Device and method for quickly recovering denitrification performance of synchronous nitrification and denitrification process impacted by low COD / N (Chemical Oxygen Demand / Nitrogen)

Abstract

The invention relates to a device and a method for rapidly recovering denitrification performance of a synchronous nitrification and denitrification process impacted by low COD / N, and belongs to the technical field of biological sewage treatment. The device comprises a sewage tank, an SBBR (Sequencing Batch Biofilm Reactor), a blast aerator, a water outlet tank and an online monitoring device. The method comprises the following steps: 1) impacting a synchronous nitrification and denitrification process of a sequencing batch bio-membrane reactor by low-COD / N sewage and inhibiting denitrification performance, then adding high-COD / N sewage and adding biodegradable polylactic acid micro-plastic into the SBBR reactor to recover synchronous nitrification and denitrification; and 2) gradually reducing the DO concentration of the aeration section to promote recovery of synchronous nitrification and denitrification, and enabling the synchronous nitrification and denitrification rate and the organic matter removal rate to be stable. By adding the biodegradable polylactic acid micro-plastic, synchronous nitrification and denitrification in the biological membrane can be promoted. By gradually reducing the DO concentration, synchronous nitrification and denitrification can be rapidly recovered in situ and kept stable.

Description

Technical Field

[0001] The present invention belongs to the technical field of biological sewage treatment, and in particular relates to a device and method for rapidly recovering the denitrification performance of a simultaneous nitrification and denitrification process subjected to a low COD / N ratio shock. Background Art

[0002] Traditional biological denitrification technology refers to the nitrification of ammonia nitrogen and then the removal of nitrogen gas through denitrification. Since aerobic nitrification and anoxic denitrification require different environmental conditions, the two processes are usually implemented in different operating units, and maintaining the operation of the process equipment increases operating costs. Therefore, the research and development of new sewage denitrification processes is very important. Traditional denitrification methods have problems such as high energy consumption, large demand for carbon sources, and large amounts of residual sludge production, making it difficult to meet increasingly stringent emission standards and energy-saving and consumption-reducing requirements. Therefore, the reuse of recyclable resources and the exploration of energy-saving and consumption-reducing processes have become the core direction of future sewage treatment development, and are also key challenges that need to be urgently addressed in the field of biological denitrification research.

[0003] Simultaneous nitrification and denitrification (SND) technology allows nitrification and denitrification to occur simultaneously within a single reactor under the same overall operating conditions. Under certain conditions, this technology can reduce the need for external carbon sources, reduce the number and volume of reactors, and save operating costs. Compared to traditional biological denitrification technologies, SND can reduce sludge production and adapt to varying influent water quality.

[0004] Polylactic acid (PLA) is a bio-based polymer made from renewable resources (such as corn starch or sugarcane). Due to its excellent biocompatibility and environmentally friendly properties, it has been widely used in many fields such as food packaging, 3D printing, and textile products. - -N removal mainly relies on the denitrification process involving heterotrophic denitrifying bacteria. The monomer lactic acid released by the degradation of polylactic acid (PLA) is an excellent electron donor in the denitrification process, leading to the enrichment of denitrifying bacteria on the surface of polylactic acid microplastics, thereby promoting the denitrification effect.

[0005] Compared with traditional biological denitrification processes, the SBBR process can effectively save construction costs and energy consumption due to its simplified treatment unit. Furthermore, the use of a biofilm can provide a micro-anoxic environment for denitrifying bacteria, allowing nitrification to occur in the outer aerobic layer and denitrification to occur in the inner anoxic layer, facilitating the simultaneous nitrification and denitrification, achieving deep denitrification.

[0006] In addition, in the start-up stage of the sewage biological treatment system, problems such as low denitrification activity, long start-up time, and unsatisfactory effects are often encountered. The activity of denitrifying bacteria is mainly affected by the DO concentration. At a lower DO concentration, heterotrophic denitrifying bacteria are prone to using organic matter as an electron donor to reduce NO3 - -N to N2. Reducing the DO concentration in the aeration stage is easy to achieve the progress of denitrification and maintain it stably, and can also save operating costs and sludge treatment costs.

[0007] Therefore, the present invention proposes a device and method for quickly restoring the nitrogen removal performance of the simultaneous nitrification and denitrification process impacted by low COD / N, which has obvious advantages. On the one hand, the biofilm and polylactic acid microplastics can achieve the aggregation of denitrifying bacteria in sewage and the effective utilization of carbon sources; on the other hand, reducing the DO concentration in the SBBR reactor is beneficial to the growth of denitrifying bacteria in sewage and the rapid start-up and stable maintenance of the simultaneous nitrification and denitrification process. The device not only has a simple process and obvious nitrogen removal effect, but also can reduce operating and subsequent treatment costs. Summary of the Invention

[0008] The present invention proposes a device and method for quickly restoring the nitrogen removal performance of the simultaneous nitrification and denitrification process impacted by low COD / N, which solves the problem that it is difficult to quickly start and restore the simultaneous nitrification and denitrification of sewage at present, in order to achieve a stable simultaneous nitrification and denitrification nitrogen removal process.

