Sewage treatment method based on UASB reactor

Abstract

The embodiment of the invention provides a sewage treatment method based on a UASB (Upflow Anaerobic Sludge Blanket) reactor, which comprises the following steps: a stable preparation step: continuously feeding sewage with a first COD (Chemical Oxygen Demand) concentration into the UASB reactor through a water inlet at a fixed flow speed, so that the activity of microorganisms containing anaerobic digestion sludge in the UASB reactor reaches a stable state; a high-low alternate load water inlet step: adjusting a peristaltic pump in the UASB reactor system, so that the sewage with the first COD concentration continuously enters the UASB reactor through a water inlet at a periodically high-low changing flow rate; a load increasing step: sewage continuously flows into the UASB reactor through a water inlet at a fixed flow speed, the COD concentration of the sewage flowing into the UASB reactor is increased by taking the first COD concentration as an initial concentration gradient along with time until the maximum critical value of the COD concentration of the sewage treated by the UASB reactor is reached, and the load is increased; compared with the UASB reactor in the prior art, the UASB reactor cultured through the high-low alternate load water inlet step in the method has the advantage that the performance is more excellent.

Description

Technical Field

[0001] The present application relates to the technical field of sewage treatment, and in particular to a sewage treatment method based on a UASB reactor. Background Art

[0002] With the acceleration of industrial development and urbanization, the discharge of high-concentration organic wastewater continues to increase, causing serious environmental pollution. Upflow anaerobic sludge blanket (UASB) reactors are one of the most important reactor types in anaerobic digestion technology in the field of wastewater treatment. Existing technologies based on UASB reactors for wastewater treatment use a stable, continuous water inflow method, resulting in low UASB performance. Therefore, research is needed to improve their performance. Summary of the Invention

[0003] The embodiment of the present application provides a sewage treatment method based on a UASB reactor to solve the technical problem of low UASB performance in the sewage treatment process in the prior art.

[0004] In a first aspect, embodiments of the present application provide 1. a sewage treatment method based on a UASB reactor, the method utilizing a UASB reactor system, the UASB reactor system comprising a UASB reactor, a water inlet pipe, and a peristaltic pump, wherein a water inlet is provided at the bottom of the UASB reactor, the water inlet is connected to an external sewage source through the water inlet pipe, the water inlet pipe is provided with the peristaltic pump for adjusting the water inlet speed, a water outlet is provided at the top of the UASB reactor, and the UASB reactor contains anaerobic digested sludge, characterized in that the method comprises the following steps:

[0005] a stabilization preparatory step of continuously flowing sewage having a first COD concentration into the UASB reactor through the water inlet at a fixed flow rate, so that the microbial activity of the anaerobic digested sludge contained in the UASB reactor reaches a stable state;

[0006] High-low alternating load water inlet step: adjusting the peristaltic pump so that the sewage with the first COD concentration enters the UASB reactor through the water inlet continuously at a flow rate that changes periodically.

[0007] In one possible implementation, after the high-low alternating load water intake step, the method further includes:

[0008] and increasing the load step: continuously flowing sewage into the UASB reactor through the water inlet at a fixed flow rate, wherein the COD concentration of the sewage flowing into the UASB reactor increases with the passage of time, starting from the first COD concentration, until the UASB reactor reaches a critical value for the COD removal rate of the sewage.

[0009] In one possible implementation, before the stable operation step, the method further includes:

[0010] Startup steps:

[0011] continuously flowing sewage with a second COD concentration into the UASB reactor through the water inlet at a fixed flow rate;

[0012] Taking the second COD concentration as the starting concentration, gradually increasing the COD concentration of the sewage flowing into the UASB reactor over time;

[0013] Detecting the COD removal rate of the UASB reactor for sewage with different COD concentrations;

[0014] The COD concentration of the sewage at which the COD removal rate of the UASB reactor is the highest is determined as the first COD concentration.

[0015] In one possible implementation, between the high-low alternating load water intake step and the load increasing step, the method further includes:

[0016] Stabilization recovery step: continuously flowing sewage with a first COD concentration into the UASB reactor through the water inlet at a fixed flow rate, wherein the organic load of the UASB reactor in the stabilization recovery step is the same as the organic load of the UASB reactor in the stabilization preparation step.

[0017] In one possible implementation, the anaerobic digestion sludge is activated sludge enriched with hydrogenotrophic methanogens.

[0018] In one possible implementation, the first COD concentration is 2000 mg / L.

