Sewage treatment plant

Abstract

The utility model discloses sewage treatment device belongs to sewage treatment technical field, and the existing fixed bed reactor is lack of water dissolved oxygen real -time monitoring and equipment linkage caused by the denitrification efficiency fluctuation problem of solution. Its technical scheme main points include: fixed bed reactor built -in biological carrier layer, backwash air blower is connected bottom air inlet through first pipeline, and water pump is connected water inlet end through second pipeline, and is connected top flushing port through third pipeline, sets up DO sensor on water inlet pipeline, and control system connects DO sensor, backwash air blower and water pump. The device is through real -time monitoring water dissolved oxygen and linkage control backwashing and flushing operation, guarantees the stable operation of depth denitrification process, and is mainly used for biochemical secondary sedimentation tank effluent's low carbon nitrogen ratio sewage treatment.

Description

Technical Field

[0001] This utility model relates to the field of wastewater treatment technology. More specifically, this utility model relates to wastewater treatment devices. Background Technology

[0002] In the field of wastewater treatment, advanced denitrification of effluent from biological secondary sedimentation tanks faces significant challenges. This type of effluent typically exhibits low carbon and nitrogen content and high residual nitrate concentrations. Existing fixed-bed bioreactor technology has key shortcomings in practical applications, primarily in its limitations regarding dissolved oxygen (DO) control.

[0003] The main bottleneck is the insufficient adaptability of existing technologies to fluctuations in influent dissolved oxygen. The dissolved oxygen concentration in the effluent from the biological secondary sedimentation tank is significantly affected by fluctuations in upstream processes, while the activity of denitrifying bacteria is highly sensitive to dissolved oxygen. When the influent dissolved oxygen concentration exceeds the suitable threshold for denitrification (typically >0.5 mg / L), heterotrophic bacteria preferentially utilize oxygen for metabolism, drastically inhibiting nitrate reduction efficiency and leading to a sudden drop in denitrification efficiency. Traditional systems generally lack real-time monitoring methods for influent dissolved oxygen, relying mostly on fixed parameter operation or manual sampling, which cannot promptly capture changes in influent water quality. This lack of monitoring causes the system to lose its ability to perceive key disturbance factors.

[0004] The lack of dissolved oxygen control further amplifies process risks. Due to the absence of continuous monitoring data on influent dissolved oxygen, the existing system struggles to establish a linkage mechanism between dissolved oxygen parameters and actuators such as fans and pumps. When high dissolved oxygen influent enters the reactor, it cannot automatically trigger the backwash fan or flushing pump based on real-time data. This disconnect between actuators and water quality parameters leads to delayed process adjustments, making it impossible to mitigate the impact of abnormal dissolved oxygen on the biofilm through timely intervention (such as enhanced aeration or hydraulic flushing). The system also suffers from weak anti-interference capabilities, making it difficult to guarantee the stability of effluent water quality.

[0005] The root cause of the above problems lies in the disconnect between dissolved oxygen monitoring and equipment control. Existing systems do not treat influent dissolved oxygen as a real-time control variable; fan start-up and shutdown, as well as flushing operations, primarily rely on timing mechanisms or differential pressure thresholds, which are not directly related to the actual dissolved oxygen state of the influent. Furthermore, dissolved oxygen fluctuations are sudden and random, making it difficult for fixed-program control modes to meet dynamic process requirements. Achieving closed-loop linkage between influent dissolved oxygen data and backwashing / flushing execution units has become a key breakthrough in optimizing the stable operation of fixed-bed reactors. Utility Model Content

[0006] The purpose of this invention is to provide a wastewater treatment device that establishes a closed-loop linkage mechanism for monitoring dissolved oxygen in the influent and for backwashing and flushing equipment, thereby optimizing the stability of the denitrification process in a fixed-bed reactor.

[0007] This addresses the problem of existing fixed-bed reactors lacking real-time monitoring of dissolved oxygen in the influent and equipment linkage control, thus failing to automatically respond to high dissolved oxygen influent impacts.

[0008] This invention addresses the problem of uneven water flow distribution in the carrier layer caused by clogging of traditional water distributors, leading to short-circuiting and reduced reaction efficiency.

[0009] This addresses the problems of uneven spatial distribution of dissolved oxygen inside the reactor and the lack of precise monitoring methods, as well as the difficulty in quantifying the blockage status of the carrier layer.

[0010] This addresses the problem of large suspended solids in the effluent from the secondary sedimentation tank of a biological treatment plant clogging the carrier layer when directly introduced into the reactor.

[0011] This addresses the issue of carbon source addition relying on experience-based settings, which cannot dynamically match fluctuations in the influent carbon-nitrogen ratio.

[0012] This addresses the issue of process stability degradation caused by fluctuations in hydraulic load due to a fixed influent flow rate.

[0013] This addresses the issue of improper carrier filling ratio affecting the effective volume and flow distribution of the reactor.

[0014] This addresses the problem of dead zones caused by the monotonous flow pattern in traditional fixed beds, which leads to uneven biofilm activity.

[0015] To address the aforementioned problems, this utility model provides a wastewater treatment device for treating effluent from a biological secondary sedimentation tank. The device includes:

[0016] A fixed-bed reactor is filled with a biological carrier layer. The inlet and outlet of the fixed-bed reactor are located at its bottom and top, respectively.

[0017] The backwash fan is connected to the air inlet at the bottom of the fixed-bed reactor via a first pipe;

[0018] A water pump is connected to the inlet of the fixed-bed reactor via a second pipe and to the flushing port at the top of the fixed-bed reactor via a third pipe.

[0019] DO sensor, which is installed on the inlet pipe of the fixed bed reactor;

[0020] The control system is connected to the DO sensor, backwash fan, and water pump.

[0021] Preferably, the wastewater treatment device further includes:

[0022] The perforated tube water distributor is fixed at the bottom of the fixed bed reactor. The water inlet of the perforated tube water distributor is connected to the water inlet pipe of the fixed bed reactor through a water pump. The water outlet of the perforated tube water distributor faces the bottom of the biological carrier layer. The diameter of the water outlet is 5-10 mm and the spacing between the outlets is 10-20 cm.

[0023] Preferably, the wastewater treatment device further includes:

[0024] The DO probe is inserted vertically into the biological carrier layer at a distance of 5-10 cm from 1 / 2 of the total height along the height direction of the fixed bed reactor, with the central axis as the reference and 1 / 3 of the radius outside the central axis. This is used to monitor the DO concentration in the fixed bed reactor in real time.

[0025] Two differential pressure sensors are installed on the inlet and outlet pipes of the fixed-bed reactor, respectively, to monitor the pressure difference of the biological carrier layer in real time.

[0026] The control system is connected to both the DO probe and the differential pressure sensor.

[0027] Preferably, the wastewater treatment device further includes:

[0028] Mechanical bar screens are installed at the effluent end of the secondary sedimentation tank in the biological process, with a pore size of 100-200μm.

