Sludge screening system and method of controlling the same

Abstract

The application provides a sludge screening system and a control method thereof. The system comprises a screening device, a first discharge pipeline, a first reflux pipeline, a second reflux pipeline and a second discharge pipeline. The system has a first mode for improving sedimentation and a second mode for improving the proportion of sludge organic matter. In the first mode, the feeding pipeline, the first discharge pipeline and the second reflux pipeline are opened, and the first reflux pipeline and the second discharge pipeline are closed. In the second mode, the feeding pipeline, the second discharge pipeline and the first reflux pipeline are opened, and the second reflux pipeline and the first discharge pipeline are closed. The sludge screening system and the control method thereof can improve the performance of sludge according to the deterioration of the performance of sludge, and improve the operation stability and the treatment efficiency of the biochemical treatment unit.

Description

Technical Field

[0001] This application relates to the field of wastewater treatment technology, and in particular to a sludge screening system and its control method. Background Technology

[0002] The activated sludge process is the core biochemical technology in municipal and industrial wastewater treatment. When the performance of activated sludge deteriorates, a series of chain reactions quickly emerge in the water treatment process, such as decreased organic matter removal efficiency, weakened nitrification capacity, incomplete denitrification, sludge bulking, and sludge loss in the secondary sedimentation tank, resulting in substandard effluent and insufficient treated water volume. Selective sludge screening using sludge screening devices can improve sludge performance to some extent; however, existing sludge screening devices operate in relatively simple modes, making it difficult to simultaneously improve multiple sludge performance indicators, resulting in limited performance improvement and high energy consumption. Summary of the Invention

[0003] In view of this, the purpose of this application is to propose a sludge screening system and its control method to solve the above-mentioned technical problems.

[0004] A first aspect of this application provides a sludge screening system for screening activated sludge from a biochemical treatment unit, the biochemical treatment unit comprising a biochemical reaction zone and a secondary sedimentation tank connected in sequence, the bottom of the secondary sedimentation tank being connected to the biochemical reaction zone via a sludge return pipeline, the system comprising:

[0005] A screening device includes a cylindrical body and a conical body arranged vertically and connected to each other. The cylindrical body has a top wall and a side wall. An overflow port is provided at the center of the top wall, and a tangential feed port is provided on the side wall. A first discharge port is provided on the side wall between the tangential feed port and the top wall. The conical body has a side wall, a second discharge port is provided on the side wall, and the bottom gradually narrows to form an underflow port.

[0006] The feed pipeline is connected at both ends to the tangential feed port and the sludge return pipeline, respectively, to pass a portion of the returned sludge in the sludge return pipeline into the screening device.

[0007] The first external discharge pipeline is connected to the overflow port to discharge the material from the overflow port to the outside of the system;

[0008] The first return pipeline is connected at both ends to the first discharge port and the biochemical reaction zone, respectively, to return the discharge from the first discharge port to the biochemical reaction zone;

[0009] The second return pipeline is connected at both ends to the second discharge port and the biochemical reaction zone, respectively, to return the discharge from the second discharge port to the biochemical reaction zone;

[0010] The second external discharge pipeline is connected to the underflow port to discharge the material from the underflow port to the outside of the system.

[0011] The system's operating modes include a first mode for improving settling properties and a second mode for increasing the proportion of organic matter in the sludge.

[0012] In the first mode, the feed pipeline, the first discharge pipeline and the second return pipeline are opened, and the first return pipeline and the second discharge pipeline are closed.

[0013] In the second mode, the feed line, the second discharge line, and the first return line are opened, and the second return line and the first discharge line are closed.

[0014] Furthermore, an overflow pipe section is provided at the center of the cylindrical body, the outlet end of the overflow pipe section is connected to the overflow port, and the inlet end extends to a position lower than the tangential feed port;

[0015] The system's operating modes also include a third mode for simultaneously improving the sludge settling ratio and increasing the proportion of organic matter in the sludge.

[0016] In the third mode, the feed line, the first return line, the first discharge line, and the second discharge line are opened, and the second return line is closed.

[0017] Furthermore, the axial distance between the inlet end of the overflow pipe section and the tangential feed port is 0.05~0.1 of the total height of the cylindrical body;

[0018] And / or, the nominal diameter ratio of the overflow port, the first discharge port, the second discharge port and the underflow port is 1:2:2:1 to 1:4:4:1.

[0019] Furthermore, the conical cylinder includes a first conical cylinder and a second conical cylinder that are arranged vertically and connected to each other;

[0020] The first conical cylinder gradually tapers from top to bottom, and the second discharge port is located on the side wall of the first conical cylinder; the bottom of the second conical cylinder gradually tapers to form the underflow port;

[0021] The cone angle of the first conical cylinder is greater than that of the second conical cylinder.

[0022] A second aspect of this application provides a control method for a sludge screening system, used to control the periodic operation of the sludge screening system described in the first aspect, the control method comprising:

[0023] Based on historical operating data of the biochemical treatment unit, historical influent water quality data, and historical effluent water quality data, the future sludge volume index of the activated sludge is predicted to obtain a first predicted value, and the future organic matter ratio of the activated sludge is predicted to obtain a second predicted value.

[0024] The first slope, used to characterize the changing trend of the sludge volume index, is calculated based on the historical sludge volume index of activated sludge and the first predicted value.

[0025] A second slope was calculated based on the historical organic matter content of activated sludge and the second predicted value to characterize the trend of organic matter content change.

[0026] The operating mode of the sludge screening system in each operating cycle is determined based on the first predicted value, the second predicted value, the first slope, and the second slope.

[0027] Further, determining the operating mode of the sludge screening system in each operating cycle based on the first predicted value, the second predicted value, the first slope, and the second slope includes:

[0028] A first target prediction value is determined based on the first prediction value, and a second target prediction value is determined based on the second prediction value;

[0029] In response to determining that the sludge screening system is currently in a stopped state, and that the first target predicted value, the second target predicted value, the first slope, and the second slope only meet the preset first start-up conditions, the sludge screening system is controlled to enter the first operating cycle and operate in the first mode.

[0030] In response to determining that the sludge screening system is currently in a stopped state, and that the first target predicted value, the second target predicted value, the first slope, and the second slope only meet the preset second start-up conditions, the sludge screening system is controlled to enter the first operating cycle and operate in the second mode.

[0031] Wherein, the first activation condition is that the predicted value of the first target is greater than a preset first threshold, and the first slope is greater than a preset first slope threshold;

[0032] The second activation condition is that the predicted value of the second target is less than a preset second threshold, and the second slope is less than a preset second slope threshold.

[0033] Furthermore, it also includes:

[0034] In response to determining that the current runtime's operating mode is the first mode, the following is executed:

[0035] In response to the determination that the first target prediction value and the first slope at the end of the current operating cycle do not meet the preset first stop condition, and the second target prediction value and the second slope do not meet the preset second start condition, the sludge screening system is controlled to continue operating in the first mode in the next operating cycle.

[0036] In response to determining that the first target predicted value and the first slope at the end of the current operating cycle meet the preset first stop condition, and the second target predicted value and the second slope meet the preset second start condition, the sludge screening system is controlled to operate in the second mode in the next operating cycle.

[0037] In response to determining that the current runtime's operating mode is the second mode, the following is executed:

[0038] In response to the determination that the second target prediction value and the second slope at the end of the current operating cycle do not meet the preset second stop condition, and the first target prediction value and the first slope do not meet the first start condition, the sludge screening system is controlled to continue operating in the second mode in the next cycle.

[0039] In response to the determination that the second target prediction value and the second slope at the end of the current operating cycle meet the second stop condition, and the first target prediction value and the first slope meet the first start condition, the sludge screening system is controlled to operate in the first mode in the next cycle.

[0040] Wherein, the first stopping condition is that the first target prediction value is less than or equal to a preset third threshold, and the first slope is less than or equal to a preset third slope threshold; the third threshold is less than the first threshold, and the third slope threshold is less than the first slope threshold;

[0041] The second stopping condition is that the predicted value of the second target is greater than or equal to the second threshold, and the second slope is greater than or equal to the second slope threshold.

[0042] Furthermore, it also includes:

[0043] In response to determining that the sludge screening system is currently in a stopped state, and that the first target predicted value, the second target predicted value, the first slope, and the second slope simultaneously satisfy the first start-up condition and the second start-up condition, the sludge screening system is controlled to enter the first operating cycle and operate in the third mode.

[0044] Furthermore, it also includes:

[0045] In response to determining that the current runtime's operating mode is the first mode, the following is executed:

[0046] In response to the determination that the first target predicted value and the first slope at the end of the current operating cycle do not meet the preset first stop condition, and the second target predicted value and the second slope meet the preset second start condition, the sludge screening system is controlled to operate in the third mode in the next cycle.

[0047] In response to determining that the current runtime's operating mode is the second mode, the following is executed:

[0048] In response to the determination that the second target prediction value and the second slope at the end of the current operating cycle do not meet the second stop condition, and the first target prediction value and the first slope meet the first start condition, the sludge screening system is controlled to operate in the third mode in the next cycle.

[0049] In response to determining that the current runtime's operating mode is the third mode, the following is executed:

[0050] In response to the determination that the second target prediction value and the second slope at the end of the current operating cycle meet the preset second stop condition, and the first target prediction value and the first slope do not meet the first stop condition, the sludge screening system is controlled to operate in the first mode in the next cycle.

[0051] In response to the determination that the second target prediction value and the second slope at the end of the current operating cycle do not meet the preset second stop condition, and the first target prediction value and the first slope meet the first stop condition, the sludge screening system is controlled to operate in the second mode in the next cycle.

[0052] In response to the determination that the second target prediction value and the second slope at the end of the current operating cycle do not meet the preset second stop condition, and the first target prediction value and the first slope do not meet the first stop condition, the sludge screening system is controlled to continue operating in the third mode in the next cycle.

[0053] Furthermore, it also includes:

[0054] If both the current cycle's operating mode and the next cycle's operating mode are determined to be mode 1, then execute:

[0055] In response to determining that the first slope at the end of the current operating cycle is greater than the third slope threshold, the sludge screening system is controlled to operate in the first mode with a first discharge flow rate in the next cycle;

[0056] In response to determining that the first slope at the end of the current operating cycle is less than the third slope threshold, the sludge screening system is controlled to operate in the first mode with a second discharge flow rate in the next cycle;

[0057] Wherein, the first discharge flow rate and the second discharge flow rate are the operating flow rates of the first discharge pipeline, and the first discharge flow rate is greater than the second discharge flow rate.

