An environmentally friendly biological treatment method for detoxification of high-arsenic wastewater with simultaneous and efficient nitrogen removal

Abstract

The present invention discloses an environmentally friendly biological treatment method for detoxifying and simultaneously efficiently denitrifying high-arsenic wastewater, belonging to the field of sewage treatment technology. First, anaerobic granular sludge is inoculated into the anaerobic bioreactor used for short-term stabilization. Then, simulated industrial wastewater containing gradient concentrations of As(III) is introduced into the stabilized anaerobic sludge for multi-stage acclimation. A transition period is added to each acclimation stage, and a microaerobic (anoxic) environment is used to indirectly promote the growth of anaerobic microorganisms, allowing for a smooth transition to high As(III) concentrations. This greatly shortens the acclimation time and rapidly cultivates a bacterial community that can completely convert high-concentration As(III) within 24 hours while retaining efficient denitrification properties. The present invention solves the problems of long As(III) bacterial community acclimation transition period, high As(III) toxicity to the bacterial community at high concentrations, resulting in decreased denitrification performance, severe sludge loss, and slow As(III) conversion.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and in particular to an environmentally friendly biological treatment method for detoxifying high-arsenic wastewater and simultaneously achieving efficient denitrification. Background Art

[0002] With the acceleration of industrialization, the discharge of arsenic-containing wastewater has brought many problems. Arsenic is a toxic metal element, and its compounds are widely present in nature, especially As(III), which poses a serious threat to the environment and human health due to its high toxicity and high mobility. Traditional treatment methods such as chemical precipitation, coagulation precipitation, electrochemical method, adsorption method, etc., although they can remove arsenic in wastewater to a certain extent, often have problems such as low treatment efficiency, high cost, and secondary pollution. For example, the chemical precipitation method increases the cost of sewage treatment and produces a large amount of sludge by adding chemical agents to chelate As(III) after the secondary process of sewage treatment. It is difficult to purify arsenic-containing wastewater to the discharge standard in one go, and it may cause waste of arsenic resources and secondary pollution. The coagulation precipitation method requires the addition of coagulants, which will also increase the amount of sludge and has poor treatment effect on low-concentration arsenic-containing wastewater.

[0003] Biological treatment technology has always been the main wastewater treatment process in practical applications. Compared with traditional denitrification technology, anaerobic biological treatment technology does not require the addition of a carbon source. The nitrogen generated by its own reaction can save the energy loss caused by aeration. Moreover, since anaerobic organisms are mostly autotrophic microorganisms, their slow growth can greatly reduce the sludge production of the process, showing significant advantages in green environmental protection. However, high concentrations of As(III) have a broad spectrum of biological toxicity in the environment and will have a significant impact on the normal physiological functions of microorganisms. In addition, when the As(III) concentration suddenly increases, it will also affect the immediate stability of the anaerobic biological technology operation and may even directly lead to the collapse of the reactor. There is still a great risk of failure in the acclimation stage of anaerobic sludge. Therefore, anaerobic biological treatment technology is also a challenge for the treatment of high-concentration As(III)-containing industrial wastewater.

[0004] At the same time, due to the slow growth of anaerobic organisms, certain measures need to be taken to maintain the biomass in the system. The sedimentation effect of the secondary sedimentation tank can not only remove suspended solids in the sewage to ensure the clarity of the effluent, but also ensure that the activated sludge can be effectively returned to the biological treatment system to maintain the stable operation of the biological treatment system. Therefore, incorporating the principle of this process into the anaerobic bioreactor can greatly reduce the loss of activated sludge. In summary, after the acclimation of the anaerobic bioreactor, it is expected that the anaerobic bioreactor can smoothly transition when the As(III) concentration changes exponentially, so that it can always maintain stable growth and development under the toxic effects of As(III), greatly shorten the acclimation time, and quickly cultivate anaerobic bacteria with high-concentration As(III) resistance and the ability to maintain the original denitrification performance to adapt to a wide range of As(III) concentration influent conditions. Summary of the Invention

[0005] In response to the problems of high cost and secondary pollution risk in the existing chemical precipitation or physical precipitation methods for treating high-arsenic industrial wastewater, as well as the biological toxicity and low treatment efficiency of biological methods, the present invention provides a biological treatment method for treating industrial wastewater containing high concentrations of As(III) and simultaneously achieving efficient denitrification, aiming to completely convert the As(III) in the wastewater while ensuring the efficient denitrification performance of the reactor itself.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] An environmentally friendly biological treatment method for detoxifying high-arsenic wastewater and simultaneously achieving efficient nitrogen removal is characterized in that the anaerobic bioreactor used in the biological treatment method is an upflow anaerobic sludge reactor, comprising a reactor body and a sludge return device.

