Device and method for quickly recovering denitrification performance of simultaneous nitrification and denitrification process impacted by low COD / N

Abstract

This invention relates to an apparatus and method for rapidly restoring the nitrogen removal performance of a simultaneous nitrification-denitrification (SNDT) process subjected to low COD / N shocks, belonging to the field of wastewater biological treatment technology. The apparatus includes: a wastewater tank, an SBBR reactor, an aerator, an effluent tank, and an online monitoring device. The method includes the following steps: 1) Low COD / N wastewater shocks the SNDT process in a sequencing batch reactor (SBBR) and inhibits nitrogen removal performance, then high COD / N wastewater is added and biodegradable polylactic acid (PLA) microplastics are added to the SBBR reactor to restore SNDT; 2) The DO concentration in the aeration section is gradually reduced to promote the recovery of SNDT until the SNDT rate and organic matter removal rate stabilize. This invention promotes SNDT within the biofilm by adding biodegradable PLA microplastics. By gradually reducing the DO concentration, this invention can rapidly restore and stabilize SNDT in situ.

Description

Technical Field

[0001] This invention belongs to the field of wastewater biological treatment technology, specifically relating to a device and method for rapidly restoring the nitrogen removal performance of a simultaneous nitrification-denitrification process subjected to low COD / N impact. Background Technology

[0002] Traditional biological nitrogen removal technology involves first nitrifying ammonia nitrogen and then denitrifying it to generate nitrogen gas for removal. Since aerobic nitrification and anoxic denitrification require different environmental conditions, the two processes are usually implemented in different operating units. Maintaining the operation of these units increases operating costs, making the development of novel wastewater nitrogen removal processes crucial. Traditional nitrogen removal methods suffer from high energy consumption, large carbon source requirements, and high sludge production, making it difficult to meet increasingly stringent emission standards and energy conservation requirements. Therefore, the reuse of recyclable resources and the exploration of energy-saving and energy-efficient processes have become the core direction for future wastewater treatment development and a key challenge that urgently needs to be addressed in the field of biological nitrogen removal research.

[0003] Simultaneous nitrification-denitrification (SND) technology refers to the simultaneous occurrence of nitrification and denitrification processes in a single reactor under the same overall operating conditions. Under certain conditions, this technology can reduce the demand for external carbon sources, reduce the number and volume of reactors, and save operating costs. Compared with traditional biological nitrogen removal technologies, SND technology can reduce sludge production and adapt to different influent water quality variations.

[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 environmental friendliness, it has found wide application in many fields, including food packaging, 3D printing, and textile products. NO3 in wastewater - -N removal mainly relies on the denitrification process involving heterotrophic denitrifying bacteria. The monomeric lactic acid released from the degradation of polylactic acid (PLA) is an excellent electron donor for the denitrification process, leading to the enrichment of denitrifying bacteria on the surface of PLA microplastics, thereby promoting the denitrification effect.

[0005] Compared to traditional biological nitrogen removal processes, the SBBR process simplifies the treatment unit, effectively saving construction costs and energy consumption. Simultaneously, the biofilm provides a micro-anoxic environment for denitrifying bacteria, allowing nitrification to occur in the outer aerobic layer and denitrification in the inner anoxic layer, thus facilitating simultaneous nitrification and denitrification and achieving deep nitrogen removal.

[0006] Furthermore, wastewater biological treatment systems often encounter problems during the start-up phase, such as low denitrification activity, long start-up time, and unsatisfactory results. The activity of denitrifying bacteria is mainly affected by dissolved oxygen (DO) concentration. At lower DO concentrations, heterotrophic denitrifying bacteria readily utilize organic matter as electron donors to convert NO3- into nitrogen. - -N is reduced to N2. Reducing the DO concentration during the aeration stage facilitates and stabilizes denitrification, and also saves on operating costs and sludge treatment costs.

