A method for efficient denitrification of leather wastewater based on anaerobic ammonium oxidation technology

Abstract

The present invention discloses a method for efficiently denitrifying leather wastewater based on anaerobic ammonia oxidation technology, comprising the following steps: using leather wastewater pretreated by chemical coagulation as actual wastewater, and regulating the concentration of substrates in the actual wastewater, including ammonia nitrogen (70-210 mg·L ‑1 ), nitrite nitrogen (70~210mg·L ‑1 ) and chemical oxygen demand (0-300 mg L ‑1 ), then adopting a "leather wastewater-simulated wastewater-leather wastewater" model, operating an upflow anaerobic sludge blanket reactor in stages and continuously. This invention utilizes an ANAMMOX system to treat pretreated leather wastewater, achieving efficient denitrification and laying the foundation for expanding the application of ANAMMOX processes in treating nitrogen-rich organic wastewater.

Description

(1) Technical field

[0001] The present invention belongs to the technical field of biological sewage treatment, and in particular relates to a method for efficiently denitrifying leather wastewater based on anaerobic ammonia oxidation technology. (2) Background technology

[0002] Leather is a vital industry in the national economy. The leather manufacturing process produces a number of pollutants, including high concentrations of chemical oxygen demand, ammonia nitrogen, and other toxic substances. Therefore, effective treatment of leather wastewater is essential. Biological treatment is considered an economical and green method for treating leather wastewater. However, the presence of complex toxic chemicals in leather wastewater can adversely affect removal efficiency, necessitating a combination of physical and chemical (such as chemical coagulation) and biological methods to treat leather wastewater.

[0003] Anaerobic ammonium oxidation (ANAMMOX) is an energy-efficient denitrification technology that uses ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor to generate nitrogen gas. Compared with the traditional nitrification-denitrification process, ANAMMOX technology has the advantages of not requiring an external carbon source and aeration, and producing less sludge. It has broad application prospects in biological wastewater treatment. However, the feasibility and stability of ANAMMOX technology in efficiently treating leather wastewater still face severe challenges. Therefore, in view of the complex composition of leather wastewater, how to control the substrate concentration and substrate ratio becomes the key to the treatment of leather wastewater with ANAMMOX technology. The purpose is to realize a method for efficient denitrification of leather wastewater with ANAMMOX technology, which provides a new idea for the treatment of nitrogen-rich organic wastewater with ANAMMOX process. (3) Summary of the invention

[0004] The purpose of the present invention is to provide a method for efficiently denitrifying leather wastewater based on anaerobic ammonium oxidation technology. The method utilizes anaerobic ammonium oxidation technology to treat leather wastewater after chemical pretreatment, which helps to improve the denitrification efficiency of the anaerobic ammonium oxidation system and achieve stable and efficient operation of the system.

[0005] The technical solution adopted in the present invention is:

[0006] The present invention provides a method for efficiently denitrifying leather wastewater based on anaerobic ammonium oxidation technology, the method comprising the steps of:

[0007] (1) Pretreatment: a flocculant is first added to the leather wastewater, stirred and flocculated at 30-35°C and 50-100 rpm, centrifuged, and the supernatant is taken as the pretreated leather wastewater; the flocculant includes an organic flocculant and an inorganic flocculant, the organic flocculant includes polyaluminum ferric chloride, and the inorganic flocculant includes polyacrylamide;

[0008] (2) The anaerobic ammonium oxidation reactor was inoculated with anaerobic ammonium oxidation granular sludge and fed with simulated wastewater. The reactor was operated under anaerobic conditions, in the dark, at a temperature of 35±1℃, and with a hydraulic retention time of 6 to 10 h. When the nitrite nitrogen effluent concentration of the reactor was lower than 10 mg·L -1 The reactor was successfully started; the simulated wastewater was an inorganic salt solution containing ammonia nitrogen and nitrite nitrogen, of which ammonia nitrogen was 50-210 mg·L -1 , nitrite nitrogen 50~210mg·L -1 Chemical oxygen demand 0-300 mg L -1 ;

[0009] (3) The leather wastewater pretreated in step (1) is continuously pumped into the anaerobic ammonium oxidation reactor successfully started in step (2), and operated under anaerobic light-proof conditions, a temperature of 35±1°C, and a hydraulic retention time of 6 to 10 hours; when the nitrite nitrogen concentration in the reactor effluent is lower than 10 mg·L -1 , and continue to operate stably for 3 days, gradually increase the concentrations of ammonia nitrogen, nitrite nitrogen and chemical oxygen demand in leather wastewater; when the nitrite nitrogen concentration in the effluent reaches 100 mg·L -1 When the reactor influent was changed to simulated wastewater, the concentrations of ammonia nitrogen, nitrite nitrogen and chemical oxygen demand in the simulated wastewater were gradually reduced until the nitrite nitrogen effluent concentration was lower than 10 mg·L -1 After 3 days of stable operation, the system is switched to pretreated leather wastewater again, and the "leather wastewater-simulated wastewater-leather wastewater" mode is adopted for continuous and stable operation to achieve efficient degradation of leather wastewater.

