Method for using humic acid to break down iron shell-embedded denitrification sludge

Abstract

The method for using humic acid to break down iron-shell-embedded denitrification sludge disclosed in the present invention comprises the following steps: step 1, using an upflow anaerobic sludge blanket reactor to inoculate iron-shell-embedded denitrification granular sludge; step 2, preparing simulated wastewater, introducing the simulated wastewater into the 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, using the effluent nitrate nitrogen concentration as a criterion, determining the time for adding humic acid, and adding humic acid to break down the iron-shell-embedded denitrification sludge. The method for using humic acid to break down iron-shell-embedded denitrification sludge of the present invention can quickly alleviate the reduction in sludge activity, reduction in system denitrification efficiency, or even loss of system denitrification efficiency caused by iron-shell-embedded sludge, and quickly restore the denitrification performance of the system, thereby maintaining the system denitrification efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and particularly 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 emissions during wastewater treatment has become a key topic in the field. Traditional denitrification processes, when treating wastewater with a low carbon-nitrogen ratio (C / N)—high nitrate nitrogen concentration and low organic carbon source concentration—require additional organic carbon source additions due to a lack of organic carbon source. This not only increases treatment costs but also poses the risk of secondary pollution.

[0003] In recent years, autotrophic denitrification processes mediated by inorganic electron donors, such as zero-valent iron, have gained increasing attention. These processes utilize zero-valent iron as an electron donor to complete the denitrification process, effectively addressing the electron donor shortage problem in treating low-carbon-nitrogen ratio wastewater, such as urban wastewater. However, these processes are prone to iron encapsulation of sludge during operation, leading to a sharp decrease in the system's denitrification efficiency. The iron encapsulation of the sludge surface prevents nutrients from reaching the interior of the sludge, causing the microorganisms within the sludge to die due to lack of nutrients. This hinders the denitrification process and reduces efficiency. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for breaking up iron shell-embedded denitrification sludge by using 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 down the iron shell-embedded denitrification sludge with humic acid, comprising the following steps:

[0006] Step 1: using an upflow anaerobic sludge blanket reactor and inoculating the denitrifying granular sludge embedded in an iron shell;

[0007] Step 2: preparing simulated wastewater, introducing the simulated wastewater into an upflow anaerobic sludge blanket reactor, and setting the reactor operating conditions;

[0008] Step 3, continuously monitoring the concentrations of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the effluent of the upflow anaerobic sludge blanket reactor;

[0009] Step 4: Determine the time to add humic acid based on the nitrate nitrogen concentration in the effluent, and add humic acid to break up the iron shell-embedded denitrifying sludge.

[0010] The present invention is also characterized in that:

[0011] 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.

[0012] 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.

[0013] The operating conditions in step 2 include influent nitrate nitrogen concentration, temperature, influent pH and hydraulic retention time.

[0014] 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 is 3-4.

[0015] The temperature is 25-35℃; the inlet pH is 7.5-9.0; and the hydraulic retention time is 2-3 h.

[0016] The specific process of step 4 is as follows: after the iron shell burying denitrification sludge phenomenon occurs, the operating conditions of step 2 are maintained for 30 days, and the nitrate nitrogen concentration in the reactor effluent is continuously higher than 20 mg·L -1 When humic acid is added to the influent, the upflow anaerobic sludge blanket reactor is operated and the operating conditions in step 2 are kept unchanged. When the nitrate nitrogen concentration in the effluent is lower than 10 mg·L -1 When the temperature reaches 0.05 °C, stop adding humic acid and keep the operating conditions unchanged.

[0017] The humic acid in step 4 is specifically C 14 H7NaO5S, the purity of humic acid is not less than 99%.

[0018] The beneficial effects of the present invention are:

[0019] The method provided by the present invention for using humic acid to break down iron-shell-embedded denitrification sludge can quickly and effectively corrode the iron shell by adding humic acid, releasing the iron ions (ferrous iron and ferric iron) embedded in the sludge, thereby realizing the recycling of the iron ions and constructing a physical and chemical coupled microbial enhancement regulation strategy, which can improve the denitrification efficiency while solving the problem of iron shell embedment. The addition of humic acid and the operation of an upflow anaerobic sludge blanket reactor under specific conditions can break down the iron shell-embedded sludge phenomenon while reducing the system's demand for an organic carbon source and lowering the operating cost of the wastewater treatment process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic diagram of the optimized concentration of humic acid in Example 8 of the present invention;

[0021] Figure 2 Schematic diagram of nitric nitrogen removal rate in Example 8 of the present invention

[0022] Figure 3 This is a schematic diagram of the use of humic acid at different concentrations to break down iron shell-embedded sludge in Example 8 of the present invention. DETAILED DESCRIPTION