[0007] Therefore, this invention proposes a device and method for rapidly restoring the nitrogen removal performance of a simultaneous nitrification-denitrification (SNDT) process subjected to low COD / N shocks, which has significant advantages. On the one hand, biofilms and polylactic acid microplastics can facilitate the aggregation of denitrifying bacteria in wastewater and the effective utilization of carbon sources; on the other hand, reducing the DO concentration during the aeration stage in the SBBR reactor is beneficial for the growth of denitrifying bacteria in wastewater and the rapid start-up and stable maintenance of the SNDT process. This not only results in a simple device process and significant nitrogen removal effect, but also reduces operating and subsequent treatment costs. Summary of the Invention

[0008] This invention proposes a device and method for rapidly restoring the nitrogen removal performance of a simultaneous nitrification and denitrification process subjected to low COD / N shocks, solving the current problem of difficulty in rapidly starting and restoring simultaneous nitrification and denitrification processes in wastewater, in order to achieve a stable simultaneous nitrification and denitrification nitrogen removal process.

[0009] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0010] A device for rapidly restoring the nitrogen removal performance of a simultaneous nitrification-denitrification process subjected to low COD / N shocks includes a wastewater tank, an SBBR reactor, a blower aerator, an effluent tank, an influent pump, an electric drainage pump, and an online monitoring device.

[0011] The SBBR reactor is equipped with: an inlet, a magnetic stirrer, a DO sensor, a pH sensor, a temperature sensor, a sludge discharge valve, an outlet, a rotor flow meter, a microporous aeration head, a packing support, a biofilm composite fiber packing, and a magnetic stirring rotor.

[0012] The wastewater tank is connected to the inlet of the SBBR reactor via an inlet pump, the blower aerator is connected to the microporous aeration head of the SBBR reactor via a rotor flow meter, and the outlet of the SBBR reactor is connected to the outlet tank via an electric drain pump.

[0013] The online monitoring device includes relays and measuring instruments; the relays include aeration relays, water inlet relays, water outlet relays, and agitator relays;

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

[0015] The biofilm composite fiber packing consists of fiber bundles, plastic discs, sleeves, and a central rope.

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

[0017] A method for rapidly restoring the nitrogen removal performance of a simultaneous nitrification-denitrification process subjected to low COD / N shocks using the aforementioned apparatus includes the following steps:

[0018] 1) Reactor start-up stage:

[0019] 1.1) The biofilm composite fiber packing is bundled and fixed on the packing support at the top of the SBBR reactor. Then, the synchronous nitrification and denitrification activated sludge after being impacted by low COD / N wastewater is used as the inoculum sludge. The low COD / N wastewater in the wastewater tank is run for 1 minute by the inlet pump and enters the SBBR reactor through the inlet.

[0020] 1.2) After water is introduced, the magnetic stirrer is turned on to drive the magnetic stirring rotor for aerobic stirring for 8.5 hours; at the same time, the blower is turned on, and the DO concentration is controlled to be >2.0mg / L through the rotor flow meter and microporous aeration head;

[0021] 1.3) After the above reaction is completed, turn off the blower aerator and then use the magnetic stirrer to perform anoxic stirring for 2.5 hours. Control the DO concentration to <0.2mg / L using a rotor flow meter and microporous aeration head.

[0022] After 1.4), the magnetic stirrer stops running, and after standing and settling for 56 minutes, the supernatant is discharged. The supernatant is drained through the outlet for 3 minutes by an electric drain pump and the drained water enters the outlet water tank. The drainage ratio is 50%. After the drainage is completed, one cycle ends, and the next cycle is started immediately.

[0023] 1.5) Repeat steps 1.1) to 1.4) until a large amount of activated sludge accumulates in the biofilm composite fiber packing, marking the biofilm growth as mature, thus obtaining an SBBR reactor with a mature biofilm.

[0024] 2) Normal operation and adjustment of the reactor:

[0025] 2.1) The high COD / N wastewater in the wastewater tank is pumped for 1 minute and then enters the SBBR reactor with a mature biofilm through the inlet. Biodegradable polylactic acid microplastics are added at the same time as the water is introduced.

[0026] 2.2) After water is introduced, the magnetic stirrer is turned on to drive the magnetic stirring rotor for aerobic stirring for 8.5 hours; at the same time, the blower is turned on, and the DO concentration is controlled at 0.2-0.5 mg / L through the rotor flow meter and microporous aeration head.

[0027] 2.3) After the above reaction is completed, turn off the blower aerator and then use the magnetic stirrer to perform anoxic stirring for 2.5 hours. Control the DO concentration to <0.2mg / L using a rotor flow meter and microporous aeration head.

