A multi-stage purification and filtration system for fish ponds and a filter dam device

Abstract

This invention relates to the field of aquaculture water treatment technology, and discloses a multi-stage purification and filtration system and filter dam device for fish ponds. The system includes a multi-stage flow-guiding filter dam, a piezoelectric-biocoupled reactor, and an adaptive resonant control system. The piezoelectric-biocoupled reactor is filled with piezoelectric composite biological filler. A micro-electric field is generated by ultrasonic excitation, which works synergistically with the biofilm to degrade pollutants. The adaptive resonant control system monitors the acoustic impedance value within the piezoelectric-biocoupled reactor in real time and adaptively adjusts the ultrasonic output parameters based on deviation using a differential algorithm, achieving dynamic control and in-situ renewal of the biofilm thickness. The system also includes anoxic autotrophic denitrification and reoxygenation reflux devices at the back end. Through the microscopic coupling of piezoelectric catalysis and biodegradation, and intelligent closed-loop feedback control, the system achieves simultaneous and efficient removal of recalcitrant organic matter and ammonia nitrogen, ensuring the high activity and long-term stable operation of the purification system.

Description

Technical Field

[0001] This invention relates to the field of aquaculture water treatment technology, specifically to a multi-stage purification and filtration system for fish ponds and a filter dam device. Background Technology

[0002] As a core model for achieving water conservation, emission reduction, and environmental friendliness, the key to recirculating aquaculture systems lies in the efficient purification and recycling of aquaculture wastewater.

[0003] Currently, biofilm-based water treatment technologies such as biological contact oxidation are the mainstream methods for removing ammonia nitrogen in recirculating aquaculture systems. However, in actual long-term operation, traditional fixed-bed or moving-bed biofilters face significant stability challenges. Biofilm growth often occurs in an uncontrollable natural succession process. Over time, microorganisms proliferate excessively and secrete large amounts of extracellular polymers, leading to aging and thickening of the biofilm on the filter media surface. An excessively thick biofilm not only hinders internal mass transfer, forming an ineffective anaerobic layer, but also causes pore blockage of the filter media, short-circuiting of water flow, and increased head loss, resulting in a significant decrease in the system's nitrification efficiency.

[0004] Existing maintenance methods for biological filters primarily rely on periodic manual backwashing or mechanical agitation. These methods are typically based on fixed time periods or macroscopic water quality changes, lacking a real-time sensing and precise response mechanism for the microscopic growth state of the biofilm within the reactor. Excessive or drastic cleaning can lead to excessive shedding of the active biofilm, causing a decline in system performance; while insufficient cleaning fails to fundamentally solve clogging and aging problems. Furthermore, traditional biological methods mainly target easily biodegradable carbon and nitrogen pollutants, with limited ability to remove recalcitrant organic micropollutants such as antibiotic residues and hormones that may accumulate during aquaculture. The presence of these substances, in turn, inhibits the activity of nitrifying bacteria, further exacerbating the instability of the biological treatment unit. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a multi-stage purification and filtration system for fish ponds and a filter dam device, which solves the problems of packing blockage, decreased mass transfer efficiency, and unstable system operation caused by excessive proliferation and aging of biofilm in traditional aquaculture biological treatment systems during long-term operation.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a multi-stage purification and filtration system for fish ponds, comprising:

[0007] Multi-stage flow-guiding filter dams are used for the physical pretreatment of fishpond water.

[0008] A piezoelectric-biocoupled reactor is located downstream of the multi-stage flow-guiding filter dam. It is filled with piezoelectric composite biological packing material and equipped with an ultrasonic transducer array for exciting the piezoelectric composite biological packing material.

[0009] An adaptive resonance control system, electrically connected to the ultrasonic transducer array, is configured to: monitor the acoustic impedance characterization value within the piezoelectric-biocoupled reactor in real time, and adaptively adjust the output parameters of the ultrasonic transducer array based on the deviation between the acoustic impedance characterization value and a preset target value.

[0010] Preferably, the piezoelectric composite biofiller comprises: a porous ceramic substrate, and a barium titanate piezoelectric material loaded on the surface of the porous ceramic substrate.