[0058] As described above, this application provides a sludge screening system and its control method, which can switch operating modes according to changes in the properties of sludge in the biochemical treatment unit to achieve targeted improvement of activated sludge performance characteristics. When the SVI increases, leading to poor settling, the first mode is selected to enhance the floc structure; when the MLVSS / MLSS ratio is low and inorganic matter accumulation leads to a decrease in sludge activity, the second mode is selected to enhance the proportion of organic components. Compared with traditional hydrocyclones that can only operate in a single reflux direction, this application can flexibly change the reflux path and discharge path within the same equipment according to needs, achieving precise sludge classification and on-demand control, thus adapting to various sludge performance deterioration scenarios simultaneously. This application can make targeted improvements based on sludge performance deterioration and promptly determine the equipment's operating status based on the improvement of target indicators. This not only improves the operational stability and treatment efficiency of the biochemical treatment unit but also avoids the problems of increased footprint and investment costs caused by configuring multiple hydrocyclones. Simultaneously, it optimizes equipment operating time, saves energy, and has significant comprehensive technical advantages and broad application prospects. Attached Figure Description

[0059] To more clearly illustrate the technical solutions in this application or related technologies, the drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0060] Figure 1 This is a schematic diagram of a screening device according to an embodiment of this application;

[0061] Figure 2 This is a schematic diagram of a sludge screening system in an embodiment of this application;

[0062] Figure 3 This is a schematic diagram of the control method of a sludge screening system in an embodiment of this application.

[0063] Explanation of reference numerals in the attached drawings: 10-Biological treatment unit; 11-Biological reaction zone; 12-Secondary sedimentation tank; 13-Sludge return pipeline; 14-Inlet pipeline; 15-Outlet pipeline; 20-Screening device; 21-Cylindrical body; 22-Conical body; 221-First conical cylinder; 222-Second conical cylinder; 23-Overflow section; 24-Tangential feed inlet; 25-Overflow outlet; 26-First discharge outlet; 27-Second discharge outlet; 28-Bottom flow outlet; 30-Feed pipeline; 40-First return pipeline; 50-Second return pipeline; 60-First external discharge pipeline; 70-Second external discharge pipeline. Detailed Implementation

[0064] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0065] It should be noted that, unless otherwise defined, the technical or scientific terms used in the embodiments of this application should have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms "first," "second," and similar terms used in the embodiments of this application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are only used to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0066] The activated sludge process is the core biochemical technology in urban and industrial wastewater treatment. Its principle involves the use of suspended microbial communities to complete reactions such as organic matter degradation, ammonia nitrification, denitrification, and partial phosphorus removal. Activated sludge not only contains a large number of active bacteria, fungi, protozoa, and metazoa, but also possesses excellent flocculation structure and settling characteristics, enabling it to efficiently complete metabolic reactions in the aeration zone and achieve solid-liquid separation in the sedimentation tank. The stability and treatment efficiency of the activated sludge wastewater treatment process are highly dependent on the biological activity, floc structure, settling performance, and community composition of the sludge. Maintaining good sludge properties is crucial for ensuring effluent meets standards and improving hydraulic loading.

[0067] When the performance of activated sludge deteriorates, a series of chain reactions quickly emerge in the water treatment process, such as decreased organic matter removal efficiency, weakened nitrification capacity, incomplete denitrification, increased sludge load in the secondary settling tank, sludge leakage, and effluent exceeding standards. Deterioration of sludge floc structure reduces settling and compression capacity, making the sludge separation interface unstable and leading to increased effluent turbidity. Sludge aging also causes a decrease in microbial activity, weakening the system's responsiveness to load changes or shocks, ultimately affecting the overall reliability and economy of operation.

[0068] Among the various performance indicators of activated sludge, the organic matter content and sludge volume index (SVI) are particularly important. The organic matter content is typically characterized by the ratio of mixed liquor volatile suspended solids (MLVSS) to mixed liquor suspended solids (MLSS). A low organic matter content (i.e., a low MLVSS / MLSS ratio) indicates a decrease in the proportion of active microorganisms in the sludge and excessive accumulation of inorganic matter, leading to decreased metabolic efficiency and oxygen utilization per unit of sludge, making it difficult for the system to maintain its required purification capacity. A high SVI reflects poor sludge flocculation and settling properties, often associated with problems such as filamentous bulking, colloidal enrichment, and increased EPS / SMP ratios. This can directly lead to problems such as rising sludge levels in the sedimentation tank, sludge runoff, difficulty in sludge return, and uncontrolled sludge load. In MBR systems, high SVI significantly exacerbates membrane fouling and increases transmembrane pressure difference (TMP), doubling operational risks. Therefore, a decrease in organic matter content and an increase in SVI will jointly lead to reduced treatment efficiency, increased energy consumption, and decreased system stability, making them key indicators that must be monitored and controlled during the operation of activated sludge wastewater treatment processes.

[0069] Hydrocyclones, as devices that rely on a high-speed rotating flow field to achieve solid-liquid separation, form a double-vortex structure under the action of tangential force after sludge enters the hydrocyclone. Denser particles settle downwards along the outer vortex, while less dense particles are discharged upwards with the inner vortex, thus achieving rapid separation based on differences in particle density and size. Although hydrocyclone separation itself has advantages such as high efficiency, continuous operation, and simple structure, the operation mode of traditional hydrocyclones is relatively singular, usually only optimized for a certain type of sludge index. However, in actual operation, the purpose of sludge screening can change at any time. Sometimes it is necessary to screen for denser inorganic particles to improve settling properties, and sometimes it is necessary to screen for relatively less dense, high-organic sludge to improve the activity per unit sludge. Existing hydrocyclones are difficult to cope with the changing sludge screening purposes.

[0070] In view of this, this application provides a sludge screening system for screening the activated sludge of the biochemical treatment unit 10, such as... Figures 1-2 As shown, the biochemical treatment unit 10 includes a biochemical reaction zone 11 and a secondary sedimentation tank 12 connected in sequence. The bottom of the secondary sedimentation tank 12 is connected to the biochemical reaction zone 11 through a sludge return pipeline 13. The system includes:

[0071] The screening device 20 includes a cylindrical body 21 and a conical body 22 arranged vertically and connected to each other. The cylindrical body 21 has a top wall and a side wall. An overflow port 25 is provided at the center of the top wall, and a tangential feed port 24 is provided on the side wall. A first discharge port 26 is provided on the side wall between the tangential feed port 24 and the top wall. The conical body 22 has a side wall, and a second discharge port 27 is provided on the side wall. The bottom gradually narrows to form an underflow port 28.

[0072] The feed line 30 is connected at both ends to the tangential feed port 24 and the sludge return line 13, respectively, so as to pass part of the return sludge in the sludge return line 13 into the screening device 20.

[0073] The first external discharge pipeline 60 is connected to the overflow port 25 to discharge the material from the overflow port 25 to the outside of the system;

[0074] The first return pipeline 40 is connected at both ends to the first discharge port 26 and the biochemical reaction zone 11, respectively, so as to return the discharge from the first discharge port 26 to the biochemical reaction zone 11.

[0075] The second return pipeline 50 is connected at both ends to the second discharge port 27 and the biochemical reaction zone 11, respectively, so as to return the discharge from the second discharge port 27 to the biochemical reaction zone 11.

[0076] The second external discharge pipeline 70 is connected to the underflow port 28 to discharge the material from the underflow port 28 to the outside of the system.

[0077] The system's operating modes include a first mode for improving settling properties and a second mode for increasing the proportion of organic matter in the sludge.

[0078] In the first mode, the feed line 30, the first discharge line 60 and the second return line 50 are opened, and the first return line 40 and the second discharge line 70 are closed.

[0079] In the second mode, the feed line 30, the second discharge line 70 and the first return line 40 are opened, and the second return line 50 and the first discharge line 60 are closed.

[0080] During the long-term operation of the biological treatment unit 10, the properties of the activated sludge continuously evolve with changes in influent water quality, load, and sludge age. As inorganic inert particles gradually accumulate in the system, the organic matter content of the sludge (MLVSS / MLSS) continuously decreases, microbial activity weakens, and aging occurs. Conversely, when filamentous bacteria grow vigorously or the floc structure is damaged, the sludge volume index (SVI) easily increases, leading to deterioration of settling performance and increased sludge runoff. These two issues often occur alternately or simultaneously. Based on these changes in sludge properties, this system is equipped with a switchable first mode (primarily improving settling performance) and a second mode (primarily increasing organic matter content) to allow for the selection of appropriate operating modes for different sludge conditions.

[0081] In the first mode, primarily designed to improve settling properties, the feed line 30, the first discharge line 60, and the second return line 50 are opened, while the first return line 40 and the second discharge line 70 are closed. Part of the returned sludge from the sludge return line 13 enters the screening device 20 tangentially via the feed line 30, forming a double vortex flow field inside, moving from the outside in and from the bottom up. Dense inorganic particles and tightly packed flocs are thrown towards the outer vortex by centrifugal force, contacting the cylinder wall and then accumulating downwards along the side wall of the conical cylinder 22. Finally, they are discharged through the second outlet 27 located on the side wall of the conical cylinder 22 and returned to the biochemical reaction zone 11 via the second return line 50. Meanwhile, loosely structured, lightweight sludge containing more filamentous bacteria migrates upwards with the central inner vortex, is discharged through the overflow outlet 25, and finally, this portion of lightweight flocs is directly discharged from the system via the first discharge line 60. By controlling the flow direction, the first mode can effectively remove filamentous bacteria and loose flocs that cause SVI to increase, while retaining dense sludge with good settling properties, thereby inhibiting sludge bulking, improving floc structure and significantly reducing SVI, and improving the settling performance and separation effect of the entire biological treatment unit 10.

[0082] In the second mode, primarily used to increase the organic matter content of sludge, the feed line 30, the second discharge line 70, and the first return line 40 are opened, while the second return line 50 and the first discharge line 60 are closed. Return sludge from the sludge return line 13 enters the screening device 20 through the tangential feed inlet 24, forming a typical double-vortex structure within the device. Light sludge and microorganisms with high volatile suspended solids (VSS) content and high activity tend to aggregate towards the central area and migrate upwards with the internal vortex, forming a distinct enrichment zone on the sidewall of the columnar section near the first discharge port 26. Light sludge rich in active microorganisms and high MLVSS content is discharged through the first discharge port 26 and ultimately returned to the biochemical reaction zone 11 along the first return line 40 to restore and improve the overall organic component ratio and biochemical activity of the system. Meanwhile, the sludge descending along the wall of the outer vortex zone is enriched with a large amount of inorganic inert particles, aged flocs, and low-activity solids. After being further compacted at the bottom of the conical cylinder 22, it is discharged from the underflow port 28 and directly discharged from the system through the second external discharge pipeline 70, thereby reducing the accumulation of inorganic solids and avoiding the continuous impact of sludge aging on biochemical performance. Through screening path control, the proportion of organic components and microbial activity in the system can be effectively improved in the second mode, enhancing the biochemical reaction rate and shock resistance, and providing direct support for the system to restore normal metabolism.

[0083] This application enables the switching of operating modes based on changes in the properties of the sludge in the biochemical treatment unit 10, thereby achieving targeted improvements in the performance characteristics of activated sludge. When an increase in SVI leads to poor settling properties, the first mode is selected to enhance the floc structure. When a low MLVSS / MLSS ratio and inorganic matter accumulation lead to a decrease in sludge activity, the second mode is selected to enhance the proportion of organic components. Compared to traditional hydrocyclones that can only operate in a single return direction, this application allows for flexible changes in the return and discharge paths within the same equipment, enabling precise sludge classification and on-demand control, thus adapting to various sludge performance deterioration scenarios simultaneously. This application's ability to provide targeted improvements based on sludge performance deterioration not only enhances the operational stability and treatment efficiency of the biochemical treatment unit 10 but also avoids the problems of increased footprint and investment costs associated with configuring multiple hydrocyclones, demonstrating significant comprehensive technical advantages and broad application prospects.