[0028] 2.4) After that, the magnetic stirrer stops running, and after standing and settling for 56 minutes, the supernatant is discharged. The supernatant is drained through the outlet for 3 minutes by an electric drain pump and the drained water enters the outlet water tank. The drainage ratio is 50%. After the drainage is completed, one cycle ends, and the next cycle is started immediately.

[0029] 2.5) During the operation of the SBBR reactor, sludge needs to be discharged periodically through the sludge discharge valve to remove the detached biofilm.

[0030] Furthermore, in the above method, step 1.1), the volume of the biofilm composite fiber packing accounts for 20% to 30% of the effective volume of the entire SBBR reactor.

[0031] Furthermore, in step 1.5 of the above method, the monitoring indicators for the growth and maturity of the biofilm are: visually, the surface of the biofilm composite fiber packing is uniformly covered with activated sludge, with no large areas exposed; during aeration, bubbles rise uniformly, with no large pieces of biofilm falling off.

[0032] Furthermore, in step 2.1) of the above method, the polylactic acid microplastic has a particle size of 150 μm and is added to the wastewater in the SBBR reactor at a concentration of 5 mg / L.

[0033] Furthermore, in the above method, steps 1.2), 1.3), 2.2), and 2.3), the magnetic stirrer is set to rotate at 500 rpm.

[0034] Furthermore, in the above method, in steps 1) and 2), the temperature of the wastewater in the wastewater tank and the SBBR reactor is controlled to be 15℃~30℃ and the pH is 7.5~8.0.

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

[0036] Furthermore, the above method achieved a simultaneous nitrification-denitrification (SND) rate and COD removal rate of over 80%, which remained stable for more than 15 days, indicating successful recovery of simultaneous nitrification-denitrification.

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

[0038] 1. In this invention, polylactic acid microplastics can not only be used as a biodegradable external solid carbon source, but also as a biofilm carrier in a biofilm reactor, turning waste into treasure, which is economical and affordable, and can be widely used in wastewater treatment in production and daily life.

[0039] 2. This invention makes full use of the limited carbon sources in wastewater to achieve deep nitrogen removal and saves aeration energy consumption.

[0040] 3. This invention can quickly restore the nitrogen removal performance of a simultaneous nitrification-denitrification process subjected to low COD / N shock within a few days, and the restored nitrogen removal effect is significant and stable. Attached Figure Description

[0041] Figure 1 A schematic diagram of the device for rapidly restoring the nitrogen removal performance of a simultaneous nitrification-denitrification process subjected to low COD / N shocks. The components are: 1-Wastewater tank, 2-SBBR reactor, 3-Aerator, 4-Effluent tank, 5-Inlet pump, 6-Inlet, 7-Magnetic stirrer, 8-DO sensor, 9-pH sensor, 10-Temperature sensor, 11-Sludge discharge valve, 12-Outlet, 13-Electric drainage pump, 14-Rotameter, 15-Microporous aeration head, 16-Packaging support, 17-Biofilm composite fiber packing, 17-1-Fiber bundle, 17-2-Plastic disc, 17-3-Shell, 17-4-Center rope, 18-Relay, 18-1-Aeration relay, 18-2-Inlet relay, 18-3-Effluent relay, 18-4-Stirrer relay, 19-Measuring instrument, 20-Magnetic stirring rotor.

[0042] Figure 2 A process flow diagram for a method to rapidly restore the nitrogen removal performance of a simultaneous nitrification-denitrification process subjected to low COD / N shocks.

[0043] Figure 3 The diagram shows the operational performance of SBBR reactors A1 and A2. Figure 3 (a): SND rate and TIN removal rate during the operation of A1 and A2; Figure 3 (b): COD concentration and COD removal rate of influent and effluent during the operation of A1 and A2.

[0044] Figure 4 The diagram shows the operating results of SBBR reactors B1 and B2. Figure 4(a): COD concentration and COD removal rate of influent and effluent 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

[0045] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings and examples.

[0046] Example 1

[0047] like Figure 1 The apparatus shown includes: a wastewater tank 1, an SBBR reactor 2, a blower aerator 3, an effluent tank 4, an influent pump 5, an electric drain pump 13, and an online monitoring device.