[0009] To achieve the above object, the present invention is realized through the following technical solutions:

[0010] A device for quickly restoring the nitrogen removal performance of the simultaneous nitrification and denitrification process impacted by low COD / N, comprising a sewage water tank, an SBBR reactor, a blower aerator, an effluent water tank, a feed water pump, an electric drainage pump, and an on-line monitoring device;

[0011] The SBBR reactor is provided with: a water inlet, a magnetic stirrer, a DO sensor, a pH sensor, a temperature sensor, a sludge discharge valve, a water outlet, a rotameter, a microporous aeration head, a packing support, a biofilm composite fiber packing, and a magnetic stirring rotor;

[0012] The sewage water tank is connected to the water inlet of the SBBR reactor through a feed water pump, the blower aerator is connected to the microporous aeration head of the SBBR reactor through a rotameter, and the water outlet of the SBBR reactor is connected to the effluent water tank through an electric drainage pump;

[0013] The on-line monitoring device includes a relay and a detector; the relay includes an aeration relay, a water inlet relay, a water outlet relay, and a stirrer relay;

[0014] The aeration relay is connected to the blower aerator, the influent relay is connected to the influent pump, the stirrer relay is connected to the magnetic stirrer, and the effluent relay is connected to the electric drainage pump; the DO sensor, pH sensor, and temperature sensor are respectively connected to the measuring instrument.

[0015] The biological film combined fiber packing is composed of fiber bundles, plastic discs, sleeves, and a central rope;

[0016] The fiber bundles are bundled on the plastic discs and spread out and evenly distributed around. The central rope connects all the plastic discs from top to bottom. The upper end of the central rope is bundled and fixed on the packing support, and the lower end is respectively bundled and fixed on both sides of the inner wall of the SBBR reactor. Sleeves are provided on the central rope between adjacent plastic discs to fix the plastic discs.

[0017] A method for rapidly restoring the nitrogen removal performance of the simultaneous nitrification and denitrification process impacted by low COD / N using the above device includes the following steps:

[0018] 1) Reactor startup stage:

[0019] 1.1) Bundle and fix the biological film combined fiber packing on the packing support at the top end inside the SBBR reactor. Then, use the simultaneous nitrification and denitrification activated sludge impacted by low COD / N sewage as the inoculation sludge. The low COD / N sewage in the sewage tank runs through the influent pump for 1 min and enters the SBBR reactor through the influent port;

[0020] 1.2) After water inflow, start the magnetic stirrer to drive the magnetic stirrer rotor for aerobic stirring for 8.5 h; meanwhile, start the blower aerator and control the DO concentration > 2.0 mg / L through the rotameter and microporous aeration head;

[0021] 1.3) After the above reaction ends, turn off the blower aerator, and the magnetic stirrer then conducts anoxic stirring for 2.5 h, controlling the DO concentration < 0.2 mg / L through the rotameter and microporous aeration head;

[0022] 1.4) Then, stop the magnetic stirrer, let it stand and precipitate for 56 min, and then drain the supernatant. The supernatant is drained through the electric drainage pump through the effluent port for 3 min, and the drainage enters the effluent tank. The drainage ratio is 50%. After the drainage is completed, one cycle ends, and then immediately start the next cycle;

[0023] 1.5) Repeat steps 1.1) to 1.4) until a large amount of activated sludge accumulates on the biological film combined fiber packing, indicating that the biological film has grown mature, thus obtaining an SBBR reactor with a grown and mature biological film;

[0024] 2) Reactor normal operation adjustment:

[0025] 2.1) The high COD / N sewage in the sewage tank is pumped by the inlet pump for 1 min and enters the SBBR reactor with a grown and mature biofilm through the inlet. At the same time of inlet, biodegradable polylactic acid microplastics are added.

[0026] 2.2) After inlet, turn on the magnetic stirrer to drive the magnetic stirring rotor for aerobic stirring for 8.5 h. At the same time, turn on the air blower aerator and control the DO concentration at 0.2 - 0.5 mg / L through the rotameter and microporous aeration head.

[0027] 2.3) After the above reaction ends, turn off the air blower aerator, and the magnetic stirrer then conducts anoxic stirring for 2.5 h, and control the DO concentration < 0.2 mg / L through the rotameter and microporous aeration head.