[0019] In one possible implementation, the pH value of the sewage with the first COD concentration flowing into the UASB reactor is 7-8;

[0020] The temperature of the insulation layer is 37±1°C.

[0021] In one possible implementation, the volume of the anaerobic digested sludge contained in the UASB reactor is 1 / 2 of the volume of the UASB reactor.

[0022] In one possible implementation, the UASB reactor is provided with a tube body and a sludge hopper, the sludge hopper is arranged below the tube body, the water inlet is arranged in the sludge hopper, the tube body includes an inner tube and an outer tube, an insulation layer is provided between the inner tube and the outer tube, the inner tube is a main reaction chamber, and an exhaust port and a water outlet are provided at the top of the UASB reactor.

[0023] In one possible implementation, in the high-low alternating load water inlet step, the organic load of the UASB reactor varies periodically.

[0024] Regarding the sewage treatment method based on the UASB reactor proposed in the embodiment of the present application, experiments have shown that the performance of the UASB reactor after being cultured in the high and low alternating load water inlet steps in the method is superior to that of the UASB reactor in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0026] Figure 1 A schematic structural diagram of a UASB reactor system provided in one embodiment of the present application;

[0027] Figure 2 A schematic flow chart of a sewage treatment method based on a UASB reactor provided in an embodiment of the present application;

[0028] Figure 3 This is a diagram showing the COD concentration changes in the inlet and outlet water of the UASB reactor during the startup step provided in the embodiment of the present application;

[0029] Figure 4 A comparison chart of the COD removal rates of the sewage treatment method based on the UASB reactor provided in the embodiment of the present application and the comparative example;

[0030] Figure 5 A comparison chart of the methane content in the gas produced by the sewage treatment method based on the UASB reactor provided in the embodiment of the present application and the UASB reactor of the comparative example;

[0031] Figure 6 This is a comparison chart of the gas production of the sewage treatment method based on the UASB reactor provided in the embodiment of the present application and the UASB reactor of the comparative example.

[0032] The above drawings illustrate specific embodiments of the present application, which will be described in more detail below. These drawings and the textual description are not intended to limit the scope of the present application in any way, but rather to illustrate the concepts of the present application to those skilled in the art by reference to specific embodiments. DETAILED DESCRIPTION

[0033] Exemplary embodiments will be described in detail herein, with examples illustrated in the accompanying drawings. In the following description, when referring to the drawings, identical numerals in different figures represent identical or similar elements, unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all embodiments consistent with the present application. Rather, they are merely examples of systems and methods consistent with certain aspects of the present application, as detailed in the appended claims.

[0034] UASB reactor is one of the most important reactor types in anaerobic digestion technology. The existing technology for sewage treatment based on UASB reactor adopts a stable continuous water inlet method, which makes the performance of UASB low. Therefore, it is necessary to study how to improve its performance.

[0035] See Figure 1 , is a structural diagram of a UASB reactor system provided by an embodiment of the present application, comprising: a UASB reactor 1, a water inlet pipe 2 and a peristaltic pump 3. A water inlet 121 is provided at the bottom of the UASB reactor 1. The UASB reactor 1 is provided with a pipe body 11 and a sludge hopper 12. The sludge hopper 12 is provided below the pipe body 11. Optionally, the sludge hopper is funnel-shaped. The water inlet 121 can be specifically provided at the bottom of the sludge hopper 12. The water inlet 121 is connected to an external sewage source through the water inlet pipe 2. The water pipe 2 is equipped with a peristaltic pump 3 for controlling the inlet flow rate. The main reaction chamber is located within the pipe body 11. The upper portion of the UASB reactor is provided with an exhaust port 13 and a water outlet 14. Furthermore, the pipe body 11 may include an inner tube 111 and an outer tube 112. The inner tube 111 contains the aforementioned main reaction chamber, and an insulation layer 113 is provided between the inner and outer tubes 111 and 112. The upper portion of the UASB reactor is provided with an exhaust port 13 and a water outlet 14. The UASB reactor 1 contains anaerobic digested sludge. In this embodiment of the present application, the peristaltic pump 3 can be used to adjust the inlet flow rate, thereby adjusting the organic load of the UASB reactor within a certain period of time, such as 1 hour or 12 hours.

[0036] See Figure 2 , is a schematic flow chart of a sewage treatment method based on a UASB reactor provided in an embodiment of the present application, wherein the method utilizes Figure 1 The UASB reactor system shown includes the following steps:

[0037] S201: Startup steps:

[0038] Sewage with a second COD (Chemical Oxygen Demand) concentration is continuously fed into the UASB reactor through the water inlet at a fixed flow rate; the COD concentration of the sewage flowing into the UASB reactor is gradually increased over time, starting from the second COD concentration; the COD removal rate of the UASB reactor for sewage with different COD concentrations is detected; and the COD concentration of the sewage with the highest COD removal rate of the UASB reactor is determined as the first COD concentration.

