Method for breaking iron shell embedded denitrification sludge by humic acid

Abstract

The invention discloses a method for breaking iron shell embedded denitrifying sludge by humic acid, which comprises the following steps: step 1, inoculating iron shell embedded denitrifying granular sludge by adopting an up-flow anaerobic sludge blanket reactor; 2, preparing simulated wastewater, introducing the simulated wastewater into an up-flow anaerobic sludge blanket reactor, and setting operation conditions of the reactor; 3, continuously monitoring the concentrations of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the effluent of the up-flow anaerobic sludge blanket reactor; and step 4, determining humic acid adding time by taking the concentration of nitrate nitrogen in effluent as a criterion, adding humic acid, and breaking iron shells to embed the denitrified sludge. According to the method for breaking the iron shell embedded denitrified sludge by using the humic acid, the purposes of rapidly relieving the reduction of sludge activity and the reduction of system denitrification efficiency caused by the iron shell embedded sludge and even rapidly recovering the denitrification performance of the lost system and maintaining and stabilizing the denitrification efficiency of the system can be achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a method for using humic acid to break down iron shell-embedded denitrification sludge. Background Art

[0002] The synergistic effect of reducing pollution and carbon in the wastewater treatment process has become an important topic in the field of wastewater treatment. When treating low carbon-nitrogen ratio wastewater with high nitrate nitrogen concentration and low organic carbon source concentration, the traditional denitrification process needs to add additional organic carbon source for denitrification due to the lack of organic carbon source, which not only increases the treatment cost, but also may bring the risk of secondary pollution.

[0003] In recent years, the autotrophic denitrification process mediated by inorganic electron donors represented by zero-valent iron has gradually attracted attention. This process uses zero-valent iron as an electron donor to complete the denitrification process, which can effectively solve the problem of insufficient electron donors in the treatment of low carbon-nitrogen ratio wastewater such as urban wastewater. However, during the operation of the above process, the iron shell is prone to burying the sludge, resulting in a sharp decrease in the system's denitrification efficiency. The sludge surface is buried by the iron shell, and the nutrients in the wastewater cannot reach the inside of the sludge, causing the microorganisms in the sludge to die due to lack of nutrients, resulting in the denitrification process being blocked and the efficiency being reduced. Summary of the invention

[0004] The purpose of the invention is to provide a method for breaking iron shell-embedded denitrification sludge by humic acid, thereby solving the problem of iron shell-embedded denitrification sludge.

[0005] The technical solution adopted by the present invention is a method for breaking the iron shell-embedded denitrification sludge with humic acid, comprising the following steps: Step 1: using an upflow anaerobic sludge blanket reactor to inoculate the denitrifying granular sludge embedded in an iron shell; Step 2: preparing simulated wastewater, introducing the simulated wastewater into an upflow anaerobic sludge blanket reactor, and setting the reactor operating conditions; Step 3, continuously monitoring the concentrations of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the effluent of the upflow anaerobic sludge blanket reactor; Step 4: Determine the time to add humic acid based on the effluent nitrate nitrogen concentration, and add humic acid to break up the iron shell-embedded denitrifying sludge.

[0006] The present invention is also characterized in that: The simulated wastewater in step 2 specifically includes the following substances: NO3 --N (NaNO3), NaH2PO4·2H2O, COD(CH3COONa), NaHCO3, NaOH, CaCl2, CoCl2·2H2O, CuSO4·5H2O, EDTA, FeSO4·7H2O, H3BO3, MnCl2·4H2O, NaMoO4·2H2O, NiCl2·6H2O and ZnSO4·7H2O.

[0007] The mass percentage ratio of each substance in the simulated wastewater is: NO3 - -N (NaNO3): NaH2PO4·2H2O: COD(CH3COONa): NaHCO3: NaOH: CaCl2: CoCl2·2H2O: CuSO4·5H2O: EDTA: FeSO4·7H2O: H3BO3: MnCl2·4H2O: NaMoO4·2H2O: NiCl2·6H2O: ZnSO4·7H2O: = (91~182): 618: (0~700): 500: 108: 0.13: 0.76: 0.08: 4.9: 3: 0.05: 0.30: 0.76: 0.7: 0.15.

[0008] The operating conditions in step 2 include influent nitrate nitrogen concentration, temperature, influent pH and hydraulic retention time.

