An on-line wastewater toxicity detection system and method based on nitrifying bacteria biofilm

Abstract

The present invention discloses an on-line wastewater toxicity detection system and method based on nitrifying bacteria biofilm. The present invention uses nitrifying bacteria as a model organism, ensures the concentration of the bacterial community through the biofilm, and at the same time avoids the interference of miscellaneous bacteria through ultraviolet sterilization; by flushing the nutrient solution in the intermittent stage, the biological activity of nitrifying bacteria is protected, providing a highly sensitive and highly stable method and equipment for wastewater toxicity detection. By detecting the concentration of dissolved oxygen in the solutions flowing into and out of the nitrifying bacteria biofilm reactor, the toxicity of wastewater can be evaluated quickly and with high stability. When the wastewater flows through the biofilm reactor, its toxicity can be evaluated in real time through the rate of dissolved oxygen consumption by the nitrifying bacteria biofilm.

Description

Technical Field

[0001] The present invention belongs to the technical field of on-line wastewater detection, and particularly relates to an on-line wastewater toxicity detection system and method based on nitrifying bacteria biofilm. Background Art

[0002] Industrial wastewater often contains various toxic pollutants, such as heavy metals (copper, cobalt, lead, etc.), cyanides / cyanic acid, phenols, thiols, anilines, halogenated hydrocarbons, etc., which can inhibit the biological activity of activated sludge, interfere with the normal operation of sewage treatment plants, and reduce the treatment load. Therefore, toxicity testing of wastewater is a necessary technology for optimizing the operation of industrial sewage treatment plants and a necessary tool for ensuring the stable operation of sewage treatment plants. Commonly used toxicity testing technologies generally include the luminescent bacteria method, the zebrafish method, the cell culture method, and the biological respiration rate method. Among them, the first three methods are cumbersome to operate, the equipment is complex, and the data fluctuates greatly, while the biological respiration method feeds back the biological inhibition by measuring the oxygen consumption rate of aerobic microorganisms, and the equipment is simple and highly sensitive.

[0003] The traditional respiration method uses activated sludge as the test flora. However, activated sludge belongs to a typical mixed flora, and the flora in different water plants varies greatly, and their toxicity feedback to pollutants also has great differences. Therefore, the repeatability of the test results of this method is poor. Summary of the Invention

[0004] The purpose of this part is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Simplifications or omissions may be made in this part, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this part, the abstract, and the title, and such simplifications or omissions shall not be used to limit the scope of the present invention.

[0005] As one aspect of the present invention, the present invention provides an on-line wastewater toxicity detection system based on nitrifying bacteria biofilm, which includes,

[0006] An aeration unit, the aeration unit includes a feed tank, an aeration device is arranged in the feed tank, the aeration device continuously introduces air or oxygen into the feed tank through an air pump, an ultraviolet sterilization lamp is arranged at the top of the feed tank; a second dissolved oxygen detector is connected to the feed tank; a pure water tank is connected to the feed tank through a pure water input pump and a pure water input valve; a nutrient solution tank is connected to the feed tank through a nutrient solution input pump and a nutrient solution input valve; a wastewater tank is connected to the feed tank through a wastewater input pump and a wastewater input valve;

[0007] A wastewater detection unit, including a biofilm reactor connected to the feed tank through a biofilm reactor input valve and a biofilm reactor input pump, and a filler is laid in the biofilm reactor; a first dissolved oxygen detector is connected to the biofilm reactor.

[0008] As a preferred embodiment of the on-line wastewater toxicity detection system based on nitrifying bacteria biofilm of the present invention: a drain valve of the feed tank is provided on the outlet pipe of the feed tank.

[0009] As a preferred embodiment of the on-line wastewater toxicity detection system based on nitrifying bacteria biofilm of the present invention: a drain valve of the biofilm reactor is provided on the outlet pipe of the biofilm reactor.

[0010] As a preferred embodiment of the on-line wastewater toxicity detection system based on nitrifying bacteria biofilm of the present invention: the input pump of the biofilm reactor is connected to the lower end of the biofilm reactor; a drain port is provided at the upper end of the biofilm reactor.