[0011] Preferably, the ultrasonic transducer array is evenly distributed in a matrix or ring pattern on the outer wall or bottom of the piezoelectric-biocoupled reactor.

[0012] Preferably, the adaptive resonance control system is configured to monitor the acoustic impedance characterization value by instructing the ultrasonic transducer array to emit probe sound waves and receive echo signals, and calculating the acoustic impedance characterization value by analyzing the amplitude or phase of the echo signals.

[0013] Preferably, the adaptive resonant control system is further configured to: compare the real-time acoustic impedance characterization value with a preset target acoustic impedance value to obtain a deviation, and calculate the adjustment amount based on the deviation using a differential control algorithm.

[0014] Preferably, the adaptive resonance control system is further configured to adjust the output power and operating mode of the ultrasonic transducer array according to the adjustment amount.

[0015] Preferably, the system also includes:

[0016] Anoxic autotrophic denitrification unit is located downstream of the piezoelectric-biocoupled reactor and is used for deep denitrification of the water body;

[0017] The reoxygenation recirculation device is located downstream of the anoxic autotrophic denitrification unit and is used to reoxygenate the purified water before it is returned to the fishpond.

[0018] Preferably, the interior of the anoxic autotrophic denitrification unit is filled with conductive carbon felt as a carrier for microbial attachment.

[0019] A multi-stage purification and filtration method for fish ponds includes the following steps:

[0020] Physical pretreatment of fishpond water;

[0021] Pretreated water is introduced into a piezoelectric-biocoupled reactor, where adaptive piezoelectric-biocoupled synergistic purification is implemented. This purification process includes: generating a micro-electric field by ultrasonically exciting a piezoelectric composite biological packing material within the reactor; utilizing this micro-electric field to catalyze the generation of active species, which synergistically purify the water through a biofilm attached to the packing material surface; simultaneously, real-time monitoring of the acoustic impedance characterization value within the piezoelectric-biocoupled reactor, and adaptively adjusting the ultrasonic parameters used to excite the piezoelectric effect based on the deviation between the acoustic impedance characterization value and the target value.

[0022] Deep denitrification treatment is carried out on the water body after synergistic purification.

[0023] A multi-stage flow-guiding filter dam, comprising:

[0024] Filter box;

[0025] A grid is disposed inside the filter frame;

[0026] A detachable mesh is movably installed outside the filter frame and located outside the grille;

[0027] A limiting strip is provided on the inner wall of the filter frame;

[0028] Multiple filter boxes are slidably connected between the limiting strips;

[0029] A barrier plate is fixedly connected to the inside of the filter box.

[0030] This invention provides a multi-stage purification and filtration system for fish ponds and a filter dam device. It has the following beneficial effects:

[0031] 1. This invention sets up a piezoelectric-biocoupled reactor and uses ultrasonic waves to excite the piezoelectric composite biological packing to generate an in-situ micro-electric field, which catalyzes the generation of highly oxidizing active species to mineralize recalcitrant organic matter. At the same time, it works synergistically with the biofilm on the surface of the packing to carry out nitrification. Through the microscopic coupling of the above-mentioned physical catalysis and biological metabolism, the shortcomings of traditional biological methods in treating recalcitrant substances are overcome and the purification efficiency is improved.

[0032] 2. This invention employs an adaptive resonant control system to monitor the growth status of the biofilm within the reactor in real time using acoustic impedance characterization values. It dynamically adjusts the output parameters of the ultrasonic waves through a differential algorithm. A closed-loop feedback mechanism enhances the exfoliation effect of the ultrasonic waves when the biofilm is too thick, preventing packing blockage, and reduces power to promote growth when the biofilm is too thin. This consistently maintains the biofilm within the optimal thickness range where mass transfer efficiency is highest and activity is strongest.