[0009] Influent nitrate nitrogen concentration 90-180 mg·L -1 The chemical oxygen demand concentration of the simulated wastewater is 270-540 mg·L -1 , the initial carbon-nitrogen ratio of the simulated wastewater was 3-4.

[0010] The temperature is 25-35℃; the inlet pH is 7.5-9.0; the hydraulic retention time is 2-3 h.

[0011] The specific process of step 4 is as follows: after the iron shell burying denitrification sludge phenomenon occurs, the operating conditions in step 2 are maintained for 30 days, and the nitrate nitrogen concentration in the reactor effluent continues to be higher than 20 mg·L -1 When the nitrate nitrogen concentration in the effluent is lower than 10 mg·L -1 When the temperature reaches 0.0400 °C, stop adding humic acid and keep the operating conditions unchanged.

[0012] In step 4, the humic acid is specifically C 14 H7NaO5S, the purity of humic acid is not less than 99%.

[0013] The beneficial effects of the present invention are: The method for using humic acid to break down iron shell-embedded denitrification sludge provided by the present invention can quickly and effectively corrode the iron shell by adding humic acid, release the iron ions (ferrous iron and ferric iron) embedded in the sludge, realize the recycling of iron ions, and construct a physical and chemical coupled microbial enhancement regulation strategy, which can solve the problem of iron shell embedding while improving the denitrification efficiency; adding humic acid and operating an upflow anaerobic sludge bed reactor under specific conditions can break down the iron shell-embedded sludge phenomenon while reducing the system's demand for organic carbon sources and reducing the operating cost in the wastewater treatment process. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a schematic diagram of the optimized concentration of humic acid in Example 8 of the present invention; Figure 2 Schematic diagram of nitric nitrogen removal rate in Example 8 of the present invention Figure 3 This is a schematic diagram of using humic acid of different concentrations to break down iron shell-embedded sludge in Example 8 of the present invention. DETAILED DESCRIPTION

[0015] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0016] Example 1 The method for using humic acid to break down the iron shell-embedded denitrification sludge proposed in this embodiment comprises the following steps: Step 1: using an upflow anaerobic sludge blanket reactor to inoculate the denitrifying granular sludge embedded in an iron shell; Step 2: preparing simulated wastewater, introducing the simulated wastewater into an upflow anaerobic sludge blanket reactor, and setting the reactor operating conditions; Step 3, continuously monitoring the concentrations of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the effluent of the upflow anaerobic sludge blanket reactor; Step 4: Determine the time to add humic acid based on the effluent nitrate nitrogen concentration, and add humic acid to break up the iron shell-embedded denitrifying sludge.

[0017] Example 2 The method for using humic acid to break down the iron shell-embedded denitrification sludge proposed in this embodiment comprises the following steps: Step 1: using an upflow anaerobic sludge blanket reactor to inoculate the denitrifying granular sludge embedded in an iron shell; Step 2: preparing simulated wastewater, introducing the simulated wastewater into an upflow anaerobic sludge blanket reactor, and setting the reactor operating conditions; The simulated wastewater in step 2 specifically includes the following substances: NO3 --N (NaNO3), NaH2PO4·2H2O, COD(CH3COONa), NaHCO3, NaOH, CaCl2, CoCl2·2H2O, CuSO4·5H2O, EDTA, FeSO4·7H2O, H3BO3, MnCl2·4H2O, NaMoO4·2H2O, NiCl2·6H2O and ZnSO4·7H2O; Step 3, continuously monitoring the concentrations of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the effluent of the upflow anaerobic sludge blanket reactor; Step 4: Determine the time to add humic acid based on the effluent nitrate nitrogen concentration, and add humic acid to break up the iron shell-embedded denitrifying sludge.