[0011] As a preferred embodiment of the on-line wastewater toxicity detection system based on nitrifying bacteria biofilm of the present invention: the input pump of the biofilm reactor is connected to the upper end of the biofilm reactor, and a drain port is provided at the lower end of the biofilm reactor.

[0012] As another aspect of the present invention, the present invention provides an on-line wastewater toxicity detection method based on nitrifying bacteria biofilm, which uses the on-line wastewater toxicity detection system based on nitrifying bacteria biofilm, and the detection method includes the following two stages:

[0013] Intermittent stage: Open the pure water input valve and the nutrient solution input valve. Under the action of the pure water input pump and the nutrient solution input pump, pure water and nutrient solution are respectively input into the feed tank, and are sterilized by the ultraviolet sterilization lamp in the feed tank. When the feed tank is full, stop the operation of the pure water input pump and the nutrient solution input pump. The aeration device inputs air or oxygen into the feed tank to make the dissolved oxygen concentration saturated. The second dissolved oxygen detector records the dissolved oxygen concentration of the solution in the feed tank at this time. Then, the solution in the feed tank is input into the biofilm reactor under the action of the biofilm reactor input pump and is in full contact with the filler. After that, the dissolved oxygen concentration at this time is measured by the first dissolved oxygen detector, and then the solution flows out from the outlet of the biofilm reactor.

[0014] Detection stage: First, close the input valves of the biofilm reactor, pure water input pump, nutrient solution input pump, wastewater input pump, pure water input valve, nutrient solution input valve, and wastewater input valve, open the feed tank drain valve, and drain the solution in the feed tank; then, open the pure water input pump, nutrient solution input pump, wastewater input pump, pure water input valve, nutrient solution input valve, and wastewater input valve, input wastewater, nutrient solution, and pure water into the feed tank, and sterilize them by irradiating with an ultraviolet sterilization lamp in the feed tank. When the feed tank is full, stop the operation of the pure water input pump, nutrient solution input pump, and wastewater input pump. The aeration device introduces air or oxygen into the feed tank to make the dissolved oxygen concentration saturated. Record the dissolved oxygen concentration of the solution in the feed tank at this time through the second dissolved oxygen detector. Then, the solution in the feed tank is input into the biofilm reactor by the biofilm reactor input pump. The solution in the feed tank is input into the biofilm reactor and comes into full contact with the packing. Then, measure the dissolved oxygen concentration at this time through the first dissolved oxygen detector. Then, the solution flows out from the outlet of the biofilm reactor, calculate the difference in dissolved oxygen measured by the second dissolved oxygen detector and the first dissolved oxygen detector. After the difference is stable, calculate the biological toxicity of the wastewater.

[0015] As a preferred embodiment of the wastewater on-line toxicity detection method based on nitrifying bacteria biofilm of the present invention: The ratio of the horizontal cross-sectional area to the height of the biofilm reactor is 0.2 - 2; the materials of the packing include zeolite and polyethylene. The filling height of the packing in the biofilm reactor is greater than 20% of the height of the biofilm reactor. The packing is loaded with nitrifying bacteria, and the nitrifying bacteria form a biofilm on the surface of the packing.

[0016] As a preferred embodiment of the wastewater on-line toxicity detection method based on nitrifying bacteria biofilm of the present invention: The nutrient solution is composed of ammonium salt, sodium bicarbonate, phosphate, potassium salt, and trace elements, and its pH is 6.0 - 10.0; the ammonia nitrogen concentration in the nutrient solution is 60 - 70 mg / L.

[0017] As a preferred embodiment of the wastewater on-line toxicity detection method based on nitrifying bacteria biofilm of the present invention: The solution in the feed tank is input into the biofilm reactor under the action of the biofilm reactor input pump at a flushing speed of 6 - 7 meters per hour.

[0018] As a preferred embodiment of the wastewater on-line toxicity detection method based on nitrifying bacteria biofilm of the present invention: When calculating the biological toxicity of the wastewater, the calculation formula is: 100%·(k C -k S ) / k C , where k S is the consumption rate of dissolved oxygen in the detection stage, and k C is the consumption rate of dissolved oxygen in the intermittent stage. Among them, the rate k SObtained by dividing the difference between the second dissolved oxygen detector and the first dissolved oxygen detector in the detection stage by the residence time of the solution in the packing, the rate k C Obtained by dividing the difference between the second dissolved oxygen detector and the first dissolved oxygen detector in the intermittent stage by the residence time of the solution in the packing.

