Method and system for multi-stage treatment of aquaculture effluent

Abstract

The application belongs to the field of water pollution treatment, and provides a multi-stage aquaculture tail water treatment method, wherein tail water is coarsely filtered and then discharged into a sedimentation tank for sedimentation treatment to obtain sedimentation water; the sedimentation water is discharged into an aeration tank through a filter dam for nitrification and denitrification nitrogen removal treatment; whether the heat source of the aeration tank needs to be reduced or closed is determined by directly determining whether the area of the mesophilic zone is expanding, a signal for controlling the temperature is accurately sent, the area of the mesophilic zone can be accurately controlled by temperature control, the ammonia nitrogen biodegradation efficiency is indirectly improved by reducing the mesophilic dominant bacteria, and the nitrogen accumulation and emission problems of the greenhouse gas accumulation area in the water pollution treatment process are indirectly reduced.

Description

Technical Field

[0001] This invention belongs to the field of water pollution treatment technology, specifically relating to a multi-stage treatment method and system for aquaculture wastewater. Background Technology

[0002] In the treatment of aquaculture wastewater, appropriately increasing the temperature enhances microbial activity, accelerating the decomposition of organic nitrogen compounds and promoting the conversion of organic nitrogen to inorganic nitrogen, thus reducing the total nitrogen content of the water. Conversely, at lower temperatures, the activity of microorganisms responsible for nitrification and denitrification decreases, reducing biological treatment efficiency and slowing the conversion of ammonia nitrogen into nitrate nitrogen and other nitrogen compounds, leading to an increase in total nitrogen concentration. Since total nitrogen includes multiple forms such as ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, and organic nitrogen, a slowdown in ammonia nitrogen conversion results in a relative accumulation of total nitrogen. Furthermore, low temperatures increase the solubility of some nitrogen compounds in water, indirectly increasing the detected total nitrogen content and contributing to the accumulation of total nitrogen in aquaculture wastewater. Therefore, controlling the temperature of aquaculture wastewater to reduce its total nitrogen content has been a key area of ​​research and improvement in aquaculture wastewater treatment processes.

[0003] For example, reference CN115240793A significantly improves the early warning efficiency of abnormal total nitrogen content caused by temperature singularities by strengthening the correlation data characteristics between temperature singularities and total nitrogen operational balance. Furthermore, by compensating for neglected data and weakening insensitive data, it theoretically improves the accuracy of early warning for abnormal total nitrogen operational balance. By regulating the aquaculture water purification equipment, the total nitrogen content in the pond is kept in a relatively stable state, reducing the risk of eutrophication caused by total nitrogen imbalance. However, near the heat source of the aeration tank, high temperatures are inevitably generated, causing nitrifying and denitrifying bacteria to cease functioning. Even the thermophilic and mesophilic dominant bacteria in the aeration tank may cause nitrogen accumulation, potentially leading to the release of greenhouse gases such as nitrogen, resulting in water and air pollution. Summary of the Invention

[0004] The purpose of this invention is to propose a multi-stage treatment method for aquaculture wastewater to solve one or more technical problems existing in the prior art, and at least provide a beneficial option or create conditions.

[0005] To achieve the above objectives, according to one aspect of the present invention, a multi-stage treatment method for aquaculture wastewater is provided, the method comprising the following steps:

[0006] S100, after coarse filtration of the effluent, is discharged into a sedimentation tank for sedimentation treatment to obtain settled water.

[0007] S200 discharges the settled water through a filter dam into an aeration tank for nitrification and denitrification treatment.

[0008] The specific methods for nitrogen removal through nitrification and denitrification include:

[0009] S201, heats the effluent in the aeration tank using a heat source;

[0010] S202, thermal images of the effluent surface in the aeration tank are acquired at fixed time intervals using infrared imaging;

[0011] S203 identifies the mid-temperature zone appearing in the thermal image;

[0012] S204, control the temperature of the aeration tank according to the medium temperature zone.

[0013] Furthermore, in S100, the specific method for coarse filtration of the effluent is as follows: coarse filtration of the effluent is performed through a screen.

[0014] Among them, the grid is used to intercept large particulate pollutants such as shrimp shells, dead shrimp, uneaten bait, and aquatic plants.

[0015] Furthermore, in S200, the dam body of the filter dam is filled with filter media, which includes any one or more of oyster shells, gravel, pebbles, small stones, palm flakes, and ceramic beads, used to adsorb mud and other substances in the tailwater.

[0016] Furthermore, the specific method for nitrogen removal treatment by nitrification and denitrification in the aeration tank is as follows: nitrogen removal in the effluent is achieved through the synergistic action of nitrifying and denitrifying bacteria. Nitrogen removal in the effluent consists of two stages: nitrification and denitrification. Under aerobic conditions, nitrifying bacteria convert ammonia nitrogen into nitrite and nitrate in sequence. Under anoxic conditions, denitrifying bacteria reduce nitrate to nitrogen gas.

[0017] By installing a heat source and corresponding temperature sensors on the aeration tank, the temperature inside the aeration tank can be appropriately controlled by the heat source when changes occur. The oxygen concentration in the water is detected by the corresponding DO probe (dissolved oxygen sensor) and controller, and the oxygen supply is controlled accordingly. The oxygen content of the water can be intermittently changed at different time periods, which is conducive to the repeated chemical reactions of microorganisms in the water under aerobic and anaerobic environments (nitrifying bacteria carry out nitrification under aerobic conditions, with a suitable temperature between 20-30℃, and phosphorus-removing bacteria take up phosphorus in the water to synthesize ATP and corresponding polyphosphates; denitrifying bacteria carry out denitrification under anaerobic conditions, with a suitable temperature between 20-40℃).

[0018] In S201, the heat source includes any one of the following: a heat lamp, an electric heater, or a steam pipe.

[0019] Furthermore, in S202, the fixed time interval is set to 5 to 30 minutes.