[0028] 2.4) Then, stop the operation of the magnetic stirrer, let it stand and precipitate for 56 min, and then discharge the supernatant. The supernatant is drained through the electric drain pump through the outlet for 3 min, and the drained water enters the outlet water tank. The drainage ratio is 50%. After the drainage is completed, one cycle ends, and then immediately start the next cycle.

[0029] 2.5) During the operation of the SBBR reactor, it is necessary to regularly drain sludge through the sludge discharge valve to discharge the detached biofilm.

[0030] Further, in the above method, in step 1.1), the volume ratio of the biofilm combined fiber filler to the effective volume of the entire SBBR reactor is 20% - 30%.

[0031] Further, in the above method, in step 1.5), the monitoring indexes for the mature growth of the biofilm are: visually observing that the surface of the biofilm combined fiber filler is evenly covered with activated sludge without large - area exposure; when aerating, the bubbles rise evenly without large pieces of biofilm falling off.

[0032] Further, in the above method, in step 2.1), the particle size of the polylactic acid microplastics is 150 μm, and the dosing concentration in the sewage in the SBBR reactor is 5 mg / L.

[0033] Further, in the above method, in steps 1.2), 1.3), 2.2) and 2.3), the set rotation speed of the magnetic stirrer is 500 rpm.

[0034] Further, in the above method, in steps 1) and 2), control the temperature of the sewage in the sewage tank and the SBBR reactor at 15℃ - 30℃ and the pH at 7.5 - 8.0.

[0035] Further, in the above method, in steps 1.4) and 2.4), each cycle is 12 h.

[0036] Furthermore, in the above method, the synchronous nitrification and denitrification (SND) rate and the COD removal rate both reach over 80%, and are stably maintained for over 15 days, indicating the successful recovery of synchronous nitrification and denitrification.

[0037] The beneficial effects of the present invention are as follows:

[0038] 1. In the present invention, the polylactic acid microplastics can not only be used as a biodegradable external solid carbon source but also as a biofilm carrier in the biofilm reactor, turning waste into treasure, being economical and practical, and can be widely used in the treatment of sewage in production and life practices.

[0039] 2. The present invention makes full use of the limited carbon source in the sewage to achieve deep nitrogen removal and saves aeration energy consumption.

[0040] 3. The present invention can quickly recover the nitrogen removal performance of the synchronous nitrification and denitrification process impacted by low COD / N within several days, and the denitrification effect after recovery is obvious and stable. Description of the Drawings

[0041] Figure 1 It is a schematic structural diagram of a device for quickly recovering the nitrogen removal performance of the synchronous nitrification and denitrification process impacted by low COD / N. Among them, 1 - sewage water tank, 2 - SBBR reactor, 3 - air blower, 4 - effluent water tank, 5 - feed water pump, 6 - water inlet, 7 - magnetic stirrer, 8 - DO sensor, 9 - pH sensor, 10 - temperature sensor, 11 - sludge discharge valve, 12 - water outlet, 13 - electric drainage pump, 14 - rotameter, 15 - microporous aeration head, 16 - packing support, 17 - biofilm composite fiber packing, 17 - 1 - fiber bundle, 17 - 2 - plastic disc, 17 - 3 - sleeve, 17 - 4 - center rope, 18 - relay, 18 - 1 - aeration relay, 18 - 2 - feed water relay, 18 - 3 - effluent water relay, 18 - 4 - stirrer relay, 19 - measuring instrument, 20 - magnetic stirrer rotor.

[0042] Figure 2 It is a process flow chart of a method for quickly recovering the nitrogen removal performance of the synchronous nitrification and denitrification process impacted by low COD / N.

[0043] Figure 3 It is the operation effect diagram of SBBR reactors A1 and A2. Among them, Figure 3 (a): SND rate and TIN removal rate during the operation of A1 and A2; Figure 3 (b): Influent and effluent COD concentrations and COD removal rate during the operation of A1 and A2.

[0044] Figure 4 It is the operation effect diagram of SBBR reactors B1 and B2. Figure 4(a): Influent and effluent COD concentrations and COD removal rate during the operation of B1 and B2; Figure 4 (b): SND rate and TIN removal rate during the operation of B1 and B2. Detailed implementation manners

[0045] The implementation scheme of the present invention will be described in detail below in conjunction with the drawings and embodiments.

[0046] Embodiment 1

[0047] As shown in Figure 1 the device includes: sewage water tank 1, SBBR reactor 2, air blower 3, effluent water tank 4, feed pump 5, electric drain pump 13 and on-line monitoring device.