[0008] The reactor body is provided with a sludge discharge port, a water inlet, a sludge return port and a water outlet in sequence from the bottom to the top; the top of the reactor body is sealed by a top plate, and an air outlet is provided on the top plate;

[0009] A three-phase separator is provided inside the reactor body, between the sludge return port and the water outlet; the three-phase separator is composed of a first annular plate in an inverted cone shape and a second annular plate in a conical shape, and the second annular plate is located above the first annular plate, and an annular gap is formed between the two annular plates; the top of the first annular plate is fixed to the side wall of the reactor body, and the middle of the bottom is open; the top of the second annular plate is fixed to the top plate of the reactor body through an air outlet pipe, and is connected to the air outlet on the top plate; the bottom opening diameter of the second annular plate is larger than the bottom opening diameter of the first annular plate; the bottom position of the second annular plate is lower than the top position of the first annular plate.

[0010] A stirring magnet is added to the bottom of the reactor body, and an aeration head is provided between the water inlet and the sludge return port; the aeration head is connected to an aeration pipe, and the aeration pipe is led to the outside through the bottom opening of the first annular plate, the bottom opening of the second annular plate, and the outlet pipe in sequence, and a gap is formed between the aeration pipe and the outlet pipe for gas to flow out;

[0011] The sludge return device is provided with a water inlet at the top, a water outlet in the middle, and a mud outlet at the bottom; the water outlet of the reactor body is connected to the water inlet at the top of the sludge return device, and the mud outlet at the bottom of the sludge return device is connected to the sludge return outlet of the reactor body;

[0012] Anaerobic granular sludge is inoculated in the reactor body, and the anaerobic granular sludge is subjected to multi-stage acclimation using simulated industrial wastewater containing gradient concentrations of As(III), so that an anaerobic bacterial community with high-concentration As(III) resistance and the ability to maintain original denitrification performance is cultivated.

[0013] The method for treating high-arsenic wastewater using the anaerobic bioreactor is as follows:

[0014] The reactor body is placed on a magnetic stirrer; an inert gas aeration device is connected to the aeration pipe to ensure an anaerobic environment inside the reactor during operation; the industrial wastewater to be treated is introduced into the reactor body in an upward flow from the water inlet, and the anaerobic granular sludge is stirred by a magnetic particle to uniformly mix the sludge with the industrial wastewater and uniformly distribute the sludge below the three-phase separator; after being treated by the anaerobic bacteria, the resulting suspension continues to pass upward through the three-phase separator and then flows into the sludge reflux device through the water outlet, and excess nitrogen is naturally discharged into the air through the air outlet at the top of the reactor; the anaerobic bioreactor adopts a continuous flow operation mode;

[0015] After the suspension entering the sludge return device settles naturally, the bottom sludge is returned to the reactor body through a peristaltic pump to control the flow rate, and the upper layer of clear water is discharged from the outlet of the sludge return device as treated wastewater.

[0016] Furthermore, the method for multi-stage acclimation of the anaerobic granular sludge is:

[0017] The reactor body inoculated with anaerobic granular sludge is placed on a magnetic stirrer; the aeration pipe is connected to an inert gas aeration device;

[0018] First, the anaerobic granular sludge in the reactor was stabilized for a period of time using simulated industrial wastewater without As(III) until the denitrification efficiency was no less than 50%, which was recorded as stage I.

[0019] Then, the anaerobic granular sludge in the reactor was acclimated in stages II, III, and IV using simulated industrial wastewater containing As(III), and the As(III) concentration in the wastewater used in stages II to IV increased exponentially.

[0020] A transition period is set between two adjacent stages; nitrogen aeration is maintained during the operation of the reactor except during the transition period to maintain an anaerobic environment; aeration is stopped during the transition period, so that the internal environment of the reactor becomes an anoxic environment.