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

[0049] The biofilm composite fiber packing 17 consists of fiber bundles 17-1, plastic discs 17-2, sleeves 17-3, and a central rope 17-4. The fiber bundles 17-1 are tied to the plastic discs 17-2 and spread outwards and are evenly distributed. The central rope 17-4 connects all the plastic discs 17-2 from top to bottom. The upper end of the central rope 17-4 is tied and fixed to the packing support 16, and the lower end is tied and fixed to both sides of the inner wall of the SBBR reactor 2. The central rope 17-4 between adjacent plastic discs 17-2 is equipped with sleeves 17-3 to fix the plastic discs 17-2.

[0050] The SBBR reactor 2 has an effective volume of 5.0 L and an effective height of 50 cm. Five plastic discs 17-2, each bundled with fiber bundles 17-1, are suspended on the packing support 16. Each plastic disc 17-2 has a volume of 0.2 L, and the distance between adjacent discs is 0.1 m. They are connected by a central rope 17-4, with a sleeve 17-3 on the central rope 17-4 used to fix its position. The volume occupied by adjacent central ropes 17-4 and sleeves 17-3 is 0.1 L. A section of the central rope 17-4 is reserved at both ends for fixing the biofilm composite fiber packing 17.

[0051] Wastewater tank 1 is connected to inlet 6 of SBBR reactor 2 via inlet pump 5. Aeration blower 3 is connected to microporous aeration head 15 of SBBR reactor 2 via rotor flow meter 14. Outlet 12 of SBBR reactor 2 is connected to outlet tank 4 via electric drainage pump 13.

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

[0053] Example 2

[0054] like Figure 2 Operating parameters during the experiment:

[0055] The simulated wastewater contained the following components: ammonium chloride, crystalline sodium acetate, potassium dihydrogen phosphate, and anhydrous sodium carbonate (analytical grade). The parameters were as follows: COD = 300 ± 50 mg / L, NH4+ + -N = 30 ± 5 mg / L, TP = 7 mg / L, pH = 7.5–8.0.

[0056] Simulated wastewater was used as the feed water for two SBBR reactors 2 (A1 and A2). The operating temperature was the laboratory air temperature (15℃~30℃).

[0057] The specific operating parameters are as follows: instantaneous water inflow 1 min, aeration + stirring 8.5 h, anoxic stirring 2.5 h, static sedimentation 56 min, drainage 3 min, each cycle 12 h, 2 cycles per day.

[0058] The specific operating method is as follows:

[0059] 1) Reactor start-up stage:

[0060] ① The biofilm composite fiber packing 17 is tied and fixed on the packing support 16 at the top of the SBBR reactor 2, with a filling ratio of 20% to 30%. Activated sludge with stable and efficient simultaneous nitrification and denitrification performance is used as inoculum sludge. Wastewater in wastewater tank 1 is pumped by inlet pump 5 for 1 minute and then enters the SBBR reactor 2 through inlet 6.

[0061] The filling ratio is the proportion 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 × the packing ratio = the volume of the biofilm composite fiber packing (plastic discs + casing).

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

[0064] ③ After the above reaction is completed, turn off the blower aerator 3, and then the magnetic stirrer 7 will continue to perform anoxic stirring for 2.5 hours. The DO concentration is controlled to be <0.2mg / L by the rotor flow meter 14 and the microporous aeration head 15.

[0065] ④ After that, the magnetic stirrer 7 stops running, and after standing and settling for 56 minutes, the supernatant is discharged. The supernatant is drained through the electric drain pump 13 and the outlet 12 for 3 minutes, and the drained water enters the outlet water tank 4. The drainage ratio is 50%. After the drainage is completed, one cycle ends, and the next cycle is started immediately. There is no time interval or other operation process between the two cycles.

[0066] ⑤ Repeat steps ① to ④ until the surface of the biofilm composite fiber packing 17 is uniformly covered with activated sludge with no large areas exposed; and when bubbles rise uniformly during aeration without large pieces of biofilm falling off, the biofilm is considered to have matured. Thus, an SBBR reactor 2 with a mature biofilm is obtained.

[0067] 2) Normal operation and adjustment of the reactor:

[0068] ① Wastewater in wastewater tank 1 is pumped by inlet pump 5 for 1 minute and then enters SBBR reactor 2, which has a mature biofilm, through inlet 6. Simultaneously, biodegradable polylactic acid microplastics (150μm) are added to SBBR reactor 2 (A1), bringing its concentration in the wastewater to 5 mg / L. No polylactic acid microplastics are added to the other SBBR reactor 2 (A2), and its concentration in A2 is 0 mg / L.