[0084] In some embodiments, the biochemical reaction zone 11 is used to implement a continuous flow biochemical treatment process based on the AO process. Specifically, when implementing the AO process, the biochemical reaction zone 11 includes an anoxic tank and an aerobic tank connected in sequence; when implementing the AAO process, the biochemical reaction zone 11 includes an anaerobic tank, an anoxic tank, and an aerobic tank connected in sequence; when implementing the AOA process, the biochemical reaction zone 11 includes an anaerobic tank, an aerobic tank, and an anoxic tank connected in sequence.

[0085] In some embodiments, the biochemical treatment unit 10 further includes an inlet pipeline 14 connected to the biochemical reaction zone 11 for introducing the wastewater to be treated into the biochemical reaction zone 11; the biochemical treatment unit 10 further includes an outlet pipeline 15 connected to the secondary sedimentation tank 12 for discharging the treated wastewater to the next process.

[0086] In some embodiments, such as Figure 1 As shown, an overflow pipe section 23 is provided at the center of the cylindrical body 21. The outlet end of the overflow pipe section 23 is connected to the overflow port 25, and the inlet end extends to a position lower than the tangential feed port 24.

[0087] The system's operating modes also include a third mode for simultaneously improving the sludge settling ratio and increasing the proportion of organic matter in the sludge.

[0088] In the third mode, the feed line 30, the first return line 40, the first discharge line 60, and the second discharge line 70 are opened, and the second return line 50 is closed.

[0089] The lower end of the overflow pipe section 23 is positioned below the tangential feed inlet 24, allowing the overflow pipe section 23 to penetrate into the area where a stable internal vortex has been formed in the screening device 20. This structural arrangement not only effectively prevents the tangential feed fluid from directly entering the top area and reduces the possibility of the feed jet being discharged short-circuited along the upper wall, but also makes the overflow portion more selective: only after the sludge particles have completed the complete cycle of "outer vortex - cone bottom - inner vortex" will the light flocs and volatile components be carried by the inner vortex to the inlet of the overflow pipe section 23. Especially in the first mode, which primarily improves settling properties, the deep structure of the overflow pipe section 23 can enhance the enrichment of components that cause increased SVI, such as light, loose flocs and filamentous bacteria, in the inner vortex, making them easier to enter the top area and be discharged from the system through the first external discharge pipe 60; while the higher density, structurally complete flocs enriched in the outer vortex are drawn out on the side wall and conical cylinder 22 to return to the biochemical treatment unit 10, which is beneficial to significantly reduce SVI.

[0090] The sludge screening system of this application also has a third operating mode for simultaneously improving the sludge settling ratio and increasing the organic matter content of the sludge. In the third mode, the feed line 30, the first return line 40, the first discharge line 60, and the second discharge line 70 are opened, while the second return line 50 is closed. The returned sludge from the sludge return line 13 enters the screening device 20 through the tangential feed inlet 24, forming a high-speed rotating double vortex flow field inside the cylindrical body 21. Lightweight, loosely structured sludge containing more filamentous bacteria is less affected by centrifugal force and is more likely to converge towards the central area and move upward with the internal vortex, naturally accumulating in the upper part of the cylindrical body 21, and finally being discharged from the system through the overflow section 23 and the first discharge line 60, thereby achieving selective removal of high SVI sludge. Conversely, denser inorganic particles and high-density flocs migrate downwards along the outer vortex into the conical cylinder 22 under the action of strong centrifugal force, and further concentrate at the bottom under the compression and guidance of the conical structure, and finally exit the system through the bottom outlet 28 and the second external discharge outlet, so that highly sedimentary and inert solids can be effectively removed.

[0091] The medium-density flocs, situated between the two extreme types of sludge, form a stable equilibrium in the swirling field: their density is higher than that of the lighter flocs, insufficient to enter the rising region of the inner vortex center; simultaneously, it is far lower than that of inorganic inert particles, and under the influence of the downward thrust of the outer vortex, insufficient to continuously descend to the bottom of the cone. Therefore, these flocs form a stable annular enrichment zone in the middle sidewall region of the cylindrical body 21. This region corresponds precisely to the first discharge port 26, allowing the main flocs with intact structure, good settling properties, and suitable organic matter content to be selectively drawn out from this sidewall outlet and returned to the biological treatment unit 10.

[0092] Therefore, by using a graded path of overflowing light flocs, sidewall discharging medium-density dominant flocs, and bottom discharging the heaviest particles, this operating mode can simultaneously achieve bidirectional removal of light expanded sludge and high-density inorganic sludge in a single vortex operation, while retaining the core dominant flocs required by the system, thereby simultaneously improving settling performance and organic matter content.

[0093] Specifically, valves can be installed on the feed pipeline 30, the first discharge pipeline 60, the first return pipeline 40, the second return pipeline 50, and the second discharge pipeline 70 to control the opening and closing of the corresponding pipelines. Similarly, valves can be installed on the tangential feed inlet 24, overflow outlet 25, first discharge outlet 26, second discharge outlet 27, and underflow outlet 28 to control the opening and closing of these pipelines. No specific restrictions are imposed. A booster pump is also installed on the feed pipeline 30. When the sludge screening system of this application needs to be operated, the booster pump is activated to draw sludge from the sludge return pipeline 13 into the screening device 20.

[0094] In some embodiments, the axial distance between the inlet end of the overflow pipe section 23 and the tangential feed inlet 24 is 0.05 to 0.1 times the total height of the cylindrical body 21. The height of the cylindrical body 21 is represented by H1. The inlet end of the overflow pipe section 23 is set at a position of 0.05 to 0.1 H1 below the tangential feed inlet 24. Specifically, it can be 0.05 H1, 0.06 H1, 0.07 H1, 0.08 H1, 0.09 H1, or 0.1 H1, or other values ​​can be set according to actual conditions. There are no specific limitations. By making the lower end of the overflow pipe section 23 slightly lower than the tangential feed inlet 24 but not extending into the main classification area, this structure has a significant effect on establishing stable internal vortices, suppressing short circuits, and improving classification selectivity. It can take into account the needs of classification efficiency, short circuit suppression, internal vortex stability, and multi-mode control, so that the screening device 20 can obtain higher selectivity and stronger classification effect in different operating modes, thereby significantly improving the system's operational stability and processing performance. The inlet end of the overflow pipe section 23 can be flared outward to improve overflow efficiency.

[0095] In some embodiments, the nominal diameter ratio of the overflow port 25, the first discharge port 26, the second discharge port 27, and the underflow port 28 is 1:2:2:1 to 1:4:4:1. Specifically, the nominal diameter ratio of the overflow port 25, the first discharge port 26, the second discharge port 27, and the underflow port 28 can be 1:2:2:1, 1:3:2:1, 1:2:3:1, 1:3:3:1, 1:3:4:1, 1:4:3:1, 1:4:4:1, or other ratios.

[0096] In the sludge screening system of this application, the overflow port 25, the first discharge port 26, the second discharge port 27, and the underflow port 28 undertake the main diversion function in different operating modes. Their nominal diameter ratio is set to 1:2:2:1 to 1:4:4:1, making the size of the side wall discharge ports (first discharge port 26, second discharge port 27) significantly larger than the top overflow port 25 and the underflow port 28. This helps to accommodate the multiple operating requirements of the three operating modes and enhances the corresponding classification and control effects in different modes.

[0097] In the first mode for improving settling properties, the overflow port 25 with a smaller nominal diameter allows light, loose flocs to be stably discharged upward with the internal vortex without excessive loss of high-quality flocs; while the second discharge port 27 has a larger nominal diameter, which can ensure that medium and high density sludge can be discharged smoothly, avoiding blockage or local turbulence caused by an excessively small outlet, and improving the weight removal and expansion suppression effect of the first mode.

[0098] In the second mode, which increases the proportion of organic matter, the first discharge port 26 and the underflow port 28 are opened. During cyclone separation, inorganic particles, due to their higher density and stronger inertia, are easily detached from the floc surface and separated from the organic sludge. Setting the nominal diameter of the underflow port 28 to be smaller ensures the smooth discharge of inorganic particles while preventing larger main flocs from being excessively carried out. On the other hand, the nominal diameter of the first discharge port 26 is set to be larger, allowing medium-sized dominant flocs to be fully drawn out and returned at a lower pressure drop, maximizing the retention of the main microbial community with high activity and high organic matter content, thereby effectively improving the overall MLVSS / MLSS of the system.

[0099] In the third mode, which requires simultaneous improvement in settling properties and an increase in the proportion of organic matter, the system needs to remove both the top light sludge and the bottom heavy particles in a single operation, and return the dominant medium-density flocs. Therefore, this mode uses three outlets simultaneously: overflow outlet 25, first discharge outlet 26, and underflow outlet 28. The nominal diameters of overflow outlet 25 and underflow outlet 28 are kept to a minimum, which is conducive to the precise removal of sludge at both ends of the light and heavy sludge; while the first discharge outlet 26 maintains a larger nominal diameter to ensure that the dominant medium-density flocs in the middle enrichment zone can be stably output in the third mode, improving the mode's ability to synergistically optimize the two indicators (SVI and MLVSS / MLSS).

[0100] In summary, controlling the nominal diameter ratio of the four outlets within the range of 1:2:2:1 to 1:4:4:1 not only provides sufficient discharge capacity according to the flow requirements and density distribution characteristics of different operating modes, but also enhances the corresponding grading effect under the three modes, making the path distribution of light discharge, heavy discharge and retention of main flocs clearer and more stable, thereby improving the overall separation performance and operating efficiency of the screening device 20.

[0101] In some embodiments, the conical cylinder 22 includes a first conical cylinder 221 and a second conical cylinder 222 that are disposed vertically and communicate with each other;

[0102] The first conical cylinder 221 gradually tapers from top to bottom, and the second discharge port 27 is disposed on the side wall of the first conical cylinder 221; the bottom of the second conical cylinder 222 gradually tapers to form the bottom discharge port 28;

[0103] The cone angle of the first conical cylinder 221 is greater than that of the second conical cylinder 222.

[0104] Specifically, the cone angle of the first conical cylinder 221 is between 15° and 40°, and can be set to 15°, 20°, 25°, 30°, 35°, 40°, etc.; the cone angle of the second conical cylinder 222 is between 5° and 15°, and can be set to 5°, 8°, 10°, 12°, 15°, etc.; it can also be set to other values, and there are no specific restrictions.

[0105] In this embodiment, the cone angle of the first conical cylinder 221 is greater than that of the second conical cylinder 222, forming a flow structure that is wider at the top and narrower at the bottom, with progressively increasing grading intensity. The first conical cylinder 221 with a larger cone angle provides a transition area with moderate grading intensity and gentler radial stratification, which is conducive to the stable aggregation of the main flocs (medium-density, well-settling sludge) in the sidewall area; the second conical cylinder 222 with a smaller cone angle significantly enhances the centrifugal separation capacity, causing heavy inorganic particles and aged sludge to further concentrate at the bottom, achieving strong bottom separation.