[0023] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] Example 1

[0025] The method for using humic acid to break down the iron shell-embedded denitrification sludge proposed in this embodiment includes the following steps:

[0026] Step 1: using an upflow anaerobic sludge blanket reactor and inoculating the denitrifying granular sludge embedded in an iron shell;

[0027] Step 2: preparing simulated wastewater, introducing the simulated wastewater into an upflow anaerobic sludge blanket reactor, and setting the reactor operating conditions;

[0028] Step 3, continuously monitoring the concentrations of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the effluent of the upflow anaerobic sludge blanket reactor;

[0029] Step 4: Determine the time to add humic acid based on the nitrate nitrogen concentration in the effluent, and add humic acid to break up the iron shell-embedded denitrifying sludge.

[0030] Example 2

[0031] The method for using humic acid to break down the iron shell-embedded denitrification sludge proposed in this embodiment includes the following steps:

[0032] Step 1: using an upflow anaerobic sludge blanket reactor and inoculating the denitrifying granular sludge embedded in an iron shell;

[0033] Step 2: preparing simulated wastewater, introducing the simulated wastewater into an upflow anaerobic sludge blanket reactor, and setting the reactor operating conditions;

[0034] 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;

[0035] Step 3, continuously monitoring the concentrations of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the effluent of the upflow anaerobic sludge blanket reactor;

[0036] Step 4: Determine the time to add humic acid based on the nitrate nitrogen concentration in the effluent, and add humic acid to break up the iron shell-embedded denitrifying sludge.

[0037] Example 3

[0038] The method for using humic acid to break down the iron shell-embedded denitrification sludge proposed in this embodiment includes the following steps:

[0039] Step 1: using an upflow anaerobic sludge blanket reactor and inoculating the denitrifying granular sludge embedded in an iron shell;

[0040] Step 2: preparing simulated wastewater, introducing the simulated wastewater into an upflow anaerobic sludge blanket reactor, and setting the reactor operating conditions;

[0041] 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;

[0042] 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;

[0043] Step 3, continuously monitoring the concentrations of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the effluent of the upflow anaerobic sludge blanket reactor;

[0044] Step 4: Determine the time to add humic acid based on the nitrate nitrogen concentration in the effluent, and add humic acid to break up the iron shell-embedded denitrifying sludge.

[0045] Example 4

[0046] The method for using humic acid to break down the iron shell-embedded denitrification sludge proposed in this embodiment includes the following steps:

[0047] Step 1: using an upflow anaerobic sludge blanket reactor and inoculating the denitrifying granular sludge embedded in an iron shell;

[0048] Step 2: preparing simulated wastewater, introducing the simulated wastewater into an upflow anaerobic sludge blanket reactor, and setting the reactor operating conditions;

[0049] 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;

[0050] 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;

[0051] The operating conditions in step 2 include influent nitrate nitrogen concentration, temperature, influent pH and hydraulic retention time;

[0052] Step 3, continuously monitoring the concentrations of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the effluent of the upflow anaerobic sludge blanket reactor;

[0053] Step 4: Determine the time to add humic acid based on the nitrate nitrogen concentration in the effluent, and add humic acid to break up the iron shell-embedded denitrifying sludge.

[0054] Example 5

[0055] The method for using humic acid to break down the iron shell-embedded denitrification sludge proposed in this embodiment includes the following steps:

[0056] Step 1: using an upflow anaerobic sludge blanket reactor and inoculating the denitrifying granular sludge embedded in an iron shell;

[0057] Step 2: preparing simulated wastewater, introducing the simulated wastewater into an upflow anaerobic sludge blanket reactor, and setting the reactor operating conditions;

[0058] 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;

[0059] 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;

[0060] The operating conditions in step 2 include influent nitrate nitrogen concentration, temperature, influent pH and hydraulic retention time;

[0061] 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 is 3-4;

[0062] Step 3, continuously monitoring the concentrations of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the effluent of the upflow anaerobic sludge blanket reactor;

[0063] Step 4: Determine the time to add humic acid based on the nitrate nitrogen concentration in the effluent, and add humic acid to break up the iron shell-embedded denitrifying sludge.