[0021] Furthermore, the acclimation time for stages II and III was 30 days, and the acclimation time for stage IV was 20 days. The As(III) concentrations of the simulated industrial wastewater used in each stage were as follows:

[0022] Phase II: acclimatization using simulated industrial wastewater containing 20 mg / L As(III);

[0023] Phase III: acclimatization using simulated industrial wastewater containing 40 mg / L As(III);

[0024] Phase IV: Acclimation using simulated industrial wastewater containing 80 mg / L As(III).

[0025] Furthermore, each transition period lasts for 6 days, including the last three days of the previous stage and the first three days of the next stage.

[0026] The simulated industrial wastewater contained 500 mg / L NaHCO₃, 100 mg / L NH₄Cl, 130 mg / L NaNO₂, 27.2 mg / L K₂HPO₄, 300 mg / L MgSO₄·7H₂O, 180 mg / L CaCl₂·2H₂O, 5 mg / L FeSO₄, and 1 mL / L trace element solution. As(III) in the simulated industrial wastewater was provided by sodium arsenite (NaAsO₂). The trace element solution contained 430 mg / L ZnSO₄·7H₂O, 240 mg / L CoCl₂·6H₂O, 990 mg / L MnCl₂·4H₂O, 250 mg / L CuSO₄·5H₂O, 220 mg / L NaMoO₄·2H₂O, 190 mg / L NiCl₂·6H₂O, 210 mg / L NaSeO₄·10H₂O, and 14 mg / L H₃BO₃.

[0027] In the technical solution of the present invention:

[0028] Anaerobic granular sludge is inoculated in the bottom area of ​​the reactor, and the internal magnetic particles are stirred by a magnetic stirrer to promote better contact with industrial wastewater and improve the utilization rate of the sludge; the built-in three-phase separator and sludge return device can reduce the sludge loss inside the reactor, improve the stable operation of the reactor and its ability to cope with different concentrations of As(III) and nitrogen load shocks.

[0029] The anaerobic sludge is subjected to multi-stage acclimation with simulated industrial wastewater containing As(III) ranging from low concentration to high concentration. A transition period of stopping aeration is set between two adjacent stages, and the growth of anaerobic microorganisms is indirectly promoted by using a micro-aerobic (anoxic) environment, so that a smooth transition to high concentration of As(III) is carried out, so that the anaerobic microorganisms always maintain stable growth and development under the toxic effect of As(III), greatly shortening the acclimation time, and quickly cultivating an anaerobic bacterial community with high concentration As(III) resistance and the ability to maintain the original denitrification performance, so as to adapt to the influent conditions of a wide range of As(III) concentrations.

[0030] The three-phase separator consists of two parts, each consisting of annular plates, designed to minimize sludge loss. The lower, inverted-conical first annular plate is welded directly to the inner wall of the reactor body, with an opening at the bottom for normal upper drainage. The top of the upper, conical second annular plate is welded to the reactor's roof via an outlet pipe. This outlet pipe allows nitrogen to be discharged to maintain a stable internal pressure.

[0031] The principle of the present invention is to increase the As(III) concentration in the influent by doubling from low to high concentrations through four stages of acclimatization at As(III) concentrations of 0 mg / L, 20 mg / L, 40 mg / L, and 80 mg / L. A transition period of stopping aeration is added to each stage of change. The short-term microaerobic (anoxic) environment is used to promote the metabolic activity of aerobic microorganisms in the sludge, thereby indirectly promoting the growth of anaerobic microorganisms to enhance the stress resistance of the activated sludge. The microorganisms in the reactor quickly adapt to As(III) to cultivate an anaerobic bacterial community with high-concentration As(III) resistance. Microscopically, this is manifested in the enrichment of arsenic oxidation genes detected in the extracted microbial DNA and the activity of arsenic invertase in the extracted microbial protein. Macroscopically, the reactor can smoothly transition when the As(III) concentration changes exponentially, allowing it to maintain stable and efficient denitrification under the toxic effects of As(III) while achieving complete conversion of As(III) within 24 hours. The agitator at the bottom allows the sludge and wastewater in the reactor to be fully mixed and reacted. The setting of the sludge return device can ensure sufficient biomass in the reactor through sludge return and prevent the loss of cultivated bacteria.