[0106] Especially in the third mode, which simultaneously improves settling performance and increases the proportion of organic matter, the two-section conical structure forms a clearer and more stable radial classification environment inside the screening device 20. After the mixed liquor enters the screening device 20 tangentially, typical outer and inner vortex structures are established in the cylindrical body 21, the first conical cylinder 221, and the second conical cylinder 222: In the outer vortex, high-density inorganic particles and deeply compacted aged sludge migrate downward along the outer side under the action of centrifugal force, while low-density, loosely flocculated light sludge gradually migrates towards the inner vortex under the action of centripetal force and pressure gradient, and flows upward with the inner vortex; the main sludge, which is in between the two, with medium density and stable floc structure, forms a stable radial enrichment zone in the transition zone between the outer and inner vortices. In this graded environment, the larger cone angle of the first cone 221 facilitates the stable existence of medium-density, well-settling, and moderately active main flocs near the interface between the outer and inner vortices. This allows these main sludge particles to be more accurately drawn out by the first discharge port 26 in the third mode and returned to the biological treatment unit 10 via the first return pipeline 40, providing core support for maintaining the system's biomass and settling performance. The smaller cone angle of the second cone 222 enhances the centrifugal grading intensity in the bottom region, causing the heavy inorganic particles, still inside the outer vortex and flowing downwards, to further concentrate at the bottom of the cone. This enhanced grading results in the underflow being mainly enriched with high-density inorganic matter and deeply aged sludge, which is easily discharged continuously through the underflow port 28 and the second discharge pipeline 70, thereby reducing the accumulation of inorganic solids in the system and increasing the organic matter content of the sludge. Therefore, the two-section conical structure strengthens the outer and inner vortices through radial distribution and graded intensity, enabling the third mode to simultaneously improve settling performance and organic matter ratio in a single operation by relying on the zonal migration characteristics of light, medium and high density sludge naturally formed by the vortex flow field.

[0107] In some embodiments, the height ratio of the cylindrical body 21, the first conical cylinder 221, and the second conical cylinder 222 is 2:2:1 to 4:4:1. Specifically, the heights of the cylindrical body 21, the first conical cylinder 221, and the second conical cylinder 222 are represented by H1, H2, and H3, respectively. H1:H2:H3 can be 2:2:1, 3:2:1, 2:3:1, 4:4:1, or other ratios, without any specific limitation.

[0108] In some embodiments, the axial distance between the tangential feed port 24 and the top wall of the cylindrical body 21 is 3 / 4 to 4 / 5 of the total height of the cylindrical body 21; and / or, the axial distance between the first discharge port 26 and the top wall of the cylindrical body 21 is 1 / 2 to 3 / 4 of the total height of the cylindrical body 21.

[0109] And / or, the axial distance between the second discharge port 27 and the top of the first conical cylinder 221 is 1 / 4 to 1 / 2 of the total height of the first conical cylinder 221.

[0110] The tangential feed inlet 24 is typically located on the cylindrical body 21 at a distance of 3 / 4H1 to 4 / 5H1 from the top wall of the cylindrical body 21. Its axial distance is neither too close to the top wall nor too low to enter the high-grading region near the conical body 22. This helps the feed jet to immediately form a stable outer vortex upon entering the device, while avoiding direct impact on the top region that could cause short circuits. This allows the sludge to achieve sufficient rotational distance in the cylindrical section, resulting in good initial radial stratification. The first discharge port 26 is located on the cylindrical body 21 at a distance of 1 / 2H1 to 3 / 4H1 from the top wall of the cylindrical body 21. Positioning the first discharge port 26 within this range helps avoid extracting light sludge still in the rising inner vortex during the grading process in the third mode, while also avoiding the high centrifugal intensity zone very close to the conical section, thus ensuring a more stable and uniform composition of the returned sludge. The axial distance between the second discharge port 27 and the top of the first conical cylinder 221 is 1 / 4H2 to 1 / 2H2. Medium and high density flocs are enriched here and can be drawn out through the second discharge port 27.

[0111] Based on the same inventive concept, this application also provides a control method for a sludge screening system, used to control the periodic operation of a sludge screening system as described in any of the above embodiments, such as... Figure 3 As shown, the control method includes:

[0112] S101. Based on the historical operating data of the biochemical treatment unit, the historical influent water quality data and the historical effluent water quality data, the future sludge volume index of the activated sludge is predicted to obtain the first predicted value, and the future organic matter ratio of the activated sludge is predicted to obtain the second predicted value.

[0113] Specifically, historical operational data of the biological treatment unit (e.g., water temperature, pH, sludge concentration, historical sludge volume index, MLVSS / MLSS, presence and dosage of external carbon source, etc.) can reflect the growth status of the microbial community, changes in floc structure, and sludge metabolic level. Influent water quality data (e.g., COD, TN, TP, SS, etc.) characterize the organic matter load, nutrient levels, and suspended solids load entering the system. These factors affect the competition between activated sludge and filamentous bacteria and the floc formation process, thus significantly influencing subsequent trends in SVI and organic matter proportion. Effluent water quality data (e.g., COD, TN, TP, etc.) to some extent reflect the biological treatment unit's ability to remove organic matter and nutrients, and can be used to characterize sludge age, microbial activity, and the overall operational equilibrium of the reactor. Continuous changes in effluent quality also indicate changes in the organic degradation efficiency, inorganic matter accumulation rate, and microbial metabolic capacity within the sludge, providing an indication of future MLVSS / MLSS. By comprehensively utilizing the aforementioned historical operational data, influent water quality, and effluent water quality to construct a predictive model, the correlation between sludge performance changes and system operating conditions can be revealed from a time perspective. This allows for reasonable prediction of future trends in SVI and MLVSS / MLSS, providing a reliable basis for automated decision-making in subsequent operating modes. Optionally, historical operational data from 5 days prior to the current time, historical influent water quality data, and historical effluent water quality data can be used to predict future sludge volume index and future organic matter percentage. Alternatively, historical operational data from 7, 6, and 4 days prior to the current time, historical influent water quality data, and historical effluent water quality data can be used for prediction; there are no specific limitations.

[0114] S102. Based on the historical sludge volume index of activated sludge and the first predicted value, the first slope used to characterize the changing trend of the sludge volume index is calculated.

[0115] Specifically, the first predicted value may include SVI predicted values ​​at multiple future times, such as SVI predicted values ​​for days 1, 2, 3, and 4, or it may be the SVI predicted value at a specific future time, such as only including the SVI predicted value for day 3. There are no specific restrictions.

[0116] For example, the first forecast value includes SVI forecast data for the next 3 days, and the first slope is calculated using the historical 5-day and the forecasted SVI for the next 3 days. The historical 5-day and forecasted SVI data for the next 3 days are combined to form N=8 time series points (X). i Y i ), where X i Indicates the time sequence number (e.g., X1, X2... corresponding to day 1, day 2, etc.), Y iThis represents the SVI value for the corresponding date, including both historical actual values ​​and future projected values. Based on these 8 data points, the first slope k1 can be calculated using a linear fitting method, with the following formula:

[0117] k1 = (N × Σ(X)) i × Y i ) ΣX i × ΣY i ) / (N×Σ(X i ²) (ΣX) i ) 2 );

[0118] The calculated first slope k1 characterizes the overall direction and magnitude of SVI change: a positive k1 indicates a deteriorating trend in sludge settling properties; a negative k1 indicates improving sludge settling properties; and a k1 close to zero indicates relatively stable settling performance. By incorporating a first predicted value into the trend fitting, the trend calculation can anticipate upcoming increases or decreases in SVI, avoiding lag in judgments due to reliance solely on historical data.

[0119] S103. The second slope, used to characterize the trend of change in organic matter proportion, is calculated based on the historical organic matter proportion of activated sludge and the second predicted value.

[0120] Specifically, the second prediction value includes MLVSS / MLSS prediction values ​​at multiple future times, such as MLVSS / MLSS prediction values ​​for days 1, 2, 3, and 4; or it can be SVI prediction value at a certain future time, such as only including MLVSS / MLSS prediction values ​​for day 3 in the future, without any specific restrictions.

[0121] For example, the second predicted value includes predicted MLVSS / MLSS data for the next 3 days. The second slope is calculated using the historical MLVSS / MLSS data for the past 5 days and the predicted MLVSS / MLSS data for the next 3 days. The historical MLVSS / MLSS data for the past 5 days and the predicted MLVSS / MLSS data for the next 3 days constitute a total of N=8 time series points (Xi, Zi), where Xi is the time sequence number (e.g., days 1-8), and Zi is the organic matter percentage for the corresponding date, including historical actual measurements and future predicted values. Based on these data points, the second slope k2 can be calculated using the same linear fitting method as the first slope, and its calculation formula is:

[0122] k2 = (N×Σ(X) i ×Z i ) ΣX i ×ΣZ i ) / (N×Σ(Xi ²) (ΣX) i )²)

[0123] The calculated second slope, k2, reflects the future trend of MLVSS / MLSS: a positive k2 indicates an increasing proportion of organic matter and potentially enhanced sludge activity; a negative k2 indicates a decreasing proportion of organic matter and may indicate risks of sludge aging, inorganic matter accumulation, or weakened microbial community activity; and a k2 close to zero indicates relatively stable changes in the proportion of organic matter. By incorporating a second predictive value into the trend fitting, the trend analysis not only includes historical trends but also anticipates future downward or upward trends, improving the ability to predict changes in MLVSS / MLSS and avoiding predictive lag caused by relying solely on historical data.

[0124] S104. Determine the operating mode of the sludge screening system in each operating cycle based on the first predicted value, the second predicted value, the first slope, and the second slope.

[0125] Specifically, the operating time for each cycle can be 3 days, or it can be set to 2, 4, or 5 days, etc., without any specific restrictions. Changes in activated sludge properties usually have a significant lag; whether it's an improvement in settling performance or an increase in organic matter content, it takes a continuous period of time for the effects to become apparent. Therefore, through periodic operation, the system can maintain a relatively stable control strategy within each cycle, avoiding disturbances caused by frequent mode switching, and more effectively promoting the continuous improvement of sludge performance. The first and second predicted values ​​can reflect the future changes in sludge settling properties and organic matter content in advance, while the first and second slopes can further characterize the direction and speed of change, thereby avoiding misjudgments caused by instantaneous detection data or short-term water quality fluctuations, and ensuring that the selection of operating modes is based on a more stable and forward-looking assessment of sludge status.