[0029] Preferably, the wastewater treatment device further includes:

[0030] The microbial sampling port is located on the side wall of the fixed-bed reactor, to the side of the biological carrier layer.

[0031] A metering pump, whose outlet is connected to the inlet of the fixed-bed reactor via a fourth pipe, is used to add liquid sodium acetate to the inlet water;

[0032] The COD sensor, nitrate nitrogen sensor, and ammonia nitrogen sensor are all installed on the inlet pipe of the fixed-bed reactor and connected to the control system.

[0033] Preferably, the wastewater treatment device further includes:

[0034] An electric flow regulating valve is installed on the second pipeline, located downstream of the water pump outlet, and connected to the control system.

[0035] The outlet of the aerobic aeration blower is connected to the aerobic aeration unit upstream of the biological secondary sedimentation tank via a pipeline.

[0036] The frequency converter is connected to the motor of the aerobic aeration blower and to the control system.

[0037] Preferably, in the wastewater treatment device, the volume of the biological carrier layer accounts for 60-70% of the total volume of the fixed bed reactor, the distance between the bottom of the biological carrier layer and the bottom of the fixed bed reactor is 200-300mm, and the distance between the top of the biological carrier layer and the top of the fixed bed reactor is greater than 300mm.

[0038] Preferably, in the wastewater treatment device, the inner wall of the fixed bed reactor is welded with multiple layers of guide plates at intervals along the vertical direction. The guide plates are horizontally arranged and located inside the biological carrier layer, and are coaxially arranged with the fixed bed reactor. The spacing between adjacent guide plates is 1 / 5 to 1 / 3 of the height of the fixed bed reactor.

[0039] The diameter of the central opening of the guide plate is 40-50% of the diameter of the guide plate. Auxiliary guide holes with a diameter of 1-3mm are evenly opened on the annular plate of the guide plate, and the opening ratio of the guide holes is 15-20%.

[0040] A guide tube is vertically welded inside the central opening. The top of the guide tube is flush with the upper surface of the guide plate. The distance between the bottom of the upper guide tube and the top of the lower guide tube in two adjacent guide tubes is 80-150mm.

[0041] Spiral guide grooves are opened on the outer wall of the guide tube, and the depth of the guide grooves is 1-2mm;

[0042] The bottommost guide tube is 200-300mm from the bottom of the fixed-bed reactor.

[0043] Preferably, in the wastewater treatment device, the effluent end of the fixed-bed reactor is located at the top.

[0044] This utility model has at least the following beneficial effects:

[0045] This invention uses a DO sensor to monitor the dissolved oxygen concentration of the influent in real time. Combined with the control system, it links the backwash fan and water pump. When an abnormal increase in dissolved oxygen is detected, it automatically starts the coordinated operation of air washing and water washing to quickly reduce the dissolved oxygen concentration to a suitable denitrification range.

[0046] This invention adopts a structure that combines a bottom air inlet with a top flushing port. By simultaneously operating air washing and water washing, a counter-flow state is formed, which enhances the turbulence intensity of the carrier layer, efficiently peels off the aging biofilm and carries out the fragments, and avoids carrier fluidization instability or local flushing blind spots.

[0047] This invention precisely controls the backwashing operation through a dissolved oxygen threshold triggering mechanism, avoiding redundant rinsing of fixed-cycle backwashing, optimizing the synergistic ratio of air washing intensity and water washing flow rate, and reducing the ineffective operating time of fans and water pumps.

[0048] This utility model features a combined structure of a pre-perforated pipe water distributor and a flow guide plate-flow guide cylinder, which optimizes the uniform distribution of water flow and the radial vortex mass transfer effect, eliminates dead zones in the flow, and maintains the uniformity of biofilm activity.

[0049] This invention uses a mechanical grid to intercept large suspended particles, and combines differential pressure sensors and carrier layer DO probes for dual monitoring to accurately determine the blockage status and optimize the backwashing trigger timing, thereby reducing the risk of carrier layer blockage.

[0050] This invention integrates multiple sensors to monitor the carbon-nitrogen ratio of the influent in real time and dynamically adjusts the carbon source dosage of the metering pump, thereby avoiding fluctuations in denitrification efficiency and waste of reagents.

[0051] This invention limits the volume ratio of the biological carrier layer, balances the biological attachment capacity and the water flow channel space, and maintains the optimal hydraulic residence time in conjunction with the flow regulation mechanism.

[0052] Other advantages, objectives and features of this invention will be partly apparent from the following description, and partly understood by those skilled in the art through study and practice of this invention. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of the structure of a sewage treatment device according to an embodiment of the present invention;

[0054] Figure 2 This is a schematic diagram of the structure of the guide plate and guide cylinder according to an embodiment of the present utility model;

[0055] The attached diagrams are labeled as follows: Fixed bed reactor-1; Water pump-2; Second pipe-3; Third pipe-4; DO sensor-5; DO probe-6; Differential pressure sensor-7; Microbial sampling port-8; COD sensor-9; Nitrate nitrogen sensor-10; Ammonia nitrogen sensor-11; Baffle plate-12; Baffle tube-13. Detailed Implementation

[0056] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0057] It should be noted that in the description of this utility model, the terms "horizontal", "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0058] like Figure 1 As shown, this utility model provides a wastewater treatment device for treating effluent from a biological secondary sedimentation tank. The wastewater treatment device includes:

[0059] Fixed-bed reactor 1, which is filled with a biological carrier layer, has its inlet and outlet located at its bottom and top, respectively.

[0060] The backwash fan is connected to the air inlet at the bottom of the fixed-bed reactor via a first pipe; air can be used for air washing.

[0061] Water pump 2 is connected to the water inlet of the fixed bed reactor through the second pipe 3 and to the flushing port at the top of the fixed bed reactor through the third pipe 4;

[0062] DO sensor 5 is installed on the inlet pipe of the fixed bed reactor;

[0063] The control system is connected to the DO sensor, backwash fan, and water pump.

[0064] The reactor body adopts a cylindrical shell structure, which can be made of carbon steel or fiberglass. The biological carrier layer fills the central area inside the reactor; the carrier can be made of porous polyethylene suspension packing or corrugated polypropylene packing. Alternatively, the biological carrier can be prepared using the following method: [The text abruptly ends here, so the translation stops as well.] 2+ and Fe 3+ FeSO4 and FeCl3 solutions were mixed in a molar ratio of 1:2; the pH of the mixed solution was adjusted to 10-12 to generate a black iron oxide precipitate, with nitrogen gas purging throughout the process; the resulting iron oxide precipitate was mixed with volcanic rock at a weight ratio of 100:1 and dried at 200-300℃.

[0065] The backwash fan outlet is connected to the air inlet at the bottom of the fixed-bed reactor via a first pipe. The air inlet at the bottom of the fixed-bed reactor is located near the center of the reactor bottom. The first pipe is equipped with a manual maintenance valve and a check valve.

[0066] The water pump outlet is connected to two pipelines:

[0067] The water inlet at the bottom of the fixed-bed reactor is connected via a second pipe.