[0048] The SBBR reactor 2 is provided with: water inlet 6, magnetic stirrer 7, DO sensor 8, pH sensor 9, temperature sensor 10, sludge discharge valve 11, water outlet 12, rotameter 14, microporous aeration head 15, packing support 16, biofilm composite fiber packing 17, magnetic stirring rotor 20;

[0049] The biofilm composite fiber packing 17 is composed of fiber bundles 17-1, plastic discs 17-2, sleeves 17-3 and central ropes 17-4; the fiber bundles 17-1 are bundled on the plastic discs 17-2 and spread out and evenly distributed around, the central ropes 17-4 connect all the plastic discs 17-2 from top to bottom, the upper ends of the central ropes 17-4 are bundled and fixed on the packing support 16, and the lower ends are respectively bundled and fixed on both sides of the inner wall of the SBBR reactor 2. The sleeves 17-3 are arranged on the central ropes 17-4 between adjacent plastic discs 17-2 to fix the plastic discs 17-2.

[0050] The effective volume of the SBBR reactor 2 is 5.0L, and the effective height is 50cm. A total of 5 plastic discs 17-2 bundled with fiber bundles 17-1 are hung on the packing support 16. The volume of a single plastic disc 17-2 is 0.2L, the distance between adjacent two plastic discs 17-2 is 0.1m, and they are connected by the central ropes 17-4. The sleeves 17-3 on the central ropes 17-4 are used to fix their positions, and the volume occupied by adjacent central ropes 17-4 and sleeves 17-3 is 0.1L. A section of the central rope 17-4 with a certain distance is reserved at both ends for fixing the biofilm composite fiber packing 17.

[0051] The sewage water tank 1 is communicated with the water inlet 6 of the SBBR reactor 2 through the feed pump 5, the air blower 3 is connected with the microporous aeration head 15 of the SBBR reactor 2 through the rotameter 14, and the water outlet 12 of the SBBR reactor 2 is communicated with the effluent water tank 4 through the electric drain pump 13.

[0052] The on-line monitoring device includes a relay 18 and a measuring instrument 19; the relay 18 includes an aeration relay 18-1, a water inlet relay 18-2, a water outlet relay 18-3 and a stirrer relay 18-4; the aeration relay 18-1 is connected to the blower aerator 3 for controlling the opening and closing of the blower aerator 3; the water inlet relay 18-2 is connected to the water inlet pump 5 for controlling the opening and closing of the water inlet pump 5; the stirrer relay 18-4 is connected to the magnetic stirrer 7 for controlling the rotation speed of the magnetic stirrer 7; the water outlet relay 18-3 is connected to the electric drainage pump 13 for controlling the opening and closing of the electric drainage pump 13; the DO sensor 8, the pH sensor 9 and the temperature sensor 10 are respectively connected to the measuring instrument 19, and the DO, pH and temperature in the SBBR reactor 2 are respectively displayed on the measuring instrument 19 through the DO sensor 8, the pH sensor 9 and the temperature sensor 10.

[0053] Example 2

[0054] Such as Figure 2 , the operating parameters during the experiment are as follows:

[0055] The composition of the simulated sewage is as follows: ammonium chloride, crystalline sodium acetate, potassium dihydrogen phosphate, anhydrous sodium carbonate (analytical pure). The indicators are as follows: COD = 300 ± 50 mg / L, NH4 + -N = 30 ± 5 mg / L, TP = 7 mg / L, pH is 7.5 - 8.0.

[0056] Using the simulated sewage as the influent water for two SBBR reactors 2 (A1, A2). The operating temperature is the laboratory air temperature (15°C - 30°C).

[0057] The specific operating parameters are as follows: instantaneous influent for 1 min, aeration + stirring for 8.5 h, anoxic stirring for 2.5 h, static sedimentation for 56 min, drainage for 3 min, each cycle is 12 h, and 2 cycles are run in 1 day.

[0058] The specific operating method is as follows:

[0059] 1) Reactor startup stage:

[0060] ① Bundle and fix the biofilm composite fiber packing 17 on the packing support 16 at the top inside the SBBR reactor 2, and the filling ratio is 20% - 30%. Using the activated sludge with stable and efficient synchronous nitrification and denitrification performance as the inoculation sludge, the sewage in the sewage tank 1 is run through the water inlet pump 5 for 1 min and enters the SBBR reactor 2 through the water inlet 6.

[0061] The filling ratio is the ratio of the volume of the biofilm composite fiber packing 17 to the effective volume of the entire SBBR reactor 2.

[0062] The effective volume of the SBBR reactor × filling ratio = the volume of the combined biofilm fiber packing (the volume of plastic discs + sleeves).

[0063] ② After the water inlet, turn on the magnetic stirrer 7 to drive the magnetic stirrer rotor 20 for aerobic stirring for 8.5 h, and control the rotation speed of the magnetic stirrer 7 to be 500 rpm. At the same time, turn on the air blower aerator 3, and control the DO concentration > 2.0 mg / L through the rotameter 14 and the microporous aeration head 15.