[0126] In this embodiment, the future sludge volume index (SVI) and organic matter ratio (ORR) of the activated sludge are predicted based on historical operating data of the biochemical treatment unit, historical influent water quality data, and historical effluent water quality data. This allows for the prediction of future trends before sludge settling properties or the ORR deteriorates, enabling the sludge screening system to proactively adjust its operation mode in each operating cycle based on future predictions, rather than relying on current single-point detection values. This significantly improves the foresight and stability of operation mode switching. Simultaneously, the first slope calculated based on the historical sludge volume index and the first predicted value, and the second slope calculated based on the historical ORR and the second predicted value, can characterize the direction and rate of change of SVI and ORR using trend metrics. The introduction of slopes not only weakens the impact of short-term influent water quality fluctuations and instantaneous disturbances on the judgment results, avoiding accidental triggering of mode switching due to occasional water quality shocks, but also more accurately reflects the true state of sludge performance—whether it is continuously deteriorating, continuously improving, or remaining stable. The trend slope shifts the mode decision-making from static threshold judgment to dynamic change judgment, making the selection of operating mode more sensitive, robust, and reliable. Determining the operating mode for each operating cycle based on the first and second predicted values, as well as the first and second slopes, not only allows for early intervention against the risks of increased SVI, decreased organic matter content, or both, but also ensures that mode switching is based on a stable slope reflecting the true trend, rather than being triggered by momentary deviations caused by occasional water quality fluctuations. Since the improvement of sludge properties (including the recovery of settling performance and the increase in organic matter content) has a certain lag and requires a continuous period to show its effects, a periodic operation is adopted. After completing one cycle, the operating mode for the next cycle is re-determined, ensuring that the sludge screening system maintains an appropriate operating mode within each cycle and avoiding disturbances caused by frequent switching. Through such periodic predictive control, this application enables the sludge screening system to maintain sludge settling performance and organic matter content more stably and efficiently, thereby further improving the overall operating effect of the biological treatment unit.

[0127] Optionally, a pre-built sludge performance prediction model can be used to predict the first and second predicted values. The sludge performance prediction model is constructed using a sliding window-based Long Short-Term Memory (LSTM) network. LSTM is a type of recurrent neural network, a special type of recursive neural network, capable of analyzing inputs using time series data. LSTM is an improved recurrent neural network that, by introducing forget gates, input gates, and output gates, can retain or discard historical information at different time scales, thus possessing the ability to capture long-term dependencies and complex temporal features. Compared to traditional neural networks, LSTM can more effectively handle nonlinear, periodic, and highly abrupt time series, making it particularly suitable for activated sludge performance prediction.

[0128] In LSTM, a sliding window is used to construct model input samples from continuous time series, allowing a fixed-length historical data segment to be used as input for a single prediction. For example, if the sliding window length is 7 days, when the model predicts the sludge volume index and organic matter ratio for a certain day, it will use the influent data from the previous 7 consecutive days as input. By continuously sliding the window and generating new input sequences, LSTM can continuously learn from the latest historical patterns, thereby improving its response capability for future sludge volume index and organic matter ratio. Specifically, the sludge performance prediction model can be constructed through the following steps: acquiring training data, which includes historical operating data of multiple consecutive historical moments of the biochemical treatment unit, historical influent water quality data, and historical effluent water quality data; constructing an initial model based on a long short-term memory neural network; pre-training the initial model using the training data until a preset termination condition is reached, determining the model parameters at the time of training termination as the final model parameters, and applying the final model parameters to the initial model to obtain the sludge performance prediction model.

[0129] When the sludge performance prediction model predicts the sludge volume index and organic matter ratio for the next few days based on historical data (i.e., historical operating data, historical influent water quality data, and historical effluent water quality data) from a historical sliding window, it first predicts the sludge volume index and organic matter ratio for the first day of the future. Then, it uses the sludge volume index and organic matter ratio of the next day as historical data for the next day's prediction. Finally, it obtains the sludge volume index and organic matter ratio for the next few days, thus obtaining the first and second predicted values. For example, when using historical data from the past 5 days to predict the sludge volume index and organic matter ratio for the next 3 days, first predict the sludge volume index and organic matter ratio for the first day of the future; when predicting the sludge volume index and organic matter ratio for the second day of the future, the predicted sludge volume index and organic matter ratio for the first day of the future are used as historical data for the prediction of the second day of the future; when predicting the sludge volume index and organic matter ratio for the third day of the future, the predicted sludge volume index and organic matter ratio for the first and second days of the future are used as historical data for the prediction of the third day of the future, thus obtaining the sludge volume index and organic matter ratio for the next 3 days.

[0130] The sludge performance prediction model employs a multi-layer LSTM stacked structure, with each layer containing several memory units (e.g., up to 256) to learn long-short-term dependencies in the input sequence. The number of neurons in the input layer is consistent with the feature dimension. A dropout layer is set after the LSTM layer to reduce the risk of overfitting, with a dropout rate of 0.2–0.5. Subsequently, a fully connected layer maps the LSTM output to the prediction space, and the output layer containing single neurons generates the predicted SVI and organic matter percentage for the next time step. The model uses a rolling prediction inference approach, that is, it first predicts the SVI and organic matter percentage for the next time step based on the current sequence, then fills the input window with the predicted value, and repeats the prediction by sliding the time series, enabling the model to generate prediction results for multiple future time steps. To improve prediction accuracy, Bayesian optimization can be used during model training to automatically search for the optimal combination of hyperparameters, including: time series window length L (e.g., 7–30 days), number of LSTM layers (e.g., 1–3 layers), learning rate (e.g., 0.001–0.01), and dropout ratio (e.g., 0.2–0.5). Through the above structural design and parameter optimization, the constructed sludge performance prediction model can effectively extract the variation patterns of sludge settling performance, organic matter ratio, and time, obtaining reliable predictions of future trends in SVI and organic matter ratio, providing an accurate basis for the selection of operating modes.

[0131] In some embodiments, the prediction of the future sludge volume index of activated sludge based on historical operating data of the biochemical treatment unit, historical influent water quality data, and historical effluent water quality data to obtain a first predicted value, and the prediction of the future organic matter content of activated sludge to obtain a second predicted value, includes:

[0132] S201. Based on the first historical operating data of the biochemical treatment unit and the first historical influent water quality data, predict the future sludge volume index of the activated sludge and obtain the first predicted value.

[0133] Specifically, the first set of operational data includes parameters such as water temperature, pH, amount of added carbon source, sludge concentration in the biochemical reaction zone, and actual sludge volume index. The first set of water quality data includes parameters such as Chemical Oxygen Demand (COD), Total Nitrogen (TN), and Total Phosphorus (TP). COD, TN, and TP are used to characterize the concentrations of organic matter, nitrogenous pollutants, and phosphorus-containing pollutants in wastewater, respectively, and are important water quality indicators reflecting the biodegradability of wastewater, nutrient balance, and microbial growth conditions.

[0134] The sludge volume index (SVI) is influenced by a combination of factors, including microbial growth status, floc structure, sludge age, nutrient ratio, and aquatic environmental conditions. Therefore, historical influent water quality and operational data can be used to predict future SVI. Specifically, influent COD and the amount of added carbon source determine the amount of organic matter available for microbial use, affecting sludge yield and floc formation characteristics. Essentially, it reflects the organic load and is one of the core factors affecting SVI. At low organic loads, microorganisms are in a state of starvation; filamentous bacteria, with their larger specific surface area, have a higher absorption rate of low-concentration substrates, giving them an advantage in competition and making them prone to low-load sludge bulking and increased SVI. At high organic loads, flocs grow rapidly, entering an exponential growth phase, making it difficult to form dense flocs and reducing settling performance.

[0135] TN and TP represent indicators of microbial nutrient balance, affecting the nitrogen and phosphorus nutrient supply to microorganisms. A suitable carbon-nitrogen-phosphorus ratio contributes to the stability of activated sludge systems. Excess carbon sources are converted into glycogen or extracellular polymeric substances (EPS) by microorganisms and stored within the body or secreted externally. A large amount of hydrophilic EPS leads to increased water content in sludge flocs, resulting in a loose, viscous structure, non-filamentous bulking, and increased SVI.

[0136] Water temperature and pH are core environmental factors affecting the structure and metabolic activity of microbial communities. When the water temperature is between 15-35℃, flocs and filamentous bacteria are in dynamic equilibrium, resulting in well-structured sludge flocs and a relatively normal SVI (Sludge Volume Index). At low temperatures (<15℃), microbial metabolism slows down, but filamentous bacteria have a better ability to utilize the substrate than floc bacteria, gaining a growth advantage and multiplying, leading to filamentous bacteria expansion and an increase in SVI. High temperatures (>35℃) accelerate the reaction, causing excessive consumption of dissolved oxygen (DO), creating an anoxic environment within the flocs and providing growth conditions for filamentous bacteria. At excessively low pH (<6), some fungal filamentous bacteria survive preferentially, inhibiting the activity of floc bacteria, causing floc disintegration and an increase in SVI. The sludge concentration in the biochemical reaction zone affects the sludge volume index (SVI) by influencing the system's feed-to-microbe ratio (F / M) and dissolved oxygen gradient. F / M (food-to-microbe ratio) refers to the organic pollutant load borne by a unit mass of activated sludge microorganisms per unit time. Its calculation formula is usually F / M = (total amount of organic matter entering the biochemical reaction zone) / (total amount of microorganisms in the system). It is a core parameter for regulating the health and balance of the activated sludge system.

[0137] Therefore, by acquiring historical first operating data and historical first influent water quality data, we can reflect the microbial growth conditions and sludge formation characteristics of the biochemical system over a period of time. This allows the sludge performance prediction model to learn the correlation between the above factors and SVI changes, thereby achieving accurate prediction of future sludge volume index.

[0138] S202. Based on the historical second operating data of the biochemical treatment unit, the historical second water quality data of the influent, and the historical third water quality data of the effluent, the future organic matter ratio of the activated sludge is predicted to obtain the second predicted value.

[0139] Specifically, the second set of operational data includes water temperature, sludge concentration in the biochemical reaction zone, and MLVSS / MLSS ratio; the second set of water quality data includes COD, ammonia nitrogen concentration, and SS concentration; and the third set of water quality data includes COD and ammonia nitrogen concentration. The second set of operational data (such as water temperature and sludge concentration in the biochemical reaction zone) reflects the long-term changes in microbial growth activities, biochemical reaction intensity, and the internal environment of the system. The second set of water quality data (such as influent COD, ammonia nitrogen concentration, and SS concentration) characterizes the composition of pollutants entering the system and the structure of suspended solids. In particular, the influent SS and its inorganic particle content have a direct impact on sludge ash accumulation and the proportion of active ingredients. The third set of water quality data (such as effluent COD and ammonia nitrogen concentration) reflects the system's organic matter removal capacity, nutrient conversion efficiency, and the overall equilibrium state of the reactor. It can be used to indirectly indicate changes in sludge retention time (SRT) and microbial activity, and changes in SRT directly affect the evolution trend of MLVSS / MLSS. With longer sludge ages, microorganisms enter the endogenous respiration stage, and cellular material is gradually decomposed, causing MLVSS to decrease slowly. With shorter sludge ages, the system is in a high-proliferation state, with a higher proportion of active microorganisms and a shorter accumulation time of inorganic particles, so MLVSS / MLSS usually remains at a relatively high level. Therefore, by using historical second-stage operational data, historical second-stage influent water quality data, and historical third-stage effluent water quality data, the key factors affecting MLVSS / MLSS can be comprehensively reflected from aspects such as organic loading, inorganic matter accumulation, microbial activity, and changes in sludge age, thereby reasonably predicting the future trend of organic matter proportion and obtaining a second predicted value.