[0019] Advantages of the present invention: The present invention uses nitrifying bacteria as a model organism, ensures the concentration of the bacterial community through a biofilm, and at the same time avoids interference from miscellaneous bacteria through ultraviolet lamp sterilization; by flushing the nutrient solution in the intermittent stage, the biological activity of nitrifying bacteria is protected, providing a highly sensitive and highly stable method and device for wastewater toxicity detection. By detecting the concentration of dissolved oxygen in the solution flowing into and out of the nitrifying bacteria biofilm reactor, the toxicity of the wastewater can be evaluated quickly and with high stability. When the wastewater flows through the biofilm reactor, its toxicity can be evaluated in real time through the rate at which the nitrifying bacteria biofilm consumes dissolved oxygen. Description of the Drawings

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings. Among them:

[0021] Figure 1 It is a schematic diagram of an upflow nitrifying bacteria biofilm reactor.

[0022] Figure 2 It is a schematic diagram of a downflow nitrifying bacteria biofilm reactor.

[0023] Figure 3 It is the difference in dissolved oxygen before and after the solution of Research Example 1 enters the nitrifying bacteria biofilm reactor 1.

[0024] Figure 4 It is the difference in dissolved oxygen before and after the solution of Research Example 2 enters the nitrifying bacteria biofilm reactor 1.

[0025] In the figure: 1. Biofilm reactor; 2. Packing; 3. First dissolved oxygen detector; 4. Feed tank; 5. Ultraviolet sterilization lamp; 6. Second dissolved oxygen detector; 7. Pure water tank; 8. Nutrient solution tank; 9. Wastewater tank; 10. Air pump; 11. Aeration device; 12. Biofilm reactor input valve; 13. Pure water input pump; 14. Nutrient solution input pump; 15. Wastewater input pump; 16. Biofilm reactor input pump; 17. Pure water input valve; 18. Nutrient solution input valve; 19. Wastewater input valve; 20. Biofilm reactor drain valve; 21. Feed tank drain valve. Detailed Embodiments

[0026] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention will be given in conjunction with specific embodiments.

[0027] Embodiment 1:

[0028] As Figure 1 shown, the wastewater on-line toxicity detection system based on a nitrifying bacteria biofilm reactor of the present invention includes an aeration unit. The aeration unit includes a feed tank 4, in which an aeration device 11 is provided. The aeration device 11 continuously introduces air or oxygen into the feed tank 4 through an air pump 10, so that the dissolved oxygen in the feed tank 4 reaches a saturated state; an ultraviolet sterilization lamp 5 is provided at the top inside the feed tank 4; a second dissolved oxygen detector 6 is connected to the feed tank 4, and the second dissolved oxygen detector 6 is used to measure the dissolved oxygen content in the feed tank 4; a pure water tank 7 is connected to the feed tank 4 through a pure water input pump 13 and a pure water input valve 17; a nutrient solution tank 8 is connected to the feed tank 4 through a nutrient solution input pump 14 and a nutrient solution input valve 18; a wastewater tank 9 is connected to the feed tank 4 through a wastewater input pump 15 and a wastewater input valve 19;

[0029] a wastewater detection unit, including a biofilm reactor 1 connected to the feed tank 4 through a biofilm reactor input valve 12 and a biofilm reactor input pump 16. A filler 2 is laid in the biofilm reactor 1; a first dissolved oxygen detector 3 is connected to the biofilm reactor 1, and the first dissolved oxygen detector is used to measure the dissolved oxygen content in the filler 2 in the biofilm reactor 1.

[0030] Nitrifying bacteria are inoculated in the filler 2, so that a biofilm structure mainly composed of nitrifying bacteria is formed on the surface of the filler.