[0020] During the nitrification and denitrification process in the aeration tank, nitrite (NO2) often accumulates in the mesophilic zone. - Regarding the issues of nitrogen monoxide (N2O), according to the latest findings in the reference: "Li Ma, Liuqin Huang*, Yuanguo Xie, Yang Luo, Yinuo Zhao, Jie Feng, Geng Wu, Jianyu Jiao, Wenjun Li, Hongchen Jiang* (2025). Temperature-Dependent Regulation of Denitrification Intermediates in High-Temperature Ecosystems. Environmental Science & Technology, DOI: 10.1021 / acs.est.5c00174", when the water temperature reaches a high temperature, the efficiency of microbial denitrification decreases. This is a self-protection strategy of microorganisms against high temperatures. By adjusting the temperature or adding specific microorganisms, the denitrification efficiency in aquaculture wastewater treatment can be optimized. When the temperature drops from the peak to the mesophilic level, the production line will experience a "job change": newly emerging mesophilic dominant bacteria, such as Tepidimonas, will replace the original thermophilic dominant bacteria, Thermus, and directly remove some of the NO3-. - The conversion to N2O leads to the formation of nitrite (NO2) in the intermediate temperature range. - Areas with high levels of nitrite (NO2) and the greenhouse gas N2O, which should have been completely decomposed, are now experiencing a significant increase in nitrite production. - Nitrous oxide (N2O) and other greenhouse gases begin to accumulate in large quantities. Existing technologies generally involve simple temperature measurement and overall temperature control. However, the mesothermal zone is a region with insignificant temperature differences after the temperature reaches its peak and then cools down. Furthermore, the temperature of the mesothermal zone is the same as or close to that of the normal sub-high temperature zone (the region where normal temperature rise and maintenance do not come from the peak cooling). Therefore, it is difficult to measure the temperature using simple sensor points. If the mesothermal zone lasts for a long time, it will lead to the release of a large amount of greenhouse gases (nitrous oxide (N2O)). However, in aquaculture wastewater, some areas have a large amount of microalgae, suspended matter, and the distance from the heat source and the impeller will cause the thermal properties (specific heat capacity, temperature gradient, and potential temperature) of different water areas to be completely different. Therefore, thermal images taken on the liquid surface of the aeration tank will show different grayscale differences. This application proposes the following method for accurately identifying the mesothermal zone based on this principle.

[0021] Furthermore, in S203, the method for identifying the intermediate temperature region appearing in the thermal image includes the following steps:

[0022] The grayscale images of the acquired thermal images are converted to grayscale, and the edge lines are extracted using the watershed algorithm. Each edge line divides the image into multiple different temperature difference regions. The average grayscale of all points in the grayscale image is used as the equilibrium grayscale. The temperature difference regions where the average grayscale of all points is greater than the equilibrium grayscale are marked as hot temperature regions (the hot temperature regions are the regions with higher temperatures compared to other temperature difference regions).

[0023] Following the acquisition time sequence, the grayscale images corresponding to each thermal image are used to initially locate the high-temperature zone: if the average grayscale value of each point in a grayscale image's hot zone exceeds the grayscale threshold for the first time, this hot zone is marked as a high-temperature zone, and the acquisition time of the thermal image corresponding to the high-temperature zone is the trigger time for that high-temperature zone; (the high-temperature zone appearing at the trigger time corresponds to a high-heat area appearing on the liquid surface in the aeration tank. At this time, when the water temperature exceeds a certain level, nitrite (NO2) that should have been completely decomposed will be released.) - Nitrous oxide (N2O) and nitrogen oxides begin to accumulate in large quantities in this region. Note that there may be more than one high-temperature zone; multiple zones may appear at the same time and may appear later. In high-temperature zones, microorganisms develop self-protection strategies to reduce denitrification efficiency, but overall, nitrogen accumulation will not occur.

[0024] For all high-temperature zones, starting from the trigger time corresponding to each high-temperature zone, the location of the high-temperature zone on the thermal image acquired after the trigger time is monitored and identified as a medium-temperature zone.

[0025] Preferably, if the corresponding high-temperature area disappears or shrinks in the thermal image after the trigger time, the high-temperature area location is re-established (since heat transfer is from the part with a higher temperature to the part with a lower temperature, shrinking area means that the area of ​​the high-temperature area will not expand, and the high-temperature area needs to be re-established).

[0026] Furthermore, the method for monitoring and identifying the medium-temperature zone is as follows: if a new edge line is identified within the corresponding position of the high-temperature zone in the thermal image, the area formed by the edge line is identified as the identification zone; if the average gray value of each pixel in the identification zone is less than the average gray value of each pixel in the high-temperature zone, the identification zone is marked as the medium-temperature zone.

[0027] The intermediate temperature zone naturally forms after the high temperature zone cools down. It may appear in one or more places within the high temperature zone. Alternatively, after the entire high temperature zone cools down, the temperature difference between the intermediate temperature zone and the normal temperature control zone after it has not been cooled down may not be significant. However, the intermediate temperature zone is actually an accumulation area of ​​the greenhouse gas N2O. In the automatic temperature control of the aeration tank, this can cause confusion and lead to misjudgment by the control system, generating incorrect cooling signals. Although the above method can initially locate the static intermediate temperature zone, multiple intermediate temperature zones with different average temperatures within the high temperature zone may merge during the expansion process. Due to the different temperature differences, the average temperature value of the merged zone may be temporarily equal to or even slightly higher than the average temperature value of the high temperature zone. This phenomenon can lead to the loss of the intermediate temperature zone target or incorrect identification.

[0028] Preferably, the method for monitoring and identifying the medium-temperature zone is as follows: if a new edge line is identified within the corresponding position of the high-temperature zone in the thermal image, the area formed by this edge line is identified as the identification zone; if there is only one identification zone, then if the average gray value of each pixel in the identification zone is less than the average gray value of each pixel in the high-temperature zone, the identification zone is marked as a medium-temperature zone; if there are more than one identification zone, after the identification zone appears, the thermal images are sorted according to the acquisition time sequence, with i as the sequence number of the thermal image and j as the sequence number of the identification zone in the high-temperature zone. Let TempA(i) represent the maximum average gray value of all pixels in the high-temperature region at the corresponding position on the first to i thermal images, excluding the recognition area; let TempB(i,j) represent the average gray value of pixels in the j-th recognition area formed by the high-temperature region at the corresponding position on the i-th thermal image; let the absolute value of the difference between TempB(i,j) and TempA(i) be the temperature difference gray value difference value WC(j) of the j-th recognition area; (the temperature difference gray value difference value is the difference in gray value difference that the thermal properties of each recognition area can reflect in the thermal image).

[0029] After sorting the recognition areas (excluding the current recognition area) according to the distance between the geometric centroid of each recognition area and the geometric centroid of the current recognition area from smallest to largest, it is then determined whether each recognition area of ​​the current recognition area is a virtual merged area of ​​the current recognition area.

[0030] The method for determining the virtual merging area is as follows: if the temperature difference grayscale difference value of the previous identification area is greater than that of the current identification area, and the temperature difference grayscale difference value of the next identification area is greater than that of the current identification area, then the previous and next identification areas are marked as virtual merging areas; (since the direction of heat transfer is unidirectional, it always flows from high temperature to low temperature, and the marked virtual merging area is the area that is more likely to merge with the current identification area after the temperature difference grayscale difference value changes).

[0031] Synonymous with the above, the method for determining the virtual merging area is as follows: traverse each recognition area sequentially within the range of k. If WC(k) > WCU and WCU < WC(k+1); k is the sorted recognition area number, WCU is the temperature difference grayscale difference value of the current recognition area, and WC(k) is the temperature difference grayscale difference value of the kth recognition area.