[0140] In some embodiments, the prediction of the future sludge volume index of activated sludge based on historical operating data of the biochemical treatment unit, historical influent water quality data, and historical effluent water quality data to obtain a first predicted value, and the prediction of the future organic matter content of activated sludge to obtain a second predicted value, includes:

[0141] Based on the first historical operating data of the biochemical treatment unit and the first historical influent water quality data, the future sludge volume index of the activated sludge is predicted, and the first predicted value is obtained.

[0142] Based on the historical second operating data of the biochemical treatment unit, the historical second water quality data of the influent, the historical third water quality data of the effluent, and the first predicted value, the future organic matter ratio of the activated sludge is predicted to obtain the second predicted value.

[0143] In this embodiment, the first predicted value characterizes the future trend of sludge volume index (SVI), reflecting the comprehensive impact of settling performance, floc structure density, and filamentous bacteria proliferation on the system's microbial community and sludge composition. Changes in settling performance are closely related to the relative proportions of organic and inorganic components within the sludge. For example, loose flocs and a higher proportion of filamentous bacteria are usually accompanied by a decrease in the proportion of active microorganisms, and the accumulation rate of inorganic particles also shows significant differences between the deterioration and improvement stages of settling performance. Therefore, the future trend of SVI changes has a certain indicative effect on future MLVSS / MLSS. Using the first predicted value as input allows the generation of the second predicted value to simultaneously consider the impact of future settling performance changes on the proportion of organic matter. This enables the sludge performance prediction model to more comprehensively characterize the dynamic evolution of organic and inorganic components under multi-factor coupling conditions, thereby improving the accuracy of MLVSS / MLSS predictions and making the prediction results more consistent with the actual process of sludge structure evolution, thus providing more reliable data support for the automatic selection of subsequent operating modes.

[0144] In some embodiments, determining the operating mode of the sludge screening system in each operating cycle based on the first predicted value, the second predicted value, the first slope, and the second slope includes:

[0145] A first target prediction value is determined based on the first prediction value, and a second target prediction value is determined based on the second prediction value;

[0146] In response to determining that the sludge screening system is currently in a stopped state, and that the first target predicted value, the second target predicted value, the first slope, and the second slope only meet the preset first start-up conditions, the sludge screening system is controlled to enter the first operating cycle and operate in the first mode.

[0147] In response to determining that the sludge screening system is currently in a stopped state, and that the first target predicted value, the second target predicted value, the first slope, and the second slope only meet the preset second start-up conditions, the sludge screening system is controlled to enter the first operating cycle and operate in the second mode.

[0148] Wherein, the first activation condition is that the predicted value of the first target is greater than a preset first threshold, and the first slope is greater than a preset first slope threshold;

[0149] The second activation condition is that the predicted value of the second target is less than a preset second threshold, and the second slope is less than a preset second slope threshold.

[0150] Specifically, the first and second predicted values ​​can be predictions for a single future time point or prediction sequences containing predictions for multiple future time points. To enhance the adaptability of the operational mode determination, a target predicted value can be further determined after obtaining the predicted values. When the first or second predicted value contains only the result for a single prediction time point, it can be directly used as the first or second target predicted value. When the first predicted value contains predictions for multiple time points, any representative statistic can be selected from the prediction sequence as the first target predicted value, such as the maximum, average, or median value, without restriction on the specific selection method. When the second predicted value contains predictions for multiple time points, any representative statistic can be selected from the prediction sequence as the second target predicted value, such as the minimum, average, or median value, without restriction on the specific selection method.

[0151] The first threshold can be set to 120 ml / g, or to 90, 92, 95, 98, 100, 102, 105, 108, 110, or 115 ml / g, or other values ​​depending on the actual situation. There are no specific restrictions. The first slope threshold is 3, or can be set to 1.5, 2, 2.5, 3.5, 4, or 8, or other values ​​depending on the actual situation. There are no specific restrictions. The second threshold is 0.65, or can be set to 0.55, 0.58, 0.6, 0.65, or 0.7, or other values ​​depending on the actual situation. There are no specific restrictions. The second slope threshold is -0.05, or can be set to -0.02, -0.01, -0.03, -0.06, -0.08, or -0.10, or other values ​​depending on the actual situation. There are no specific restrictions.

[0152] When the system is stopped, if the predicted value of the first target is greater than the first threshold, it indicates that the predicted sludge volume index is higher than the acceptable range for the system, suggesting an impending deterioration in settling performance. Simultaneously, if the first slope is greater than the first slope threshold, it indicates that the sludge volume index is showing a continuous upward trend, rather than an occasional increase caused by short-term influent fluctuations. In this case, if it is further determined that the predicted value of the second target is not lower than the second threshold or the second slope is not lower than the second slope threshold, it indicates that the organic matter content of the sludge has not shown a decreasing trend, and the second start-up condition has not been triggered. Therefore, it is considered that only the preset first start-up condition is met, and the second start-up condition is not met. Based on the above judgment, the system enters its first operating cycle and controls the sludge screening system to operate in the first mode to prioritize improving the sludge settling performance. In this way, the system can intervene before the SVI reaches an uncontrollable state, avoiding problems such as sludge bulking and increased effluent turbidity caused by further deterioration of settling performance.

[0153] Similarly, when the system is in a stopped state and the predicted value of the second target is determined to be lower than the second threshold, it indicates that the predicted proportion of organic matter in the sludge will be lower than the requirements for normal operation, posing a risk of decreased activated sludge ratio and insufficient microbial activity in the system. Simultaneously, if the second slope is less than the second slope threshold, it indicates that the proportion of organic matter is showing a continuous downward trend, rather than a momentary deviation caused by a temporary increase in influent concentration. In this case, if the predicted value of the first target does not exceed the first threshold or the first slope does not exceed the first slope threshold, it indicates that the sludge settling properties have not yet shown a significant deterioration trend, and it is considered that only the preset second start-up condition is met, but the first start-up condition is not. At this time, the sludge screening system enters its first operating cycle and operates in the second mode to prioritize increasing the proportion of organic matter in the sludge, preventing further decline in microbial activity, reduced reaction efficiency, and possible sludge age disorder.

[0154] Based on the above judgment logic, the system can clearly identify the deterioration trend of sedimentation and the decreasing trend of organic matter content according to the actual physical meaning of the predicted and trend values, thereby accurately selecting the operating mode during the start-up phase. Compared with traditional control methods that rely solely on instantaneous sludge indicators, this method, by combining predicted indices and trend slopes, makes the determination of the start-up mode more reasonable, stable, and forward-looking, which is conducive to ensuring the performance recovery and risk pre-control of the biochemical treatment system in the initial stage of operation.

[0155] In some embodiments, it also includes:

[0156] In response to determining that the current runtime's operating mode is the first mode, the following is executed:

[0157] In response to the determination that the first target prediction value and the first slope at the end of the current operating cycle do not meet the preset first stop condition, and the second target prediction value and the second slope do not meet the preset second start condition, the sludge screening system is controlled to continue operating in the first mode in the next operating cycle.

[0158] In response to determining that the first target predicted value and the first slope at the end of the current operating cycle meet the preset first stop condition, and the second target predicted value and the second slope meet the preset second start condition, the sludge screening system is controlled to operate in the second mode in the next operating cycle.

[0159] In response to determining that the current runtime's operating mode is the second mode, the following is executed:

[0160] In response to the determination that the second target prediction value and the second slope at the end of the current operating cycle do not meet the preset second stop condition, and the first target prediction value and the first slope do not meet the first start condition, the sludge screening system is controlled to continue operating in the second mode in the next cycle.

[0161] In response to the determination that the second target prediction value and the second slope at the end of the current operating cycle meet the second stop condition, and the first target prediction value and the first slope meet the first start condition, the sludge screening system is controlled to operate in the first mode in the next cycle.

[0162] Wherein, the first stopping condition is that the first target prediction value is less than or equal to a preset third threshold, and the first slope is less than or equal to a preset third slope threshold; the third threshold is less than the first threshold, and the third slope threshold is less than the first slope threshold;

[0163] The second stopping condition is that the predicted value of the second target is greater than or equal to the second threshold, and the second slope is greater than or equal to the second slope threshold.

[0164] Specifically, the third threshold can be determined based on the first threshold. For example, it can be obtained by subtracting a difference or multiplying by a percentage from the first threshold. For instance, the third threshold = first threshold - 10, or the third threshold = first threshold × 90%, etc., with no specific restrictions. The third slope threshold can be set to 0, indicating that the sludge settling trend is stabilizing. SVI deterioration is characterized by its sudden onset, significant impact on the system, and delayed recovery. Setting the third threshold and the third slope threshold to be less than the first threshold and the third slope threshold to be less than the first slope threshold ensures that stopping the first mode requires a more substantial improvement effect, thus avoiding the risks associated with repeated deterioration of settling performance.

[0165] After the sludge screening system enters its first operating cycle, the sludge condition of the biological treatment unit is reassessed at the end of that cycle to determine the operating mode required for the next cycle. This assessment is also based on updated first and second target predicted values ​​and their corresponding first and second slopes, and is matched with preset stop and start conditions to determine whether to maintain the current mode or switch to another mode.

[0166] When the current operating cycle is in mode one, the latest predicted value of the first target and the first slope are obtained before the end of the cycle. If the predicted value of the first target is still higher than the third threshold or the first slope is still higher than the third slope threshold, i.e., the preset first stop condition is not met, and the predicted value of the second target is not lower than the second threshold or the second slope is not lower than the second slope threshold, i.e., the second start condition is not met, it means that the trend of deterioration in settling has not been sufficiently alleviated and there is no risk of a decrease in the proportion of organic matter. Therefore, the system will continue to operate in mode one in the next operating cycle to avoid repeated deterioration caused by premature cessation of settling remediation. If, at the end of the operating cycle, it is determined that the predicted value of the first target has decreased to below the third threshold and the first slope has decreased to below the third slope threshold, i.e., the first stop condition is met, and the predicted value of the second target is lower than the second threshold and the second slope is also lower than the second slope threshold, i.e., the second start condition is met, it means that the risk of settling has been controlled and the proportion of organic matter has shown a downward trend. In this case, the system will switch to mode two in the next operating cycle to suppress the downward trend of MLVSS / MLSS as early as possible and maintain the microbial activity of activated sludge.

[0167] When the current operating cycle is in the second mode, the system will determine whether the organic matter ratio has recovered based on the latest second target prediction value and the second slope. If the second target prediction value is still lower than the second threshold or the second slope is still less than the second slope threshold (i.e., the second stop condition is not met), and the first target prediction value does not exceed the first threshold or the first slope does not exceed the first slope threshold (i.e., the first start condition is not met), it indicates that the downward trend of the organic matter ratio has not been reversed and there is no risk of deterioration in sedimentation. Therefore, the system will continue to operate in the second mode in the next operating cycle to ensure that MLVSS / MLSS is fully recovered. Conversely, if at the end of the cycle it is determined that the second target prediction value is no lower than the second threshold and the second slope is no less than the second slope threshold (i.e., the second stop condition is met), and the first target prediction value exceeds the first threshold and the first slope also exceeds the first slope threshold (i.e., the first start condition is met), it indicates that the organic matter ratio has recovered but the sedimentation has shown a deteriorating trend. The system will switch to the first mode in the next operating cycle to prioritize addressing the risk of declining sedimentation.