[0068] The flushing port at the top of the fixed-bed reactor is connected via a third pipe;

[0069] The DO sensor is installed on the inlet pipe of the fixed bed reactor. The DO sensor probe is inserted vertically into the inlet pipe of the fixed bed reactor through a threaded interface.

[0070] The control cabinet houses the PLC controller and relay group. The DO sensor signal line is connected to the control cabinet terminal block, the backwash fan power line is controlled via relay contacts, and the water pump control line is connected to the contactor circuit. The cabinet also includes a power switch and status indicator lights.

[0071] Working process: Wastewater enters from the inlet at the bottom of the fixed bed reactor through the second pipe, flows through the biological carrier layer, and is discharged from the outlet at the top.

[0072] The linkage control logic of the DO sensor, backwash fan, and water pump is as follows:

[0073] 1) Triggering conditions

[0074] The DO sensor continuously monitors the dissolved oxygen concentration in the inlet water pipe. When the concentration exceeds a preset value (such as exceeding the suitable denitrification threshold of 0.5 mg / L), it sends a signal to the control system.

[0075] 2) Collaborative Response Process

[0076] Step 1: Start the backwash fan. The control system immediately starts the backwash fan. Gas is injected into the biological carrier layer through the first pipe from the air inlet at the bottom of the reactor. The rising gas disturbs the carrier, peels off the aging biofilm, and enhances oxygen mass transfer to consume excess dissolved oxygen.

[0077] Step 2: Activate the water pump and simultaneously start the top flushing function of the water pump (through the third pipe). The water flow sprays downward from the top flushing port to flush the detached biofilm fragments out of the reactor and dilute the high dissolved oxygen concentration in the influent.

[0078] The drawbacks of single-operation:

[0079] If only gas washing is used: the gas cannot effectively remove the detached biofilm fragments and may clog the carrier pores;

[0080] If only water is used for washing, it is difficult to quickly eliminate the supersaturated state of dissolved oxygen, and the denitrification efficiency recovers slowly.

[0081] Advantages of synchronous linkage:

[0082] Air washing and water washing can be performed simultaneously, reducing the DO concentration to below 0.5 mg / L within 5 minutes.

[0083] The combined use of air washing and water washing reduces processing time by 40% compared to operating them separately.

[0084] Backwashing can also be performed after the reactor has been running for a certain period of time, such as 3-7 days. During backwashing, the backwash fan is started first to backwash the biological carrier and remove the aging microorganisms on the biological carrier. Then, the water pump is started to draw water from the inlet of the fixed bed reactor to backwash the biological carrier.

[0085] Technical effects:

[0086] 1) By monitoring the dissolved oxygen concentration in the influent in real time and automatically adjusting the equipment, sudden fluctuations in denitrification efficiency are effectively reduced, ensuring stable effluent quality.

[0087] This is because the DO sensor continuously monitors the dissolved oxygen concentration in the inlet pipe. When the concentration exceeds a preset value (e.g., dissolved oxygen exceeds the suitable denitrification threshold of 0.5 mg / L, leading to inhibition of denitrifying bacteria activity), the control system immediately and simultaneously starts the backwash fan and water pump. The backwash fan injects gas through the air inlet, disturbing the biological carrier layer and rapidly consuming excess dissolved oxygen; the water pump sprays water through the flushing port to dilute the high dissolved oxygen inlet water. This closed-loop control based on real-time dissolved oxygen data avoids the lag in manual response or errors in experience-based judgment, allowing the dissolved oxygen concentration in the biological carrier layer to quickly recover to a suitable denitrification level, thereby maintaining stable denitrification efficiency.

[0088] 2) Optimize the backwashing effect through equipment linkage mechanism to prevent blockage of biological carrier layer and reduce human operation errors.

[0089] This is because the control system links the DO sensor signal with the start / stop logic of the backwash fan and water pump. When an abnormal dissolved oxygen level is triggered, the backwash fan introduces gas from the bottom (creating bottom-up disturbance to slough off aged biofilm), while the water pump sprays water from the top (creating top-down water flow to wash away sloughed material and dilute the incoming water). Both operate synchronously (rather than sequentially), enhancing the turbulence of the carrier layer through counter-current air-water flow, avoiding insufficient biofilm removal with water flushing alone or carrier fluidization instability with air flushing alone. This linkage is automatically executed by the control system, eliminating operational errors from manual switching of equipment modes and ensuring a highly efficient and reliable backwashing process.

[0090] 3) Reduce the impact of upstream water quality changes (such as a sudden increase in dissolved oxygen) on the process and extend the continuous operation cycle.

[0091] This is because a DO sensor is pre-installed in the inlet pipe, allowing it to send a signal to the control system at the initial stage of water quality abnormalities (such as fluctuations in dissolved oxygen in the effluent from the biological secondary sedimentation tank). Based on this signal, the control system responds in milliseconds, triggering the blower and water pump to initiate backwashing. For example, gas injection accelerates oxygen consumption, while water spray dilutes the inlet water concentration; together, they work to reduce dissolved oxygen below the safe threshold within a short time (e.g., within 5 minutes). This rapid adaptive mechanism reduces process recovery time and avoids the continuous efficiency losses associated with traditional timed or manual control methods.

[0092] 4) By precisely triggering backwashing operations, ineffective equipment operation is reduced, saving energy and water resources.

[0093] This is because the control system only activates the backwash fan and water pump when the DO sensor detects an anomaly, avoiding redundant operations of fixed-cycle backwashing (such as routine backwashing every 3-7 days, which may include unnecessary rinsing). The air-water coordinated design optimizes the rinsing intensity: bottom air disturbance reduces the hydraulic rinsing flow requirement, and top spraying shortens the air rinsing time, thereby reducing the overall operating time of the fan and water pump.

[0094] This solution establishes a closed-loop dissolved oxygen control mechanism by using DO sensors to monitor and control the synchronous operation of the fan and water pump in real time. Its effectiveness stems from the integration of physical structure (such as the three-dimensional layout of the bottom air inlet and top flushing outlet) and electrical connection (direct control of equipment via sensor signals).

[0095] The DO sensor provides real-time data input, which the control system translates into execution commands.

[0096] The backwash fan and water pump work together to quickly correct abnormalities through the reverse air-water action.

[0097] This solution directly addresses the problems of unstable denitrification, low backwashing efficiency, and high energy consumption caused by fluctuations in dissolved oxygen in the influent.

[0098] In another embodiment, the wastewater treatment device further includes:

[0099] The perforated tube water distributor is fixed at the bottom of the fixed bed reactor. The water inlet of the perforated tube water distributor is connected to the water inlet of the fixed bed reactor through a water pump and a second pipe. The water outlet of the perforated tube water distributor faces the bottom of the biological carrier layer. The diameter of the water outlet is 5-10 mm and the spacing between the outlets is 10-20 cm.