[0032] If the average gray value of each pixel in the recognition area and all corresponding virtual merged areas is less than the average gray value of each pixel in the high temperature area, then the recognition area and all corresponding virtual merged areas are marked as the medium temperature area.

[0033] Furthermore, in S202, the aeration tank is also equipped with a submersible impeller aeration device.

[0034] Furthermore, in S204, the specific method for controlling the temperature of the aeration tank according to the medium-temperature zone includes:

[0035] If the area of ​​all medium-temperature zones in the most recently acquired thermal image is greater than the area of ​​all medium-temperature zones in the previously acquired thermal image, then the heat source is turned off. After turning off the heat source, if the watershed algorithm cannot detect the existence of edge lines in the area corresponding to the high-temperature zone in the newly acquired thermal image (i.e., all medium-temperature zones have disappeared), then the heat source is restarted.

[0036] Preferably, in S204, the specific method for controlling the temperature of the aeration tank according to the medium-temperature zone includes:

[0037] If the area of ​​all medium-temperature zones in the most recently acquired thermal image is greater than the area of ​​all medium-temperature zones in the previous thermal image, then the heat source is turned off; after the heat source is turned off, if the area of ​​all medium-temperature zones in the most recently acquired thermal image is less than the area of ​​all medium-temperature zones in the previous thermal image, then the heat source is turned back on.

[0038] Preferably, the shutdown of the heat source in this application is replaced by a reduction of the heat source power by 10% to 30%.

[0039] The above methods determine whether the heat source of the aeration tank needs to be reduced or shut down by directly judging whether the area of ​​the mesothermal zone is expanding. Although this can accurately control the area of ​​the mesothermal zone through temperature control, thereby indirectly reducing the biodegradation efficiency of ammonia nitrogen by mesothermal dominant bacteria and reducing nitrogen accumulation in the accumulation area of ​​greenhouse gas N2O, sometimes when multiple mesothermal zones exist within the same high-temperature zone, the mesothermal zone may merge with other mesothermal zones during expansion. When the temperature difference between the two mesothermal zones before merging is large, the average temperature value after merging may briefly be the same as or even slightly higher than the average temperature value of the high-temperature zone, thus losing the target and issuing incorrect temperature control signals. To solve this problem, this application proposes the following improved method:

[0040] Preferably, in S204, the specific method for controlling the temperature of the aeration tank according to the medium-temperature zone includes:

[0041] The degree of sustained expansion in the mid-temperature zone is calculated. If the degree of sustained expansion in the mid-temperature zone of the thermal image shows an increasing trend, cooling is performed. If the degree of sustained expansion in the mid-temperature zone of the thermal image shows a decreasing trend, reheating is performed.

[0042] The specific method for calculating the degree of sustained expansion in the mid-temperature region is as follows:

[0043] Iterate through each medium-temperature zone in the high-temperature zone in turn, and take the medium-temperature zone that has been traversed as the current medium-temperature zone. Calculate the degree of maintenance and expansion of the current medium-temperature zone. Specifically, mark the gray difference value of the temperature difference between each medium-temperature zone in the high-temperature zone that is greater than the gray difference value of the current medium-temperature zone as the expansion difference gray value, otherwise mark it as the contraction difference gray value.

[0044] The difference between the expanded grayscale value and the current temperature difference grayscale value in the medium temperature zone is calculated and recorded as the first difference. The sum of all first differences is recorded as the expansion amplitude.

[0045] The difference between the temperature difference grayscale value and the contraction difference grayscale value in the current medium temperature zone is calculated and recorded as the second difference. The sum of all the first differences is recorded as the contraction amplitude. The sum of the expansion amplitude and the contraction amplitude is recorded as the maintenance amplitude.

[0046] The current sustained expansion level in the medium temperature zone is the ratio of the expansion amplitude to the sustained expansion amplitude multiplied by 100; (Note: Multiplying by 100 is to limit the sustained expansion level value to between 1 and 100 for easy display on the control software interface).

[0047] The method for performing cooling when the sustained expansion of the mid-temperature zone in the thermal image shows an increasing trend, and performing reheating when the sustained expansion of the mid-temperature zone in the thermal image shows a decreasing trend, is as follows:

[0048] The average degree of sustained expansion of all medium-temperature zones on the most recently acquired thermal image is calculated as the current degree of expansion. The average degree of sustained expansion of all medium-temperature zones on the previously acquired thermal image is calculated as the previous degree of expansion. If the current degree of expansion is greater than the previous degree of expansion, cooling is performed.

[0049] Furthermore, in S204, the cooling process is as follows: turn off the heat source. After turning off the heat source, if the watershed algorithm cannot detect the edge line in the area corresponding to the high temperature area in the newly acquired thermal image (i.e., the medium temperature area has completely disappeared), restart the heat source.

[0050] Furthermore, in S204, the method for cooling is to reduce the power of the heat source by 10%, or to turn off the heat source and wait for the restart time threshold before restarting the heat source.

[0051] The restart time threshold is set to 5 to 30 minutes.

[0052] The grayscale threshold is the grayscale value of a thermal image when the water temperature exceeds 50 to 60 degrees Celsius, as determined in advance.

[0053] The invention also provides a multi-stage treatment system for aquaculture wastewater, the system comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, the processor executing the computer program in a unit of the following system:

[0054] The aeration tank heating unit is used to heat the effluent in the aeration tank using a heat source.

[0055] The thermal image acquisition unit is used to acquire thermal images of the effluent surface in the aeration tank at fixed time intervals using infrared imaging.

[0056] The medium-temperature zone recognition unit is used to identify the medium-temperature zone appearing in the thermal image;

[0057] The medium-temperature zone temperature control unit is used to control the temperature of the aeration tank according to the medium-temperature zone.

[0058] The beneficial effects of this disclosure are as follows: This invention provides a multi-stage treatment method and system for aquaculture wastewater. By directly determining whether the area of ​​the mesothermal zone is expanding, it can determine whether the heat source of the aeration tank needs to be reduced or shut down, accurately issuing a temperature control signal. This allows for precise temperature control of the mesothermal zone area, indirectly reducing the area of ​​the dominant mesothermal bacteria and improving the biodegradation efficiency of ammonia nitrogen. This indirectly reduces nitrogen accumulation and emissions in greenhouse gas accumulation areas during water pollution treatment, and reduces nitrite (NO2). - Water pollution caused by nitrous oxide (N2O) and air pollution caused by nitrous oxide (N2O) greenhouse gas. Attached Figure Description

[0059] The above and other features of the present invention will become more apparent from the detailed description of the embodiments shown in conjunction with the accompanying drawings. In the accompanying drawings, the same reference numerals denote the same or similar elements. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort. In the drawings:

[0060] Figure 1 The diagram shows the structure of a multi-stage treatment system for aquaculture wastewater. Detailed Implementation

[0061] The following will provide a clear and complete description of the concept, specific structure, and technical effects of the present invention in conjunction with the embodiments and accompanying drawings, so as to fully understand the purpose, solution, and effects of the present invention. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0062] Example 1

[0063] S100, after coarse filtration of the effluent, is discharged into a sedimentation tank for sedimentation treatment to obtain settled water.