[0033] 3. The multi-stage flow-guiding filter dam set up in this invention intercepts suspended solids and extends the hydraulic retention time through the S-shaped flow channel design of the detachable mesh and internal corrugated baffle plate, reducing the load on the subsequent biological treatment unit. Combined with the anoxic autotrophic denitrification and reoxygenation return device, it fully covers the entire process from solid-liquid separation, carbon and nitrogen synergistic removal to deep denitrification and reoxygenation, ensuring that all indicators of the returned aquaculture water reach excellent levels. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the system framework of the present invention;

[0035] Figure 2 This is a schematic diagram of the piezoelectric-biocoupled reactor structure of the present invention;

[0036] Figure 3 This is a schematic diagram of the piezoelectric composite biological filler structure of the present invention;

[0037] Figure 4 This is a block diagram illustrating the working principle of the adaptive resonance control system of the present invention.

[0038] Figure 5 This is a three-dimensional view of the multi-stage flow-guiding filter dam of the present invention;

[0039] Figure 6 This is a schematic diagram of the filter frame structure of the present invention;

[0040] Figure 7 This is a schematic diagram of the filter box structure of the present invention.

[0041] The components include: 1. Filter frame; 2. Grille; 3. Removable mesh; 4. Limiting strip; 5. Filter box; and 6. Barrier plate. Detailed Implementation

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] Please see the appendix Figure 1 - Appendix Figure 7 This invention provides a multi-stage purification and filtration system for fish ponds, including a multi-stage flow-guiding filter dam installed in the fish pond, a water pump, a piezoelectric-biocoupled reactor (PBR), an anoxic autotrophic denitrification unit, a reoxygenation recirculation device, and an adaptive resonance control system for regulating the PBR reactor, all installed on the bank of the fish pond.

[0044] A multi-stage flow-guiding filter dam is installed in the fishpond, dividing the water into an aquaculture zone and a purification zone. Its structure, from the direction of water flow in the aquaculture zone to the direction of water flow in the purification zone, includes a detachable mesh 3, an external grille 2, and a filter frame 1. The detachable mesh 3 serves as the first line of defense, consisting of a fine mesh made of polymer or stainless steel, and is fixed to a frame that can be quickly separated from and joined to the filter frame 1, used to intercept the main suspended solids in the water.

[0045] The outer grille 2 is located adjacent to the inner side of the removable mesh 3 and is composed of multiple rigid bars arranged in a grid pattern with a spacing greater than the mesh size of the removable mesh 3. When the removable mesh 3 is operating normally, the outer grille 2 serves as secondary protection. During maintenance when the removable mesh 3 is removed, it acts as the primary coarse filter component, preventing large floating objects from entering the filter frame 1.

[0046] The filter frame 1 is the main supporting structure of the multi-stage flow-guiding filter dam. Inside the filter frame 1 are multiple independent filter boxes 5, which are arranged in series along the water flow direction to form a graded treatment channel. In one specific embodiment, a first filter box, a second filter box, and a third filter box are provided. The first filter box is filled with large-particle porous volcanic rock for further physical interception and to provide an attachment surface for aerobic microorganisms; the second filter box is filled with natural zeolite, which adsorbs ammonia nitrogen ions in the water through its ion exchange properties; the third filter box is filled with granular activated carbon, which adsorbs dissolved organic matter, pigments, and odor molecules in the water through its high specific surface area.

[0047] Inside each filter box 5, there is a corrugated baffle plate 6. These baffle plates, made of PVC or stainless steel, are fixed in an alternating pattern within the filter box 5, forcing the water flow to bypass the plates and thus forming a continuous S-shaped flow path within the box. This structure prolongs the hydraulic residence time of water in contact with the purification medium inside the box. At the same time, the corrugated surface increases fluid turbulence and enhances the mass transfer process of pollutants to the medium surface.

[0048] The piezoelectric-biocoupled reactor (PBR) is installed in the shore-based equipment area. The reactor's main body is a sealed cylindrical or square shell made of stainless steel or fiberglass, with an inlet and an outlet. The reactor interior is filled with piezoelectric composite biological packing material. This packing material uses porous ceramic rings as the substrate, and nano-sized barium titanate piezoelectric particles are loaded onto its inner and outer surfaces and pore structure through an impregnation-calcination process. An array of ultrasonic transducers is evenly distributed in a matrix or ring pattern on the outer wall or bottom of the PBR reactor. Each transducer in this array has dual functions of signal transmission and reception. It serves both as an excitation source for applying micro-mechanical stress and as a sensor for acquiring the system's acoustic response signals.