[0010] Furthermore, the flocculants in step (1) are a polyaluminum ferric chloride aqueous solution with a mass concentration of 0.1-2% (preferably 1%) and a polyacrylamide aqueous solution with a mass concentration of 0.05-1% (preferably 0.1%), the volume of the polyaluminum ferric chloride aqueous solution is 20-50 mL / L (preferably 30 mL / L), and the volume of the polyacrylamide aqueous solution is 1-5 mL / L (preferably 3 mL / L).

[0011] Furthermore, the COD concentration of the leather wastewater in step (1) is 1000-1500 mg·L -1 , ammonia nitrogen concentration is 150~250mg·L -1 , nitrite nitrogen concentration is 0~1mg·L -1 , nitrate nitrogen concentration is 40~100mg·L -1 .

[0012] Furthermore, the pretreatment method in step (1) is as follows: taking leather wastewater, first adding a 0.1-2% polyaluminum chloride ferric aqueous solution, stirring at 35°C and 100 rpm to produce alum flowers, then adding a 0.05-1% polyacrylamide aqueous solution, continuing to stir at 35°C and 100 rpm for 2 hours, and centrifuging at 5000 rpm for 10 minutes. The supernatant is the pretreated leather wastewater; preferably, the ammonia nitrogen, nitrite nitrogen and chemical oxygen demand concentrations in the supernatant are 70, 70 and 100 mg·L, respectively. -1 .

[0013] Furthermore, the anaerobic ammonium oxidation granular sludge activity in step (2) was 340.8±65.3 mg·N·g -1 VSS·d -1 .

[0014] Furthermore, the inorganic salt solution in step (2) is composed of: KH2PO4 10mg·L -1 、CaCl2·2H2O 5.6mg·L -1 , MgSO4·7H2O 300mg·L -1 , KHCO3 1250mg·L -1 , trace element solution 0.15mL / L, solvent is water; trace element solution composition: EDTA 15000mg·L -1 、FeSO4·7H2O 9140mg·L -1 、MnCl2·4H2O 990mg·L -1 、ZnSO4·7H2O 430mg·L -1 、CuSO4·5H2O 250mg·L -1 、CoCl2·6H2O 240mg·L -1 、NaMoO4·2H2O220mg·L -1 、NiCl2·6H2O 210mg·L -1 , H3BO4 14mg·L -1 , the solvent is water.

[0015] Furthermore, the molar ratio of ammonia nitrogen to nitrite nitrogen in the simulated wastewater in step (2) is 1:1, and the ratio of chemical oxygen demand to total nitrogen concentration is 0.5-2.0:1 (preferably 0.7:1).

[0016] Furthermore, the concentrations of ammonia nitrogen, nitrite nitrogen and chemical oxygen demand in the leather wastewater in step (3) were increased by 50 to 120 mg·L -1 More preferably, 70, 70 and 100 mg·L -1 The concentrations of ammonia nitrogen, nitrite nitrogen and chemical oxygen demand increased synchronously.

[0017] Furthermore, in step (3), the simulated wastewater was 110 and 110 mg·L -1 The concentrations of ammonia nitrogen and nitrite nitrogen were reduced simultaneously.

[0018] Furthermore, the pH of the leather wastewater after pretreatment in step (3) is adjusted to neutral.

[0019] Compared with the existing technology, the beneficial effects of the present invention are mainly reflected in: (1) the chemical coagulation combined with microbial wastewater treatment technology of the present invention is not only simple to operate but also low in cost; (2) the present invention makes full use of the anaerobic ammonium oxidation system to utilize additional carbon sources to accelerate the denitrification process, thereby effectively improving the overall denitrification efficiency of the system, and providing a new idea for the efficient treatment of nitrogen-rich organic wastewater with anaerobic ammonium oxidation technology. (IV) Description of the accompanying drawings

[0020] Figure 1 This is a curve chart showing the change in denitrification efficiency of the anaerobic ammonium oxidation system. (V) Specific implementation methods

[0021] The present invention will be further described below in conjunction with the accompanying drawings and specific examples. It should be understood that these examples are intended to illustrate the present invention and are not intended to limit the scope of the invention. The operating methods in the following examples where no specific conditions are specified are generally performed under conventional conditions or as recommended by the manufacturer.