[0031] The wastewater on-line toxicity detection method based on a nitrifying bacteria biofilm reactor: The filler 2 in the biofilm reactor 1 is zeolite (particle size 2-4 mm). Preferably, the width of the biofilm reactor 1 is 8.1 cm; the effective height is 90 cm; the filling height of the filler 2 in the biofilm reactor 1 is 30 cm. Nitrifying bacteria are inoculated on the zeolite of the filler 2, so that a biofilm structure mainly composed of nitrifying bacteria is formed on the surface of the filler. Preferably, the nitrifying bacteria concentration in the biofilm reactor 1 is 0.11 g / L. The feed tank 4 is preferably a sealed container with a volume of 5 L. An aeration device 11 is provided at the bottom inside the feed tank 4 to increase the dissolved oxygen concentration of the solution, and an ultraviolet sterilization lamp 5 is provided at the top inside the feed tank 4 to kill the miscellaneous bacteria in the feed tank so as to protect the nitrifying bacteria in the biofilm reactor 1. The pure water tank 7 contains pure water (distilled water), the nutrient solution tank 8 contains nutrient solution (the nutrient solution is used to supply the growth of nitrifying bacteria), and the wastewater tank 9 contains wastewater; the nutrient solution, pure water, and wastewater are mixed evenly in the feed tank 4 according to the required ratio by adjusting the flow rate of the water pump. After a certain period of aeration, the dissolved oxygen reaches saturation and is input into the biofilm reactor 1 through the biofilm reactor input pump 16.

[0032] Preferably, the nutrient solution is composed of 14 g / L ammonium sulfate, 11 g / L sodium bicarbonate, 3 g / L dipotassium hydrogen phosphate and 3 g / L potassium dihydrogen phosphate. The wastewater toxicity detection is divided into an intermittent stage and a detection stage; in the intermittent stage, the nutrient solution and pure water are input into the feed tank 4 at a flow rate ratio of 11:539 under the action of the pure water input pump 13 and the nutrient solution input pump 14 through the pure water input valve 17 and the nutrient solution input valve 18, and are sterilized by the ultraviolet sterilization lamp 5 in the feed tank 4. When the feed tank 4 is filled, the operation of the pure water input pump 13 and the nutrient solution input pump 14 is stopped, and the aeration device 11 introduces air or oxygen into the feed tank 4 to make the dissolved oxygen concentration saturated. The dissolved oxygen concentration of the solution in the feed tank 4 at this time is recorded by the second dissolved oxygen detector 6. Then, the solution in the feed tank 4 is input into the biofilm reactor 1 from the lower end at a flushing speed of 6.5 meters per hour through the biofilm reactor input pump 16. There is packing zeolite in the biofilm reactor 1. The solution in the feed tank 4 is input into the biofilm reactor 1 and is in full contact with the packing 2, that is, the solution in the feed tank 4 is in full contact with nitrifying bacteria. Then, the dissolved oxygen concentration at this time is measured by the first dissolved oxygen detector 3. Then the solution flows out from the upper outlet of the biofilm reactor 1, and the difference in dissolved oxygen measured by the second dissolved oxygen detector 6 and the first dissolved oxygen detector 3 is calculated. After the difference is stable, the operation of the intermittent stage is ended and the wastewater toxicity detection stage is entered.

[0033] Detection stage: Taking 2,4-dichlorophenol with a concentration of 10 mg / L as an example of simulated industrial wastewater: In the wastewater toxicity detection stage, first close the biofilm reactor input valve 12, pure water input pump 13, nutrient solution input pump 14, wastewater input pump 15, pure water input valve 17, nutrient solution input valve 18 and wastewater input valve 19, and open the feed tank drain valve 21 to drain the solution in the feed tank 4; then, open the pure water input pump 13, nutrient solution input pump 14, wastewater input pump 15, pure water input valve 17, nutrient solution input valve 18 and wastewater input valve 19, and input wastewater, nutrient solution and pure water into the feed tank 4 at a ratio of 13.8:11:525.2. The three liquids are mixed in the feed tank 4 and are sterilized by the ultraviolet sterilization lamp 5 in the feed tank 4. When the feed tank 4 is filled, stop the operation of the pure water input pump 13, nutrient solution input pump 14 and wastewater input pump 15.