[0049] The hardware of an adaptive resonant control system includes a central processing unit (such as a programmable logic controller (PLC) or an ARM-based microcontroller), a human-machine interface, a signal generation module for generating specific waveform signals, a power drive module for driving the transducer array, and a data acquisition module for collecting and converting echo signals. Its software architecture includes functional modules for data monitoring, PID algorithm processing, decision logic judgment, and data recording and alarm functions.

[0050] The anoxic autotrophic denitrification unit is also installed on the shore, downstream of the PBR reactor. This unit is a sealed container filled with conductive carbon felt with a high specific surface area. Submersible or centrifugal pumps are used to lift water from the filtration dam's purification zone to the shore-based treatment system. A reoxygenation recirculation device, located at the end of the system, can be in the form of a drop weir or microporous aeration discs, to increase the dissolved oxygen content of the purified water before it is returned to the fishpond.

[0051] This invention also provides a purification method for a multi-stage purification and filtration system for fish ponds. This method is achieved by operating the aforementioned purification system and may specifically include the following steps:

[0052] S10, System Initialization and Biofilm Acclimation: Before the system is put into formal operation, functional microbial communities are inoculated into the piezoelectric-biocoupled reactor (PBR) and the anoxic autotrophic denitrification unit, respectively, and the system is run until the biofilm is stable and mature.

[0053] S20, implement multi-stage physical pretreatment: guide the water flow in the fishpond aquaculture area so that it passes through the detachable mesh 3 of the multi-stage guide filter dam, the external grid 2 and multiple filter boxes 5 filled with different purification media in sequence, to complete the interception and preliminary adsorption of suspended solids.

[0054] S30, Pumping and Lifting: Using a water pump, the pre-treated purified water is lifted from the fishpond and transported to the piezoelectric-biocoupled reactor (PBR) on the shore.

[0055] S40, implementing adaptive piezoelectric-biological coupling synergistic purification: In the PBR reactor, the ultrasonic parameters are adjusted in real time through an adaptive resonance control system to excite the piezoelectric effect of the piezoelectric packing, generating trace amounts of active substances in situ. These substances, along with the attached nitrifying biofilm, achieve simultaneous removal of ammonia nitrogen and recalcitrant organic matter (DOC) from the water, and the biofilm thickness is dynamically controlled.

[0056] S50, implementing deep anoxic denitrification: the effluent from the PBR reactor is introduced into the anoxic autotrophic denitrification unit, where the nitrates in the water are reduced to nitrogen under the action of anoxic and autotrophic denitrifying bacteria.

[0057] S60, implementing reoxygenation and reflux: The purified water, after undergoing deep denitrification treatment, is sent back to the fishpond aquaculture area after its dissolved oxygen content is increased by passing it through a reoxygenation and reflux device, thus completing the purification cycle.

[0058] Before operating the aforementioned purification system, the biological treatment unit within the system needs to be initialized to cultivate and enrich a highly efficient and stable functional microbial community. This initialization process specifically includes the following steps:

[0059] S101, Perform hydraulic commissioning and microbial inoculation preparation for the system. Fill the entire purification system with the fishpond water or clean water to be treated, and start the water pump to circulate the water according to the preset path. This step aims to check the airtightness and watertightness of the system and to purge air from the pipeline. During this period, the adaptive resonant control system of the piezoelectric-biocoupled reactor (PBR) remains off.

[0060] S102, Inoculation and acclimatization of aerobic nitrifying bacteria in the piezoelectric-biocoupled reactor (PBR). A seed source containing functional bacteria, specifically nitrifying bacteria, is added to the PBR reactor. This seed source can be obtained from activated sludge from a stably operating municipal wastewater treatment plant, mature biofilm from a similar aquaculture purification system, or commercially available compound nitrifying bacteria preparations. In one specific embodiment, the nitrifying bacteria include microorganisms of the genera *Nitrobacter* and *Nitrobacter*. After inoculation, the PBR reactor is continuously aerated to maintain the dissolved oxygen concentration within the reactor. During the acclimatization period, the existing ammonia nitrogen in the fishpond water is used as the nitrogen source for microbial growth; to accelerate the acclimatization process, a measured amount of inorganic nitrogen source, such as ammonium chloride, can also be added to the influent to maintain the ammonia nitrogen concentration at a suitable level.