[0018] Example 3 The method for using humic acid to break down the iron shell-embedded denitrification sludge proposed in this embodiment comprises the following steps: Step 1: using an upflow anaerobic sludge blanket reactor to inoculate the denitrifying granular sludge embedded in an iron shell; Step 2: preparing simulated wastewater, introducing the simulated wastewater into an upflow anaerobic sludge blanket reactor, and setting the reactor operating conditions; The simulated wastewater in step 2 specifically includes the following substances: NO3 - -N (NaNO3), NaH2PO4·2H2O, COD(CH3COONa), NaHCO3, NaOH, CaCl2, CoCl2·2H2O, CuSO4·5H2O, EDTA, FeSO4·7H2O, H3BO3, MnCl2·4H2O, NaMoO4·2H2O, NiCl2·6H2O and ZnSO4·7H2O; The mass percentage ratio of each substance in the simulated wastewater is: NO3 - -N (NaNO3): NaH2PO4·2H2O: COD(CH3COONa): NaHCO3: NaOH: CaCl2: CoCl2·2H2O: CuSO4·5H2O: EDTA: FeSO4·7H2O: H3BO3: MnCl2·4H2O: NaMoO4·2H2O: NiCl2·6H2O: ZnSO4·7H2O: = (91~182): 618: (0~700): 500: 108: 0.13: 0.76: 0.08: 4.9: 3: 0.05: 0.30: 0.76: 0.7: 0.15; Step 3, continuously monitoring the concentrations of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the effluent of the upflow anaerobic sludge blanket reactor; Step 4: Determine the time to add humic acid based on the effluent nitrate nitrogen concentration, and add humic acid to break up the iron shell-embedded denitrifying sludge.

[0019] Example 4 The method for using humic acid to break down the iron shell-embedded denitrification sludge proposed in this embodiment comprises the following steps: Step 1: using an upflow anaerobic sludge blanket reactor to inoculate the denitrifying granular sludge embedded in an iron shell; Step 2: preparing simulated wastewater, introducing the simulated wastewater into an upflow anaerobic sludge blanket reactor, and setting the reactor operating conditions; The simulated wastewater in step 2 specifically includes the following substances: NO3 - -N (NaNO3), NaH2PO4·2H2O, COD(CH3COONa), NaHCO3, NaOH, CaCl2, CoCl2·2H2O, CuSO4·5H2O, EDTA, FeSO4·7H2O, H3BO3, MnCl2·4H2O, NaMoO4·2H2O, NiCl2·6H2O and ZnSO4·7H2O; The mass percentage ratio of each substance in the simulated wastewater is: NO3 - -N (NaNO3): NaH2PO4·2H2O: COD(CH3COONa): NaHCO3: NaOH: CaCl2: CoCl2·2H2O: CuSO4·5H2O: EDTA: FeSO4·7H2O: H3BO3: MnCl2·4H2O: NaMoO4·2H2O: NiCl2·6H2O: ZnSO4·7H2O: = (91~182): 618: (0~700): 500: 108: 0.13: 0.76: 0.08: 4.9: 3: 0.05: 0.30: 0.76: 0.7: 0.15; The operating conditions in step 2 include influent nitrate nitrogen concentration, temperature, influent pH and hydraulic retention time; Step 3, continuously monitoring the concentrations of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the effluent of the upflow anaerobic sludge blanket reactor; Step 4: Determine the time to add humic acid based on the effluent nitrate nitrogen concentration, and add humic acid to break up the iron shell-embedded denitrifying sludge.

[0020] Example 5 The method for using humic acid to break down the iron shell-embedded denitrification sludge proposed in this embodiment comprises the following steps: Step 1: using an upflow anaerobic sludge blanket reactor to inoculate the denitrifying granular sludge embedded in an iron shell; Step 2: preparing simulated wastewater, introducing the simulated wastewater into an upflow anaerobic sludge blanket reactor, and setting the reactor operating conditions; The simulated wastewater in step 2 specifically includes the following substances: NO3- -N (NaNO3), NaH2PO4·2H2O, COD(CH3COONa), NaHCO3, NaOH, CaCl2, CoCl2·2H2O, CuSO4·5H2O, EDTA, FeSO4·7H2O, H3BO3, MnCl2·4H2O, NaMoO4·2H2O, NiCl2·6H2O and ZnSO4·7H2O; The mass percentage ratio of each substance in the simulated wastewater is: NO3 - -N (NaNO3): NaH2PO4·2H2O: COD(CH3COONa): NaHCO3: NaOH: CaCl2: CoCl2·2H2O: CuSO4·5H2O: EDTA: FeSO4·7H2O: H3BO3: MnCl2·4H2O: NaMoO4·2H2O: NiCl2·6H2O: ZnSO4·7H2O: = (91~182): 618: (0~700): 500: 108: 0.13: 0.76: 0.08: 4.9: 3: 0.05: 0.30: 0.76: 0.7: 0.15; The operating conditions in step 2 include influent nitrate nitrogen concentration, temperature, influent pH and hydraulic retention time; Influent nitrate nitrogen concentration 90-180 mg·L -1 The chemical oxygen demand concentration of the simulated wastewater is 270-540 mg·L -1 , the initial carbon-nitrogen ratio of the simulated wastewater was 3-4; Step 3, continuously monitoring the concentrations of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the effluent of the upflow anaerobic sludge blanket reactor; Step 4: Determine the time to add humic acid based on the effluent nitrate nitrogen concentration, and add humic acid to break up the iron shell-embedded denitrifying sludge.