[0100] The perforated tube distributor is installed at the center of the bottom of the fixed-bed reactor to ensure a uniform upward flow of water from the bottom. This distributor can be a commercially available annular or multi-branched perforated tube structure, fixed to the bottom plane of the reactor's inner wall via flanges or welding. Materials can be 316L stainless steel or UPVC to resist wastewater corrosion. During assembly, ensure the distributor is horizontally aligned to avoid affecting water flow distribution. During operation, a pump draws wastewater into the distributor's inlet via a second pipe; the water diffuses within the pipe and then sprays out from the outlet. Parameter settings are based on the reactor size and flow rate: for example, when the reactor diameter is 2m, the distributor diameter is selected as 1.8m; the orifice diameter and orifice spacing need to be set through computational fluid dynamics simulation to ensure that the flow rate deviation per unit area does not exceed 5%. A 1:1 reactor model was used in the experiment, with different flow rates (5-20m³). 3 / h), measuring the water flow coverage of the carrier layer; the results show that an 8mm aperture and a 15cm spacing between pores can cover 95% of the area.

[0101] The outlet holes are oriented vertically upwards towards the bottom of the biological carrier layer to prevent water flow from directly impacting the sidewalls and causing short-circuiting. Hole diameters can be selected from 5mm, 6mm, 7mm, 8mm, 9mm, or 10mm; hole spacing can be selected from 10cm, 12cm, 15cm, 18cm, or 20cm. Specific values ​​will be determined experimentally at a flow rate of 10m³ / h. 3Under certain conditions, different combinations of pore diameters (5-10 mm) and pore spacing (10-20 cm) were tested, and the pressure difference of the carrier layer was monitored. The lowest pressure difference (approximately 0.5 kPa) was observed when the pore diameter was 7 mm and the pore spacing was 15 cm. The assembly positions were evenly distributed on the upper surface of the water distributor, with the central axis of the pores perpendicular to the bottom surface of the carrier layer. During operation, water is ejected from the pores to form a jet, propelling the water upward and reducing bottom sedimentation. Functional tests showed that this design improved the water flow distribution uniformity coefficient to 0.92 (the ideal value is 1), avoiding carrier damage caused by localized high flow velocities.

[0102] Technical benefits: The perforated tube water distributor is fixed to the bottom of the reactor and directly connected to the water pump through its inlet, forcing the water flow to diffuse. With the outlet holes facing the bottom of the carrier layer and the pore size and spacing optimized, a stable upward flow pattern is formed, eliminating low-velocity dead zones. Uniform water distribution reduces the local accumulation of suspended solids in the carrier pores, thereby reducing the probability of clogging; at the same time, it avoids short-circuiting and ensures stable reaction efficiency.

[0103] In another embodiment, the wastewater treatment device further includes:

[0104] DO probe 6 is inserted vertically into the biological carrier layer at 5-10 cm from 1 / 2 of the total height along the height direction of the fixed bed reactor, with the central axis as the reference and 1 / 3 of the radius outside it. It is used to monitor the DO concentration in the fixed bed reactor in real time.

[0105] Two differential pressure sensors 7 are respectively installed on the inlet and outlet pipes of the fixed bed reactor to monitor the pressure difference of the biological carrier layer in real time.

[0106] The control system is connected to both the DO probe and the differential pressure sensor.

[0107] The DO probe is installed at half the total height of the fixed-bed reactor, along its height direction. The specific height can be chosen as 50% of the total height, i.e., at the center point. Using the reactor's central axis as a reference, the installation radius can be chosen at one-third of the outer radius, with a specific offset of 33% of the radius. The vertical insertion depth of the DO probe into the biological carrier layer can be 5cm, 6cm, 7cm, 8cm, 9cm, or 10cm. Commercially available dissolved oxygen fluorescence or polarographic probes can be used, and the probe sheath material can be 316L stainless steel. The assembly position needs to be fixed using a positioning bracket to ensure the probe is parallel to the reactor's central axis. During operation, the DO probe continuously monitors the dissolved oxygen concentration inside the biological carrier layer, and the monitoring data is transmitted to the control system in real time. Parameter settings are based on the carrier layer thickness: for a 4m high reactor, the installation point is located at a height of 2m; the insertion depth is determined by the carrier particle size; when the carrier particle size is 10mm, an insertion depth of 8cm can avoid damage. In the experiment, multiple sets of probes (insertion depths of 5-10cm) were set in a 1:1 model reactor to compare dissolved oxygen measurements; the results showed that an insertion depth of 8cm resulted in the best data stability.

[0108] Two differential pressure sensors are installed on the inlet and outlet pipes of the fixed-bed reactor, respectively. The differential pressure sensors can be capacitive differential pressure transmitters or resistive differential pressure gauges, and the measuring diaphragm material can be Hastelloy. The pressure measurement point on the inlet pipe is installed within 1 meter of the reactor inlet, and the pressure measurement point on the outlet pipe is installed within 1 meter of the reactor outlet. The installation locations must be horizontal pipe sections with full flow, connected to the pressure taps via a three-valve manifold. During operation, the differential pressure sensors continuously monitor the pressure difference between the reactor inlet and outlet, reflecting the clogging status of the biological carrier layer. During functional testing, the zero point is calibrated under clean water conditions; a pressure difference exceeding 0.5 kPa during operation is considered abnormal clogging. Clogging severity is graded as follows: 0.5-1.0 kPa is mild, 1.0-1.5 kPa is moderate, and above 1.5 kPa is severe. The experimental method involves injecting wastewater containing suspended solids (SS) (200 mg / L) into the reactor and recording the pressure difference curve; the data acquisition interval is set to 5 minutes.

[0109] The control system connects the DO probe signal output and the differential pressure sensor analog interface via shielded twisted-pair cables. The controller can be a PLC analog input module, and the wiring terminals can be gold-plated copper core interfaces. The DO probe signal is connected to the control system's AI1 channel, with a range set to 0-10 mg / L; the differential pressure sensor signal is connected to the AI2 channel, with a range set to 0-2.0 kPa. During operation, the control system collects data every 10 seconds. When both the carrier layer DO concentration and differential pressure are simultaneously satisfied (e.g., 1.0 mg / L > preset value) and the differential pressure is also greater than the preset value (e.g., 1.0 kPa), the backwashing procedure is automatically triggered. The threshold setting is based on denitrifying bacteria activity experiments: denitrifying bacteria activity decreases by 50% when DO > 0.5 mg / L, therefore the warning value is set to 0.5 mg / L. The differential pressure threshold is calculated based on the carrier porosity. Functional testing uses a step disturbance method: the influent dissolved oxygen is manually increased to 2 mg / L, and high-SS wastewater is added to verify that the system response time is less than 15 seconds.

[0110] Technical Benefits: Vertical insertion at key points at 1 / 2 height and 1 / 3 radius of the carrier layer directly captures dissolved oxygen concentration at the biofilm interface (not indirect data from the inlet), avoiding monitoring blind spots. The pressure difference between the inlet and outlet pipes reflects the flux resistance of the carrier layer in real time, forming a dual-parameter decision-making basis combined with DO data (e.g., initiating backwash when DO > 0.5 mg / L and pressure difference > 1.0 kPa). The control system integrates both types of signals, eliminating misjudgments based on a single parameter (e.g., relying solely on pressure difference might overlook dissolved oxygen anomalies), and improving the accuracy of backwash timing.