[0039] For example, see Figure 3 , is a rendering of the COD concentration changes in the inlet and outlet water of the UASB reactor during the startup step provided by the embodiment of the present application. The COD concentration of the UASB reactor inlet water increases from 1000mg / L to 3000mg / L at intervals of 200mg / L. When the inlet COD concentration begins to increase, the COD concentration of the UASB reactor effluent shows a downward trend. This is mainly due to the fact that during the anaerobic digestion process of the UASB reactor, the functional microbial community needs to undergo a certain period of acclimatization to adapt to the system environment, thereby gradually restoring its metabolic activity and treatment efficiency. After running for a period of time, when the inlet COD concentration is 2000mg / L, the UASB reactor effluent COD concentration is about 200mg / L, and the removal rate can reach 90%, which is the organic load condition with the highest removal rate during the entire startup phase. Continuing to gradually increase the inlet COD concentration, it can be seen that the UASB reactor effluent COD concentration shows an upward trend. When the inlet COD concentration reaches 3000mg / L, the UASB reactor effluent COD concentration is about 430mg / L, with a removal rate of about 85%, and the system gradually stabilizes. 2000 mg / L can be set as the first COD concentration. In order to prevent the system from crashing and acidifying when the feed method is changed in the subsequent experiments, the subsequent experiments are carried out under the organic load conditions with the best reactor performance.

[0040] It should be noted that step S201 is an optional step, and an empirical value can be selected as the first COD concentration to directly enter S202.

[0041] S202: Stabilization preparatory steps:

[0042] Sewage with a first COD concentration is continuously fed into the UASB reactor through the water inlet at a fixed flow rate, so that the microbial activity of the anaerobic digestion sludge contained in the UASB reactor reaches a stable state. Specifically, when the COD removal rate in the effluent stabilizes at a certain value within a preset time window, it can be considered that the microbial activity of the anaerobic digestion sludge contained in the UASB reactor has reached a stable state. System operation data shows that the anaerobic digestion process has gradually returned to a stable operating state, indicating that the functional microbial community in the UASB reactor has completed adaptive domestication to the influent COD load, thereby promoting the reaction system to enter a stable operating state, providing a good operating foundation for subsequent process optimization. In this step, while efficiently treating wastewater, the UASB reactor maintains a dynamic equilibrium state of internal biological, chemical and physical processes, ensuring stable treatment effects, good sludge activity, regular gas production and no abnormal fluctuations.

[0043] S203: High-low alternating load water inlet step: adjusting the peristaltic pump so that the sewage with the first COD concentration enters the UASB reactor through the water inlet continuously at a flow rate that changes periodically.

[0044] For example, a 24-hour cycle is set, with wastewater entering the UASB reactor at a high rate during the first half of the cycle, or the first 12 hours, and at a low rate during the second half of the cycle, or the last 12 hours. During this step, the organic load of the UASB reactor periodically fluctuates.

[0045] S204: Stabilization recovery step: sewage with a first COD concentration is continuously flowed into the UASB reactor through the water inlet at a fixed flow rate.

[0046] This step has the same inlet parameters as step S202, that is, the organic load of the UASB reactor is the same and remains stable. Furthermore, when the COD removal rate in the effluent stabilizes at a certain value within a preset time window, it can be considered that the UASB reactor has reached a stable state, the purpose of which is to provide a good operating foundation for subsequent system operation.

[0047] S205: Load increase step: Sewage is continuously fed into the UASB reactor through the water inlet at a fixed flow rate, wherein the COD concentration of the sewage flowing into the UASB reactor increases with time starting from the first COD concentration, until the UASB reactor reaches the critical value of the COD removal rate of the sewage by the UASB reactor. It should be noted that as the COD concentration of the influent sewage increases, the COD removal rate of the UASB reactor will decrease. When it decreases to the critical value, continuing to increase the COD concentration of the sewage will cause the UASB reactor to acidify and collapse. The critical value of the COD removal rate of the UASB reactor is the specification parameter corresponding to the UASB reactor. In the embodiment of the present application, the organic load of the reactor is increased by 0.8gCOD / L / d (d: day) every three days until the reactor removal rate reaches about 77% and the system reaches a critical value, and then the increase in the influent load is stopped to maintain stable operation at this concentration.