[0021] Example 6 The method for using humic acid to break down the iron shell-embedded denitrification sludge proposed in this embodiment comprises the following steps: Step 1: using an upflow anaerobic sludge blanket reactor to inoculate the denitrifying granular sludge embedded in an iron shell; Step 2: preparing simulated wastewater, introducing the simulated wastewater into an upflow anaerobic sludge blanket reactor, and setting the reactor operating conditions; The simulated wastewater in step 2 specifically includes the following substances: NO3 --N (NaNO3), NaH2PO4·2H2O, COD(CH3COONa), NaHCO3, NaOH, CaCl2, CoCl2·2H2O, CuSO4·5H2O, EDTA, FeSO4·7H2O, H3BO3, MnCl2·4H2O, NaMoO4·2H2O, NiCl2·6H2O and ZnSO4·7H2O; The mass percentage ratio of each substance in the simulated wastewater is: NO3 - -N (NaNO3): NaH2PO4·2H2O: COD(CH3COONa): NaHCO3: NaOH: CaCl2: CoCl2·2H2O: CuSO4·5H2O: EDTA: FeSO4·7H2O: H3BO3: MnCl2·4H2O: NaMoO4·2H2O: NiCl2·6H2O: ZnSO4·7H2O: = (91~182): 618: (0~700): 500: 108: 0.13: 0.76: 0.08: 4.9: 3: 0.05: 0.30: 0.76: 0.7: 0.15; The operating conditions in step 2 include influent nitrate nitrogen concentration, temperature, influent pH and hydraulic retention time; Influent nitrate nitrogen concentration 90-180 mg·L -1 The chemical oxygen demand concentration of the simulated wastewater is 270-540 mg·L -1 , the initial carbon-nitrogen ratio of the simulated wastewater was 3-4; The temperature is 25-35℃; the inlet pH is 7.5-9.0; the hydraulic retention time is 2-3 h; Step 3, continuously monitoring the concentrations of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the effluent of the upflow anaerobic sludge blanket reactor; Step 4: Determine the time to add humic acid based on the effluent nitrate nitrogen concentration, and add humic acid to break up the iron shell-embedded denitrifying sludge.

[0022] Example 7 The method for using humic acid to break down the iron shell-embedded denitrification sludge proposed in this embodiment comprises the following steps: Step 1: using an upflow anaerobic sludge blanket reactor to inoculate the denitrifying granular sludge embedded in an iron shell; Step 2: preparing simulated wastewater, introducing the simulated wastewater into an upflow anaerobic sludge blanket reactor, and setting the reactor operating conditions; The simulated wastewater in step 2 specifically includes the following substances: NO3 --N (NaNO3), NaH2PO4·2H2O, COD(CH3COONa), NaHCO3, NaOH, CaCl2, CoCl2·2H2O, CuSO4·5H2O, EDTA, FeSO4·7H2O, H3BO3, MnCl2·4H2O, NaMoO4·2H2O, NiCl2·6H2O and ZnSO4·7H2O; The mass percentage ratio of each substance in the simulated wastewater is: NO3 - -N (NaNO3): NaH2PO4·2H2O: COD(CH3COONa): NaHCO3: NaOH: CaCl2: CoCl2·2H2O: CuSO4·5H2O: EDTA: FeSO4·7H2O: H3BO3: MnCl2·4H2O: NaMoO4·2H2O: NiCl2·6H2O: ZnSO4·7H2O: = (91~182): 618: (0~700): 500: 108: 0.13: 0.76: 0.08: 4.9: 3: 0.05: 0.30: 0.76: 0.7: 0.15; The operating conditions in step 2 include influent nitrate nitrogen concentration, temperature, influent pH and hydraulic retention time; Influent nitrate nitrogen concentration 90-180 mg·L -1 The chemical oxygen demand concentration of the simulated wastewater is 270-540 mg·L -1 , the initial carbon-nitrogen ratio of the simulated wastewater was 3-4; The temperature is 25-35℃; the inlet pH is 7.5-9.0; the hydraulic retention time is 2-3 h; Step 3, continuously monitoring the concentrations of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the effluent of the upflow anaerobic sludge blanket reactor; Step 4: Determine the time to add humic acid based on the effluent nitrate nitrogen concentration, and add humic acid to break the iron shell-embedded denitrification sludge; The specific process is as follows: after the iron shell burying denitrification sludge phenomenon occurs, the operating conditions in step 2 are maintained for 30 days, and the nitrate nitrogen concentration in the reactor effluent continues to be higher than 20 mg·L -1 When humic acid was added to the influent, the upflow anaerobic sludge blanket reactor was operated and the operating conditions in step 2 were kept unchanged. When the nitrate nitrogen concentration in the effluent was lower than 10 mg·L -1 When , stop adding humic acid and keep the operating conditions unchanged; Humic acid is specifically C 14 H7NaO5S, the purity of humic acid is not less than 99%.