[0034] The aeration device 11 introduces air or oxygen into the feed tank 4 to saturate the dissolved oxygen concentration. The dissolved oxygen concentration of the solution in the tank 4 is recorded by the second dissolved oxygen detector 6. Then, the solution in the feed tank 4 is input into the biofilm reactor 1 through the biofilm reactor input pump 16 at a flushing speed of 6.5 meters per hour. There is packing zeolite in the biofilm reactor 1. The solution in the feed tank 4 is input into the biofilm reactor 1 and comes into full contact with the packing 2, that is, the solution in the feed tank 4 comes into full contact with nitrifying bacteria. Then, the dissolved oxygen concentration is measured by the first dissolved oxygen detector 3. Then the solution flows out from the outlet at the upper end of the biofilm reactor 1. The difference in dissolved oxygen measured by the second dissolved oxygen detector 6 and the first dissolved oxygen detector 3 is calculated. After the difference is stable, the biological toxicity of 2,4-dichlorophenol at different concentrations (that is, the inhibition rate of the wastewater solution on nitrifying bacteria) is calculated.

[0035] Adjust the liquid flow rates of the pure water input pump 13, the nutrient solution input pump 14, and the wastewater input pump 15 so that the mixing ratios of wastewater, nutrient solution, and pure water are 27.5∶11∶511.5, 55∶11∶484, 110∶11∶429, 220∶11∶319, 275∶11∶264 respectively. Calculate the biological toxicity of 2,4-dichlorophenol at different concentrations (that is, the inhibition rate of the wastewater solution on nitrifying bacteria). The calculation method is as follows:

[0036] 100%·(k C -k S ) / k C

[0037] Where k S is the consumption rate of dissolved oxygen in the detection stage, and k C is the consumption rate of dissolved oxygen in the intermittent stage. Among them, the rate k S is obtained by dividing the difference between the second dissolved oxygen detector 6 and the first dissolved oxygen detector 3 in the detection stage by the residence time of the solution in the packing. The rate k C is obtained by dividing the difference between the second dissolved oxygen detector 6 and the first dissolved oxygen detector 3 in the intermittent stage by the residence time of the solution in the packing.

[0038] This formula reflects the inhibition rate of the wastewater on the activity of nitrifying bacteria by the change in the rate of dissolved oxygen consumption by nitrifying bacteria in the wastewater solution, thereby reflecting the toxicity level of toxic substances in the wastewater.

[0039] The calculation results are shown in Table 1.

[0040] Table 1 Toxicity test results of simulated wastewater with different concentrations of 2,4-dichlorophenol

[0041] Concentration [mg / L] Nitrifying bacteria inhibition rate [%] 0.5 4 1 11 2 21 4 46 5 67

[0042] According to the experimental results in Table 1, a standard curve is drawn, and EC is calculated.50 It is about 4.1 mg / L or so, indicating that the on-line wastewater toxicity detection system of the present invention has very high sensitivity.

[0043] In summary, the present invention uses nitrifying bacteria as a model organism, ensures the concentration of the bacterial community through a biofilm, and at the same time avoids the interference of miscellaneous bacteria through ultraviolet sterilization; by flushing the nutrient solution in the intermittent stage, the biological activity of nitrifying bacteria is protected, providing a highly sensitive and highly stable method and equipment for wastewater toxicity detection. By detecting the concentration of dissolved oxygen in the solutions flowing into and out of the nitrifying bacteria biofilm reactor, the toxicity of wastewater can be evaluated quickly and with high stability. When the wastewater flows through the biofilm reactor, its toxicity can be evaluated in real time through the rate at which the nitrifying bacteria biofilm consumes dissolved oxygen.

[0044] Research Example 1:

[0045] Reference Figure 3 , to study whether the flow rate of the solution in the biofilm reactor 1 affects the rate at which nitrifying bacteria consume dissolved oxygen during the intermittent stage. The difference between this research example and Example 1 is that the solutions in the feed tank 4 are respectively input into the biofilm reactor 1 from the lower end through the biofilm reactor input pump 16 at flushing speeds of 6.75, 3.73, 12, 10.48, and 9.31 meters per hour, and the remaining conditions are exactly the same as those in the intermittent stage of Example 1. The difference in dissolved oxygen before and after the solution enters the nitrifying bacteria biofilm reactor 1 is as Figure 3 shown. As can be seen from Figure 3 , the flow rate of the solution in the biofilm reactor 1 will affect the rate at which nitrifying bacteria consume dissolved oxygen. In Figure 3 , the "inlet water" curve represents the dissolved oxygen concentration value measured by the first dissolved oxygen detector 3, and the "outlet water" curve represents the dissolved oxygen concentration value measured by the second dissolved oxygen detector 6. As can be obtained from Figure 3 , when the flow rate of the solution in the biofilm reactor 1 is too fast, since the nitrifying bacteria do not fully utilize the dissolved oxygen in the solution, the dissolved oxygen concentration value measured by the second dissolved oxygen detector 6 is relatively high. When the flow rate of the solution in the biofilm reactor 1 is too slow, there is too little dissolved oxygen, resulting in too low a dissolved oxygen concentration value measured by the second dissolved oxygen detector 6 at the outlet. Therefore, when the flushing speed of 6.75 meters per hour is the optimal one, this flushing speed ensures that the nitrifying bacteria can fully utilize the dissolved oxygen under the condition of sufficient dissolved oxygen supply, preparing for the subsequent accurate detection of wastewater toxicity. The flow rate of the solution in the biofilm reactor 1 is preferably 6 - 7 meters per hour.

[0046] Research Example 2:

[0047] Reference Figure 4, study whether the flow rate ratio of nutrient solution to pure water affects the rate of dissolved oxygen consumption by nitrifying bacteria during the intermittent stage. The difference between this study example and Example 1 is that the flow rate ratios of nutrient solution to pure water are 0:550, 3.7:546.3, 11:539, and 18.5:531.5 (corresponding to ammonia nitrogen concentrations of 0, 20, 60, and 100 mg / L in the solution respectively), and the remaining conditions are exactly the same as those in the intermittent stage of Example 1. The difference in dissolved oxygen before and after the solution enters the nitrifying bacteria biofilm reactor 1 is as Figure 4 shown. It can be seen from Figure 4 that the concentration of nutrient solution in the solution will affect the rate of dissolved oxygen consumption by nitrifying bacteria, and the optimal flow rate ratio of nutrient solution to pure water is 11:539 (ammonia nitrogen concentration 60 mg / L).

[0048] Example 2:

[0049] Referring to Figure 2 , the difference between this example and Example 1 is that in this example, a downflow biofilm reactor is used. The input pump 16 of the biofilm reactor inputs the solution into the biofilm reactor 1 from the upper end of the biofilm reactor 1, and the solution flows out from the outlet at the lower end of the biofilm reactor 1. The remaining conditions are the same as those in Example 1.