[0064] ③ After the above reaction ends, turn off the air blower aerator 3, and the magnetic stirrer 7 then performs anoxic stirring for 2.5 h, and controls the DO concentration < 0.2 mg / L through the rotameter 14 and the microporous aeration head 15.

[0065] ④ After that, the magnetic stirrer 7 stops running. After static sedimentation for 56 min, the supernatant is discharged. The supernatant is drained through the electric drain pump 13 through the water outlet 12 for 3 min, and the drained water enters the effluent water tank 4, and the drainage ratio is 50%. After the drainage is completed, one cycle ends, and then the next cycle is immediately started. There is no need for a time interval and other operating processes between two cycles.

[0066] ⑤ Repeat steps ① to ④. When it is observed with the naked eye that the surface of the combined biofilm fiber packing 17 is evenly covered with activated sludge and there is no large area exposed; when aerating, the bubbles rise evenly and there is no large piece of biofilm falling off, it indicates that the biofilm has grown mature. Thus, the SBBR reactor 2 with a maturely grown biofilm is obtained.

[0067] 2) Reactor normal operation adjustment:

[0068] ① The sewage in the sewage water tank 1 is pumped by the water inlet pump 5 for 1 min and enters the SBBR reactor 2 with a maturely grown biofilm through the water inlet 6. While the water is inlet, biodegradable polylactic acid microplastics (150 μm) are added to the SBBR reactor 2 (A1) so that its concentration in the sewage in A1 is 5 mg / L. No polylactic acid microplastics are added to the other SBBR reactor 2 (A2), and the concentration of polylactic acid microplastics in A2 is 0 mg / L.

[0069] ② After the water inlet, turn on the magnetic stirrer 7 to drive the magnetic stirrer rotor 20 for aerobic stirring for 8.5 h, and control the rotation speed of the magnetic stirrer 7 to be 500 rpm. At the same time, turn on the air blower aerator 3, and control the DO concentration > 2.0 mg / L through the rotameter 14 and the microporous aeration head 15.

[0070] ③After the above reaction is completed, turn off the air blower aerator 3, and the magnetic stirrer 7 then conducts anoxic stirring for 2.5 h, controlling the DO concentration <0.2 mg / L through the rotameter 14 and the microporous aeration head 15. The simultaneous nitrification and denitrification reaction occurs on the biofilm. Under low dissolved oxygen conditions, the outer biofilm oxidizes the remaining unoxidized ammonia nitrogen to nitrite, and the inner biofilm uses the carbon source to reduce nitrate or nitrite to produce N2, which is discharged from the SBBR reactor 2, thereby achieving the purpose of nitrogen removal.

[0071] ④After that, the magnetic stirrer 7 stops operating. After standing and sedimenting for 56 min, the supernatant is discharged. The supernatant is drained through the electric drain pump 13 through the water outlet 12 for 3 min, and the drained water enters the outlet water tank 4, and the drainage ratio is 50%. After the drainage is completed, one cycle ends, and then the next cycle is immediately started. There is no need for a time interval or other operating processes between the two cycles.

[0072] ⑤During the operation of the SBBR reactor 2, it is necessary to regularly discharge sludge through the sludge discharge valve 11 to discharge the shed biofilm.

[0073] During the experiment, the concentrations of ammonia nitrogen and COD in the influent and effluent are regularly detected. At the same time, the concentrations of nitrite nitrogen and nitrate nitrogen in the effluent are detected, and the COD removal rate, total inorganic nitrogen (TIN) removal rate, and simultaneous nitrification and denitrification (SND) rate are calculated. The main calculation formulas are as follows:

[0074]

[0075] The experimental results are shown in Figure 3 。 Figure 3 To observe the operation effects of the A1 and A2 reactors recorded during the normal operation adjustment stage after the biofilm is mature. At this time, the simultaneous nitrification and denitrification are not damaged by shock.

[0076] From Figure 3 It can be obtained that after operating for 50 d, the average COD removal rates of the A1 and A2 reactors are 82.93% and 89.08% respectively, the TIN removal rates are 75.16% and 71.79% respectively, and the SND rates are 89.36% and 79.38% respectively. It shows that adding polylactic acid microplastics can promote the simultaneous nitrification and denitrification nitrogen removal of SBBR.

[0077] Example 3

[0078] As Figure 2 , the operating parameters during the experiment are:

[0079] Using simulated sewage as the influent for the two SBBR reactors 2 (B1, B2). The indicators of the simulated sewage are as follows: high COD / N sewage: COD = 300 ± 50 mg / L, NH4 +- N = 30 ± 5 mg / L, TP = 7 mg / L, pH is 7.5 - 8.0. Low COD / N sewage: COD = 150 ± 30 mg / L, NH4 + - N = 30 ± 5 mg / L, TP = 7 mg / L, pH is 7.5 - 8.0.