[0111] In another embodiment, the wastewater treatment device further includes:

[0112] Mechanical bar screens are installed at the effluent end of the secondary sedimentation tank in the biological process, with a pore size of 100-200μm.

[0113] Mechanical bar screens can be commercially available rotary drum bar screens or stepped bar screens. The material can be 304 stainless steel or 316L stainless steel to resist wastewater corrosion. During operation, the effluent from the secondary biological sedimentation tank flows into the bar screen, where the bars intercept suspended impurities.

[0114] The pore size parameters can be selected as 100μm, 120μm, 150μm, 180μm, or 200μm. Specific values ​​were selected experimentally: different particle sizes of suspended solids (50-300μm) were added to the biological secondary sedimentation tank, and the interception efficiency under different pore sizes was tested. The experimental method involved collecting effluent samples and analyzing the distribution of residual particles using a laser particle size analyzer; the results showed that a pore size of 150μm could intercept 95% of suspended solids larger than 150μm. The spacing tolerance of the grid bars was controlled within ±5μm, and the flatness of the grid surface was required to be less than 0.1mm / m. During operation, the gaps between the grid bars allow water flow while trapping large particles such as fibers and gravel. The trapped material is automatically removed to the collection tank by the rake teeth, avoiding manual cleaning. Functional testing was conducted using wastewater containing 200mg / L of suspended solids (SS), and the carrier layer was checked for blockage after 24 hours of operation.

[0115] Technical Benefits: Reduces the risk of clogging in the carrier layer of a fixed-bed reactor. A mechanical bar screen is pre-installed at the effluent outlet of the secondary biological sedimentation tank, physically intercepting large suspended particles through a specific pore size (100-200μm). This interception occurs before the wastewater enters the fixed-bed reactor, preventing impurities such as fibers and gravel from entering the pores of the biological carrier layer. This reduces the likelihood of carrier pore clogging, thereby extending the reactor's continuous operating cycle.

[0116] In another embodiment, the wastewater treatment device further includes:

[0117] Microbial sampling port 8 is located on the side wall of the fixed-bed reactor and to the side of the biological carrier layer.

[0118] A metering pump, whose outlet is connected to the inlet of the fixed-bed reactor via a fourth pipe, is used to add liquid sodium acetate to the inlet water;

[0119] COD sensor 9, nitrate nitrogen sensor 10, and ammonia nitrogen sensor 11 are all installed on the inlet pipe of the fixed-bed reactor and connected to the control system.

[0120] The microbial sampling port is located at the mid-height of the side of the fixed-bed reactor. A commercially available flanged sampling valve or quick-connect ball valve can be used, with valve diameters of 10mm, 15mm, or 20mm. The sealing material can be PTFE or fluororubber. The port should be positioned away from the welded area of ​​the baffle plate, at least 50mm from the nearest baffle plate edge. During operation, operators collect biofilm samples from the edge of the carrier layer using this sampling valve. Functional testing verifies the representativeness of the sampling: During reactor operation, samples are simultaneously taken from the sampling port and the central area, comparing the differences in microbial community composition; experiments show that the similarity between the edge sampling and the central area microbial community is over 90%.

[0121] The metering pump outlet is connected to the inlet of the fixed-bed reactor via a fourth pipe. The metering pump can be a mechanical diaphragm or plunger type, with a flow rate range of 0.5-5 L / h, and a stepper motor can be used as the drive motor. The fourth pipe can be a flexible or rigid pipe, made of polyethylene or polyvinyl chloride. Assembly requirements: The metering pump outlet is connected to the fourth pipe with clamps, and the end of the fourth pipe is connected to the inlet pipe tee, with the connection located within 1m downstream of the pump in a straight pipe section. During operation, the outlet of the liquid sodium acetate storage tank is connected to the metering pump inlet, and the control system adjusts the pump speed based on water quality data. Dosage setting is based on the inlet COD / TN ratio: the metering pump is started when the inlet COD / TN ratio is less than the preset value (e.g., 4). The initial dosage is calculated based on the requirement of 3 mg COD to remove 1 mg of nitrate. The experimental method involves adding sodium acetate to inlet water with a low COD / TN ratio (COD / TN=3), gradually increasing the dosage, and monitoring the change in effluent conductivity to determine the optimal dosage threshold.

[0122] COD, nitrate nitrogen, and ammonia nitrogen sensors are installed in parallel on the inlet pipe of the fixed-bed reactor. The three sensors can be a UV absorption COD meter, an ion-selective electrode nitrate meter, or an ammonia-sensitive electrode ammonia nitrogen meter. The sensor probes can have Hastelloy housings, and the seals can be made of nitrile rubber. Assembly requirements: Installed sequentially at 20cm intervals along the water flow direction, with the sensor insertion depth at 1 / 3 of the pipe diameter, located on the horizontal section of the inlet pipe and at least 5 times the pipe diameter away from bends. During operation, the three sensors monitor the inlet water quality parameters in real time, and the signals are transmitted to the control system via a 4-20mA analog signal. Functional testing verifies anti-interference performance: An interfering agent (NaCl 500mg / L) is added to wastewater containing suspended solids (SS=100mg / L), and the data drift is less than 5%. The control system collects data every 5 minutes. When COD / TN < preset value (e.g., 4) and nitrate > preset value (10mg / L), the metering pump is activated to add sodium acetate.

[0123] Technical benefits: The COD / nitrate nitrogen / ammonia nitrogen sensors provide real-time influent carbon-to-nitrogen ratio data, which the control system uses to dynamically adjust the metering pump dosage, preventing insufficient or excessive carbon source. The three sensors and the metering pump are connected to the main influent flow via independent pipelines, eliminating measurement lag and ensuring that the dosage response is synchronized with water quality fluctuations.

[0124] In another embodiment, the wastewater treatment device further includes:

[0125] An electric flow regulating valve is installed on the second pipeline, located downstream of the water pump outlet, and connected to the control system;

[0126] The outlet of the aerobic aeration blower is connected to the aerobic aeration unit upstream of the biological secondary sedimentation tank via a pipeline.

[0127] The frequency converter is connected to the motor of the aerobic aeration blower and to the control system.

[0128] The electric flow regulating valve is installed on the second pipeline, located within 1 meter downstream of the pump outlet in a straight pipe section. The valve diameter can be selected as DN50, DN80, DN100, DN125, or DN150. This valve can be an electric ball valve or an electric butterfly valve, and the valve body material can be 304 stainless steel or UPVC plastic. During operation, the control system adjusts the valve opening to control the inlet water flow, thereby changing the hydraulic residence time. For example, decreasing the opening reduces the flow rate and prolongs the hydraulic residence time; increasing the opening increases the flow rate and shortens the hydraulic residence time.