[0061] S103, Inoculation and acclimatization of denitrifying bacteria in the anoxic autotrophic denitrification unit. A seed source containing functional bacteria, specifically autotrophic denitrifying bacteria, is added to the unit. This seed source can be taken from an anaerobic or anoxic treatment system with denitrification capabilities. In one specific embodiment, the autotrophic denitrifying bacteria include microorganisms capable of utilizing inorganic matter as electron donors, such as *Thiobacillus denitrifyingus*. After inoculation, the unit is ensured to be in an anoxic environment. During acclimatization, the abundant nitrates from the PBR reactor effluent are used as electron acceptors. To accelerate acclimatization, a measured amount of nitrates, such as potassium nitrate, can also be added to the unit's influent.

[0062] S104. Monitor the biofilm acclimatization process and determine its maturity. Throughout the acclimatization period, influent and effluent samples are periodically collected from the PBR reactor and the anoxic autotrophic denitrification unit to detect key water quality indicators, including the concentrations of ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen. The maturity of the biofilm is determined by the following indicators: In the effluent of the PBR reactor, the ammonia nitrogen concentration remains consistently low, while the nitrite nitrogen concentration initially increases, then decreases, and finally stabilizes at an extremely low level, indicating that a complete nitrification chain has been established; in the effluent of the anoxic autotrophic denitrification unit, the nitrate nitrogen concentration remains consistently low, indicating that the denitrification function has been stably established. When the above indicators remain stable for a continuous period of time (e.g., one week), the system initialization and biofilm acclimatization are considered complete, and the system is ready for formal operation.

[0063] After the system's functional microbial community has matured, routine purification treatment of the fishpond water begins. The first step involves physical pretreatment and influent delivery, which includes:

[0064] S201 performs primary and secondary solid-liquid separation on the raw water in the aquaculture area. The raw water, rich in suspended solids (such as fish excrement and uneaten feed), is guided or uses natural hydraulic power to flow towards a multi-stage flow-guiding filter dam. The water first passes through a removable mesh 3 located at the front of the filter dam. This mesh, with its open structure, intercepts most large suspended solid particles in the water, completing the primary solid-liquid separation. This mesh is connected to the filter frame 1 via a sliding groove or snap-fit ​​structure, allowing operators to regularly disassemble, clean, or replace it to maintain its filtration efficiency and prevent clogging. After passing through the mesh, the water continues through the external grille 2 behind it. This grille intercepts large floating objects that may enter during mesh maintenance or in case of accidents, thus protecting the subsequent filter box 5 structure.

[0065] S202, multi-stage adsorption and fine filtration are implemented within filter box 5. After the aforementioned solid-liquid separation, the water flows into filter frame 1 and is guided sequentially through the first, second, and third filter boxes arranged in series. Inside filter box 5, due to the staggered arrangement of the corrugated baffles 6, the water flow is forced to form a continuous S-shaped flow path. This specific path setting ensures that the actual flow distance of the water within the box is much greater than the straight-line length of the box, thereby extending the hydraulic residence time. Simultaneously, as the water flows around the surface of the corrugated plates, its laminar boundary layer is disrupted, fluid turbulence is enhanced, and the mass transfer efficiency of pollutant molecules in the water to the surface of the purification medium is improved. In the first filter box, the water comes into contact with large particles of volcanic rock, further intercepting fine suspended matter; in the second filter box, it comes into contact with natural zeolite, removing some ammonia nitrogen through ion exchange; in the third filter box, it comes into contact with granular activated carbon, removing dissolved organic matter, odors, and pigments through physical adsorption. After this progressive treatment, the turbidity of the water is significantly reduced, and some dissolved pollutants are initially removed.