[0032] The present invention provides an environmentally friendly biological treatment method for detoxifying high-arsenic wastewater and simultaneously removing nitrogen with high efficiency, which has the following beneficial effects:

[0033] 1. In the anaerobic bioreactor provided by the present invention: the magnetic stirrer at the bottom of the reactor ensures full contact between the sludge and industrial wastewater, avoiding the deterioration of the treatment effect caused by bottom sedimentation; the three-phase separator can separate the sludge area from the water outlet to achieve mud and water separation; the sludge return device can ensure sufficient biomass in the reactor through sludge return, preventing the loss of cultivated strains.

[0034] 2. The acclimation method of the present invention for the sludge in the reactor can stably resist the toxic effects of As(III) during the process of 0-80 mg / LAs(III) concentration multiple changes, always maintain normal growth and metabolism, and maintain high denitrification efficiency.

[0035] 3. The UASB reactor of the present invention can achieve efficient treatment of industrial wastewater under the condition of 0-80 mg / LAs(III), with the removal rate of ammonia nitrogen and nitrite nitrogen being stable at more than 95%, and can also achieve complete conversion of As(III). BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a schematic diagram of an anaerobic bioreactor used in an embodiment of the present invention;

[0037] Figure 2 The changes of ammonia nitrogen and nitrite nitrogen in the reactor in the four acclimation stages (with transition period) in the embodiment;

[0038] Figure 3 The changes of As(III) in the reactor during the four acclimation stages (with transition period) in the embodiment;

[0039] Figure 4 The changes of ammonia nitrogen and nitrite nitrogen in the reactor in the four acclimation stages (without transition period) in the embodiment;

[0040] Figure 5 The changes of As(III) in the reactor during the four acclimation stages (without transition period) in the embodiment;

[0041] Figure 6 This is a heat map of the relative abundance changes of As(III) oxidation genes in the anaerobic granular sludge after each acclimation stage of the reactor in the embodiment;

[0042] Figure 7 This is a graph showing the test results of arsenic oxidase activity extracted from the anaerobic granular sludge in the reactor before and after acclimation in the embodiment;

[0043] Figure 8 This is the treatment effect of the reactor that completed the anaerobic granular sludge acclimation in the example to treat high-concentration As(III)-containing simulated industrial wastewater. DETAILED DESCRIPTION

[0044] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below.

[0045] Example 1

[0046] like Figure 1 As shown, the anaerobic bioreactor used in this embodiment for treating high-concentration As(III) industrial wastewater is an upflow anaerobic sludge reactor, which includes a reactor body and a sludge return device.

[0047] On the reactor body, from bottom to top, there are arranged a mud discharge port, a water inlet, a sludge return port and a water outlet in sequence; the top of the reactor body is sealed by a top plate, and an air outlet is arranged on the top plate.

[0048] A three-phase separator is provided inside the reactor body, between the sludge return port and the water outlet; the three-phase separator consists of a first annular plate in the shape of an inverted cone and a second annular plate in the shape of a cone, and the second annular plate is located above the first annular plate, with an annular gap formed between the two annular plates; the top of the first annular plate is fixed to the side wall of the reactor body, and the middle of the bottom is open; the top of the second annular plate is fixed to the top plate of the reactor body through an outlet pipe, and is connected to the outlet on the top plate; the bottom opening diameter of the second annular plate is larger than the bottom opening diameter of the first annular plate.

[0049] Inside the reactor body, a stirring magnet is added to the bottom, and an aeration head is set between the water inlet and the sludge return port; the aeration head is connected to the aeration pipe, and the aeration pipe is led to the outside through the bottom opening of the first annular plate, the bottom opening of the second annular plate and the outlet pipe in sequence, and a gap is formed between the aeration pipe and the outlet pipe for gas to flow out.

[0050] The sludge return device is provided with a water inlet at the top, a water outlet in the middle and a mud outlet at the bottom; the water outlet of the reactor body is connected to the water inlet at the top of the sludge return device, and the mud outlet at the bottom of the sludge return device is connected to the sludge return outlet of the reactor body.