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

[0070] ③ After the above reaction is completed, the blower aerator 3 is turned off, and the magnetic stirrer 7 is then used for anoxic stirring for 2.5 hours. The DO concentration is controlled to be <0.2 mg / L by the rotor flow meter 14 and the microporous aerator head 15. Simultaneous nitrification and denitrification reactions are carried out on the biofilm. Under low dissolved oxygen conditions, the outer biofilm oxidizes the remaining unoxidized ammonia nitrogen to nitrite, while the inner biofilm uses a carbon source to reduce nitrate or nitrite to produce N2, which is discharged from the SBBR reactor 2, thereby achieving the purpose of denitrification.

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

[0072] ⑤ During the operation of SBBR reactor 2, sludge needs to be discharged periodically through sludge discharge valve 11 to remove the detached biofilm.

[0073] The concentrations of ammonia nitrogen and COD in the influent and effluent were periodically measured during the experiment. Simultaneously, the concentrations of nitrite nitrogen and nitrate nitrogen in the effluent were measured. The COD removal rate, total inorganic nitrogen (TIN) removal rate, and simultaneous nitrification-denitrification (SND) rate were calculated. The main calculation formulas are as follows:

[0074]

[0075] The experimental results are shown in Figure 3 . Figure 3 To observe the operational performance of reactors A1 and A2 during the normal operation and adjustment phase after biofilm maturation, the simultaneous nitrification and denitrification processes were not disrupted by shock.

[0076] Depend on Figure 3 After 50 days of operation, the average COD removal rates of reactors A1 and A2 were 82.93% and 89.08%, respectively; the TIN removal rates were 75.16% and 71.79%, respectively; and the SND rates were 89.36% and 79.38%, respectively. This indicates that the addition of polylactic acid microplastics can promote simultaneous nitrification and denitrification in SBBR.

[0077] Example 3

[0078] like Figure 2 Operating parameters during the experiment:

[0079] Simulated wastewater was used as the influent to two SBBR reactors 2 (B1 and B2). The simulated wastewater parameters are as follows: High COD / N wastewater: COD = 300 ± 50 mg / L, NH4+... +-N = 30±5 mg / L, TP = 7 mg / L, pH 7.5–8.0. Low COD / N wastewater: COD = 150±30 mg / L, NH4+ + -N = 30 ± 5 mg / L, TP = 7 mg / L, pH = 7.5–8.0.

[0080] The operating temperature is the laboratory air temperature (15℃~30℃).

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

[0082] The specific operating method is as follows:

[0083] 1) Reactor start-up stage:

[0084] ① The biofilm composite fiber packing 17 is bundled and fixed on the packing support 16 at the top of the SBBR reactor 2, with a filling ratio of 20% to 30%. The activated sludge of simultaneous nitrification and denitrification after being subjected to low COD / N wastewater impact is used as inoculum sludge. The low COD / N wastewater in the wastewater tank 1 is run through the inlet pump 5 for 1 minute and enters the SBBR reactor 2 through the inlet 6.

[0085] The filling ratio is the proportion of the volume of the biofilm composite fiber packing 17 to the effective volume of the entire SBBR reactor 2.

[0086] The effective volume of the SBBR reactor × the packing ratio = the volume of the biofilm composite fiber packing (plastic discs + casing).

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

[0088] ③ After the above reaction is completed, turn off the blower aerator 3, and then the magnetic stirrer 7 will continue to perform anoxic stirring for 2.5 hours. The DO concentration is controlled to be <0.2mg / L by the rotor flow meter 14 and the microporous aeration head 15.

[0089] ④ After that, the magnetic stirrer 7 stops running, and after standing and settling for 56 minutes, the supernatant is discharged. The supernatant is drained through the electric drain pump 13 and the outlet 12 for 3 minutes, and the drained water enters the outlet water tank 4. The drainage ratio is 50%. After the drainage is completed, one cycle ends, and the next cycle is started immediately. There is no time interval or other operation process between the two cycles.

[0090] ⑤ Repeat steps ① to ④ until the surface of the biofilm composite fiber packing 17 is uniformly covered with activated sludge with no large areas exposed; and when bubbles rise uniformly during aeration without large pieces of biofilm falling off, the biofilm is considered to have matured. This yields an SBBR reactor 2 with a mature biofilm. The reactor is then run for 10 days, and data is recorded.