[0064] S200 discharges the settled water through a filter dam into an aeration tank for nitrification and denitrification treatment.

[0065] The specific methods for nitrogen removal through nitrification and denitrification include:

[0066] S201, heats the effluent in the aeration tank using a heat source;

[0067] S202, thermal images of the effluent surface in the aeration tank are acquired at fixed time intervals using infrared imaging;

[0068] S203 identifies the mid-temperature zone appearing in the thermal image;

[0069] S204, control the temperature of the aeration tank according to the medium temperature zone.

[0070] Furthermore, in S100, the specific method for coarse filtration of the effluent is as follows: coarse filtration of the effluent is performed through a screen.

[0071] Specifically: a rake bar screen (model: GS-2000, screen gap 5mm); a booster pump (flow rate 20m³ / h, head 10m); and a 3KW motor. The wastewater is treated by the rake bar screen to intercept large particles of impurities. The screen is tilted at 60° and cleaned twice daily.

[0072] Among them, the grid is used to intercept large particulate pollutants such as shrimp shells, dead shrimp, uneaten bait, and aquatic plants.

[0073] The sedimentation tank is a horizontal flow sedimentation tank (dimensions: L×W×H=10m×3m×4m), with a hydraulic retention time (HRT) of 2h, a surface loading rate of 1.2m³ / (m²·h), and a sludge return ratio of 30%. The effluent is allowed to settle in the horizontal flow sedimentation tank for 2h, with the surface loading rate controlled at 1.2m³ / (m²·h).

[0074] Furthermore, in S200, the dam body of the filter dam is filled with filter media, which has a layered structure: an upper layer of 10-20mm oyster shells, a middle layer of 5-10mm gravel, and a lower layer of 2-5mm activated carbon, which is used to adsorb mud and other substances in the effluent.

[0075] The aeration tank is a plug-flow aeration tank (effective volume 50m³, DO probe + PLC control system).

[0076] In S201, the heat source is an immersion stainless steel electric heater with a power of 5~20kW (calculated based on the tank volume, 0.1~0.2kW is required per cubic meter of water), a temperature range of 0~80℃ (constant temperature control target 25±2℃), and a protection rating of IP68 (completely waterproof).

[0077] Furthermore, the specific method for nitrogen removal treatment by nitrification and denitrification in the aeration tank is as follows: nitrogen removal in the effluent is achieved through the synergistic action of nitrifying and denitrifying bacteria. Nitrogen removal in the effluent consists of two stages: nitrification and denitrification. Under aerobic conditions, nitrifying bacteria convert ammonia nitrogen into nitrite and nitrate in sequence. Under anoxic conditions, denitrifying bacteria reduce nitrate to nitrogen gas.

[0078] By setting up a heat source and corresponding temperature sensors on the aeration tank, the temperature inside the aeration tank can be appropriately controlled by the heat source when it changes. The oxygen concentration in the water is detected by the corresponding DO probe (dissolved oxygen sensor) and controller, and the oxygen supply is controlled. The oxygen content of the water can be changed intermittently at different time periods, which is conducive to the repeated chemical reactions of microorganisms in the water under aerobic and anaerobic environments.

[0079] Furthermore, in S202, the fixed time interval is set to 10 minutes.

[0080] Furthermore, in S203, the method for identifying the intermediate temperature region appearing in the thermal image includes the following steps:

[0081] The edge lines of the grayscale images after graying are extracted using the watershed algorithm. Each edge line divides the image into multiple different temperature difference regions. The average gray level of all points on the grayscale image is taken as the equilibrium gray level. The temperature difference regions where the average gray level of all points is greater than the equilibrium gray level are marked as the hot temperature regions.

[0082] According to the acquisition time sequence, the initial high temperature zone is located for each grayscale image corresponding to each thermal image in turn: if the average gray value of each point in the hot temperature zone of a grayscale image exceeds the gray value threshold for the first time, the hot temperature zone is marked as a high temperature zone, and the acquisition time of the thermal image corresponding to the high temperature zone is the trigger time of the high temperature zone.

[0083] For all high-temperature zones, starting from the trigger time corresponding to each high-temperature zone, the location of the high-temperature zone on the thermal image acquired after the trigger time is monitored and identified as a medium-temperature zone.

[0084] Preferably, if the corresponding high-temperature area disappears or shrinks in the thermal image after the trigger time, the high-temperature area location is re-established.

[0085] Furthermore, the method for monitoring and identifying the medium-temperature zone is as follows: if a new edge line is identified within the corresponding position of the high-temperature zone in the thermal image, the area formed by the edge line is identified as the identification zone; if the average gray value of each pixel in the identification zone is less than the average gray value of each pixel in the high-temperature zone, the identification zone is marked as the medium-temperature zone.

[0086] The following is the key source code of the PLC structured text (ST) corresponding to the method for identifying the medium-temperature zone in thermal images:

[0087] METHOD ProcessThermalImage : BOOL

[0088] VAR_INPUT

[0089] ImageData : ARRAY[1..1024, 1..768] OF BYTE; / / Input grayscale image data

[0090] END_VAR

[0091] VAR i, j : INT;

[0092] NewEdges : ARRAY[1..100] OF TemperatureZone;

[0093] EdgeCount : INT := 0;

[0094] CurrentZone : TemperatureZone;

[0095] END_VAR

[0096] / / Step 1: Extract edge lines using the watershed algorithm

[0097] EdgeCount := WatershedAlgorithm(ImageData, NewEdges);

[0098] / / Step 2: Calculate the uniform grayscale

[0099] EquilibriumGray := 0.0;

[0100] FOR i := 1 TO 1024 DO

[0101] FOR j := 1 TO 768 DO

[0102] EquilibriumGray := EquilibriumGray + ImageData[i,j];

[0103] END_FOR

[0104] END_FOR

[0105] EquilibriumGray := EquilibriumGray / (1024 * 768);

[0106] / / Step 3: Mark the hot temperature zone

[0107] FOR i := 1 TO EdgeCount DO

[0108] CurrentZone := NewEdges[i];

[0109] CurrentZone.AverageGray := CalculateAverageGray(CurrentZone.BoundingBox, ImageData);

[0110] IF CurrentZone.AverageGray > EquilibriumGray THEN

[0111] CurrentZone.IsHotZone := TRUE;

[0112] HotZones[i] := CurrentZone; / / Store in the cache

[0113] END_IF

[0114] END_FOR

[0115] / / Step 4: High temperature zone determination

[0116] FOR i := 1 TO EdgeCount DO

[0117] IF HotZones[i].IsHotZone AND NOT HotZones[i].IsHighTempZone THEN

[0118] IF HotZones[i].AverageGray > GrayThreshold THEN

[0119] HotZones[i].IsHighTempZone := TRUE;

[0120] HotZones[i].TriggerTime := CurrentImageTime;

[0121] AddToHighTempZones(HotZones[i]); / / Add to the high-temperature zone array

[0122] END_IF

[0123] END_FOR

[0124] END_METHOD.