[0048] Preferably, the anaerobic digestion sludge is activated sludge enriched with hydrogenotrophic methanogens.

[0049] Preferably, the temperature of the insulation layer is 37±1°C.

[0050] Preferably, the first COD concentration is 2000 mg / L.

[0051] Preferably, the pH value of the wastewater flowing into the UASB reactor is 7-8.

[0052] Preferably, the volume of anaerobic digested sludge accommodated in the UASB reactor is 1 / 2 of the volume of the UASB reactor.

[0053] The following is an experimental description of the examples and comparative examples of the present application.

[0054] Example

[0055] The system of the present invention (such as Figure 1 As shown) is placed in the Environmental Chemistry and Science Laboratory of the Central Campus of Shenyang University of Technology to implement the method described in the embodiment of the present invention.

[0056] The specific implementation method is as follows:

[0057] The sludge inoculated in the laboratory was activated sludge enriched with hydrogenotrophic methanogens. The total suspended solids concentration of the mixed liquor was 24.5 g / L, the volatile suspended solids concentration of the mixed liquor was 15.5 g / L, its VSS / TSS (VSS, Volatile Suspended Solids, volatile suspended solids; TSS, Total Suspended Solids) was 0.63, and the initial settling velocity was 59.4 m. The experimental wastewater was artificial synthetic organic wastewater, with a COD:N:P ratio of 200:5:1 and a pH of 7. Table 1 shows the composition, concentration, and supplier of the artificial synthetic organic wastewater used in the experiment provided in this application.

[0058] Table 1

[0059] Element concentration supplier Peptone 0.80g / L Shenyang Tiexi District Chemical Reagent Factory beef paste 0.50g / L Shenyang Tiexi District Chemical Reagent Factory glucose 0.40g / L Shenyang Tiexi District Chemical Reagent Factory <![CDATA[K2HPO4]]> 0.40g / L Shenyang Tiexi District Chemical Reagent Factory <![CDATA[NH4Cl]]> 0.1g / L Shenyang Tiexi District Chemical Reagent Factory <![CDATA[CaCl2]]> 0.05g / L Shenyang Chemical Co., Ltd. <![CDATA[MgCl2]]> 0.04g / L Shenyang Chemical Co., Ltd. <![CDATA[FeSO4]]> 0.02g / L Shenyang Tiexi District Chemical Reagent Factory zinc sulfate 0.00037mol / L Shenyang Tiexi District Chemical Reagent Factory Manganese sulfate 0.0025mol / L Shenyang Chemical Co., Ltd. copper sulfate 0.00014mol / L Shenyang Chemical Co., Ltd. Cobalt chloride 0.0084mol / L Shenyang Chemical Co., Ltd. Nickel chloride 0.00025mol / L Shenyang Chemical Co., Ltd. Boric acid 0.0008mol / L Shenyang Tiexi District Chemical Reagent Factory EDTA 0.0034 mol / L Liaoning Guangfu Fine Chemical Research Institute

[0060] See Figure 1 Sewage enters through inlet 121 and is discharged from outlet 14 after treatment. Inlet water samples are collected from the sewage source, outlet water samples are collected from outlet 14, gas samples are collected from exhaust port 13, and sludge samples are collected from sludge sampling port 15. A water bath insulation layer 113 is installed in the middle of the UASB reactor to control the UASB reactor temperature to maintain 37±1°C.

[0061] The entire study involved a UASB reactor startup phase, a stabilization preparatory phase (Phase 1), alternating high and low load inflow (Phase 2), a stabilization recovery phase (Phase 3), and an increased load phase (Phase 4). COD removal is a core performance metric for evaluating UASB reactors, reflecting their ability to degrade organic matter in wastewater and a key parameter for assessing the efficiency of the anaerobic digestion process.

[0062] The startup step lasted for 35 days, and the influent COD concentration was gradually increased to stimulate sludge activity. The influent COD concentration of the UASB reactor was increased from 1000 mg / L to 3000 mg / L at intervals of 200 mg / L over time. When the influent COD concentration began to increase, the effluent COD concentration of the UASB reactor showed a downward trend. This was mainly attributed to the fact that during the anaerobic digestion process of the UASB reactor, the functional microbial community needed to undergo a certain period of acclimatization to adapt to the system environment, thereby gradually restoring its metabolic activity and treatment efficiency. After a period of operation, when the influent COD concentration was 2000 mg / L, the effluent COD concentration of the UASB reactor was about 200 mg / L, and the removal rate could reach 90%, which was the organic load condition with the highest removal rate during the entire startup phase. Continue to gradually increase the influent COD concentration, you can see that the UASB reactor effluent COD concentration shows an upward trend. When the influent COD concentration reaches 3000mg / L, the UASB reactor effluent COD concentration is around 430mg / L, the removal rate is around 85%, and the system gradually stabilizes. In order to prevent the system from collapsing and acidifying when the subsequent feed method experiment is carried out, the subsequent experiments are carried out under the organic load conditions with the best performance of the UASB reactor, which is an influent COD concentration of 2000mg / L and an organic load of 4gCOD / L / d (d: day).