[0168] When the current operating cycle is in the first operating mode, and the first target predicted value and first slope at the end of the current operating cycle meet the preset first stop condition, but the second target predicted value and second slope do not meet the preset second start condition, then the sludge screening system is controlled to stop operating. When the current operating cycle is in the second operating mode, and the first target predicted value and first slope at the end of the current operating cycle do not meet the preset first start condition, but the second target predicted value and second slope meet the preset second stop condition, then the sludge screening system is controlled to stop operating.

[0169] By jointly judging the predicted values ​​of the first and second targets, as well as the first and second slopes, at the end of each operating cycle, this method can reflect the improvement in settling performance and organic matter ratio in real time. This allows mode switching to be based on the actual degree of improvement rather than a single detection result, thereby improving the system's adaptability to changes in sludge condition and enabling timely targeted improvements to activated sludge. Compared to traditional control methods that rely on instantaneous indicators, this method uses periodic judgment, enabling the system to maintain stable operation within each cycle, avoiding disturbances caused by frequent switching, and making sludge structure improvement more consistent and controllable.

[0170] In some implementations, this also includes:

[0171] In response to determining that the sludge screening system is currently in a stopped state, and that the first target predicted value, the second target predicted value, the first slope, and the second slope simultaneously satisfy the first start-up condition and the second start-up condition, the sludge screening system is controlled to enter the first operating cycle and operate in the third mode.

[0172] In this embodiment, when the sludge screening system is stopped, and within the same judgment time, the predicted value of the first target is greater than the first threshold and the first slope is greater than the first slope threshold, it indicates that the settling performance of the activated sludge is not only predicted to deteriorate significantly, but this deterioration trend is also persistent. Simultaneously, the predicted value of the second target is lower than the second threshold and the second slope is lower than the second slope threshold, indicating that the organic matter content of the activated sludge also shows a downward trend, and this trend is not an occasional deviation caused by short-term fluctuations, but rather has a risk of continuous decline. Under these circumstances, the system determines that both the first and second start-up conditions are met simultaneously, meaning that the two risks of deteriorating settling performance and decreasing organic matter content are occurring simultaneously, and both require intervention. At this time, the system directly operates in the third mode during the first operating cycle. The third mode can simultaneously remove light flocs that cause deterioration in settling performance and heavy inorganic particles that cause a decrease in organic matter content, and selectively recirculates the main sludge with medium density and both good settling performance and active structure. This allows for simultaneous correction of both types of indicators within one operating cycle, preventing further deterioration of sludge properties in both directions. This embodiment detects the predicted values ​​of the first and second targets, as well as the first and second slopes during the startup phase. When both the first and second startup conditions are met simultaneously, the system automatically enters a third mode of operation. This allows the system to synergistically intervene when settling properties deteriorate and the organic matter content decreases simultaneously, avoiding the situation where improving only one indicator leads to further deterioration of the other. Since the third mode can selectively regulate the removal of light, heavy, and medium-weight sludge, this strategy can comprehensively correct sludge performance in the early stages of system operation, enabling SVI and MLVSS / MLSS to return to reasonable ranges simultaneously, thereby significantly improving the system's stability and risk response capabilities.

[0173] In some embodiments, it also includes:

[0174] In response to determining that the current runtime's operating mode is the first mode, the following is executed:

[0175] In response to the determination that the first target predicted value and the first slope at the end of the current operating cycle do not meet the preset first stop condition, and the second target predicted value and the second slope meet the preset second start condition, the sludge screening system is controlled to operate in the third mode in the next cycle.

[0176] In response to determining that the current runtime's operating mode is the second mode, the following is executed:

[0177] In response to the determination that the second target prediction value and the second slope at the end of the current operating cycle do not meet the second stop condition, and the first target prediction value and the first slope meet the first start condition, the sludge screening system is controlled to operate in the third mode in the next cycle.

[0178] In response to determining that the current runtime's operating mode is the third mode, the following is executed:

[0179] In response to the determination that the second target prediction value and the second slope at the end of the current operating cycle meet the preset second stop condition, and the first target prediction value and the first slope do not meet the first stop condition, the sludge screening system is controlled to operate in the first mode in the next cycle.

[0180] In response to the determination that the second target prediction value and the second slope at the end of the current operating cycle do not meet the preset second stop condition, and the first target prediction value and the first slope meet the first stop condition, the sludge screening system is controlled to operate in the second mode in the next cycle.

[0181] In response to the determination that the second target prediction value and the second slope at the end of the current operating cycle do not meet the preset second stop condition, and the first target prediction value and the first slope do not meet the first stop condition, the sludge screening system is controlled to continue operating in the third mode in the next cycle.

[0182] Specifically, when the current operating cycle is in mode one, the system first determines whether the first target predicted value and the first slope at the end of the operating cycle have met the first stopping condition. If the first stopping condition is not met, it indicates that the deteriorating trend of sludge settling properties has not been fully reversed; at this time, the system continues to determine whether the second target predicted value and the second slope meet the second starting condition. If both the second target predicted value and the second slope meet the second starting condition, it indicates that the proportion of organic matter in the biological system has a significant downward trend. Under the dual effects of incompletely improved settling properties and the risk of a decrease in the proportion of organic matter, the system switches to mode three in the next operating cycle to simultaneously intervene in both settling performance and the proportion of organic matter.

[0183] When the current operating cycle is in the second mode, the system also determines at the end of the cycle whether the second target prediction value and the second slope meet the second stopping condition. If the second stopping condition is not met, it indicates that the downward trend of the organic matter proportion has not been fully reversed; if the first target prediction value and the first slope have met the first starting condition, it indicates that the sedimentation is simultaneously deteriorating. In this case of simultaneous deterioration of both indicators, the system will operate in the third mode in the next operating cycle to simultaneously address the issues of decreasing sedimentation and decreasing organic matter proportion.

[0184] When the current operating cycle is in mode three, the system needs to determine whether to continue in mode three, revert to mode one, or switch to mode two in the next cycle based on the sludge state at the end of the cycle. If the second target predicted value and the second slope meet the second stopping condition at the end of the mode three operating cycle, but the first target predicted value and the first slope do not meet the first stopping condition, it indicates that the organic matter ratio has stabilized, but settling performance still faces risks. The system will switch to mode one in the next cycle to continue improving settling performance. If the second target predicted value and the second slope do not meet the second stopping condition at the end of the cycle, but the first target predicted value and the first slope meet the first stopping condition, it indicates that settling performance has reached a normal level, but the organic matter ratio is still declining. The system will switch to mode two in the next cycle to repair the organic matter ratio. If neither of the two indicators meets their respective stopping conditions at the end of the mode three operating cycle, it indicates that both settling performance and organic matter ratio have not fully recovered. Mode three needs to be continued to ensure that the system maintains synergistic improvement of both indicators in the next cycle.

[0185] In the third mode, if at the end of the current operating cycle, the first target predicted value and the first slope meet the first stopping condition, and the second target predicted value and the second slope also meet the second stopping condition, meaning that both settling performance and organic matter ratio have recovered to a stable operating range and there is no further deterioration trend, then it indicates that both types of indicators have reached the sufficient degree of improvement required for the system to stop operating in the third mode. In this case, the sludge screening system is controlled to exit the three operating modes and enter a stopped state in the next operating cycle to avoid continuing unnecessary separation operations and ensure that the system maintains an energy-saving and stable operating state under normal sludge properties.

[0186] It should be noted that the improvement in a single indicator (sedimentation or organic matter content) in the third mode is generally weaker than the targeted enhancement of the first or second modes. When the SVI (Sedimentation Performance Index) shows a deteriorating trend, running the first mode alone can improve sludge settling performance faster and more efficiently. Similarly, when the organic matter content of sludge decreases, running the second mode alone can improve sludge performance faster and more efficiently. When two indicators need to be adjusted simultaneously, the third mode is activated. Although the third mode improves two sludge performance indicators less quickly than the targeted enhancement of the first and second modes, the water treatment capacity of activated sludge is essentially determined by multiple performance indicators. When multiple performance indicators deteriorate, improving only one indicator cannot guarantee a simultaneous improvement in the overall system treatment efficiency. When multiple key performance indicators such as sludge settling, activity, or ash content deteriorate simultaneously, the third mode can simultaneously regulate both light and heavy components in a single operation, while retaining medium-density sludge with a compact structure and high activity, allowing multiple performance indicators to converge to the ideal range in a shorter time. Compared to a single operating mode that improves one indicator before moving on to another, the third mode significantly reduces the repetitive adjustments caused by alternating control, lowers the probability of indicator fluctuations, and shortens the time required for the overall performance of activated sludge to recover. Therefore, even though its individual optimization effect is not as good as the individual modes, it has higher practical application value in comprehensively improving sludge quality and water treatment performance.

[0187] In this embodiment, based on the index at the end of the operating cycle and the dynamic switching of the operating mode, the sludge screening system can automatically select the most suitable operating mode under different sludge conditions, achieving timely, stable, and precise control over deterioration of settling performance, decrease in sludge activity, or simultaneous deterioration of both indicators. Through a multi-mode collaborative operating strategy, the system can not only proactively switch to the appropriate mode to correct deviations before risks occur, but also promptly exit to a stopped state after sufficient improvement in sludge performance, avoiding unnecessary grading operations and thus reducing energy consumption and operating costs. This embodiment can significantly improve operating efficiency while ensuring effluent quality and system stability, and achieve energy saving and consumption reduction through timely shutdown and reasonable mode selection, enhancing the anti-disturbance capability and long-term operational reliability of the entire biological treatment unit.

[0188] In some embodiments, it also includes:

[0189] If both the current cycle's operating mode and the next cycle's operating mode are determined to be mode 1, then execute:

[0190] In response to determining that the first slope at the end of the current operating cycle is greater than the third slope threshold, the sludge screening system is controlled to operate in the first mode with a first discharge flow rate in the next cycle;

[0191] In response to determining that the first slope at the end of the current operating cycle is less than the third slope threshold, the sludge screening system is controlled to operate in the first mode with a second discharge flow rate in the next cycle;

[0192] Wherein, the first discharge flow rate and the second discharge flow rate are the operating flow rates of the first discharge pipeline, and the first discharge flow rate is greater than the second discharge flow rate.