[0091] 2) Normal operation and adjustment of the reactor:

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

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

[0094] ③ After the above reaction is completed, the blower aerator 3 is turned off, and the magnetic stirrer 7 is then used for anoxic stirring for 2.5 hours. The DO concentration is controlled to be <0.2 mg / L by the rotor flow meter 14 and the microporous aerator head 15. Simultaneous nitrification and denitrification reactions are carried out on the biofilm. Under low dissolved oxygen conditions, the outer biofilm oxidizes the remaining unoxidized ammonia nitrogen to nitrite, while the inner biofilm uses a carbon source to reduce nitrate or nitrite to produce N2, which is discharged from the SBBR reactor 2, thereby achieving the purpose of denitrification.

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

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

[0097] The concentrations of ammonia nitrogen and COD in the influent and effluent were periodically measured during the experiment. Simultaneously, the concentrations of nitrite nitrogen and nitrate nitrogen in the effluent were measured. The COD removal rate, total inorganic nitrogen (TIN) removal rate, and simultaneous nitrification-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 were the later stage of reactor start-up, during which the operating performance of reactors B1 and B2 was observed after the biofilm matured. At this time, simultaneous nitrification and denitrification had not yet resumed. During the first 10 days, the average COD removal rates of reactors B1 and B2 were 77.80% and 80.68%, respectively; the TIN removal rates were 30.22% and 31.82%, respectively; and the SND rates were 37.01% and 46.26%, respectively.

[0100] Depend on Figure 4 It can be seen that the B1 reactor requires a shorter time to resume simultaneous nitrification and denitrification and reach stability, only 4 days; while the B2 reactor requires 12 days to resume simultaneous nitrification and denitrification and reach stability.

[0101] Within 26 days of the resumption of simultaneous nitrification and denitrification in reactor B1, the average COD removal rates of reactors B1 and B2 were 90.04% and 88.70%, respectively; the TIN removal rates were 63.05% and 56.65%, respectively; and the SND rates were 89.50% and 84.82%, respectively.

[0102] Within 18 days of the resumption of simultaneous nitrification and denitrification in reactor B2, the average COD removal rates of reactors B1 and B2 were 89.84% and 89.22%, respectively; the TIN removal rates were 66.90% and 65.18%, respectively; and the SND rates were 91.91% and 90.58%, respectively.