[0066] S301, Pumping and Lifting Implemented. Water, after complete treatment by a multi-stage diversion filtration dam, collects in the purification zone inside the dam. At this point, a water pump installed on the shore or within the purification zone is started. The pump's suction inlet is placed in the water body of the purification zone, lifting and transporting the fully pretreated, low-turbidity water through the pipeline system to the piezoelectric-bioreactor (PBR) installed on the shore, providing a stable influent for the subsequent biological purification stage.

[0067] After pretreatment and pumping, the water enters a shore-based piezoelectric-biocoupled reactor (PBR), where a synergistic process integrating advanced oxidation, biodegradation, and adaptive control is used to achieve efficient removal of dissolved pollutants.

[0068] S401, stimulating the piezoelectric effect and generating a micro-electric field. An adaptive resonant control system drives the ultrasonic transducer array on the PBR reactor to emit sound waves with preset parameters into the reactor. These sound waves propagate in the liquid medium, applying periodic micro-mechanical stress to the piezoelectric composite bio-filler packed within the reactor. Based on the positive piezoelectric effect, this mechanical stress acts on the piezoelectric material (such as barium titanate) supported by the filler, causing lattice deformation and charge polarization. This polarization phenomenon generates an alternating micro-electric field in situ and instantaneously on the filler surface. The relationship between charge and stress follows the piezoelectric equation, and the resulting electric displacement can be expressed as: ;

[0069] in:

[0070] This is the electric displacement vector component, and its rate of change is directly related to the surface charge density;

[0071] is the piezoelectric strain tensor, a material constant characterizing the electromechanical conversion capability of piezoelectric materials;

[0072] The applied mechanical stress tensor.

[0073] S402 implements synergistic purification through piezoelectric catalysis and biodegradation. The alternating micro-electric field generated in situ on the packing surface serves as a catalytic energy source, effectively activating surrounding water molecules and dissolved oxygen. This generates reactive organic species (ROS) with extremely strong oxidizing capabilities through electrochemical reactions; this process is piezoelectric catalysis. These ROS, including but not limited to hydroxyl radicals and superoxide anion radicals, are non-selective strong oxidants. They can rapidly attack and decompose recalcitrant dissolved organic matter (DOC) in water that is difficult to utilize biologically, mineralizing it into carbon dioxide, water, or converting it into easily biodegradable small-molecule organic matter.

[0074] Meanwhile, the nitrifying biofilm attached to the surface of the piezoelectric composite biological packing material undergoes conventional biological nitrification under aerobic conditions. This reaction is synergistically completed by ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), gradually oxidizing ammonia nitrogen in the water to nitrate nitrogen. Therefore, within the PBR reactor, the advanced oxidation process based on piezoelectric catalysis and the traditional biofilm-based biodegradation process occur simultaneously at the micron scale, without interference and with complementary functions, achieving simultaneous and efficient removal of recalcitrant organic matter and ammonia nitrogen.

[0075] S403 enables dynamic self-renewal of biofilm thickness. The trace active substances generated during piezoelectric catalysis, in addition to degrading DOC in the water, also oxidatively strip the biofilm attached to the packing material surface. This action preferentially occurs on the outermost layer of the biofilm, the part with the lowest physiological activity and the most aged. Through this continuous stripping, excessively thick and dense biofilm layers can be effectively removed, preventing packing material blockage and internal mass transfer limitations caused by excessive biomass growth. This process achieves dynamic regulation and in-situ self-renewal of biofilm thickness, ensuring that the biofilm is always maintained within the optimal thickness range with the highest mass transfer efficiency and biological activity.