[0125] METHOD MonitorMediumZone : BOOL

[0126] VAR_INPUT

[0127] HighZoneID : INT; / / High-temperature zone ID

[0128] CurrentImage: ARRAY[1..1024, 1..768] OF BYTE;

[0129] END_VAR

[0130] VAR

[0131] DetectedSubZones : ARRAY[1..10] OF TemperatureZone;

[0132] SubZoneCount : INT := 0;

[0133] k : INT;

[0134] OriginalAvgGray : REAL := HighTempZones[HighZoneID].AverageGray;

[0135] END_VAR

[0136] / / Step 1: Check if the high-temperature area has disappeared / shrunk

[0137] IF NOT CheckZoneExists(HighZoneID, CurrentImage) THEN

[0138] RecheckHighZone(HighZoneID); / / Relocate the high-temperature zone

[0139] RETURN FALSE;

[0140] END_IF;

[0141] / / Step 2: Identify new edge lines (sub-regions)

[0142] SubZoneCount := DetectSubRegions(HighZoneID, CurrentImage,DetectedSubZones);

[0143] / / Step 3: Mark the medium temperature zone

[0144] FOR k := 1 TO SubZoneCount DO

[0145] IF DetectedSubZones[k].AverageGray < OriginalAvgGray * 0.7 THEN / / Threshold adjustable

[0146] DetectedSubZones[k].IsHighTempZone := FALSE; / / Mark as medium temperature zone

[0147] LogMediumZoneEvent(HighZoneID, DetectedSubZones[k]); / / Log the event

[0148] END_IF

[0149] END_FOR

[0150] END_METHOD.

[0151] Furthermore, in S204, the specific method for controlling the temperature of the aeration tank according to the medium-temperature zone includes:

[0152] If the area of ​​all medium-temperature zones in the most recently acquired thermal image is greater than the area of ​​all medium-temperature zones in the previously acquired thermal image, then the heat source is turned off. After turning off the heat source, if the watershed algorithm cannot detect the existence of an edge line in the area corresponding to the high-temperature zone in the newly acquired thermal image, then the heat source is restarted.

[0153] The grayscale threshold is the grayscale value of the thermal image when the water temperature exceeds 50 degrees Celsius, which is determined in advance.

[0154] Example 2

[0155] The method for monitoring and identifying the medium-temperature zone in Example 1 is replaced with:

[0156] Preferably, the method for monitoring and identifying the medium-temperature zone is as follows: If a new edge line is identified within the corresponding position of the high-temperature zone in the thermal image, the area formed by this edge line is identified as the identification zone; if there is only one identification zone, then if the average gray value of each pixel in the identification zone is less than the average gray value of each pixel in the high-temperature zone, the identification zone is marked as a medium-temperature zone; if there is more than one identification zone, after the identification zone appears, the thermal images are sorted according to the acquisition time order, with i as the sequence number of the thermal image and j as the sequence number of the identification zone in the high-temperature zone. TempA(i) represents the maximum value of the average gray value of all pixels in the corresponding position of the high-temperature zone (excluding the identification zone) in the first to i thermal images; TempB(i,j) represents the high-temperature zone... The average gray level of pixels in the j-th recognition area formed at the corresponding position on the i-th thermal image; the absolute value of the difference between TempB(i,j) and TempA(i) is the temperature difference gray level difference value WC(j) of the j-th recognition area; after sorting the recognition areas except the current recognition area according to the distance between the geometric centroid of each recognition area and the geometric centroid of the current recognition area from smallest to largest, it is determined in turn whether each recognition area of ​​the current recognition area is a virtual merged area of ​​the current recognition area; the method for determining the virtual merged area is: if the temperature difference gray level difference value of the previous recognition area is greater than the temperature difference gray level difference value of the current recognition area, and the temperature difference gray level difference value of the next recognition area is greater than the temperature difference gray level difference value of the current recognition area, then the previous recognition area and the next recognition area are marked as virtual merged areas;

[0157] If the average gray value of each pixel in the recognition area and all corresponding virtual merged areas is less than the average gray value of each pixel in the high temperature area, then the recognition area and all corresponding virtual merged areas are marked as the medium temperature area.

[0158] The following is the key source code of the PLC structured text (ST) corresponding to the method for monitoring and identifying the medium temperature zone in Example 2:

[0159] METHOD IdentifyMediumZones : BOOL

[0160] VAR_INPUT

[0161] HighZoneID : INT; / / High-temperature zone ID

[0162] CurrentImage : ARRAY[1..1024,1..768] OF BYTE;

[0163] END_VAR

[0164] VAR i, j, k : INT;

[0165] CurrentWC : REAL;

[0166] SortedZones : ARRAY[1..5] OF RecognitionZone;

[0167] MergeCandidate : ARRAY[1..5] OF BOOL;

[0168] AvgGrayMainZone : REAL := HighTempZones[HighZoneID].AverageGray;

[0169] BEGIN

[0170] / / Step 1: Detect new edge lines and initialize the recognition area

[0171] ImageHistory[CurrentSeqIndex].ZoneCount :=

[0172] DetectNewEdges(HighZoneID, CurrentImage, ImageHistory[CurrentSeqIndex].Zones);

[0173] / / Step 2: Calculate TempA(i) (historical maximum value)

[0174] IF CurrentSeqIndex = 1 THEN

[0175] ImageHistory[CurrentSeqIndex].TempA := AvgGrayMainZone;

[0176] ELSE

[0177] ImageHistory[CurrentSeqIndex].TempA :=

[0178] MAX(ImageHistory[CurrentSeqIndex-1].TempA, CalcNonZoneGray(HighZoneID, CurrentImage));

[0179] END_IF;

[0180] / / Step 3: Handling the simple case of a single recognition area

[0181] IF ImageHistory[CurrentSeqIndex].ZoneCount = 1 THEN

[0182] IF ImageHistory[CurrentSeqIndex].Zones[1].AverageGray <AvgGrayMainZone THEN

[0183] ImageHistory[CurrentSeqIndex].Zones[1].IsMediumZone :=TRUE;

[0184] END_IF;

[0185] RETURN TRUE;

[0186] END_IF;