[0051] The present invention has no special restrictions on the size of the reactor body. The reactor body used in this embodiment is 52.2 cm high and has a bottom area of ​​78.5 cm. 2 , effective volume 3.94L, actual usage volume 3L.

[0052] Anaerobic granular sludge is inoculated in the reactor body. The present invention has no special limitation on the inoculated anaerobic granular sludge, and commercially available anaerobic granular sludge can be directly used. In this embodiment, the concentration of the anaerobic granular sludge in the reactor is 3 g / L.

[0053] In this example, the inoculated anaerobic granular sludge was subjected to multi-stage acclimation using simulated industrial wastewater containing gradient concentrations of As(III), so as to cultivate an anaerobic bacterial community that is resistant to high concentrations of As(III) and can maintain its original denitrification performance. The acclimation method (the operation method of the reactor is the same as the method for treating high-arsenic wastewater) is as follows:

[0054] The reactor body, inoculated with anaerobic granular sludge, was placed on a magnetic stirrer. The aeration pipe was connected to an inert gas aeration device. Simulated industrial wastewater containing the appropriate concentration of As(III) was introduced into the reactor body through the inlet in an upward flow, and the anaerobic granular sludge was stirred by a magnetic stirrer.

[0055] First, the anaerobic granular sludge in the reactor was stabilized for 30 days using simulated industrial wastewater containing 0 mg / L of As(III); then, the anaerobic granular sludge in the reactor was acclimated for 30 days using simulated industrial wastewater containing 20 mg / L of As(III); then, the anaerobic granular sludge in the reactor was acclimated for 30 days using simulated industrial wastewater containing 40 mg / L of As(III); and finally, the anaerobic granular sludge in the reactor was acclimated for 20 days using simulated industrial wastewater containing 80 mg / L of As(III). A transition period was set between adjacent stages, each lasting 6 days, including the last three days of the previous stage and the first three days of the next stage. During the operation of the reactor, nitrogen aeration was maintained except during the transition period to maintain an anaerobic environment; aeration was stopped during the transition period, so that the internal environment of the reactor became an anoxic environment.

[0056] As described above, in this example, the acclimation process was divided into four stages. The anaerobic granular sludge in the reactor was acclimated using simulated industrial wastewater containing 0 mg / L, 20 mg / L, 40 mg / L, and 80 mg / L As(III) for 30 days, 30 days, 30 days, and 20 days, respectively. During the acclimation process, the reactor maintained a hydraulic retention time of 24 hours, a pH of 8.0, and a temperature of 35°C.

[0057] The simulated industrial wastewater used in this example contained 500 mg / L NaHCO, 100 mg / L NH4Cl, 130 mg / L NaNO, 27.2 mg / L K2HPO4·, 300 mg / L MgSO4·7H2O, 180 mg / L CaCl2·2H2O, 5 mg / L FeSO4, and 1 mL / L trace element solution. The trace element solution contained 430 mg / L ZnSO4·7H2O, 240 mg / L CoCl2·6H2O, 990 mg / L MnCl2·4H2O, 250 mg / L CuSO4·5H2O, 220 mg / L NaMoO4·2H2O, 190 mg / L NiCl2·6H2O, 210 mg / L NaSeO4·10H2O, and 14 mg / L H3BO3. The As(III) in the simulated industrial wastewater is NaAsO2 (sodium arsenite).

[0058] This example investigates the treatment effect of simulated industrial wastewater during the acclimation process and compares the wastewater treatment effects with and without a transition period (the difference between the acclimation method without a transition period and the acclimation method with a transition period is that nitrogen aeration is maintained throughout the acclimation period).

[0059] The treatment effect of the acclimation process with a transition period on the simulated industrial wastewater is as follows Figure 2 As shown in Figure 2, as the As(III) content in the influent increases, the nitrogen removal efficiency of the reactor remains above 90%. Figure 3 As shown in the figure, the As(III) in the influent water was always able to complete the complete conversion.

[0060] The treatment effect of the acclimation process without adding a transition period on the simulated industrial wastewater is as follows Figure 4 and Figure 5 As shown in the figure, with the increase of influent As(III), the effluent nitrogen and As(III) concentrations increased each time the influent As(III) concentration was increased, indicating that its denitrification and arsenic removal effects would deteriorate, and would gradually stabilize after a few days.