[0080] The operating temperature is the laboratory air temperature (15°C - 30°C).

[0081] The specific operating parameters are as follows: instantaneous water inlet for 1 min, aeration + stirring for 8.5 h, anoxic stirring for 2.5 h, static sedimentation for 56 min, drainage for 3 min, each cycle is 12 h, and 2 cycles are run in 1 day.

[0082] The specific operating method is as follows:

[0083] 1) Reactor startup stage:

[0084] ① Bundle and fix the biological membrane composite fiber filler 17 on the filler support 16 at the top inside the SBBR reactor 2, and the filling ratio is 20% - 30%. Use the simultaneous nitrification and denitrification activated sludge after being impacted by low COD / N sewage as the inoculation sludge. The low COD / N sewage in the sewage tank 1 runs for 1 min through the feed pump 5 and enters the SBBR reactor 2 through the water inlet 6;

[0085] The filling ratio is the proportion of the volume of the biological membrane composite fiber filler 17 in the effective volume of the entire SBBR reactor 2.

[0086] Effective volume of the SBBR reactor × filling ratio = volume of the biological membrane composite fiber filler (volume of plastic disc + casing).

[0087] ② After water inlet, turn on the magnetic stirrer 7 to drive the magnetic stirring rotor 20 for aerobic stirring for 8.5 h, and control the rotation speed of the magnetic stirrer 7 to be 500 rpm. At the same time, turn on the air blower aerator 3, and control the DO concentration > 2.0 mg / L through the rotameter 14 and the microporous aeration head 15.

[0088] ③ After the above reaction ends, turn off the air blower aerator 3, and the magnetic stirrer 7 then conducts anoxic stirring for 2.5 h, and control the DO concentration < 0.2 mg / L through the rotameter 14 and the microporous aeration head 15.

[0089] ④ Then, stop the operation of the magnetic stirrer 7, let it stand and sediment for 56 min, then drain the supernatant. The supernatant is drained for 3 min through the electric drain pump 13 via the water outlet 12, and the drained water enters the effluent water tank 4, and the drainage ratio is 50%. After the drainage is completed, one cycle ends, and then immediately start the next cycle without any time interval and other operating processes between the two cycles.

[0090] ⑤ Repeat steps ① through ④ until the surface of the biofilm-combined fiber packing 17 is visually uniformly covered with activated sludge, with no large exposed areas. Aeration indicates that the biofilm has matured when bubbles rise evenly and no large pieces of biofilm fall off. This results in an SBBR reactor 2 with a mature biofilm. Operate for 10 days and record data.

[0091] 2) Normal operation adjustment of reactor:

[0092] ① The high COD / N sewage in the sewage tank 1 runs through the water inlet pump 5 for 1 minute and enters the SBBR reactor 2 with mature biofilm through the water inlet 6. At the same time, biodegradable polylactic acid microplastics (150 μm) are added to the two SBBR reactors 2 (B1 and B2) so that their concentration in the sewage in the two SBBR reactors 2 is 5 mg / L.

[0093] ② After the water is introduced, the magnetic stirrer 7 is turned on to drive the magnetic stirring rotor 20 for aerobic stirring for 8.5 hours, and the speed of the magnetic stirrer 7 is controlled to 500 rpm. At the same time, the aerator 3 is turned on, and the DO concentration in the SBBR reactor 2 (B1) is controlled to 0.2-0.5 mg / L and the DO concentration in the SBBR reactor 2 (B2) is controlled to be >2.0 mg / L via the rotor flowmeter 14 and the microporous aeration head 15.

[0094] ③ After the reaction is complete, the aerator 3 is turned off, and the magnetic stirrer 7 continues to perform anoxic stirring for 2.5 hours. The DO concentration is controlled to <0.2 mg / L using the rotor flowmeter 14 and the microporous aeration head 15. Simultaneous nitrification and denitrification reactions occur on the biofilm. Under low dissolved oxygen conditions, the outer biofilm oxidizes the remaining unoxidized ammonia nitrogen into nitrite. The inner biofilm uses the carbon source to reduce the nitrate or nitrite to produce nitrogen, which is discharged from the SBBR reactor 2, thereby achieving the purpose of denitrification.

[0095] ④ After that, the magnetic stirrer 7 stops operating, and after settling for 56 minutes, the supernatant is discharged. The supernatant is then drained through the water outlet 12 by the electric drainage pump 13 for 3 minutes and enters the water outlet tank 4. The drainage ratio is 50%. After the drainage is completed, one cycle ends and the next cycle is immediately started. There is no need for a time interval or other operating process between the two cycles.