[0023] Example 8 The method for using humic acid to break down the iron shell-embedded denitrification sludge proposed in this embodiment comprises the following steps: Step 1: Take an upflow anaerobic sludge blanket reactor, named R1, with an effective volume of 1.0 L, and inoculate 0.8 L of iron-shell-embedded denitrifying granular sludge; the volatile suspended solids concentration is detected to be 7.32 g·L-1, that is, each contains 0.24 g of volatile suspended solids; Step 2: R1 influent is simulated wastewater, which specifically includes the following substances: NO3 - -N (NaNO3), NaH2PO4·2H2O, COD (CH3COONa), NaHCO3, NaOH, CaCl2, CoCl2·2H2O, CuSO4·5H2O, EDTA, FeSO4·7H2O, H3BO3, MnCl2·4H2O, NaMoO4·2H2O, NiCl2·6H2O and ZnSO4·7H2O; The mass percentage ratio of each substance in the simulated wastewater is: NO3 - -N (NaNO3): NaH2PO4·2H2O: COD(CH3COONa): NaHCO3: NaOH: CaCl2: CoCl2·2H2O: CuSO4·5H2O: EDTA: FeSO4·7H2O: H3BO3: MnCl2·4H2O: NaMoO4·2H2O: NiCl2·6H2O: ZnSO4·7H2O: = (91~182): 618: (0~700): 500: 108: 0.13: 0.76: 0.08: 4.9: 3: 0.05: 0.30: 0.76: 0.7: 0.15; The operating conditions in step 2 include influent nitrate nitrogen concentration, temperature, influent pH and hydraulic retention time; Influent nitrate concentration: 91 mg·L -1 The chemical oxygen demand concentration of the simulated wastewater is 270-540 mg·L -1 , the initial carbon-nitrogen ratio of the simulated wastewater was 3; The temperature is 30°C; the inlet pH is 8.0; the hydraulic retention time is 2.4h; Step 3, continuously monitoring the concentrations of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the effluent of the upflow anaerobic sludge blanket reactor; Step 4: Determine the time to add humic acid based on the effluent nitrate nitrogen concentration, and add humic acid to break the iron shell-embedded denitrification sludge; The specific process is as follows: after the iron shell burying denitrification sludge phenomenon occurs, the operating conditions in step 2 are maintained for 30 days, and the nitrate nitrogen concentration in the reactor effluent continues to be higher than 20 mg·L -1 When Figure 1 As shown, 100 mg·L was added to the influent -1 Humic acid, it can be seen that at 100 mg·L -1 The SDA value of denitrification activity was the highest when humic acid was used, indicating that the denitrification activity of functional microorganisms was the highest, which was more conducive to the operation of the process. The upflow anaerobic sludge blanket reactor was operated and the operating conditions in step 2 were kept unchanged. When the nitrate nitrogen concentration in the effluent was lower than 10 mg·L -1 When , stop adding humic acid and keep the operating conditions unchanged; The above data show that adding 100 mg·L -1 After one week of humic acid, the denitrification performance of the reactor was improved, such as Figure 2 As shown in Figure 2, the nitrate removal efficiency (NRE) increased from 67.53% ± 2.72% of the initial inoculum sludge to 87.94% ± 0.71%. Figure 3 As shown in the figure, the iron shell embedding phenomenon of the sludge in the reactor has been effectively alleviated. It can be seen that with the addition of humic acid, the iron in the iron shell embedded sludge is released and falls off. With the addition of humic acid, the iron shell is gradually corroded, and the iron ions inside the sludge are gradually released and returned to the reactor to participate in various denitrification pathways, thereby improving the denitrification efficiency of the system and achieving sludge shell breaking.