[0129] Hydraulic retention time (HRT) is achieved through flow rate regulation: when the effective reactor volume is fixed, HRT is inversely proportional to the influent flow rate. An electrically operated flow control valve directly controls the HRT value by changing the water flow velocity in the pipeline (range 0.1-4.0 m / h). When it is necessary to extend the HRT, the valve opening is reduced to decrease the flow velocity; when it is necessary to shorten the HRT, the opening is increased to increase the flow velocity. The specific flow rate setting is calculated based on the reactor dimensions. For example, for a reactor with a diameter of 2m and a height of 4m, increasing the flow velocity from 1m / h to 4m / h reduces the HRT from 28 hours to 7 hours.

[0130] The control system triggers valve action based on the dissolved oxygen threshold (1 mg / L): when dissolved oxygen > 1 mg / L, the valve opening is gradually reduced to decrease the flow rate and prolong the hydraulic residence time; when dissolved oxygen ≤ 1 mg / L, the valve opening is increased to raise the flow rate to the target range. The valve opening adjustment response time is ≤ 3 seconds, and the flow control error is ≤ 5%. An ultrasonic flow meter was used in the experiment to calibrate the opening-flow curve to ensure HRT control accuracy.

[0131] The electric flow regulating valve linearly adjusts the inlet water flow rate (range 0.1-4.0 m³ / h). 3 / h), directly control HRT within the target range (e.g., HRT≤40min when dissolved oxygen meets the standard).

[0132] The valve is installed on the straight pipe section downstream of the water pump (≤1m from the outlet) to avoid eddy current interference with flow accuracy; the flange is coaxially assembled to ensure stable flow.

[0133] In conjunction with the aeration adjustment unit, a two-level control chain is formed – first adjust the aeration rate, and then adjust the flow rate if ineffective, to avoid sudden changes in process parameters impacting the biological carrier layer.

[0134] The outlet of the aerobic aeration blower is connected via a pipeline to the main air inlet pipe of the aerobic aeration unit upstream of the secondary biological sedimentation tank. The blower's airflow can be selected as 5m³ / h. 3 / min, 8m 3 / min, 10m 3 / min, 15m3 / min or 20m 3 / min. This blower can be a Roots blower or a centrifugal blower, and the casing material can be cast iron. Assembly requirements: The blower base is fixed to the concrete foundation with shock-absorbing pads, and a rubber expansion joint is installed on the outlet pipe. During operation, when dissolved oxygen > 1 mg / L, the control system gradually reduces the blower speed via the frequency converter, with each adjustment not exceeding 5% of the rated speed, at 5-minute intervals, until the speed drops to 40% of the rated value or dissolved oxygen ≤ 1 mg / L. The speed adjustment range is 0-50 Hz, with a normal operating frequency of 40-45 Hz.

[0135] The frequency converter is installed inside the electrical control cabinet, and its output cable is connected to the three-phase motor of the aerobic aeration blower. The frequency converter power can be selected from 7.5kW, 11kW, 15kW, 18.5kW, or 22kW. Vector control type frequency converters can be used, and the heat dissipation casing can be made of aluminum alloy. Assembly requirements: The frequency converter should be installed vertically, with a 100mm heat dissipation space around it. Shielded twisted-pair cables should be used for the control system PLC module to connect the control signal lines. During operation, the control system performs graded regulation based on real-time dissolved oxygen data: first, the aeration rate is reduced via the frequency converter (primary regulation); if this is ineffective, the flow rate is reduced via the electric flow regulating valve (secondary regulation); the two levels of regulation signals are coordinated and output through the same PLC module.

[0136] Technical Benefits: The electric flow regulating valve and the variable frequency aeration blower are positioned downstream and upstream of the process chain, respectively, achieving cross-unit linkage through data exchange in the control system. When dissolved oxygen > 1 mg / L, the upstream aeration rate is adjusted first; if this is ineffective, the downstream flow rate is adjusted instead, avoiding sudden parameter changes that could impact the process. The frequency converter adjusts in steps (5% / 5min) to maintain the stability of the aeration system; the flow valve sets the flow rate based on the hydraulic residence time, ensuring that the adjustment amount matches the effective volume of the reactor. The electric valve is installed in the straight pipe section downstream of the water pump to ensure flow control accuracy; the blower and frequency converter are centrally installed in the cabinet, shortening the signal response delay to the millisecond level.

[0137] In actual use, the device is operated according to Fe. 2+ and Fe 3+ FeSO4 and FeCl3 solutions were mixed in a molar ratio of 1:0.2-2; the pH of the mixed solution was adjusted to 10-12 to generate a black iron oxide precipitate, with nitrogen gas purging throughout the process; the resulting iron oxide precipitate was mixed with volcanic rock at a weight ratio of 30-300:1 and dried at 200-300℃ to prepare a biological carrier;

[0138] The prepared biological carrier is used to treat the effluent from the secondary sedimentation tank of the biological treatment unit. After the treatment unit has been running for 3-7 days, backwashing is performed. During backwashing, the backwash blower is started first to backwash the biological carrier and remove the aging microorganisms on the biological carrier. Then, the water pump is started to draw water from the inlet of the treatment unit to backwash the biological carrier.

[0139] Control the DO concentration of the incoming water to ≤1mg / L; when the DO concentration of the incoming water is >1mg / L, reduce the aeration rate upstream or increase the HRT of the treatment unit; when the DO concentration of the incoming water is ≤1mg / L, control the HRT of the treatment unit to ≤40min.

[0140] In another embodiment, the volume of the biological carrier layer in the wastewater treatment device accounts for 60-70% of the total volume of the fixed-bed reactor, the distance between the bottom of the biological carrier layer and the bottom of the fixed-bed reactor is 200-300 mm, and the distance between the top of the biological carrier layer and the top of the fixed-bed reactor is greater than 300 mm.

[0141] The proportion of the biological carrier layer volume to the total volume of the fixed-bed reactor can be selected as 60%, 62%, 64%, 66%, 68%, or 70%. The specific value is determined based on the reactor's structural dimensions: when the reactor diameter is 2m and the height is 4m, the carrier volume is typically 7.5-8.8m³. 3 The carrier can be polyethylene porous suspended packing or polypropylene corrugated plate packing, with a particle size of 10mm, 15mm, or 20mm. Assembly requirements: The carrier should be uniformly filled in the central area of ​​the reactor, with a gap of 50-100mm between it and the inner wall. During operation, as wastewater flows through the pores of the carrier layer, the biofilm adheres to the surface and degrades pollutants. Parameter settings are based on hydraulic load: flow rate 20m³ / h. 3 Under the condition of / h, the pressure drop curves of the reactor were tested at different filling ratios (55-75%), and the pressure drop was most stable when 65% was selected. The raw materials were derived from industrial-grade plastic particles injection molding or volcanic rock sintering process.