[0022] The leather wastewater used in the present invention was collected from a leather factory in Xinhui, Guangdong, with a COD concentration of 1007±134.5 mg·L -1 , ammonia nitrogen concentration was 176.2±12.2 mg·L -1 , nitrite nitrogen concentration is 0.5±0.01mg·L -1 , nitrate nitrogen concentration was 54.1±1.2 mg·L -1 .

[0023] Example 1. Screening of flocculants

[0024] Take 100mL of leather wastewater and place it in a 1L beaker. First add 100mg·L -1 Polyaluminium ferric chloride, stirred at 35℃ and 100rpm to produce flocs, then 100mg·L -1 Polyacrylamide was stirred at 35°C and 100 rpm, and samples were taken every 10 minutes. The supernatant was the pretreated leather wastewater, and the chemical oxygen demand in the supernatant was determined by potassium permanganate method. Polyaluminium ferric chloride and polyacrylamide were prepared into aqueous solutions respectively, and the chemical oxygen demand in the supernatant was screened to be 100-300 mg·L -1 The concentration and addition amount of aqueous solution of polyaluminium ferric chloride and polyacrylamide at the time of use.

[0025] The optimal flocculant dosage was determined to be 30 mL (1% polyaluminum ferric chloride aqueous solution) / L and 3 mL (0.1% polyacrylamide aqueous solution) / L.

[0026] Example 2: Efficient denitrification of leather wastewater based on anaerobic ammonium oxidation technology

[0027] 1. Preprocessing:

[0028] Take 1000mL of leather wastewater, first add 1% polyaluminum chloride ferric aqueous solution at a mass concentration of 30mL / L, stir at 35°C and 100rpm to produce alum flowers, then add 0.1% polyacrylamide aqueous solution at a mass concentration of 30mL / L, stir at 35°C and 100rpm for 2h to obtain pretreated leather wastewater.

[0029] 2. Anaerobic ammonium oxidation reaction:

[0030] (1) Reactor inoculation

[0031] A 1.5 L upflow anaerobic sludge blanket reactor was used. The dominant bacteria in the inoculated anaerobic ammonium oxidation granular sludge was Candidatus Kuenenia, with a relative abundance of 26.5% and an activity of 340.8 ± 65.3 mg·N·g -1 VSS·d -1 The inoculum volume was 1.0 L. The culture medium was covered with shade cloth to avoid photoinhibition.

[0032] (2) Reactor startup

[0033] Containing 100mg·L -1 Ammonia nitrogen and 100mg·L -1 The influent was an inorganic salt solution of nitrite (i.e., simulated wastewater), operating at a temperature of 35±1°C, a hydraulic retention time of 8 hours, and an influent pH of 7.4±0.1. The concentrations of ammonia nitrogen and nitrite nitrogen in the reactor influent were manually adjusted according to reaction requirements, with a 1:1 ratio. Ammonia nitrogen and nitrite nitrogen were provided as (NH₄)₂SO₄ and NaNO₂, respectively. The ratio of chemical oxygen demand to total nitrogen concentration in the reactor influent was set at 0.7. The reactor was successfully started up after operating until the total nitrogen removal efficiency stabilized at approximately 90%.

[0034] Inorganic salt solution composition: KH2PO4 10mg·L -1 、CaCl2·2H2O 5.6mg·L -1 , MgSO4·7H2O300mg·L -1 , KHCO3 1250mg·L -1, trace element solution 0.15mL / L, solvent is water; trace element solution composition: EDTA 15000mg·L -1 、FeSO4·7H2O 9140mg·L -1 、MnCl2·4H2O 990mg·L -1 、ZnSO4·7H2O430mg·L -1 、CuSO4·5H2O 250mg·L -1 、CoCl2·6H2O 240mg·L -1 、NaMoO4·2H2O 220mg·L -1 、NiCl2·6H2O 210mg·L -1 , H3BO4 14mg·L -1 , the solvent is water.