[0187] / / Step 4: Multi-recognition area processing flow

[0188] FOR j := 1 TO ImageHistory[CurrentSeqIndex].ZoneCount DO

[0189] / / Calculate WC(j) = |TempB(i,j) - TempA(i)|

[0190] CurrentWC := ABS(ImageHistory[CurrentSeqIndex].Zones[j].AverageGray -

[0191] ImageHistory[CurrentSeqIndex].TempA);

[0192] ImageHistory[CurrentSeqIndex].Zones[j].WC := CurrentWC;

[0193] END_FOR;

[0194] / / Step 5: Sort the recognition areas by geometric centroid distance

[0195] SortedZones := SortZonesByDistance(ImageHistory[CurrentSeqIndex].Zones);

[0196] / / Step 6: Virtual Merge Area Determination

[0197] FOR k := 2 TO ImageHistory[CurrentSeqIndex].ZoneCount-1 DO

[0198] IF (SortedZones[k-1].WC > SortedZones[k].WC) AND

[0199] (SortedZones[k+1].WC > SortedZones[k].WC) THEN

[0200] SortedZones[k-1].IsVirtualMerged := TRUE;

[0201] SortedZones[k+1].IsVirtualMerged := TRUE;

[0202] END_IF;

[0203] END_FOR;

[0204] / / Step 7: Final marking of the medium temperature zone

[0205] FOR j := 1 TO ImageHistory[CurrentSeqIndex].ZoneCount DO

[0206] IF SortedZones[j].IsVirtualMerged THEN CONTINUE; END_IF;

[0207] / / Calculate the joint average gray level of the current recognition area and its virtual merged area

[0208] IF CheckMergedZoneGray(SortedZones, j) < AvgGrayMainZone THEN

[0209] MarkAsMediumZone(SortedZones[j]);

[0210] FOR k := 1 TO ImageHistory[CurrentSeqIndex].ZoneCount DO

[0211] IF SortedZones[k].IsVirtualMerged AND

[0212] IsAdjacentZone(SortedZones[j], SortedZones[k])THEN

[0213] MarkAsMediumZone(SortedZones[k]);

[0214] END_IF;

[0215] END_FOR;

[0216] END_IF;

[0217] END_FOR;

[0218] CurrentSeqIndex := CurrentSeqIndex + 1;

[0219] RETURN TRUE;

[0220] END_METHOD.

[0221] The specific method for controlling the temperature of the aeration tank according to the medium temperature zone in Example 1 is replaced with:

[0222] Preferably, in S204, the specific method for controlling the temperature of the aeration tank according to the medium-temperature zone includes:

[0223] If the area of ​​all medium-temperature zones in the most recently acquired thermal image is larger than the area of ​​all medium-temperature zones in the previous thermal image, then reduce the heat source power by 20%; after reducing the heat source power by 20%, if the area of ​​all medium-temperature zones in the most recently acquired thermal image is smaller than the area of ​​all medium-temperature zones in the previous thermal image, then increase the heat source power by 20%.

[0224] Example 3

[0225] The specific method for controlling the temperature of the aeration tank according to the medium temperature zone in Example 1 is replaced with:

[0226] Preferably, in S204, the specific method for controlling the temperature of the aeration tank according to the medium-temperature zone includes:

[0227] The degree of sustained expansion in the mid-temperature zone is calculated. If the degree of sustained expansion in the mid-temperature zone of the thermal image shows an increasing trend, cooling is performed. If the degree of sustained expansion in the mid-temperature zone of the thermal image shows a decreasing trend, reheating is performed.

[0228] The specific method for calculating the degree of sustained expansion in the mid-temperature region is as follows:

[0229] Iterate through each medium-temperature zone in the high-temperature zone in turn, and take the medium-temperature zone that has been traversed as the current medium-temperature zone. Calculate the degree of maintenance and expansion of the current medium-temperature zone. Specifically, mark the gray difference value of the temperature difference between each medium-temperature zone in the high-temperature zone that is greater than the gray difference value of the current medium-temperature zone as the expansion difference gray value, otherwise mark it as the contraction difference gray value.

[0230] The difference between the expanded grayscale value and the current temperature difference grayscale value in the medium temperature zone is calculated and recorded as the first difference. The sum of all first differences is recorded as the expansion amplitude.

[0231] The difference between the temperature difference grayscale value and the contraction difference grayscale value in the current medium temperature zone is calculated and recorded as the second difference. The sum of all the first differences is recorded as the contraction amplitude. The sum of the expansion amplitude and the contraction amplitude is recorded as the maintenance amplitude.

[0232] The current degree of expansion in the mid-temperature region is the ratio of the expansion amplitude to the maintenance amplitude multiplied by 100;

[0233] The method for performing cooling when the sustained expansion of the mid-temperature zone in the thermal image shows an increasing trend, and performing reheating when the sustained expansion of the mid-temperature zone in the thermal image shows a decreasing trend, is as follows:

[0234] The average degree of sustained expansion of all medium-temperature zones on the most recently acquired thermal image is calculated as the current degree of expansion. The average degree of sustained expansion of all medium-temperature zones on the previously acquired thermal image is calculated as the previous degree of expansion. If the current degree of expansion is greater than the previous degree of expansion, cooling is performed.

[0235] The following is the PLC structured text (ST) key source code corresponding to the specific method for controlling the temperature of the aeration tank according to the medium temperature zone in Example 3:

[0236] METHOD CalculateExpansionRatio : REAL

[0237] VAR_INPUT

[0238] CurrentZoneID : INT; / / Current mid-temperature zone ID

[0239] AllZones : ARRAY[1..20] OF MediumZoneStatus; / / All medium-temperature zone data

[0240] ZoneCount : INT; / / Number of effective intermediate temperature zones

[0241] END_VAR

[0242] VAR i : INT;

[0243] CurrentWC : REAL := AllZones[CurrentZoneID].WC;

[0244] ExpansionSum : REAL := 0.0; / / Expansion range

[0245] ContractionSum : REAL := 0.0; / / Contraction amplitude

[0246] Delta1, Delta2 : REAL;

[0247] BEGIN

[0248] / / Step 1: Calculate the expansion and contraction amplitudes

[0249] FOR i := 1 TO ZoneCount DO

[0250] IF i = CurrentZoneID THEN CONTINUE; END_IF;

[0251] IF AllZones[i].WC > CurrentWC THEN

[0252] Delta1 := AllZones[i].WC - CurrentWC; / / First difference

[0253] ExpansionSum := ExpansionSum + Delta1;

[0254] ELSE

[0255] Delta2 := CurrentWC - AllZones[i].WC; / / Second difference

[0256] ContractionSum := ContractionSum + Delta2;

[0257] END_IF;

[0258] END_FOR;

[0259] / / Step 2: Calculate the degree of expansion maintained (%)

[0260] RETURN (ExpansionSum / (ExpansionSum + ContractionSum)) * 100.0;