[0063] The first stage of the stabilization preparation step was run for 20 days, and the organic load of the UASB reactor was controlled by adjusting the peristaltic pump speed. The influent parameter was 4 gCOD / L / d, see Figure 4 The COD removal rate of the UASB reactor remained at 90 ± 1.5%, indicating relatively stable operation. The gas production of the UASB reactor was steadily increasing, with the gas production of the UASB reactor in the example increasing from 7.61 L per day to 7.96 L per day. The proportion of methane in the gas produced by the UASB reactor was steadily increasing. In the examples of this application, the inlet water parameter refers to the organic load of the UASB reactor.

[0064] The second phase of the high and low alternating load water inlet step is 40 days. The water inlet adjustment method of this experiment is to periodically change the water inlet rate through the peristaltic pump control. Assuming that one cycle is 24 hours, the water inlet parameters are 6gCOD / L / d (in the first 12 hours of the cycle) and 2gCOD / L / d (in the last 12 hours of the cycle). At the beginning of the second phase, see Figure 4 , the COD removal rate of the UASB reactor dropped from 90.6% to 85.6%, a decrease of 5%. As the experiment progressed, the COD removal rate of the UASB reactor gradually increased. This is because under a certain external pressure, the microorganisms in the UASB reactor underwent adaptive transformation, which gradually restored the performance of the UASB reactor. Figure 6The gas production of the high and low load UASB reactor decreased from 7.96L to 7.37L. As the reaction proceeded, the gas production of the UASB reactor in the embodiment gradually recovered. At the beginning of stage 2, see Figure 5 The methane content in the gas produced by the high- and low-load UASB reactors decreased from 72.6% to 70.5%, a slight but not drastic decrease. As the experiment progressed, the methane content in the gas produced by the UASB reactor in Example 1 showed a steady upward trend. During this phase, the methane content in the gas produced by the UASB reactor reached a maximum of 82.5%, indicating that the methane content of the biogas produced by the UASB reactor in both high- and low-load modes was significantly increased.

[0065] The Phase III stabilization recovery step lasted 15 days, with an influent parameter of 4gCOD / L / d. After entering Phase III's stable operation phase, the UASB reactor's COD removal rate continued to rise, eventually leveling off, with the UASB reactor achieving a maximum removal rate of 92.6%. At the beginning of the stabilization recovery step, the UASB reactor experienced a sharp increase in gas production, reaching a maximum of 9.15L per day. Under the experimental conditions, maintaining the overall organic load constant, the high and low load feed modes showed significant improvements in gas production performance after a period of adaptation. The proportion of methane in the UASB reactor's gas production increased significantly and gradually stabilized.

[0066] Phase 4 involved a 35-day ramp-up phase. During this phase, the organic load was increased by a gradient of influent COD concentration until the UASB reactor reached a removal efficiency of approximately 75%, the maximum COD concentration that the UASB reactor could treat. The COD removal efficiency of the UASB reactor initially decreased, then increased, and finally stabilized. On day 22 of the experiment, the COD removal efficiency of the UASB reactor reached a minimum of 76.4% when the organic load reached 9.6 gCOD / L / d. At this point, the organic load increase was stopped and maintained at this level. On day 30 of the experiment, the COD removal efficiency of the UASB reactor exceeded 80%, a period of eight days. Gas production in the UASB reactor also showed an upward trend. During the first 21 days of the experiment, when the organic load was ramped up, gas production increased rapidly, rising from 9.14 L / d to 11.03 L / d, an increase of 1.99 L / d. When the organic load stopped increasing, gas production showed a slow upward trend, reaching 11.42 L / d by the end of the experiment. The methane content of the UASB reactor's gas production showed a downward trend. Initially, the methane content of the UASB reactor produced after cultivation using the method described in this example was 83.9%. After the gradient experiment, the methane content of the UASB reactor's gas production decreased to 79.3%, a 4.6% decrease.