[0096] ⑤ During the operation of the SBBR reactor 2, mud needs to be discharged regularly through the mud discharge valve 11 to remove the detached biofilm.

[0097] During the experiment, the concentrations of ammonia nitrogen and COD in the inlet and outlet water were regularly tested. At the same time, the concentrations of nitrite nitrogen and nitrate nitrogen in the outlet water were tested. The COD removal rate, total inorganic nitrogen (TIN) removal rate and simultaneous nitrification and denitrification (SND) rate were calculated. The main calculation formulas are as follows:

[0098]

[0099] The experimental results are shown in Figure 4 . The first 10 days are the later stage of the reactor startup phase. The operating effects of Reactors B1 and B2 recorded after observing the maturation of the biofilm are as follows. At this time, simultaneous nitrification and denitrification have not recovered. Within the first 10 days, the average COD removal rates of Reactors B1 and B2 are 77.80% and 80.68% respectively, the TIN removal rates are 30.22% and 31.82% respectively, and the SND rates are 37.01% and 46.26% respectively.

[0100] It can be seen from Figure 4 that Reactor B1 requires a shorter time to recover simultaneous nitrification and denitrification and reach stability, only 4 days; while Reactor B2 requires 12 days to recover simultaneous nitrification and denitrification and reach stability.

[0101] Within 26 days after Reactor B1 recovered simultaneous nitrification and denitrification, the average COD removal rates of Reactors B1 and B2 are 90.04% and 88.70% respectively, the TIN removal rates are 63.05% and 56.65% respectively, and the SND rates are 89.50% and 84.82% respectively.

[0102] Within 18 days after Reactor B2 recovered simultaneous nitrification and denitrification, the average COD removal rates of Reactors B1 and B2 are 89.84% and 89.22% respectively, the TIN removal rates are 66.90% and 65.18% respectively, and the SND rates are 91.91% and 90.58% respectively.

[0103] The test results show that after stable operation, the final effluent COD concentration < 50 mg / L, NH4 + -N concentration < 10 mg / L, NO2 - -N concentration < 1 mg / L, NO3 - -N concentration < 5 mg / L. It shows that reducing the DO concentration can promote the recovery of the nitrogen removal performance of the simultaneous nitrification and denitrification process promoted by adding polylactic acid microplastics and maintain stability.

[0104] The above are specific embodiments of the present invention, which are convenient for those skilled in the art of this technology to better understand and apply the present invention. However, the implementation of the present invention is not limited to this. Therefore, simple improvements made by those skilled in the art of this technology to the present invention are within the protection scope of the present invention.

Claims

1. An apparatus for rapidly restoring the nitrogen removal performance of a simultaneous nitrification and denitrification process impacted by low COD / N, characterized in that, The device includes a sewage tank (1), an SBBR reactor (2), a blower aerator (3), an effluent tank (4), a feed pump (5), an electric drainage pump (13), and an on-line monitoring device; The SBBR reactor (2) is provided with: an inlet (6), a magnetic stirrer (7), a DO sensor (8), a pH sensor (9), a temperature sensor (10), a sludge discharge valve (11), an outlet (12), a rotameter (14), a microporous aeration head (15), a packing support (16), a biofilm combined fiber packing (17), and a magnetic stirring rotor (20); The sewage tank (1) is communicated with the inlet (6) of the SBBR reactor (2) through the feed pump (5), the blower aerator (3) is connected with the microporous aeration head (15) of the SBBR reactor (2) through the rotameter (14), and the outlet (12) of the SBBR reactor (2) is communicated with the effluent tank (4) through the electric drainage pump (13); The on-line monitoring device includes a relay (18) and a detector (19); the relay (18) includes an aeration relay (18-1), a feed relay (18-2), an effluent relay (18-3), and a stirrer relay (18-4); The aeration relay (18-1) is connected with the blower aerator (3), the feed relay (18-2) is connected with the feed pump (5), the stirrer relay (18-4) is connected with the magnetic stirrer (7), and the effluent relay (18-3) is connected with the electric drainage pump (13); the DO sensor (8), the pH sensor (9), and the temperature sensor (10) are respectively connected with the detector (19).

2. The device for rapidly restoring the nitrogen removal performance of the simultaneous nitrification and denitrification process impacted by low COD / N according to claim 1, characterized in that, The biofilm combined fiber packing (17) is composed of fiber bundles (17-1), plastic disk plates (17-2), sleeves (17-3), and a central rope (17-4); The fiber bundles (17-1) are bundled on the plastic disk plates (17-2) and spread out and evenly distributed around, the central rope (17-4) connects all the plastic disk plates (17-2) from top to bottom, the upper end of the central rope (17-4) is bundled and fixed on the packing support (16), the lower end is respectively bundled and fixed on both sides of the inner wall of the SBBR reactor (2), and sleeves (17-3) are arranged on the central rope (17-4) between adjacent plastic disk plates (17-2) to fix the plastic disk plates (17-2).

