mechanism 4, and rapidly diffuse along the three-dimensional swirling path at different water depths and in different orientations.

[0059] Simulation results show that the concentration of the reagent is uniformly distributed at different heights and on different vertical profiles within the water collection well 1. Only a momentary, localized high-concentration area is formed near the injection point. Moreover, this area has a small spatial scale and a fast decay rate, and no continuous high-concentration retention area or reagent injection "shadow area" is formed.

[0060] By improving the diffusion path and mass transfer conditions of the agent in the water collection well 1, Example 1 effectively improved the utilization efficiency of the phosphorus removal agent, reduced the risk of local over- or under-dosage of the agent, and created a stable and uniform reaction environment for the subsequent coagulation reaction.

[0061] (6) It has good parameter self-adaptation capability and is suitable for water collection wells with different structural forms. Example 1 does not impose structural limitations on a single water collection well size or fixed working conditions. Instead, it establishes a correlation between the opening parameters of the retaining wall 5, the installation position of the retaining wall 5, and the structural parameters of the stirring mechanism 4 and the geometric conditions and inlet / outlet water arrangement conditions of the water collection well 1 through hydraulic model analysis.

[0062] When the diameter, depth, or inlet / outlet conditions of the water collection well 1 change, the design can be quickly adapted and optimized for different structural forms of the water collection well 1 by adjusting the opening height and area ratio of the retaining wall 5, the installation height and eccentricity of the agitator, as well as the number of blades and the rotation angle.

[0063] Therefore, Example 1 has good versatility and scalability, and can be promoted and applied in the collection wells of sewage treatment plants of different sizes and operating conditions, and can continuously achieve a low proportion of dead water and a high mixing uniformity.

[0064] (7) Reduce operating energy consumption and maintenance costs, and improve the overall operating efficiency of wastewater treatment plants. Because Example 1 achieves active reconstruction of the internal flow field of the water collection well 1 through the coordinated optimization of the structure of the retaining wall 5 and the arrangement of the stirring mechanism 4, the mixing efficiency is fundamentally improved and the dependence on simply increasing the stirring power is reduced.

[0065] While ensuring the mixing effect of the phosphorus removal agent, the power or operating frequency of the stirring mechanism 4 can be reduced, thereby reducing mechanical wear during long-term operation of the equipment, and lowering the failure rate and maintenance frequency.

[0066] Meanwhile, improved uniformity of reagent mixing helps reduce redundant dosage of phosphorus removal agents, improves the stability of total phosphorus compliance in effluent, comprehensively reduces operating costs, and enhances the overall economic efficiency and management level of wastewater treatment plants.

[0067] The circuits and mechanical connections involved in this invention are conventional methods used by those skilled in the art, and technical inspiration can be obtained through a limited number of experiments; they are common knowledge.

[0068] Components not described in detail in this article are existing technologies.

[0069] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A design method for a phosphorus removal and chemical dosing mixing system in a water collection well, characterized in that: When designing a water collection well, a three-dimensional hydraulic numerical model is constructed and the flow field is simulated. Key flow field characteristic parameters of the mixing effect of the water collection well are extracted, and an evaluation matrix is ​​constructed. The flow field state is judged by the evaluation matrix, and the mapping relationship between the changes in structural parameters and the flow field response law is established. Combined with the comprehensive evaluation function, the optimization is carried out by maximizing positive indicators and minimizing negative indicators.

2. The design method of the phosphorus removal and chemical dosing mixing system for water collection wells according to claim 1, characterized in that: The key flow field characteristic parameters of the mixing effect in the water collection well include the proportion of dead water zone V. dead , active region ratio V active ΔHRT (deviation between actual and theoretical residence time) and C (uniformity coefficient of reagent concentration) u The uniform intensity E of the circulating flow field throughout the pool b Energy consumption for mixing (E), risk index of retaining wall blockage (R) b Structural safety factor F s .

3. The design method of the phosphorus removal and chemical dosing mixing system for water collection wells according to claim 2, characterized in that: The flow field states include short-flow-dominated, dead-zone-dominated, vertically stratified, insufficient reagent diffusion, high-energy-consuming, clogging-risk, and structural-risk types. The structural parameters of the water collection well are adjusted according to different flow field states, which leads to changes in the flow field response law.

4. The design method of the phosphorus removal and chemical dosing mixing system for water collection wells according to claim 3, characterized in that, The comprehensive evaluation function is: F = W1×V active – W2×V dead – W3×ΔHRT + W4×C u + W5×E b – W6×E – W7×R b + W8×F s Among them, W1 to W8 are the corresponding indicator weight coefficients; When the structural parameters of the water collection well are adjusted, the change in the flow field response law leads to the change in the flow field characteristic parameters, which in turn causes the F value to change. When the F value reaches its maximum value, the structural parameters of the water collection well are output.

5. A phosphorus removal and chemical dosing system for water collection wells, characterized in that, It is obtained based on the optimization design method as described in any one of claims 1-4.

6. The phosphorus removal and chemical mixing system for water collection wells according to claim 5, characterized in that: The system includes a water collection well (1), which is connected to an inlet pipe (2) and an outlet pipe (3). The outlet pipe (3) is connected to the bottom of the water collection well (1). The water collection well (1) has a baffle wall (5). On the side of the water collection well (1) directly connected to the inlet pipe (2), there is a stirring mechanism (4). The stirring mechanism (4) is eccentrically arranged. The upper and lower parts of the baffle wall (5) have water passage holes. The water collection well (1) has a phosphorus removal dosing device above it. The dosing point of the phosphorus removal dosing device satisfies the requirement that the added agent can directly enter the main circulation flow field formed by the stirring mechanism (4). The structural parameters of the water collection well (1) are obtained by optimization using the comprehensive evaluation function.

7. The phosphorus removal and chemical mixing system for water collection wells according to claim 6, characterized in that: The stirring mechanism (4) is a paddle type. When H / D≤2, a single-layer stirring blade is used; when 2<H / D≤3, a double-layer stirring blade is used; when 3<H / D≤4, a triple-layer stirring blade is used; when H / D>4, a four-layer or higher stirring blade is used.

8. The phosphorus removal and chemical mixing system for water collection wells according to claim 7, characterized in that: When 2 < H / D, the axial vertical spacing between two adjacent layers of stirring blades is 0.5 to 1.2 times the blade diameter, and the stirring blades of two adjacent layers are offset at 90° in circumferential phase.

Images