[0193] In this embodiment, when it is determined that the operating mode of the current operating cycle and the operating mode of the next operating cycle are both the first mode, the operating parameters of the first mode in the next operating cycle are further adjusted based on the first slope at the end of the current operating cycle. Specifically, after obtaining the latest first slope at the end of the current cycle, it is first determined whether the slope is greater than a preset third slope threshold. If the first slope is greater than the third slope threshold, it indicates that the deterioration trend of settling performance is still obvious, the sludge volume index is still in the rising range, and there is still a risk of continued deterioration in the future. In this case, the system will operate in the first mode with the first discharge flow rate in the next operating cycle, that is, increase the operating flow rate of the first discharge pipeline to accelerate the discharge of the top light flocs and filamentous bacteria enriched in the system, thereby enhancing the settling performance improvement effect. If the first slope is less than the third slope threshold, it indicates that the deterioration trend of settling performance has been partially alleviated, the increase in sludge volume index has significantly weakened, and sludge performance is in a stage of recovery towards a stable state. However, the sludge solvent index is still too high. In this case, to balance improving settling performance and avoiding excessive discharge that leads to the loss of too much activated sludge, the system will operate in the first mode with the second discharge flow rate in the next operating cycle. That is, the flow rate of the first discharge pipeline will be reduced to continuously improve settling performance in a gentler manner. In this operating scheme, the first discharge flow rate is greater than the second discharge flow rate. Together, they constitute the operating intensity adjustment mechanism in the first mode, enabling the system to automatically adjust the operating intensity according to the degree of settling performance improvement when the first mode is executed continuously in consecutive cycles.

[0194] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of this application (including the claims) is limited to these examples; within the framework of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of the embodiments of this application as described above, which are not provided in the details for the sake of brevity.

[0195] Furthermore, given that details have been set forth to describe exemplary embodiments of this application, it will be apparent to those skilled in the art that embodiments of this application may be practiced without these details or with variations thereof. Therefore, these descriptions should be considered illustrative rather than restrictive.

[0196] To simplify the description and discussion, and to avoid obscuring the embodiments of this application, well-known power / ground connections to other components may or may not be shown in the provided drawings. Furthermore, the apparatus may be shown in block diagram form to avoid obscuring the embodiments of this application, and this also takes into account the fact that the details of implementation of these block diagram apparatuses are highly dependent on the platform on which the embodiments of this application will be implemented (i.e., these details should be fully understood by those skilled in the art). While specific details have been set forth to describe exemplary embodiments of this application, it will be apparent to those skilled in the art that the embodiments of this application may be implemented without these specific details or with variations thereof. Therefore, these descriptions should be considered illustrative rather than restrictive.

[0197] Although this application has been described in conjunction with specific embodiments thereof, many substitutions, modifications, and variations of these embodiments will be apparent to those skilled in the art from the foregoing description. The embodiments of this application are intended to cover all such substitutions, modifications, and variations falling within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the embodiments of this application should be included within the protection scope of this application.

Claims

1. A sludge screening system for screening activated sludge from a biochemical treatment unit, characterized in that, The biochemical treatment unit includes a biochemical reaction zone and a secondary sedimentation tank connected in sequence. The bottom of the secondary sedimentation tank is connected to the biochemical reaction zone via a sludge return pipeline. The system includes: A screening device includes a cylindrical body and a conical body arranged vertically and connected to each other. The cylindrical body has a top wall and a side wall. An overflow port is provided at the center of the top wall, and a tangential feed port is provided on the side wall. A first discharge port is provided on the side wall between the tangential feed port and the top wall. The conical body has a side wall, a second discharge port is provided on the side wall, and the bottom gradually narrows to form an underflow port. The feed pipeline is connected at both ends to the tangential feed port and the sludge return pipeline, respectively, to pass a portion of the returned sludge in the sludge return pipeline into the screening device. The first external discharge pipeline is connected to the overflow port to discharge the material from the overflow port to the outside of the system; The first return pipeline is connected at both ends to the first discharge port and the biochemical reaction zone, respectively, to return the discharge from the first discharge port to the biochemical reaction zone; The second return pipeline is connected at both ends to the second discharge port and the biochemical reaction zone, respectively, to return the discharge from the second discharge port to the biochemical reaction zone; The second external discharge pipeline is connected to the underflow port to discharge the material from the underflow port to the outside of the system. The system's operating modes include a first mode for improving settling properties and a second mode for increasing the proportion of organic matter in the sludge. In the first mode, the feed pipeline, the first discharge pipeline and the second return pipeline are opened, and the first return pipeline and the second discharge pipeline are closed. In the second mode, the feed line, the second discharge line, and the first return line are opened, and the second return line and the first discharge line are closed.

2. The system according to claim 1, characterized in that, An overflow pipe section is provided at the center of the cylindrical body. The outlet end of the overflow pipe section is connected to the overflow port, and the inlet end extends to a position lower than the tangential feed port. The system's operating modes also include a third mode for simultaneously improving the sludge settling ratio and increasing the proportion of organic matter in the sludge. In the third mode, the feed line, the first return line, the first discharge line, and the second discharge line are opened, and the second return line is closed.

3. The system according to claim 2, characterized in that, The axial distance between the inlet end of the overflow pipe section and the tangential feed inlet is 0.05~0.1 of the total height of the cylindrical body; And / or, the nominal diameter ratio of the overflow port, the first discharge port, the second discharge port and the underflow port is 1:2:2:1 to 1:4:4:

1.

4. The system according to claim 1, characterized in that, The conical cylinder includes a first conical cylinder and a second conical cylinder that are arranged vertically and connected to each other; The first conical cylinder gradually tapers from top to bottom, and the second discharge port is located on the side wall of the first conical cylinder; the bottom of the second conical cylinder gradually tapers to form the underflow port; The cone angle of the first conical cylinder is greater than that of the second conical cylinder.

5. A control method for a sludge screening system, characterized in that, The control method for controlling the periodic operation of a sludge screening system according to any one of claims 1 to 4 includes: Based on historical operating data of the biochemical treatment unit, historical influent water quality data, and historical effluent water quality data, the future sludge volume index of the activated sludge is predicted to obtain a first predicted value, and the future organic matter ratio of the activated sludge is predicted to obtain a second predicted value. The first slope, used to characterize the changing trend of the sludge volume index, is calculated based on the historical sludge volume index of activated sludge and the first predicted value. A second slope was calculated based on the historical organic matter content of activated sludge and the second predicted value to characterize the trend of organic matter content change. The operating mode of the sludge screening system in each operating cycle is determined based on the first predicted value, the second predicted value, the first slope, and the second slope.

6. The control method for a sludge screening system according to claim 5, characterized in that, Determining the operating mode of the sludge screening system in each operating cycle based on the first predicted value, the second predicted value, the first slope, and the second slope includes: A first target prediction value is determined based on the first prediction value, and a second target prediction value is determined based on the second prediction value; In response to determining that the sludge screening system is currently in a stopped state, and that the first target predicted value, the second target predicted value, the first slope, and the second slope only meet the preset first start-up conditions, the sludge screening system is controlled to enter the first operating cycle and operate in the first mode. In response to determining that the sludge screening system is currently in a stopped state, and that the first target predicted value, the second target predicted value, the first slope, and the second slope only meet the preset second start-up conditions, the sludge screening system is controlled to enter the first operating cycle and operate in the second mode. Wherein, the first activation condition is that the predicted value of the first target is greater than a preset first threshold, and the first slope is greater than a preset first slope threshold; The second activation condition is that the predicted value of the second target is less than a preset second threshold, and the second slope is less than a preset second slope threshold.

7. The control method for a sludge screening system according to claim 6, characterized in that, Also includes: In response to determining that the current runtime's operating mode is the first mode, the following is executed: In response to the determination that the first target prediction value and the first slope at the end of the current operating cycle do not meet the preset first stop condition, and the second target prediction value and the second slope do not meet the preset second start condition, the sludge screening system is controlled to continue operating in the first mode in the next operating cycle. In response to determining that the first target predicted value and the first slope at the end of the current operating cycle meet the preset first stop condition, and the second target predicted value and the second slope meet the preset second start condition, the sludge screening system is controlled to operate in the second mode in the next operating cycle. In response to determining that the current runtime's operating mode is the second mode, the following is executed: In response to the determination that the second target prediction value and the second slope at the end of the current operating cycle do not meet the preset second stop condition, and the first target prediction value and the first slope do not meet the first start condition, the sludge screening system is controlled to continue operating in the second mode in the next cycle. In response to the determination that the second target prediction value and the second slope at the end of the current operating cycle meet the second stop condition, and the first target prediction value and the first slope meet the first start condition, the sludge screening system is controlled to operate in the first mode in the next cycle. Wherein, the first stopping condition is that the first target prediction value is less than or equal to a preset third threshold, and the first slope is less than or equal to a preset third slope threshold. The third threshold is less than the first threshold, and the third slope threshold is less than the first slope threshold; The second stopping condition is that the predicted value of the second target is greater than or equal to the second threshold, and the second slope is greater than or equal to the second slope threshold.

8. The control method for a sludge screening system according to claim 7, characterized in that, Also includes: In response to determining that the sludge screening system is currently in a stopped state, and that the first target predicted value, the second target predicted value, the first slope, and the second slope simultaneously satisfy the first start-up condition and the second start-up condition, the sludge screening system is controlled to enter the first operating cycle and operate in the third mode.

9. The control method for a sludge screening system according to claim 8, characterized in that, Also includes: In response to determining that the current runtime's operating mode is the first mode, the following is executed: In response to the determination that the first target predicted value and the first slope at the end of the current operating cycle do not meet the preset first stop condition, and the second target predicted value and the second slope meet the preset second start condition, the sludge screening system is controlled to operate in the third mode in the next cycle. In response to determining that the current runtime's operating mode is the second mode, the following is executed: In response to the determination that the second target prediction value and the second slope at the end of the current operating cycle do not meet the second stop condition, and the first target prediction value and the first slope meet the first start condition, the sludge screening system is controlled to operate in the third mode in the next cycle. In response to determining that the current runtime's operating mode is the third mode, the following is executed: In response to the determination that the second target predicted value and the second slope at the end of the current operating cycle meet the preset second stopping condition, and the first target predicted value and the first slope do not meet the first stopping condition, the sludge screening system is controlled to operate in the first mode in the next cycle. In response to the determination that the second target prediction value and the second slope at the end of the current operating cycle do not meet the preset second stop condition, and the first target prediction value and the first slope meet the first stop condition, the sludge screening system is controlled to operate in the second mode in the next cycle. In response to the determination that the second target prediction value and the second slope at the end of the current operating cycle do not meet the preset second stop condition, and the first target prediction value and the first slope do not meet the first stop condition, the sludge screening system is controlled to continue operating in the third mode in the next cycle.

10. The control method for a sludge screening system according to claim 9, characterized in that, Also includes: If both the current cycle's operating mode and the next cycle's operating mode are determined to be mode 1, then execute: In response to determining that the first slope at the end of the current operating cycle is greater than the third slope threshold, the sludge screening system is controlled to operate in the first mode with a first discharge flow rate in the next cycle; In response to determining that the first slope at the end of the current operating cycle is less than the third slope threshold, the sludge screening system is controlled to operate in the first mode with a second discharge flow rate in the next cycle; Wherein, the first discharge flow rate and the second discharge flow rate are the operating flow rates of the first discharge pipeline, and the first discharge flow rate is greater than the second discharge flow rate.

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