[0076] S404 implements adaptive closed-loop control based on acoustic impedance. To ensure a dynamic balance between piezoelectric catalytic intensity and biofilm growth rate, the system employs an adaptive closed-loop feedback control method based on acoustic impedance. This method uses the ultrasonic transducer array as both an excitation source and an acoustic sensor, and is implemented as follows:

[0077] The first step is to monitor the acoustic impedance in real time. The adaptive resonant control system periodically instructs the transducer array to emit probe waves with specific parameters. These waves propagate and are reflected in the reactor medium, which is filled with water, packing material, and biofilm. The echo signals are received by the same transducer array. Changes in the thickness, density, and coverage of the biofilm cause alterations in the overall acoustic characteristics of the reactor system, which are directly reflected in the amplitude and phase of the echo signals. The controller uses a built-in signal processing algorithm to compare the differences between the emitted and received signals, calculating the real-time acoustic impedance value that quantifies the overall acoustic characteristics of the current system. Its functional relationship can be expressed as:

[0078] ;

[0079] in:

[0080] For time The real-time acoustic impedance characterization value;

[0081] This is the mapping function established through previous experimental calibration;

[0082] and They are time The amplitude and phase of the received echo signal.

[0083] The second step is to execute the PID control algorithm to calculate the adjustment amount. The controller will use the acoustic impedance value monitored in real time. Compared with the pre-set target acoustic impedance value representing the optimal state of the biofilm By comparison, the real-time deviation can be obtained. Based on this deviation, the controller calculates the current overall control output using a proportional-integral-derivative (PID) algorithm. :

[0084] ;

[0085] in:

[0086] For time The overall control output quantity.

[0087] , , These are the proportional, integral, and derivative coefficients of the PID controller, respectively, and their values ​​are determined during system debugging.

[0088] It is the integral variable.

[0089] The third step is to adjust the ultrasonic output parameters. The controller's built-in decision logic module will calculate the overall control output. The mapping is used to specify the adjustment commands for the output parameters of the ultrasonic transducer array, including the output power. Work mode In one specific implementation, an allowable target deviation range is set.

[0090] when When the biofilm is too thick, it indicates that the biofilm is too thick. The value is a large positive value. The controller executes an enhanced stripping strategy, correspondingly increasing the output power of the ultrasound. or work mode Switch to pulse mode for stronger peeling effect.

[0091] when When this time is reached, it indicates that the biofilm is in its optimal state. Fluctuating around zero. The controller executes a smooth maintenance strategy, reducing the output power. Maintaining a low baseline level ensures sustained piezoelectric catalytic activity while avoiding excessive consumption of the biofilm.

[0092] when When the biofilm is too thin, it indicates that the biofilm is too thin. The value is negative. The controller executes a growth-promoting strategy, significantly reducing the output power. Even reducing it to zero, in order to minimize the physical and chemical impact on biofilms, is beneficial for their recovery and proliferation.

[0093] After core purification is completed in the PBR reactor, the water rich in nitrate nitrogen is introduced into the subsequent treatment unit to complete deep denitrification and final reoxygenation recirculation. The specific steps are as follows:

[0094] S501 implements anoxic autotrophic denitrification. Effluent from a piezoelectric-biocoupled reactor (PBR) is introduced into the shore-based anoxic autotrophic denitrification unit. This unit is a closed container, pre-inoculated and acclimated with autotrophic denitrifying bacteria, and filled with conductive carbon felt as a carrier for microbial attachment. Due to the unit's sealed design and the aerobic activity of the microorganisms, a strictly anoxic environment is maintained inside. Under this environment, the autotrophic denitrifying bacteria attached to the carbon felt surface utilize nitrate nitrogen in the water as the final electron acceptor, and obtain electrons from inorganic reducing substances remaining from upstream processes or through other autotrophic metabolic pathways, performing denitrifying respiration. This biochemical process gradually reduces nitrate nitrogen to harmless nitrogen gas through a series of intermediate products.

[0095] The generated nitrogen gas escapes from the water in gaseous form and is discharged from the system, thereby reducing the total nitrogen content of the water and completing deep denitrification.