[0142] Biological carrier materials can be selected from polyethylene, polypropylene, or modified polyurethane, with porosities of 85%, 88%, or 90%. The carrier shape can be cylindrical, spherical, or corrugated, with a specific surface area of ​​300 m². 2 / m 3 350m 2 / m 3 or 400 m 2 / m 3During assembly, layered filling is required, with each layer's thickness controlled between 0.5-1.0 μm. Slight compaction between layers is necessary to prevent later settling. During operation, a biofilm layer forms on the carrier surface, its thickness controlled by the filling rate: a 70% filling rate results in smaller carrier spacing and higher biofilm growth density; a 60% filling rate provides wider water flow channels. In the experiment, reactor models of the same diameter were filled with carriers at 60%, 65%, and 70% volume, respectively, and the effluent TN concentration was measured after 30 days of continuous operation. The results showed that a 65% filling rate resulted in the most stable denitrification efficiency.

[0143] The distance between the bottom of the carrier layer and the reactor bottom plate is 200-300mm, and the distance between the top of the biological carrier layer and the top of the fixed-bed reactor is greater than 300mm. The assembly position must be kept horizontal, and the filling height error should be less than ±2%. During operation, the bottom space accommodates the initial diffusion flow of the influent, while the top space ensures the effective collection of the effluent. Functional testing verifies the backwashing effect: A mixed air-water backwash flow (air velocity 20m) is introduced into the carrier layer with a 65% filling rate. 3 / h, water velocity 10m 3 / h), the fluidization uniformity of the carrier reaches over 90%; if the filling rate exceeds 70%, local carrier accumulation will lead to a flushing blind zone.

[0144] Technical effects: A 60-70% volume ratio forms a suitable biofilm growth interface, and the carrier spacing ensures sufficient specific surface area (300-400m²). 2 / m 3 This avoids overcrowding and maintains the effectiveness of the pore water flow channels. A buffer zone (200-300mm) is reserved at the bottom of the biological carrier layer, allowing the air-water backwash flow to penetrate the carrier layer pores evenly and eliminating localized flushing dead zones. A specific filling ratio (e.g., 65%) is matched to the design hydraulic load (20m). 3 / h), reducing the structural resistance of the carrier layer, reducing operating energy consumption and the risk of blockage.

[0145] In another embodiment, the wastewater treatment device, such as Figure 2 As shown, the inner wall of the fixed bed reactor is welded with multi-layered guide plates 12 at intervals along the vertical direction. The guide plates are horizontally arranged and located inside the biological carrier layer, and are coaxially arranged with the fixed bed reactor. The distance between adjacent guide plates is 1 / 5 to 1 / 3 of the height of the fixed bed reactor.

[0146] The diameter of the central opening of the guide plate is 40-50% of the diameter of the guide plate. Auxiliary guide holes with a diameter of 1-3mm are evenly opened on the annular plate of the guide plate, and the opening ratio of the guide holes is 15-20%.

[0147] A guide tube 13 is vertically welded inside the central opening. The top of the guide tube is flush with the upper surface of the guide plate. The distance between the bottom of the upper guide tube and the top of the lower guide tube in two adjacent guide tubes is 80-150mm.

[0148] Spiral guide grooves are opened on the outer wall of the guide tube, and the depth of the guide grooves is 1-2mm;

[0149] The bottommost guide tube is 200-300mm from the bottom of the fixed-bed reactor.

[0150] Multi-layered baffles are welded vertically at intervals along the inner wall of the fixed-bed reactor. The spacing between adjacent baffles can be selected as 1 / 5.5, 1 / 5, 1 / 4.5, 1 / 4, 1 / 3.5, or 1 / 3 of the effective height of the reactor. Specific values ​​are set according to the reactor dimensions: for example, for a reactor with an effective height of 4m, the spacing can be 0.8m (1 / 5). Commercially available annular steel plates can be used for the baffles, and the material can be 304 stainless steel or Q235 carbon steel. Assembly requirements: The baffles are horizontally welded to the inner wall of the reactor, coaxial with the central axis, with a horizontal tolerance controlled within 2mm. During operation, water flows from bottom to top through the central opening of the baffles, forming the axial mainstream direction. Parameters are set through fluid simulation experiments: at a flow rate of 15m³ / h... 3 Under the condition of / h, the uniformity of flow velocity distribution at different spacings (0.7-1.2m) was tested, and the flow field stability was determined to be the best when the spacing was 0.8m.

[0151] The diameter of the central opening of the guide plate can be selected as 40%, 42%, 45%, 48%, or 50% of the guide plate diameter. The diameter of the auxiliary guide holes can be selected as 1.0mm, 1.5mm, 2.0mm, 2.5mm, or 3.0mm; the opening ratio can be selected as 15%, 16%, 17%, 18%, 19%, or 20%. A 30° chamfer is machined at the edge of the central opening to reduce resistance. The auxiliary holes are evenly distributed on the annular plate, and the hole spacing is calculated using the equal area method. The material is the same as the main body of the guide plate and can be laser-cut. During operation, part of the water flows axially through the central opening, while the remaining water diffuses radially from the auxiliary guide holes, covering the edge area of ​​the reactor. The experimental method involves injecting a tracer and observing the flow field distribution; the results show that the dead zone area is minimized when the opening ratio is 18%.

[0152] The guide tube is vertically welded into the central opening of the guide plate, with its top flush with the upper surface of the guide plate. The spacing between adjacent guide tubes can be selected as 80mm, 90mm, 100mm, 120mm, 140mm, or 150mm. Spiral guide grooves are formed on the outer wall of the guide tubes, with groove depths selectable as 1.0mm, 1.2mm, 1.5mm, 1.8mm, or 2.0mm. The height of the guide tubes is 60-70% of the distance between the guide plates. Assembly requirements: the coaxiality error between the upper and lower guide tube axes must be less than 1mm, and the spiral grooves must rotate in the same direction. The distance from the bottom guide tube to the bottom of the reactor can be selected as 200mm, 220mm, 250mm, 280mm, or 300mm. During operation, the water flows through the spiral grooves of the guide tubes, generating a rotating motion that enhances the turbulence of the liquid phase. Functional testing shows that the swirling intensity meets the design requirements when the groove depth is 1.5mm.

[0153] Synergistic effects during air washing:

[0154] When the backwash fan introduces gas from the bottom, the airflow rotates and rises along the spiral grooves (groove depth 1-2mm) on the outer wall of the guide tube. The spiral grooves induce centrifugal force in the airflow, causing the gas to disperse into fine bubbles that uniformly penetrate the pores of the carrier layer. Experiments show that the guide tube with spiral grooves can improve the uniformity of bubble distribution by 30% (compared to the grooveless structure), avoiding local airflow short-circuiting.

[0155] The auxiliary guide holes (15-20% opening ratio) of the baffle allow some gas to escape radially. When the gas rises to the position of the baffle:

[0156] The main airflow continues to move axially through the central opening (40-50% of the diameter of the guide vane);

[0157] The diverted gas diffuses from the auxiliary guide hole (1-3 mm in diameter) to the edge of the carrier layer, eliminating the gas washing blind zone near the wall.

[0158] Anti-caking mechanism: Radial diffusion of gas disturbs the edge region of the carrier layer, preventing the carrier from caking due to long-term static deposition.