Claims

1. A method for breaking iron shell-embedded denitrification sludge by humic acid, characterized in that: The following steps are involved: Step 1: using an upflow anaerobic sludge blanket reactor to inoculate the denitrifying granular sludge embedded in an iron shell; Step 2: preparing simulated wastewater, introducing the simulated wastewater into an upflow anaerobic sludge blanket reactor, and setting the reactor operating conditions; Step 3, continuously monitoring the concentrations of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the effluent of the upflow anaerobic sludge blanket reactor; Step 4: Determine the time to add humic acid based on the effluent nitrate nitrogen concentration, and add humic acid to break up the iron shell-embedded denitrifying sludge.

2. The method for denitrifying sludge by using humic acid to break down iron shells according to claim 1, characterized in that: The simulated wastewater in step 2 specifically includes the following substances: NO3 - -N (NaNO3), NaH2PO4·2H2O, COD (CH3COONa), NaHCO3, NaOH, CaCl2, CoCl2·2H2O, CuSO4·5H2O, EDTA, FeSO4·7H2O, H3BO3, MnCl2·4H2O, NaMoO4·2H2O, NiCl2·6H2O and ZnSO4·7H2O.

3. The method for breaking iron shell-embedded denitrification sludge by humic acid according to claim 2, characterized in that: The mass percentage ratio of each substance in the simulated wastewater is: NO3 - -N (NaNO3):NaH2PO4·2H2O:COD (CH3COONa): NaHCO3: NaOH: CaCl2: CoCl2·2H2O: CuSO4·5H2O: EDTA: FeSO4·7H2O: H3BO3: MnCl2·4H2O: NaMoO4·2H2O: NiCl2·6H2O: ZnSO4·7H2O: = (91~182): 618: (0~700): 500: 108: 0.13: 0.76: 0.08: 4.9: 3: 0.05: 0.30: 0.76: 0.7: 0.

15.

4. The method for denitrifying sludge by using humic acid to break down iron shells according to claim 1, characterized in that: The operating conditions described in step 2 include influent nitric nitrogen concentration, temperature, influent pH and hydraulic retention time.

5. The method for breaking down the iron shell-embedded denitrification sludge by humic acid according to claim 4, characterized in that: The influent nitrate nitrogen concentration is 90-180 mg·L -1 The chemical oxygen demand concentration of the simulated wastewater is 270-540 mg·L -1 , the initial carbon-nitrogen ratio of the simulated wastewater was 3-4.

6. The method for breaking down the iron shell-embedded denitrification sludge by humic acid according to claim 4, characterized in that: The temperature is 25-35°C; the influent pH is 7.5-9.0; and the hydraulic retention time is 2-3 h.

7. The method for breaking down the iron shell-embedded denitrification sludge by humic acid according to claim 1, characterized in that: The specific process of step 4 is: after the iron shell burying denitrification sludge phenomenon occurs, the operating conditions in step 2 are maintained for 30 days, and the nitrate nitrogen concentration in the reactor effluent continues to be higher than 20 mg·L -1 When humic acid was added to the influent, the upflow anaerobic sludge blanket reactor was operated and the operating conditions in step 2 were kept unchanged. When the nitrate nitrogen concentration in the effluent was lower than 10 mg·L -1 When the temperature reaches 0.0400 °C, stop adding humic acid and keep the operating conditions unchanged.

8. The method for breaking down the iron shell-embedded denitrification sludge by humic acid according to claim 1, characterized in that: The humic acid in step 4 is specifically C 14 H7NaO5S, the purity of the humic acid is not less than 99%.

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