[0067] Comparative Example

[0068] Compared with the embodiment, the difference is that the influent parameters of stage 2 of the comparative example are the same as those of stages 1 and 3. That is, in stage 2, the sewage with the first COD concentration is continuously fed into the UASB reactor at a fixed flow rate. The other conditions and operating methods are the same as those of the embodiment. As a comparative example, the specific operating method is as follows:

[0069] Startup steps: Under a constant temperature of 37±1℃, the COD:N:P ratio of the organic sewage components is set to 200:5:1, and the influent pH is 7-8. While ensuring that the hydraulic load remains unchanged, the influent COD concentration gradient is increased during the startup phase of the UASB reactor to stimulate sludge activity. In order to prevent the system from collapsing and acidifying when the subsequent feeding method experiment is carried out, the organic load with the highest treatment efficiency is selected as the organic load for the feeding method experiment to avoid the collapse of the UASB reactor during the feeding method experiment.

[0070] Phase 1: Preparatory steps for stabilization: The organic load condition with the best performance of the UASB reactor was selected for the experiment, and a continuous water inflow method was adopted with the water inflow parameters, i.e., the organic load of the UASB reactor was 4 gCOD / L / d.

[0071] Phase 2: Continuous stabilization: The organic loading of the UASB reactor was varied by adjusting the flow pump speed, with the inlet parameter set at 4 gCOD / L / d. Furthermore, the inlet pattern was controlled to maintain a constant flow rate. This pushed the reaction system into a stable operating state, providing a good foundation for subsequent process optimization trials.

[0072] The water inlet parameters of the stage 3 stabilization recovery step are the same as those of the stage 1 stabilization preparation step, with the aim of providing a good operating basis for subsequent experiments.

[0073] In Phase 4, the load increase step involves conducting a gradient organic load experiment by increasing the influent COD value. While maintaining all other UASB reactor parameters, the concentrations of various simulated organic wastewater substances were proportionally increased, thereby increasing the influent COD value and, consequently, the UASB reactor's organic load. The UASB reactor's organic load was increased by 0.8 gCOD / L / day every three days until the UASB reactor achieved a removal efficiency of approximately 77%, marking criticality. The influent load was then stopped, maintaining steady operation at this concentration.

[0074] Comparison results:

[0075] Figure 4A comparison chart of the COD removal rates of the sewage treatment method based on the UASB reactor provided in the embodiment of the present application and the comparative example. Stage one: Preparatory step for stabilization: The COD removal rates of the embodiment and comparative example UASB reactors changed in roughly the same manner, remaining at 90±1.5%, and the UASB reactor operated relatively stably. Stage two: The COD removal rate of the comparative example UASB reactor remained stable throughout the entire process. At the beginning of the experiment in this stage, the COD removal rate of the comparative example UASB reactor was higher than that of the embodiment UASB reactor. As the experiment progressed, the COD removal rate of the embodiment UASB reactor gradually increased. At the end of the experiment in this stage, the COD removal rate of the embodiment UASB reactor was briefly higher than that of the comparative example UASB reactor.

[0076] Stage 3 Stabilization recovery step: The COD removal rate of the comparative UASB reactor remained stable throughout the process and was lower than that of the example UASB reactor.

[0077] Phase 4: Load increase step: The COD removal rate of the comparative UASB reactor showed a trend of first decreasing, then increasing, and finally gradually stabilizing. On the 16th day of this phase of the experiment, the COD removal rate of the comparative UASB reactor reached its lowest value of 76.1% when the organic load was 8gCOD / L / d. At this point, the increase in organic load was stopped and the operation was maintained at this organic load. On the 31st day of this phase of the experiment, the COD removal rate of the UASB reactor reached over 80%, which lasted for 15 days. On the 22nd day of the experiment, the COD removal rate of the example UASB reactor reached its lowest value of 76.4% when the organic load reached 9.6gCOD / L / d. At this point, the increase in organic load was stopped and the operation was maintained at this organic load. On the 30th day of the experiment, the COD removal rate of the UASB reactor reached over 80%, which lasted for 8 days. The COD removal rate of the example UASB reactor reached over 80% in just 8 days, which was less than the 15 days of the comparative example. This shows that the UASB reactor cultivated through the high and low alternating load inlet steps has better organic load tolerance, faster recovery from unstable conditions, and superior performance.