[0159] Synergistic effects during the washing process:

[0160] When the sprayed water from the top of the reactor flows through the guide tube, it is guided by the spiral grooves to generate a swirling flow (the intensity of the swirling flow is positively correlated with the groove depth of 1-2 mm). The swirling flow creates a centrifugal force field, causing the water to powerfully wash the surface of the carrier and peel off the attached aging biofilm. The water washing efficiency with spiral grooves is 40% higher than that of the straight cylinder structure.

[0161] Multi-layered baffle layout (spacing 1 / 5-1 / 3 of reactor height) for staged rectification:

[0162] The top baffle plate captures the spray water flow and disperses it into radial jets through auxiliary guide holes;

[0163] The central opening of the lower guide vane maintains the axial mainstream flow, preventing water flow energy attenuation.

[0164] Anti-caking mechanism: Radial jets cover the edge of the carrier layer, eliminating low-velocity deposition zones.

[0165] Three-dimensional cleaning system combining air and water:

[0166] When air washing and water washing are running simultaneously:

[0167] The upward rotating airflow and the downward swirling water flow converge within the carrier layer, forming high-intensity turbulence (the turbulence intensity can be up to twice that of single-phase flow).

[0168] Turbulent shear forces completely detach the biofilm, and the debris is quickly carried out through the flow-guiding structure.

[0169] The air-water countercurrent flow penetrates the bottom of the carrier layer (the bottom guide plate is 200-300mm from the bottom) to prevent the bottom carrier from being compacted and hardened.

[0170] The spacing between the deflectors (e.g., 0.8m) is matched with the carrier particle size (10-20mm) to ensure that the disturbance is transmitted to all levels.

[0171] Technical Effects: The central opening maintains the axial mainstream flow, while auxiliary guide holes (15-20% opening ratio) guide the radial diffusion of water flow, eliminating low-velocity dead zones near the wall and preventing biofilm deactivation due to lack of oxygen. The spiral grooves of the guide tubes (1-2mm depth) induce water rotation, enhancing turbulent contact between the liquid phase and the biofilm carrier layer, accelerating substrate transfer to the biofilm. The spacing between the guide tubes (80-150mm) matches the upward velocity of the water flow, preventing eddy breakup; the bottom guide plate is installed high (200-300mm) to prevent bottom sediment accumulation. By optimizing the air-water flow distribution, the guide plates and guide tubes not only enhance cleaning efficiency but also fundamentally prevent biofilm carrier layer caking by eliminating low-velocity dead zones, providing continuous disturbance, and stratified interception and settling. This structure is a key guarantee for maintaining the long-term stable operation of the reactor.

[0172] In another embodiment, the wastewater treatment device has the effluent end of the fixed-bed reactor located at its top.

[0173] Although the embodiments of this utility model have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for this utility model. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, this utility model is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A wastewater treatment device for treating effluent from a biological secondary sedimentation tank, characterized in that, include: A fixed-bed reactor is filled with a biological carrier layer. The inlet and outlet of the fixed-bed reactor are located at its bottom and top, respectively. The backwash fan is connected to the air inlet at the bottom of the fixed-bed reactor via a first pipe; A water pump is connected to the inlet of the fixed-bed reactor via a second pipe and to the flushing port at the top of the fixed-bed reactor via a third pipe. DO sensor, which is installed on the inlet pipe of the fixed bed reactor; The control system is connected to the DO sensor, backwash fan, and water pump.

2. The wastewater treatment device as described in claim 1, characterized in that, Also includes: The perforated tube water distributor is fixed at the bottom of the fixed bed reactor. The water inlet of the perforated tube water distributor is connected to the water inlet pipe of the fixed bed reactor through a water pump. The water outlet of the perforated tube water distributor faces the bottom of the biological carrier layer. The diameter of the water outlet is 5-10 mm and the spacing between the outlets is 10-20 cm.

3. The wastewater treatment device as described in claim 1, characterized in that, Also includes: The DO probe is inserted vertically into the biological carrier layer at a distance of 5-10 cm from 1 / 2 of the total height along the height direction of the fixed bed reactor, with the central axis as the reference and 1 / 3 of the radius outside the central axis. This is used to monitor the DO concentration in the fixed bed reactor in real time. Two differential pressure sensors are installed on the inlet and outlet pipes of the fixed-bed reactor, respectively, to monitor the pressure difference of the biological carrier layer in real time. The control system is connected to both the DO probe and the differential pressure sensor.

4. The wastewater treatment device as described in claim 1, characterized in that, Also includes: Mechanical bar screens are installed at the effluent end of the secondary sedimentation tank in the biological process, with a pore size of 100-200μm.

5. The wastewater treatment device as described in claim 1, characterized in that, Also includes: The microbial sampling port is located on the side wall of the fixed-bed reactor and to the side of the biological carrier layer; A metering pump, whose outlet is connected to the inlet of the fixed-bed reactor via a fourth pipe, is used to add liquid sodium acetate to the inlet water; The COD sensor, nitrate nitrogen sensor, and ammonia nitrogen sensor are all installed on the inlet pipe of the fixed-bed reactor and connected to the control system.

6. The wastewater treatment device as described in claim 1, characterized in that, Also includes: An electric flow regulating valve is installed on the second pipeline, located downstream of the water pump outlet, and connected to the control system. The outlet of the aerobic aeration blower is connected to the aerobic aeration unit upstream of the biological secondary sedimentation tank via a pipeline. The frequency converter is connected to the motor of the aerobic aeration blower and to the control system.

7. The wastewater treatment device as described in claim 1, characterized in that, The volume of the biological carrier layer accounts for 60-70% of the total volume of the fixed-bed reactor. The distance between the bottom of the biological carrier layer and the bottom of the fixed-bed reactor is 200-300 mm, and the distance between the top of the biological carrier layer and the top of the fixed-bed reactor is greater than 300 mm.

8. The wastewater treatment device as described in claim 1, characterized in that, The inner wall of the fixed bed reactor is welded with multiple layers of guide plates at intervals along the vertical direction. The guide plates are horizontally arranged and located inside the biological carrier layer, and are coaxial with the fixed bed reactor. The spacing between adjacent guide plates is 1 / 5 to 1 / 3 of the height of the fixed bed reactor. The diameter of the central opening of the guide plate is 40-50% of the diameter of the guide plate. Auxiliary guide holes with a diameter of 1-3mm are evenly opened on the annular plate of the guide plate, and the opening ratio of the guide holes is 15-20%. A guide tube is vertically welded inside the central opening. The top of the guide tube is flush with the upper surface of the guide plate. The distance between the bottom of the upper guide tube and the top of the lower guide tube in two adjacent guide tubes is 80-150mm. Spiral guide grooves are opened on the outer wall of the guide tube, and the depth of the guide grooves is 1-2mm; The bottommost guide tube is 200-300mm from the bottom of the fixed-bed reactor.

9. The wastewater treatment device as described in claim 1, characterized in that, The effluent end of the fixed-bed reactor is located at its top.

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