[0261] END_METHOD

[0262] METHOD UpdateTemperatureControl : BOOL

[0263] VAR_INPUT

[0264] NewZones : ARRAY[1..20] OF MediumZoneStatus; / / Newly detected medium-temperature zones

[0265] NewZoneCount : INT;

[0266] END_VAR

[0267] VAR

[0268] i, ValidCount : INT;

[0269] RatioSum : REAL := 0.0;

[0270] BEGIN

[0271] / / Step 1: Update the expansion level of all medium-temperature zones

[0272] ValidCount := 0;

[0273] FOR i := 1 TO NewZoneCount DO

[0274] IF NewZones[i].ZoneID = 0 THEN CONTINUE; END_IF; / / Skip invalid entries

[0275] NewZones[i].ExpansionRatio :=

[0276] CalculateExpansionRatio(i, NewZones, NewZoneCount);

[0277] NewZones[i].Timestamp := NOW();

[0278] MediumZones[i] := NewZones[i]; / / Save to global range

[0279] RatioSum := RatioSum \+ NewZones[i].ExpansionRatio;

[0280] ValidCount := ValidCount + 1;

[0281] END_FOR;

[0282] / / Step 2: Calculate the average degree of expansion

[0283] PrevExpansionAvg := CurrentExpansionAvg;

[0284] IF ValidCount > 0 THEN

[0285] CurrentExpansionAvg := RatioSum / ValidCount;

[0286] ELSE

[0287] CurrentExpansionAvg := 0.0;

[0288] END_IF;

[0289] / / Step 3: Temperature Control Decision

[0290] CoolingOutput := FALSE;

[0291] HeatingOutput := FALSE;

[0292] IF CurrentExpansionAvg > PrevExpansionAvg AND PrevExpansionAvg >0 THEN

[0293] CoolingOutput := TRUE; / / Trigger cooling

[0294] ELSIF CurrentExpansionAvg < PrevExpansionAvg THEN

[0295] HeatingOutput := TRUE; / / Trigger heating recovery

[0296] END_IF;

[0297] RETURN TRUE;

[0298] END_METHOD

[0299] PROGRAM MAIN

[0300] VAR

[0301] ThermalCycleCounter : INT := 0;

[0302] NewMediumZones : ARRAY[1..20] OF MediumZoneStatus;

[0303] DetectedZoneCount : INT;

[0304] BEGIN

[0305] / / Performed once every 5 scan cycles (can be adjusted according to the thermal imager's frame rate)

[0306] IF ThermalCycleCounter MOD 5 = 0 THEN

[0307] / / Simulate to obtain the latest mid-temperature range data (in practice, this needs to be replaced with a detection function).

[0308] DetectedZoneCount := GetLatestMediumZones(NewMediumZones);

[0309] / / Update control state

[0310] UpdateTemperatureControl(NewMediumZones, DetectedZoneCount);

[0311] / / Output control signal

[0312] IF CoolingOutput THEN

[0313] ActivateCoolingValve(OPEN_PERCENT := 70); / / Open the cooling valve to 70%

[0314] ELSIF HeatingOutput THEN

[0315] ActivateHeater(POWER := 50); / / Heater at 50% power

[0316] END_IF;

[0317] END_IF;

[0318] ThermalCycleCounter := ThermalCycleCounter + 1;

[0319] END_PROGRAM.

[0320] Furthermore, in S204, the cooling process is as follows: turn off the heat source. After turning off the heat source, if the watershed algorithm cannot detect the edge line in the area corresponding to the high temperature zone in the newly acquired thermal image, restart the heat source.

[0321] Preferably, the cooling process involves controlling the heat source using a PLC control system.

[0322] Comparative example:

[0323] S100, after coarse filtration of the effluent, is discharged into a sedimentation tank for sedimentation treatment to obtain settled water.

[0324] S200 discharges the settled water through a filter dam into an aeration tank for nitrification and denitrification.

[0325] The sedimentation tank and other conditions used in the comparative examples were the same as those in Examples 1, 2, and 3.

[0326] Apart from the specific methods of nitrification and denitrification in Examples 1, 2, and 3, the aeration process is simply carried out by using a heat source and equipment installed in the aeration tank: microporous aerator (pore size 50μm, oxygen utilization rate ≥25%).

[0327] Submersible mixer (3kW power, 120rpm speed);

[0328] Nitrification stage: Turn on the microporous aerator (air-to-water ratio 8:1), maintain DO=3mg / L, pH=7.5~8.0. Ammonia nitrogen (NH4⁺) is converted to NO3⁻.

[0329] Denitrification stage: Turn off aeration, start the mixer (120 rpm), and add sodium acetate (C / N=4:1). NO3⁻ is reduced to N2.

[0330] Test results:

[0331] After one week of treatment of the effluent using Examples 1, 2, 3 and the comparative example, the concentration of N2O at a position 30 cm above the aeration tank was measured using an N2O gas sensor within 24 hours. The results showed that the maximum N2O concentration was low in Example 1 (<0.5%), low in Example 2 (<0.3%), and low in Example 3 (<0.3%), while the maximum N2O concentration was high in the comparative example (>5%).

[0332] It is evident that Examples 1, 2, and 3 significantly improved the N2O concentration escaping from the aeration tank compared to the comparative example.

[0333] This invention also provides an embodiment of a computer system, which is a multi-stage treatment system for aquaculture wastewater, such as... Figure 1 The diagram shows a multi-stage treatment system for aquaculture wastewater according to the present invention. This embodiment of the multi-stage treatment system for aquaculture wastewater includes: a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps described in the embodiment of the multi-stage treatment system for aquaculture wastewater.

[0334] The system includes: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program in units of the following system:

[0335] The aeration tank heating unit is used to heat the effluent in the aeration tank using a heat source.

[0336] The thermal image acquisition unit is used to acquire thermal images of the effluent surface in the aeration tank at fixed time intervals using infrared imaging.

[0337] The medium-temperature zone recognition unit is used to identify the medium-temperature zone appearing in the thermal image;

[0338] The medium-temperature zone temperature control unit is used to control the temperature of the aeration tank according to the medium-temperature zone.

[0339] The aforementioned multi-stage aquaculture wastewater treatment system can run on computing devices such as desktop computers, laptops, handheld computers, cloud servers, and PLC control systems. The system that can run on this multi-stage aquaculture wastewater treatment system may include, but is not limited to, processors and memory. Those skilled in the art will understand that the example described is merely an illustration of a multi-stage aquaculture wastewater treatment system and does not constitute a limitation on such a system. It may include more or fewer components, or a combination of certain components, or different components. For example, the aforementioned multi-stage aquaculture wastewater treatment system may also include input / output devices, network access devices, buses, etc.

[0340] The processor referred to can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor. The processor is the control center of the multi-stage aquaculture wastewater treatment system, connecting various parts of the system via various interfaces and lines.