[0078] Figure 5A comparison chart of the methane content in the gas produced by the sewage treatment method based on the UASB reactor provided in the embodiment of the present application and the UASB reactor of the comparative example. In the stage one stabilization preparation step, the proportion of the methane content in the gas produced by the comparative example UASB reactor is on a steadily increasing trend, and is roughly the same as that of the embodiment UASB reactor. In stage two, the proportion of the methane content in the gas produced by the comparative example UASB reactor is at its highest point of 77.2%, and in the middle of stage two, the proportion of the methane content in the gas produced by the comparative example UASB reactor is exceeded by the embodiment UASB reactor. In the stage three stabilization recovery step, the proportion of the methane content in the gas produced by the comparative example UASB reactor is lower than that of the embodiment UASB reactor throughout the process. In the stage four load increase step, the proportion of the methane content in the gas produced by the comparative example UASB reactor shows a downward trend, but the methane content in the gas produced by the embodiment UASB reactor remains higher than that of the comparative example.

[0079] Figure 6 A comparison chart of the gas production of the sewage treatment method based on the UASB reactor provided in the embodiment of the present application and the UASB reactor of the comparative example. In the first stage, the stabilization preparation step, the operation of the comparative example and the embodiment UASB reactor is relatively stable, and the gas production of the UASB reactor is on a steady upward trend. The gas production of the embodiment UASB reactor increases from 7.64L to 7.98L per day. At the beginning of the second stage, the gas production of the comparative example UASB reactor is higher than that of the embodiment UASB reactor. As the reaction proceeds, on the 33rd day of the reaction, the gas production of the embodiment UASB reactor exceeds that of the comparative example UASB reactor. In the third stage, the stabilization recovery step, the maximum gas production of the comparative example UASB reactor is 8.4L, which is lower than that of the embodiment UASB reactor throughout the process. In the fourth stage, the load increase step, the comparative example and embodiment UASB reactors show an upward trend in gas production. However, the gas production of the comparative example UASB reactor is always lower than that of the embodiment.

[0080] After the stabilization recovery step in stage 3, the bottom sludge of the UASB reactors of the embodiment and the comparative example was uniformly measured. In the biological signal analysis, the bacterial structure of the reactors underwent significant changes after being cultured with different feeding methods.

[0081] In the initial sludge, the relative abundance of Bacteroidetes_vadinHA17 bacteria is 16.12%, the relative abundance of Anaerolineaceae bacteria is 10.52%, and the relative abundance of Aminicenantales bacteria is 9.6%, which are the more dominant species in the system. In the reactors after cultivation with different feeding modes, the relative abundance of Bacteroidetes_vadinHA17 bacteria, Anaerolineaceae bacteria and Aminicenantales bacteria all decreased. Among them, the genus Anaerolineaceae performed the most significantly, and the relative abundance of Anaerolineaceae bacteria in the embodiment and comparative reactors was less than 1%. Anaerolineaceae bacteria belong to the genus Anaerolineaceae. During the anaerobic digestion process, Anaerolineaceae bacteria participate in the decomposition and metabolism of complex organic matter, converting large molecular organic matter into small molecular organic acids, alcohols, etc., providing methanogens with more easily utilized substrates, and indirectly promoting the growth of methanogens and the methane production process. Anaerolineaceae bacteria are acetate-producing fermenters that exhibit strong synergistic interactions with other microorganisms, such as Methanosaeta. When the abundance or function of these symbiotic microorganisms decreases, this can negatively impact the growth of Anaerolineaceae. This phenomenon in the present study is hypothesized to be due to a decrease in the abundance of methanogenic archaea within Methanosaeta, which in turn reduces the relative abundance of Anaerolineaceae.

[0082] Given the phylogenetic characteristics that methanogens mainly belong to the Euryarchaeota, this study conducted a species abundance analysis on the sequencing data at the genus level of each sample. The experimental samples mainly contain two genera, namely Methanobacterium and Methanosaeta. The relative abundance of Methanosaeta in the initial sludge was 29.1%, and the relative abundance of Methanobacterium was 64.3%. It can be seen that the initial reactor was dominated by hydrogenotrophic methanogens. After conducting experiments with different feeds, the relative abundance of Methanosaeta in the control reactor was 14.6%, and the relative abundance of Methanobacterium was 76.3%. The relative abundance of Methanosaeta in the example reactor was 12.7%, and the relative abundance of Methanobacterium was 78.2%. Methanobacterium bacteria increased in both modes, and the increase was most significant in the example state. This shows that both reactors are transforming to hydrogenotrophic methanogenesis. The growth of Methanobacterium bacteria in the comparative example shows that in a community dominated by hydrogenotrophic methanogens, stable continuous culture under low load conditions will also show the transformation of acetotrophic methanogens to hydrogenotrophic methanogens. It is worth mentioning that Methanosarcina bacteria only showed growth in the embodiment mode. Methanosarcina bacteria have multiple methane-producing metabolic pathways. The diversified metabolic pathways enable them to efficiently produce methane under different substrate conditions. Compared with microorganisms with only a single methane-producing pathway, they can more fully convert substrates into methane, thereby improving the methane yield and production efficiency of the anaerobic digestion system. Methanosarcina bacteria can grow on a variety of complex organic substrates, which enables them to degrade substrates more comprehensively and improve the treatment effect of the system. Methanosarcina bacteria also have a strong biofilm formation ability and can form a stable biofilm structure on the surface of the filler or granular sludge of the anaerobic reactor to protect it from the influence of external environmental factors, which is beneficial to the interaction and material transfer between microorganisms and enhances the stability of the anaerobic digestion system.