[0035] (3) Reactor operation

[0036] According to Table 1, the reactor was operated continuously in the "leather wastewater-simulated wastewater-leather wastewater" operation mode, with an operating temperature of 35±1°C, a hydraulic retention time of 8h, and an influent pH of 7.4±0.1. The concentrations of ammonia nitrogen and nitrite nitrogen in the reactor influent matrix can be manually adjusted according to the reaction requirements, with a ratio of 1:1. The specific operation is as follows:

[0037] After the reactor was successfully started, the leather wastewater pretreated in step 1 was pumped in as influent on the first day of the experimental operation. The initial influent matrix ammonia nitrogen, nitrite nitrogen, and chemical oxygen demand concentrations of the reactor were 70, 70, and 100 mg·L, respectively. -1 When the nitrite nitrogen concentration in the reactor outlet water is lower than 10 mg·L -1 , and continued to run stably for 3 days, the experiment entered the next stage. Each stage was based on the previous stage and gradually increased the influent matrix concentration. Stages I-III used the leather wastewater pretreated in step 1 as the influent and used 70, 70 and 100 mg·L -1 The concentrations of ammonia nitrogen, nitrite nitrogen, and chemical oxygen demand were increased synchronously. The concentrations of ammonia nitrogen and nitrite nitrogen in the influent matrix could be adjusted manually according to the reaction needs. The ratio between the two was 1:1. The ratio of chemical oxygen demand to total nitrogen concentration in the influent was 0.7. The operation was carried out for 30, 20, and 30 days respectively. Phase III was operated until the nitrite nitrogen concentration in the effluent was higher than 100 mg·L -1 , stop the operation of this stage and immediately proceed to the next stage. Stage IV adopts the simulated wastewater operation mode and -1 The concentrations of ammonia nitrogen, nitrite nitrogen and chemical oxygen demand were reduced synchronously. After 10 days of operation, when the nitrite nitrogen in the effluent was lower than 10 mg·L -1Phase V adopted the leather wastewater operation mode and used 100, 100 and 300 mg·L -1 The concentrations of ammonia nitrogen, nitrite nitrogen and chemical oxygen demand were increased significantly. The ratio of ammonia nitrogen and nitrite nitrogen in the influent matrix was 1:1, and the ratio of chemical oxygen demand to total nitrogen in the influent was 1.5. After 30 days of operation, when the nitrite nitrogen in the effluent was lower than 10 mg·L -1 The anammox treatment of leather wastewater was completed after three days of stable operation. The specific operating parameters of the reactor are shown in Table 1 below.

[0038] Table 1 Reactor operating parameters at different stages

[0039]

[0040] The denitrification performance results of anaerobic ammonium oxidation reactor in treating leather wastewater are as follows Figure 1 As shown in Figure 2, the reactors can operate stably in the “real” wastewater operation mode in phases I and II, with a total nitrogen removal load and total nitrogen removal efficiency of 0.43–0.45 kg N·m, respectively. -3 ·d -1 When the substrate concentration continued to increase (stage III), the denitrification performance of the reactor decreased significantly. Therefore, in stage IV, the reactor was regulated by the “simulated” wastewater operation mode, and the denitrification performance recovered rapidly. In stage V, the “actual” wastewater operation mode was adopted, and the total nitrogen removal load and total nitrogen removal efficiency were 0.38±0.20 kg N·m -3 ·d -1 and 84.4±8.6%.

[0041] Depend on Figure 1 It can be seen that when the substrate concentration in the leather wastewater gradually increases, the denitrification performance of the anaerobic ammonium oxidation reactor first gradually stabilizes, then fluctuates, and then returns to a continuously stable state, indicating that the anaerobic ammonium oxidation system can treat leather wastewater.

[0042] The present invention provides a method for efficiently treating leather wastewater using anaerobic ammonium oxidation technology, which helps to broaden the engineering application of anaerobic ammonium oxidation technology in industrial wastewater.