[0341] The memory can be used to store the computer programs and / or modules. The processor implements various functions of the multi-stage aquaculture wastewater treatment system by running or executing the computer programs and / or modules stored in the memory and calling the data stored in the memory. The memory may mainly include a program storage area and a data storage area. The program storage area may store the operating system, at least one application program required for a function (such as sound playback function, image playback function, etc.), etc.; the data storage area may store data created based on the use of the mobile phone (such as audio data, phonebook, etc.). In addition, the memory may include high-speed random access memory, and may also include non-volatile memory, such as hard disk, memory, plug-in hard disk, smart media card (SMC), secure digital card (SD card), flash card, at least one disk storage device, flash memory device, or other volatile solid-state storage device.

[0342] Although the invention has been described in considerable detail and particularly with regard to several of the described embodiments, it is not intended to limit itself to any of these details or embodiments or any particular embodiment, thereby effectively covering the intended scope of the invention. Furthermore, the invention has been described above with respect to embodiments foreseeable by the inventors in order to provide a useful description, and non-substantial modifications to the invention that have not yet been foreseen may still represent equivalent modifications.

[0343] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A multi-stage treatment method for aquaculture wastewater, characterized in that, The method includes the following steps: S100, after coarse filtration of the effluent, is discharged into a sedimentation tank for sedimentation treatment to obtain settled water. S200 discharges the settled water through a filter dam into an aeration tank for nitrification and denitrification treatment. The specific methods for nitrogen removal through nitrification and denitrification include: S201, heats the effluent in the aeration tank using a heat source; S202, thermal images of the effluent surface in the aeration tank are acquired at fixed time intervals using infrared imaging; S203 identifies the mid-temperature zone appearing in the thermal image; S204, control the temperature of the aeration tank according to the medium temperature zone; In S203, the method for identifying the intermediate temperature zone in a thermal image includes the following steps: The edge lines of the grayscale images after graying are extracted using the watershed algorithm. Each edge line divides the image into multiple different temperature difference regions. The average gray level of all points on the grayscale image is taken as the equilibrium gray level. The temperature difference regions where the average gray level of all points is greater than the equilibrium gray level are marked as the hot temperature regions. According to the acquisition time sequence, the initial high temperature zone is located for each grayscale image corresponding to each thermal image in turn: if the average gray value of each point in the hot temperature zone of a grayscale image exceeds the gray value threshold for the first time, the hot temperature zone is marked as a high temperature zone, and the acquisition time of the thermal image corresponding to the high temperature zone is the trigger time of the high temperature zone. For all high-temperature zones, starting from the trigger time corresponding to each high-temperature zone, the location of the high-temperature zone on the thermal image acquired after the trigger time is monitored and identified as a medium-temperature zone. The method for monitoring and identifying the medium-temperature zone is as follows: if a new edge line is identified within the corresponding position of the high-temperature zone in the thermal image, the area formed by the edge line is identified as the identification zone; if the average gray value of each pixel in the identification zone is less than the average gray value of each pixel in the high-temperature zone, the identification zone is marked as the medium-temperature zone.

2. The multi-stage treatment method for aquaculture wastewater according to claim 1, characterized in that, The specific method for nitrogen removal treatment by nitrification and denitrification in the aeration tank is as follows: nitrogen removal in the effluent is achieved through the synergistic action of nitrifying and denitrifying bacteria. Nitrogen removal in the effluent consists of two stages: nitrification and denitrification. Under aerobic conditions, nitrifying bacteria convert ammonia nitrogen into nitrite and nitrate in sequence. Under anoxic conditions, denitrifying bacteria reduce nitrate to nitrogen gas.

3. The multi-stage treatment method for aquaculture wastewater according to claim 1, characterized in that, The method for monitoring and identifying medium-temperature zones is replaced as follows: If a new edge line is identified within the corresponding position of the high-temperature zone in the thermal image, the area formed by this edge line is identified as the identification zone; if there is only one identification zone, then if the average gray value of each pixel in the identification zone is less than the average gray value of each pixel in the high-temperature zone, the identification zone is marked as a medium-temperature zone; if there is more than one identification zone, after the identification zone appears, the thermal images are sorted according to the acquisition time order, with i as the sequence number of the thermal image and j as the sequence number of the identification zone in the high-temperature zone. Let TempA(i) represent the maximum value of the average gray value of all pixels in the high-temperature zone other than the identification zone within the corresponding position on the first to i thermal images. Let TempB(i,j) represent the average gray level of the pixel in the j-th recognition area formed at the corresponding position of the high temperature area on the i-th thermal image; Let the absolute value of the difference between TempB(i,j) and TempA(i) be WC(j), which is the temperature difference grayscale difference value of the j-th recognition area. Sort all recognition areas except the current recognition area according to the distance between the geometric centroid of each recognition area and the geometric centroid of the current recognition area from smallest to largest. Then, determine whether each recognition area of ​​the current recognition area is a virtual merged area of ​​the current recognition area. If the average gray value of each pixel in the recognition area and all corresponding virtual merged areas is less than the average gray value of each pixel in the high temperature area, then mark the recognition area and all corresponding virtual merged areas as the medium temperature area.

4. The multi-stage treatment method for aquaculture wastewater according to claim 3, characterized in that, The method for determining the virtual merging area is as follows: if the temperature difference grayscale difference value of the previous identification area is greater than that of the current identification area, and the temperature difference grayscale difference value of the next identification area is greater than that of the current identification area, then the previous identification area and the next identification area are marked as virtual merging areas.

5. The multi-stage treatment method for aquaculture wastewater according to claim 4, characterized in that, In S204, the specific method for controlling the temperature of the aeration tank according to the medium temperature zone includes: if the area of ​​all medium temperature zones on the most recently acquired thermal image is greater than the area of ​​all medium temperature zones on the previous thermal image, then the heat source is turned off; after the heat source is turned off, if on a newly acquired thermal image, the area of ​​all medium temperature zones on the most recently acquired thermal image is less than the area of ​​all medium temperature zones on the previous thermal image, then the heat source is restarted.

6. The multi-stage treatment method for aquaculture wastewater according to claim 4, characterized in that, In S204, the specific method of controlling the temperature of the aeration tank according to the medium temperature zone is replaced by: calculating the degree of maintenance expansion of the medium temperature zone; when the degree of maintenance expansion of the medium temperature zone in the thermal image shows an increasing trend, cooling is performed; when the degree of maintenance expansion of the medium temperature zone in the thermal image shows a decreasing trend, reheating is performed.

7. A multi-stage treatment system for aquaculture wastewater, characterized in that, The multi-stage treatment system for aquaculture wastewater includes: a processor, a memory, and a computer script program stored in the memory and running on the processor. When the processor executes the computer script program, it implements the steps of the multi-stage treatment method for aquaculture wastewater according to any one of claims 1-6.

Images