[0064] Example 6

[0065] The method for using humic acid to break down the iron shell-embedded denitrification sludge proposed in this embodiment includes the following steps:

[0066] Step 1: using an upflow anaerobic sludge blanket reactor and inoculating the denitrifying granular sludge embedded in an iron shell;

[0067] Step 2: preparing simulated wastewater, introducing the simulated wastewater into an upflow anaerobic sludge blanket reactor, and setting the reactor operating conditions;

[0068] 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;

[0069] 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;

[0070] The operating conditions in step 2 include influent nitrate nitrogen concentration, temperature, influent pH and hydraulic retention time;

[0071] 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 is 3-4;

[0072] The temperature is 25-35℃; the inlet pH is 7.5-9.0; the hydraulic retention time is 2-3 hours;

[0073] Step 3, continuously monitoring the concentrations of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the effluent of the upflow anaerobic sludge blanket reactor;

[0074] Step 4: Determine the time to add humic acid based on the nitrate nitrogen concentration in the effluent, and add humic acid to break up the iron shell-embedded denitrifying sludge.

[0075] Example 7

[0076] The method for using humic acid to break down the iron shell-embedded denitrification sludge proposed in this embodiment includes the following steps:

[0077] Step 1: using an upflow anaerobic sludge blanket reactor and inoculating the denitrifying granular sludge embedded in an iron shell;

[0078] Step 2: preparing simulated wastewater, introducing the simulated wastewater into an upflow anaerobic sludge blanket reactor, and setting the reactor operating conditions;

[0079] 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;

[0080] 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;

[0081] The operating conditions in step 2 include influent nitrate nitrogen concentration, temperature, influent pH and hydraulic retention time;

[0082] 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 is 3-4;

[0083] The temperature is 25-35℃; the inlet pH is 7.5-9.0; the hydraulic retention time is 2-3 hours;

[0084] Step 3, continuously monitoring the concentrations of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the effluent of the upflow anaerobic sludge blanket reactor;

[0085] Step 4: Determine the time to add humic acid based on the nitrate nitrogen concentration in the effluent, and add humic acid to break the iron shell-embedded denitrification sludge;

[0086] The specific process is as follows: after the iron shell embedding 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;

[0087] Humic acid is specifically C 14 H7NaO5S, the purity of humic acid is not less than 99%.

[0088] Example 8

[0089] The method for using humic acid to break down the iron shell-embedded denitrification sludge proposed in this embodiment includes the following steps:

[0090] 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 tested to be 7.32 g·L-1, that is, each contains 0.24 g of volatile suspended solids;

[0091] 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;

[0092] 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;

[0093] The operating conditions in step 2 include influent nitrate nitrogen concentration, temperature, influent pH and hydraulic retention time;

[0094] Influent nitrate nitrogen 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;

[0095] The temperature is 30°C; the inlet pH is 8.0; the hydraulic retention time is 2.4h;

[0096] Step 3, continuously monitoring the concentrations of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the effluent of the upflow anaerobic sludge blanket reactor;

[0097] Step 4: Determine the time to add humic acid based on the nitrate nitrogen concentration in the effluent, and add humic acid to break the iron shell-embedded denitrification sludge;

[0098] The specific process is as follows: after the iron shell embedding 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, such as 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;

[0099] The above data show that adding 100 mg·L -1 After one week of humic acid treatment, the denitrification performance of the reactor improved, e.g. Figure 2 As shown in Figure 2, the nitrate removal efficiency (NRE) increased from 67.53% ± 2.72% of the initial inoculated sludge to 87.94% ± 0.71%. Figure 3 As shown in the figure, the iron encapsulation 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-encapsulated sludge is released and falls off. With the addition of humic acid, the iron encapsulation is gradually corroded, and the iron ions inside the sludge are gradually released and returned to the reactor, participating in various denitrification pathways, thereby improving the system's denitrification efficiency while achieving sludge shell breaking.

Claims

1. A method for breaking down iron shell-embedded denitrification sludge using humic acid, characterized in that: The following steps are involved: Step 1: using an upflow anaerobic sludge blanket reactor and inoculating the denitrifying granular sludge embedded in the 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 nitrate nitrogen concentration in the effluent, and add humic acid to break the iron shell-embedded denitrification sludge; The specific process of step 4 is as follows: after the iron shell embedding denitrification sludge phenomenon occurs, the operating conditions in step 2 are maintained for 30 days, and the nitrate nitrogen concentration in the reactor effluent is continuously higher than 20 mg·L -1 When humic acid is added to the influent, the upflow anaerobic sludge blanket reactor is operated and the operating conditions in step 2 are kept unchanged. When the nitrate nitrogen concentration in the effluent is lower than 10 mg·L -1 When the temperature reaches 0.05 °C, stop adding humic acid and keep the operating conditions unchanged.

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

5. The method for denitrifying sludge by using humic acid to break down iron shells according to claim 4, wherein: 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 is 3-4.

6. The method for denitrifying sludge by using humic acid to break down iron shells according to claim 4, wherein: 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 denitrifying sludge by using humic acid to break down iron shells according to claim 1, wherein: 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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