Claims

1. A method for efficiently denitrifying leather wastewater based on anaerobic ammonium oxidation technology, characterized in that: The method comprises the steps of: (1) Pretreatment: a flocculant is first added to the leather wastewater, stirred and flocculated at 30-35°C and 50-100 rpm, centrifuged, and the supernatant is taken as the pretreated leather wastewater; the flocculant includes an organic flocculant and an inorganic flocculant, the organic flocculant includes polyaluminum ferric chloride, and the inorganic flocculant includes polyacrylamide; (2) The anaerobic ammonium oxidation reactor was inoculated with anaerobic ammonium oxidation granular sludge and fed with simulated wastewater. The reactor was operated under anaerobic conditions, in the dark, at a temperature of 35±1℃, and with a hydraulic retention time of 6 to 10 h. When the nitrite nitrogen effluent concentration of the reactor was lower than 10 mg·L -1 The reactor was successfully started; the simulated wastewater was an inorganic salt solution containing ammonia nitrogen and nitrite nitrogen, of which ammonia nitrogen was 50-210 mg·L -1 , nitrite nitrogen 50~210mg·L -1 Chemical oxygen demand 0-300 mg L -1 ; (3) The leather wastewater pretreated in step (1) is continuously pumped into the anaerobic ammonium oxidation reactor successfully started in step (2), and operated under anaerobic light-proof conditions, a temperature of 35±1°C, and a hydraulic retention time of 6 to 10 hours; when the nitrite nitrogen concentration in the reactor effluent is lower than 10 mg·L -1 , and continue to operate stably for 3 days, gradually increase the concentrations of ammonia nitrogen, nitrite nitrogen and chemical oxygen demand in leather wastewater; when the nitrite nitrogen concentration in the effluent reaches 100 mg·L -1 When the reactor influent was changed to simulated wastewater, the concentrations of ammonia nitrogen, nitrite nitrogen and chemical oxygen demand in the simulated wastewater were gradually reduced until the nitrite nitrogen effluent concentration was lower than 10 mg·L -1 After 3 days of stable operation, the system switches to pretreated leather wastewater again and adopts the "leather wastewater-simulated wastewater-leather wastewater" mode for continuous and stable operation to achieve efficient degradation of leather wastewater.

2. The method according to claim 1, wherein The flocculants in step (1) are a polyaluminium ferric chloride aqueous solution with a mass concentration of 0.1-2% and a polyacrylamide aqueous solution with a mass concentration of 0.05-1%.

3. The method according to claim 2, wherein The pretreatment method of step (1) is as follows: taking leather wastewater, first adding a 0.1-2% mass concentration of polyaluminum ferric chloride aqueous solution, stirring at 35°C and 100rpm to produce alum flowers, then adding a 0.05-1% mass concentration of polyacrylamide aqueous solution, continuing to stir at 35°C and 100rpm for 2h, centrifuging at 5000rpm for 10min, and the supernatant is the pretreated leather wastewater; the volume dosage of the polyaluminum ferric chloride aqueous solution is 20-50mL / L, and the volume dosage of the polyacrylamide aqueous solution is 1-5mL / L.

4. The method according to claim 1, wherein The COD concentration of leather wastewater in step (1) is 1000-1500 mg·L -1 , ammonia nitrogen concentration is 150~250mg·L -1 , nitrite nitrogen concentration is 0~1mg·L -1 , nitrate nitrogen concentration is 40~100mg·L -1 .

5. The method according to claim 1, wherein The activity of the anaerobic ammonium oxidation granular sludge in step (2) was 340.8±65.3 mg·N·g -1 VSS·d -1 .

6. The method according to claim 1, wherein The inorganic salt solution composition in step (2) is: KH2PO4 10mg·L -1 、CaCl2·2H2O 5.6mg·L -1 , MgSO4·7H2O 300mg·L -1 , KHCO3 1250mg·L -1 , trace element solution 0.15mL / L, solvent is water; trace element solution composition: EDTA 15000mg·L -1 、FeSO4·7H2O9140mg·L -1 、MnCl2·4H2O 990mg·L -1 、ZnSO4·7H2O 430mg·L -1 、CuSO4·5H2O 250mg·L -1 、CoCl2·6H2O 240mg·L -1 、NaMoO4·2H2O 220mg·L -1 、NiCl2·6H2O 210mg·L -1 , H3BO4 14mg·L -1 , the solvent is water.

7. The method according to claim 1, wherein The molar ratio of ammonia nitrogen to nitrite nitrogen in the simulated wastewater in step (2) is 1:1, and the ratio of chemical oxygen demand to total nitrogen concentration is 0.5-2.0:

1.

8. The method according to claim 1, wherein In step (3), the concentrations of ammonia nitrogen, nitrite nitrogen and chemical oxygen demand in the leather wastewater increased by 50-120 mg·L -1 .

9. The method according to claim 1, wherein Step (3) simulated wastewater with 110 and 110 mg·L -1 The concentrations of ammonia nitrogen and nitrite nitrogen were reduced simultaneously.

10. The method according to claim 1, wherein The pH of the leather wastewater after pretreatment in step (3) is adjusted to neutral.

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