[0050] It should be noted that the above examples are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. An on-line wastewater toxicity detection method based on nitrifying bacteria biofilm, characterized in that: An on-line wastewater toxicity detection system based on nitrifying bacteria biofilm is adopted. The on-line wastewater toxicity detection system based on nitrifying bacteria biofilm includes an aeration unit. The aeration unit includes a feed tank (4). An aeration device (11) is arranged in the feed tank (4). The aeration device (11) continuously introduces air or oxygen into the feed tank (4) through an air pump (10). An ultraviolet sterilization lamp (5) is arranged at the top inside the feed tank (4); A second dissolved oxygen detector (6) is connected to the feed tank (4); A pure water tank (7) is connected to the feed tank (4) through a pure water input pump (13) and a pure water input valve (17); A nutrient solution tank (8) is connected to the feed tank (4) through a nutrient solution input pump (14) and a nutrient solution input valve (18); A wastewater tank (9) is connected to the feed tank (4) through a wastewater input pump (15) and a wastewater input valve (19); The on-line wastewater toxicity detection system based on nitrifying bacteria biofilm further includes a wastewater detection unit, including a biofilm reactor (1) connected to the feed tank (4) through a biofilm reactor input valve (12) and a biofilm reactor input pump (16). Packing (2) is laid in the biofilm reactor (1). Nitrifying bacteria are loaded on the packing (2). The nitrifying bacteria form a biofilm on the surface of the packing (2); A first dissolved oxygen detector (3) is connected to the biofilm reactor (1); A feed tank drain valve (21) is arranged on the water outlet pipeline of the feed tank (4); The biofilm reactor input pump (16) is connected to the lower end of the biofilm reactor (1); A drain port is arranged at the upper end of the biofilm reactor (1); The detection method includes the following two stages: Intermittent stage: Open the pure water input valve (17) and the nutrient solution input valve (18). Under the action of the pure water input pump (13) and the nutrient solution input pump (14), pure water and nutrient solution are respectively input into the feed tank (4). After being irradiated and sterilized by the ultraviolet sterilization lamp (5) in the feed tank (4), stop the operation of the pure water input pump (13) and the nutrient solution input pump (14) when the feed tank (4) is filled; The aeration device (11) introduces air or oxygen into the feed tank (4) to make the dissolved oxygen concentration saturated. The dissolved oxygen concentration of the solution in the feed tank (4) at this time is recorded by the second dissolved oxygen detector (6). Then, the solution in the feed tank (4) is input into the biofilm reactor (1) under the action of the biofilm reactor input pump (16) and is in full contact with the packing (2). Then, the dissolved oxygen concentration at this time is measured by the first dissolved oxygen detector (3). Then the solution flows out from the drain port of the biofilm reactor (1); Detection stage: First, close the input valve (12) of the biofilm reactor, pure water input pump (13), nutrient solution input pump (14), wastewater input pump (15), pure water input valve (17), nutrient solution input valve (18) and wastewater input valve (19), open the feed tank drain valve (21) to drain the solution in the feed tank (4); then, open the pure water input pump (13), nutrient solution input pump (14), wastewater input pump (15), pure water input valve (17), nutrient solution input valve (18) and wastewater input valve (19) to input wastewater, nutrient solution and pure water into the feed tank (4), and sterilize them by irradiating with the ultraviolet sterilization lamp (5) in the feed tank (4). When the feed tank (4) is full, stop the operation of the pure water input pump (13), nutrient solution input pump (14) and wastewater input pump (15); the aeration device (11) introduces air or oxygen into the feed tank (4) to make the dissolved oxygen concentration saturated, and the second dissolved oxygen detector (6) records the dissolved oxygen concentration of the solution in the feed tank (4) at this time. Then, the solution in the feed tank (4) is input into the biofilm reactor (1) by the biofilm reactor input pump (16). The solution in the feed tank (4) is input into the biofilm reactor (1) and is in full contact with the packing (2). After that, the dissolved oxygen concentration is measured by the first dissolved oxygen detector (3). Then the solution flows out from the drain outlet of the biofilm reactor (1), calculate the difference in dissolved oxygen measured by the second dissolved oxygen detector (6) and the first dissolved oxygen detector (3). After the difference is stable, calculate the biological toxicity of the wastewater; The biological toxicity of the calculated wastewater is calculated by the formula: 100%‧(k C -k S ) / k C , where k S is the consumption rate of dissolved oxygen in the detection stage, and k C is the consumption rate of dissolved oxygen in the intermittent stage; among them, the rate k S is obtained by dividing the difference between the second dissolved oxygen detector (6) and the first dissolved oxygen detector (3) in the detection stage by the residence time of the solution in the packing, and the rate k C is obtained by dividing the difference between the second dissolved oxygen detector (6) and the first dissolved oxygen detector (3) in the intermittent stage by the residence time of the solution in the packing.

2. The on-line wastewater toxicity detection method based on nitrifying bacteria biofilm according to claim 1, characterized in that: The ratio of the horizontal cross-sectional area to the height of the biofilm reactor (1) is 0.2 - 2; the material of the packing (2) includes zeolite and polyethylene, and the filling height of the packing (2) in the biofilm reactor (1) is greater than 20% of the height of the biofilm reactor (1).

3. The on-line wastewater toxicity detection method based on nitrifying bacteria biofilm according to claim 1, characterized in that: The solution in the feed tank (4) is input into the biofilm reactor (1) under the action of the biofilm reactor input pump (16) at a flushing speed of 6 - 7 meters per hour.

4. The on-line wastewater toxicity detection method based on nitrifying bacteria biofilm according to claim 1 or 2, characterized in that: A biofilm reactor drain valve is provided on the outlet pipe of the biofilm reactor (1).

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