[0061] This example investigates the enrichment of arsenic oxidation genes in granular sludge DNA after each stage of acclimation. Arsenic oxidation-related genes are aioA, aioB, and arxA, and their changes are presented in a heat map of relative gene abundance, as shown in Figure 2. Figure 6 As shown in the figure, the values ​​are normalized relative abundance values, and larger values ​​indicate higher relative abundance. It can be seen from the figure that with the increase of As(III) in the influent, the relative abundance of aioA, aioB and arxA in the sludge increased.

[0062] This example investigates the changes in arsenic oxidase activity in protein extracted from granular sludge before and after acclimation. Arsenic oxidase activity is defined as the amount of DCIP reduced per milligram of protein per minute, with the unit being μmol DCIP / (min·mg). The greater the amount of DCIP reduced, the stronger the activity. Figure 7 As shown in the figure, the reduction amount of DCIP by the acclimated anaerobic granular sludge is much greater than that by the unacclimated anaerobic granular sludge, and the unacclimated anaerobic granular sludge has almost no reduction of DCIP.

[0063] The anaerobic bioreactor of this embodiment can be used to treat high-arsenic wastewater after multi-stage acclimation of anaerobic granular sludge in the above manner. This embodiment has no special restrictions on the composition and source of the industrial wastewater containing As(III) to be treated. Its treatment method is as follows: during operation, the reactor body is placed on a magnetic stirrer; the aeration pipe is externally connected to an inert gas aeration device to ensure an anaerobic environment inside the reactor during the operation phase, the industrial wastewater to be treated is introduced into the reactor body in an upward flow from the water inlet, and the anaerobic granular sludge is stirred by a magnetic particle to mix the sludge and industrial wastewater evenly and to evenly distribute the sludge below the three-phase separator; after being treated by the anaerobic bacteria, most of the granular sludge is intercepted and continues to react below the three-phase separator. The suspension containing a small amount of sludge is passed through the three-phase separator and then flows into the sludge reflux device through the water outlet. The excess nitrogen is naturally discharged into the air through the air outlet at the top of the reactor. After the suspended liquid enters the sludge return device and settles naturally, the active granular sludge at the bottom is returned to the reactor body through a peristaltic pump to control the flow rate. The upper layer of clear water is discharged from the outlet of the sludge return device as treated wastewater. The anaerobic bioreactor adopts a continuous flow operation mode.

[0064] The anaerobic granular sludge acclimated in this example was used to treat simulated industrial wastewater containing 120 mg / L As(III) in a continuous flow manner for eight days. The reactor hydraulic retention time was 24 h, the pH was 8.0, and the temperature was 35°C. The nitrogen and As(III) concentrations of the treated wastewater were tested every 1 or 2 days. The results were as follows: Figure 8 As shown, 120 mg / LAs(III) can be completely removed while ensuring a nitrogen removal efficiency of more than 90%.