3. A method for rapidly restoring the nitrogen removal performance of the simultaneous nitrification and denitrification process affected by low COD / N shock by using the device according to claim 1 or 2, characterized in that, It includes the following steps: 1) Reactor startup stage: 1.1) Bundle and fix the biofilm combined fiber packing (17) on the packing support (16) at the top inside the SBBR reactor (2), then use the synchronous nitrification and denitrification activated sludge after being impacted by low COD / N sewage as the inoculation sludge, and the low COD / N sewage in the sewage tank (1) runs through the feed pump (5) for 1 min and enters the SBBR reactor (2) through the inlet (6); 1.2) After the water enters, the magnetic stirrer (7) is turned on to drive the magnetic stirring rotor (20) for aerobic stirring for 8.5 hours; at the same time, the aerator (3) is turned on, and the DO concentration is controlled to be >2.0 mg / L through the rotor flow meter (14) and the microporous aeration head (15); 1.3) After the above reaction is completed, the aerator (3) is turned off and the magnetic stirrer (7) is used to perform anoxic stirring for 2.5 hours. The DO concentration is controlled to be less than 0.2 mg / L by the rotor flow meter (14) and the microporous aeration head (15); 1.4) After that, the magnetic stirrer (7) stops running, and the supernatant is discharged after settling for 56 minutes. The supernatant is drained through the water outlet (12) by the electric drainage pump (13) for 3 minutes, and the water enters the water outlet tank (4). The drainage ratio is 50%. After the drainage is completed, one cycle ends, and the next cycle is immediately started; 1.5) Repeating steps 1.1) to 1.4) until a large amount of activated sludge is accumulated on the biofilm combined fiber filler (17), indicating that the biofilm has grown maturely, thereby obtaining an SBBR reactor (2) having a mature biofilm; 2) Normal operation adjustment of reactor: 2.1) The high COD / N wastewater in the wastewater tank (1) is pumped through the water inlet pump (5) for 1 minute and enters the SBBR reactor (2) with a mature biofilm through the water inlet (6). Biodegradable polylactic acid microplastics are added during the water inlet. 2.2) After the water enters, the magnetic stirrer (7) is turned on to drive the magnetic stirring rotor (20) for aerobic stirring for 8.5 hours; at the same time, the aerator (3) is turned on, and the DO concentration is controlled to 0.2-0.5 mg / L through the rotor flow meter (14) and the microporous aeration head (15); 2.3) After the above reaction is completed, the aerator (3) is turned off and the magnetic stirrer (7) is used to perform anoxic stirring for 2.5 hours. The DO concentration is controlled to be less than 0.2 mg / L by the rotor flow meter (14) and the microporous aeration head (15); 2.4) After that, the magnetic stirrer (7) stops running, and the supernatant is discharged after settling for 56 minutes. The supernatant is drained through the water outlet (12) by the electric drainage pump (13) for 3 minutes, and the water enters the water outlet tank (4). The drainage ratio is 50%. After the drainage is completed, one cycle ends and the next cycle is immediately started; 2.5) During the operation of the SBBR reactor (2), it is necessary to regularly discharge mud through the mud discharge valve (11) to remove the detached biofilm.

4. The method according to claim 3, wherein In step 1.1), the volume of the biofilm combined fiber filler (17) accounts for 20% to 30% of the effective volume of the entire SBBR reactor (2).

5. The method according to claim 3, characterized in that, In step 1.5), the monitoring indicators of the mature growth of the biofilm are: the surface of the biofilm combined fiber filler (17) is evenly covered with activated sludge without large exposed areas when observed with the naked eye; bubbles rise evenly during aeration without large pieces of biofilm falling off.

6. The method according to claim 3, wherein In step 2.1), the particle size of the polylactic acid microplastic is 150 μm, and the concentration added to the sewage in the SBBR reactor (2) is 5 mg / L.

7. The method according to claim 3, wherein In steps 1.2), 1.3), 2.2) and 2.3), the magnetic stirrer (7) is set to rotate at 500 rpm.

8. The method according to claim 3, wherein In steps 1) and 2), the temperature of the sewage in the sewage tank (1) and the SBBR reactor (2) is controlled to be 15° C. to 30° C. and the pH is controlled to be 7.5 to 8.

0.

9. The method according to claim 3, characterized in that, In steps 1.4) and 2.4), each cycle is 12 hours.

10. The method according to claim 3, wherein The simultaneous nitrification and denitrification SND rate and COD removal rate both reached more than 80% and were maintained stably for more than 15 days, indicating that the simultaneous nitrification and denitrification had been successfully restored.

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