[0096] S601, Reoxygenation and Recirculation. After deep denitrification treatment, the dissolved pollutant content of the water is extremely low, but due to the oxygen-deficient process, its dissolved oxygen concentration remains extremely low, making it unsuitable for direct return to aquaculture water. Therefore, this water is guided to a reoxygenation and recirculation device. The function of this device is to rapidly increase the dissolved oxygen content of the water. In one specific embodiment, this device can be a drop weir structure. Water flows down from a height, increasing the gas-liquid contact area through intense contact, impact, and mixing with air, thereby dissolving oxygen from the air. In another specific embodiment, this device can be a microporous aeration disc system, where a blower forces air into the underwater microporous aeration discs, releasing it in the form of dispersed fine bubbles. These bubbles make full contact with the water as they rise, achieving oxygen transfer. Once the dissolved oxygen content of the water recovers to a level suitable for aquaculture, it is returned to the aquaculture area of ​​the fishpond through pipes or ditches, thus completing the water purification cycle.

Claims

1. A multi-stage purification and filtration system for fish ponds, characterized in that, include: Multi-stage flow-guiding filter dams are used for the physical pretreatment of fishpond water. A piezoelectric-biocoupled reactor is located downstream of the multi-stage flow-guiding filter dam. It is filled with piezoelectric composite biological packing material and equipped with an ultrasonic transducer array for exciting the piezoelectric composite biological packing material. An adaptive resonance control system, electrically connected to the ultrasonic transducer array, is configured to: monitor the acoustic impedance characterization value within the piezoelectric-biocoupled reactor in real time, and adaptively adjust the output parameters of the ultrasonic transducer array based on the deviation between the acoustic impedance characterization value and a preset target value. The piezoelectric composite biofiller includes: a porous ceramic substrate, and a barium titanate piezoelectric material loaded on the surface of the porous ceramic substrate; The ultrasonic transducer array is evenly distributed in a matrix or ring pattern on the outer wall or bottom of the piezoelectric-biocoupled reactor. The adaptive resonance control system is configured to monitor the acoustic impedance characterization value by instructing the ultrasonic transducer array to emit probe sound waves and receive echo signals, and calculating the acoustic impedance characterization value by analyzing the amplitude or phase of the echo signals. The real-time acoustic impedance characterization value is compared with the preset target acoustic impedance value to obtain the deviation, and the adjustment amount is calculated based on the deviation using a differential control algorithm. The output power and operating mode of the ultrasonic transducer array are adjusted according to the adjustment amount.

2. The multi-stage purification and filtration system for fish ponds according to claim 1, characterized in that, The system also includes: Anoxic autotrophic denitrification unit is located downstream of the piezoelectric-biocoupled reactor and is used for deep denitrification of the water body; The reoxygenation recirculation device is located downstream of the anoxic autotrophic denitrification unit and is used to reoxygenate the purified water before it is returned to the fishpond.

3. The multi-stage purification and filtration system for fish ponds according to claim 2, characterized in that, The interior of the anoxic autotrophic denitrification unit is filled with conductive carbon felt as a carrier for microbial attachment.

4. The multi-stage purification and filtration system for fish ponds according to claim 1, characterized in that, The multi-stage flow-guiding filter dam includes: Filter box (1); A grid (2) is disposed inside the filter frame (1); A detachable mesh (3) is movably installed outside the filter frame (1) and located outside the grille (2); A limiting strip (4) is provided on the inner wall of the filter frame (1); Multiple filter boxes (5) are slidably connected between the limiting strips (4); The barrier plate (6) is fixedly connected to the inside of the filter box (5).

5. A multi-stage purification and filtration method for fishponds, applied to the multi-stage purification and filtration system for fishponds according to any one of claims 1-4, characterized in that, Includes the following steps: Physical pretreatment of fishpond water; Pretreated water is introduced into a piezoelectric-biocoupled reactor, where adaptive piezoelectric-biocoupled synergistic purification is implemented. This purification includes: generating a micro-electric field by ultrasonically exciting a piezoelectric composite biological packing material within the reactor; utilizing the micro-electric field to catalyze the generation of active species; and synergistically purifying the water through a biofilm attached to the packing material surface. Simultaneously, the acoustic impedance characterization value within the piezoelectric-biocoupled reactor is monitored in real time, and the ultrasonic parameters used to excite the piezoelectric effect are adaptively adjusted based on the deviation between the acoustic impedance characterization value and the target value. Deep denitrification treatment is carried out on the water body after synergistic purification.

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