[0065] The above are merely exemplary embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An environmentally friendly biological treatment method for detoxification and simultaneous efficient nitrogen removal of high-arsenic wastewater, characterized by: The anaerobic bioreactor used in the biological treatment method is an upflow anaerobic sludge reactor, including a reactor body and a sludge return device; The reactor body is provided with a sludge discharge port, a water inlet, a sludge return port and a water outlet in sequence from the bottom to the top; the top of the reactor body is sealed by a top plate, and an air outlet is provided on the top plate; A three-phase separator is provided inside the reactor body, between the sludge return port and the water outlet. The three-phase separator comprises a first annular plate in an inverted cone shape and a second annular plate in a cone shape, wherein the second annular plate is located above the first annular plate, with an annular gap formed between the two annular plates. The top of the first annular plate is fixed to the side wall of the reactor body, and the middle of the bottom is open. The top of the second annular plate is fixed to the top plate of the reactor body via an air outlet pipe and is connected to the air outlet on the top plate. The bottom opening diameter of the second annular plate is larger than the bottom opening diameter of the first annular plate. A stirring magnet is added to the bottom of the reactor body, and an aeration head is provided between the water inlet and the sludge return port; the aeration head is connected to an aeration pipe, and the aeration pipe is led to the outside through the bottom opening of the first annular plate, the bottom opening of the second annular plate, and the outlet pipe in sequence, and a gap is formed between the aeration pipe and the outlet pipe for gas to flow out; The sludge return device is provided with a water inlet at the top, a water outlet in the middle, and a mud outlet at the bottom; the water outlet of the reactor body is connected to the water inlet at the top of the sludge return device, and the mud outlet at the bottom of the sludge return device is connected to the sludge return outlet of the reactor body; The reactor body is inoculated with anaerobic granular sludge, and the anaerobic granular sludge is subjected to multi-stage acclimation using simulated industrial wastewater containing gradient concentrations of As(III), so that an anaerobic bacterial community with high-concentration As(III) resistance and the ability to maintain original denitrification performance is cultivated; The method for treating high-arsenic wastewater using the anaerobic bioreactor is as follows: The reactor body is placed on a magnetic stirrer; an inert gas aeration device is connected to the aeration pipe to ensure an anaerobic environment inside the reactor during operation; the industrial wastewater to be treated is introduced into the reactor body in an upward flow from the water inlet, and the anaerobic granular sludge is stirred by a magnetic particle to uniformly mix the sludge with the industrial wastewater and uniformly distribute the sludge below the three-phase separator; after being treated by the anaerobic bacteria, the resulting suspension continues to pass upward through the three-phase separator and then flows into the sludge reflux device through the water outlet, and excess nitrogen is naturally discharged into the air through the air outlet at the top of the reactor; the anaerobic bioreactor adopts a continuous flow operation mode; After the suspension entering the sludge return device settles naturally, the bottom sludge is returned to the reactor body through a peristaltic pump to control the flow rate, and the upper layer of clear water is discharged from the outlet of the sludge return device as treated wastewater.

2. The biological treatment method according to claim 1, characterized in that The method for multi-stage acclimation of the anaerobic granular sludge is as follows: The reactor body inoculated with anaerobic granular sludge is placed on a magnetic stirrer; the aeration pipe is connected to an inert gas aeration device; First, the anaerobic granular sludge in the reactor was stabilized for a period of time using simulated industrial wastewater without As(III) until the denitrification efficiency was no less than 50%, which was recorded as stage I. Then, the anaerobic granular sludge in the reactor was acclimated in stages II, III, and IV using simulated industrial wastewater containing As(III), and the As(III) concentration in the wastewater used in stages II to IV increased exponentially. A transition period is set between two adjacent stages; nitrogen aeration is maintained during the operation of the reactor except during the transition period to maintain an anaerobic environment; aeration is stopped during the transition period, so that the internal environment of the reactor becomes an anoxic environment.

3. The biological treatment method according to claim 2, characterized in that: The acclimation time for phases II and III was 30 days, and the acclimation time for phase IV was 20 days. The As(III) concentrations of the simulated industrial wastewater used in each phase were as follows: Phase II: acclimatization using simulated industrial wastewater containing 20 mg / L As(III); Phase III: acclimatization using simulated industrial wastewater containing 40 mg / L As(III); Phase IV: Acclimation using simulated industrial wastewater containing 80 mg / L As(III).

4. The biological treatment method according to claim 2 or 3, characterized in that: Each transition period lasts 6 days, including the last three days of the previous stage and the first three days of the next stage.

5. The biological treatment method according to claim 2 or 3, characterized in that: The simulated industrial wastewater contains: 500 mg / LNaHCO3, 100 mg / LNH4Cl, 130 mg / LNaNO2, 27.2 mg / LK2HPO4, 300 mg / LMgSO4·7H2O, 180 mg / LCaCl2·2H2O, 5 mg / L FeSO4 and 1 mL / L trace element solution; As(III) in the simulated industrial wastewater is provided by sodium arsenite NaAsO2.

6. The biological treatment method according to claim 5, characterized in that: The trace element solution contains 430 mg / L ZnSO4·7H2O, 240 mg / L CoCl2·6H2O, 990 mg / L MnCl2·4H2O, 250 mg / L CuSO4·5H2O, 220 mg / L NaMoO4·2H2O, 190 mg / L NiCl2·6H2O, 210 mg / L NaSeO4·10H2O, and 14 mg / L H3BO3.

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