[0083] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A wastewater treatment method based on a UASB reactor, the method utilizing a UASB reactor system comprising a UASB reactor, a water inlet pipe, and a peristaltic pump, wherein a water inlet is provided at the bottom of the UASB reactor, the water inlet being connected to an external wastewater source via the water inlet pipe, the peristaltic pump being provided on the water inlet pipe for adjusting the water inlet speed, a water outlet being provided at the top of the UASB reactor, and anaerobic digestion sludge being contained in the UASB reactor, characterized in that: The method comprises the following steps: a stabilization preparatory step of continuously flowing sewage having a first COD concentration into the UASB reactor through the water inlet at a fixed flow rate, so that the microbial activity of the anaerobic digested sludge contained in the UASB reactor reaches a stable state; High-low alternating load water inlet step: adjusting the peristaltic pump so that the sewage with the first COD concentration enters the UASB reactor through the water inlet continuously at a flow rate that changes periodically.

2. The sewage treatment method based on the UASB reactor according to claim 1, characterized in that: After the high-low alternating load water intake step, the method further comprises: and increasing the load step: continuously flowing sewage into the UASB reactor through the water inlet at a fixed flow rate, wherein the COD concentration of the sewage flowing into the UASB reactor increases with the passage of time, starting from the first COD concentration, until the UASB reactor reaches a critical value for the COD removal rate of the sewage.

3. The sewage treatment method based on the UASB reactor according to claim 1, characterized in that: Before the stable operation step, the method further includes: Startup steps: continuously flowing sewage with a second COD concentration into the UASB reactor through the water inlet at a fixed flow rate; Taking the second COD concentration as the starting concentration, gradually increasing the COD concentration of the sewage flowing into the UASB reactor over time; Detecting the COD removal rate of the UASB reactor for sewage with different COD concentrations; The COD concentration of the sewage at which the COD removal rate of the UASB reactor is the highest is determined as the first COD concentration.

4. The sewage treatment method based on the UASB reactor according to claim 1, characterized in that: Between the high-low alternating load water intake step and the load increasing step, the method further comprises: Stabilization recovery step: continuously flowing sewage with a first COD concentration into the UASB reactor through the water inlet at a fixed flow rate, wherein the organic load of the UASB reactor in the stabilization recovery step is the same as the organic load of the UASB reactor in the stabilization preparation step.

5. The sewage treatment method based on the UASB reactor according to claim 1, characterized in that: The anaerobic digestion sludge is activated sludge enriched with hydrogenotrophic methanogens.

6. The sewage treatment method based on the UASB reactor according to claim 1, characterized in that: The first COD concentration is 2000 mg / L.

7. The sewage treatment method based on the UASB reactor according to claim 1, characterized in that: The pH value of the sewage with the first COD concentration flowing into the UASB reactor is 7-8; The temperature of the insulation layer is 37±1°C.

8. The sewage treatment method based on the UASB reactor according to claim 1, characterized in that: The volume of the anaerobic digested sludge contained in the UASB reactor is 1 / 2 of the volume of the UASB reactor.

9. The sewage treatment method based on the UASB reactor according to claim 1, characterized in that: The UASB reactor is provided with a tube body and a sludge hopper, the sludge hopper is arranged below the tube body, the water inlet is arranged in the sludge hopper, the tube body includes an inner tube and an outer tube, an insulation layer is provided between the inner tube and the outer tube, the inner tube is a main reaction chamber, and an exhaust port and a water outlet are provided at the top of the UASB reactor.

10. The sewage treatment method based on the UASB reactor according to claim 1, characterized in that: During the high-low alternating load water inlet step, the organic load of the UASB reactor varies periodically.

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