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

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

Claims

1. A method for quickly recovering the nitrogen removal performance of a simultaneous nitrification and denitrification process impacted by low COD / N by using a device for quickly recovering the nitrogen removal performance of a simultaneous nitrification and denitrification process impacted by low COD / N, characterized in that, Includes the following steps: 1) Reactor start-up stage: 1.1) The biofilm composite fiber packing (17) is tied and fixed on the packing support (16) at the top of the SBBR reactor (2). Then, the synchronous nitrification and denitrification activated sludge after being impacted by low COD / N wastewater is used as the inoculum sludge. The low COD / N wastewater in the wastewater tank (1) is run for 1 min by the inlet pump (5) and enters the SBBR reactor (2) through the inlet (6). 1.2) After water is introduced, the magnetic stirrer (7) is turned on to drive the magnetic stirring rotor (20) for aerobic stirring for 8.5 h; at the same time, the blower 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 blower aerator (3) is turned off, and the magnetic stirrer (7) is then used for anoxic stirring for 2.5 hours. The DO concentration is controlled to be <0.2 mg / L by the rotor flow meter (14) and the microporous aeration head (15). After 1.4), the magnetic stirrer (7) stops running, and after standing and settling for 56 minutes, the supernatant is discharged. The supernatant is drained through the outlet (12) by the electric drain pump (13) for 3 minutes and the drained water enters the outlet water tank (4). The drainage ratio is 50%. After the drainage is completed, one cycle ends, and the next cycle is started immediately. 1.5) Repeat steps 1.1) to 1.4) until a large amount of activated sludge accumulates in the biofilm composite fiber packing (17), marking the biofilm growth as mature, thus obtaining an SBBR reactor (2) with a mature biofilm. 2) Normal operation and adjustment of the reactor: 2.1) The high COD / N wastewater in the wastewater tank (1) is pumped by the inlet pump (5) for 1 minute and then enters the SBBR reactor (2) with a mature biofilm through the inlet (6). Biodegradable polylactic acid microplastics are added at the same time as the water is introduced. 2.2) After water is introduced, the magnetic stirrer (7) is turned on to drive the magnetic stirring rotor (20) for aerobic stirring for 8.5 h; at the same time, the blower aerator (3) is turned on, and the DO concentration is controlled at 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 blower aerator (3) is turned off, and the magnetic stirrer (7) is then used for anoxic stirring for 2.5 hours. The DO concentration is controlled to be <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 after standing and settling for 56 minutes, the supernatant is discharged. The supernatant is drained through the outlet (12) by the electric drain pump (13) for 3 minutes and the drained water enters the outlet water tank (4). The drainage ratio is 50%. After the drainage is completed, one cycle ends and the next cycle is started immediately. 2.5) During the operation of the SBBR reactor (2), sludge needs to be discharged periodically through the sludge discharge valve (11) to remove the detached biofilm; The device for rapidly restoring the nitrogen removal performance of a simultaneous nitrification-denitrification process subjected to low COD / N impact includes a wastewater tank (1), an SBBR reactor (2), a blower aerator (3), an effluent tank (4), an influent pump (5), an electric drainage pump (13), and an online monitoring device. The SBBR reactor (2) is equipped 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 rotor flow meter (14), a microporous aeration head (15), a packing support (16), a biofilm composite fiber packing (17), and a magnetic stirring rotor (20). The wastewater tank (1) is connected to the inlet (6) of the SBBR reactor (2) via the inlet pump (5), the blower aerator (3) is connected to the microporous aeration head (15) of the SBBR reactor (2) via the rotor flow meter (14), and the outlet (12) of the SBBR reactor (2) is connected to the outlet tank (4) via the electric drain pump (13). The online monitoring device includes a relay (18) and a measuring instrument (19); the relay (18) includes an aeration relay (18-1), an inlet relay (18-2), an outlet relay (18-3), and a stirrer relay (18-4). The aeration relay (18-1) is connected to the blower aerator (3), the water inlet relay (18-2) is connected to the water inlet pump (5), the stirrer relay (18-4) is connected to the magnetic stirrer (7), and the water outlet relay (18-3) is connected to the electric drain pump (13); the DO sensor (8), pH sensor (9), and temperature sensor (10) are respectively connected to the measuring instrument (19).

2. The method of claim 1, wherein, The biofilm composite fiber packing (17) consists of fiber bundles (17-1), plastic discs (17-2), sleeves (17-3), and a central rope (17-4); The fiber bundle (17-1) is bound to the plastic disc (17-2) and spread out and evenly distributed. The central rope (17-4) connects all the plastic discs (17-2) from top to bottom. The upper end of the central rope (17-4) is bound and fixed to the packing support (16), and the lower end is bound and fixed to both sides of the inner wall of the SBBR reactor (2). The central rope (17-4) between adjacent plastic discs (17-2) is equipped with a sleeve (17-3) to fix the plastic disc (17-2).

3. The method of claim 1, wherein, In step 1.1), the volume of the biofilm composite fiber packing (17) accounts for 20% to 30% of the effective volume of the entire SBBR reactor (2).

4. The method of claim 1, wherein, In step 1.5), the monitoring indicators for the growth and maturity of the biofilm are: the surface of the biofilm composite fiber packing (17) is uniformly covered with activated sludge and there is no large area of ​​exposed sludge; during aeration, the bubbles rise uniformly and there are no large pieces of biofilm falling off.

5. The method of claim 1, wherein, In step 2.1), the polylactic acid microplastic has a particle size of 150 μm and is added to the wastewater in the SBBR reactor (2) at a concentration of 5 mg / L.

6. The method of claim 1, wherein, In steps 1.2), 1.3), 2.2) and 2.3), the magnetic stirrer (7) is set to a speed of 500 rpm.

7. The method of claim 1, wherein, In steps 1) and 2), the temperature of the wastewater in the wastewater tank (1) and the SBBR reactor (2) is controlled to be 15℃~30℃ and the pH is 7.5~8.

0.

8. The method of claim 1, wherein, In steps 1.4) and 2.4), each cycle is 12 hours.

9. The method of claim 1, wherein, The simultaneous nitrification and denitrification (SND) rate and COD removal rate both reached over 80% and remained stable for more than 15 days, indicating that the simultaneous nitrification and denitrification was successfully restored.

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