A method for anaerobic ammonia oxidation and sludge reuse based on ultrasound-assisted respiration

Abstract

This invention discloses a method for reusing anaerobic ammonia oxidation (ANAO) sludge based on ultrasound-assisted respiration, comprising: assisted respiration: ANAO sludge from the three-phase separator of a UASB reactor is placed in a nutrient solution for low-intensity ultrasound treatment; if the sludge settles completely within 5 minutes after the low-intensity ultrasound treatment, a sludge reuse step is performed; otherwise, the sludge continues to undergo low-intensity ultrasound treatment in the nutrient solution; sludge reuse: the settled sludge after low-intensity ultrasound treatment is inoculated into the reactor, and the effluent nitrite nitrogen gradually decreases to 20 mg / L. ‑1 If the following occurs, increase the nitrogen load in the reactor influent; if the sludge flotation rate in the reactor reaches 20% or more, or if the nitrogen removal load per unit volume of the reactor cannot be increased within 5 days, repeat the assisted breathing and sludge reuse steps until the reactor reaches the required nitrogen removal load per unit volume.

Description

Technical Field

[0001] This invention relates to the field of anaerobic ammonia oxidation sludge treatment technology, specifically to a method for reusing anaerobic ammonia oxidation floating sludge based on ultrasound-assisted respiration. Background Technology

[0002] Anaerobic ammonia oxidation (AAO) is a novel biological nitrogen removal technology that has attracted widespread attention in the treatment of nitrogen-containing wastewater due to its advantages such as high nitrogen removal rate, low energy consumption, and low sludge production. However, the lack of inoculum sludge caused by the long proliferation time of anaerobic ammonia oxidizing bacteria is one of the main obstacles to the practical application of this process.

[0003] In the process of treating high-concentration nitrogen-containing wastewater using anaerobic ammonia oxidation (ANAO), anaerobic ammonia oxidizing bacteria produce a large amount of N2 that cannot be released. This N2 becomes trapped inside the granular sludge, causing the sludge density to decrease and thus float to the surface. The continuously generated floating sludge not only clogs the three-phase separator but also, over time, leads to sludge decay due to a lack of substrate, resulting in decreased denitrification performance, effluent deterioration, and even systemic failure of the reactor. Therefore, this floating sludge is usually collected and discharged from the reactor as excess sludge. Developing an anaerobic ammonia oxidation floating sludge reuse technology can not only effectively solve the floating sludge disposal problem but also shorten the start-up time of high-load anaerobic ammonia oxidation reactors, achieving the dual benefits of waste-to-waste treatment and cost reduction / efficiency improvement.

[0004] The current conventional method involves mechanically crushing floating sludge and then returning it to the reactor to increase the biomass within the reactor, thereby significantly improving the denitrification load of the anaerobic ammonia oxidation reactor. However, the process of regranulating crushed sludge is very lengthy and can severely impact the quality of the reactor's effluent.

[0005] Patent specification CN104085983A discloses a method for activating anaerobic ammonia oxidation sludge under low-temperature conditions using ultrasound. The low-temperature condition refers to the anaerobic ammonia oxidation reactor operating at a temperature below 30°C. The method involves adding the anaerobic ammonia oxidation sludge to be activated to a reaction vessel, followed by water bath ultrasonic treatment at a water bath temperature of 31–35°C. The ultrasonic conditions are: frequency 20 kHz, intensity 0.7–0.9 W / cm². -2 The ultrasonic treatment time is 1.7 to 2.0 minutes; activated anaerobic ammonia oxidation sludge is obtained after ultrasonic treatment.

[0006] Patent specification CN104386814A discloses a method for enhancing the start-up efficiency of an anaerobic ammonia oxidation process using ordinary activated sludge as inoculum with ultrasound. The main unit of the ultrasonic generator is placed outside the anaerobic ammonia oxidation start-up reactor, with the ultrasonic transducer submerged below the liquid surface inside the reactor. By irradiating the cultured sludge during the anaerobic ammonia oxidation process with low-intensity ultrasound, the cell membrane permeability, electron transport velocity, and functional enzyme activity of anaerobic ammonia oxidizing bacteria are improved, thereby enhancing the activity of anaerobic ammonia oxidizing bacteria and their competitive advantage within the cultured sludge, thus achieving rapid process start-up.

[0007] Although both of the above patented technologies involve ultrasonic technology, their application is not the same as the anaerobic ammonia oxidation sludge targeted by this invention. Furthermore, due to the different applications, neither of the above two patented technologies addresses the problem of anaerobic ammonia oxidation sludge floating. Summary of the Invention

[0008] To address the aforementioned technical problems and shortcomings in this field, this invention provides a method for reusing anaerobic ammonia oxidation sludge based on ultrasound-assisted respiration. This method can rapidly reduce the sludge flotation rate while preserving the macroscopic structure and physicochemical properties of anaerobic ammonia oxidation granular sludge to the greatest extent. It can rapidly increase the nitrogen removal load per unit volume of the reactor without affecting the effluent quality. It has the advantages of low loss, rapid effect, low cost, simple operation, and wide applicability.

[0009] The specific technical solution is as follows:

[0010] A method for reusing anaerobic ammonia oxidation sludge based on ultrasound-assisted respiration includes:

[0011] Assisted respiration: Anaerobic ammonia oxidation sludge from the three-phase separator of an upflow anaerobic sludge blanket (UASB) reactor was placed in a nutrient solution and subjected to low-intensity ultrasonic treatment. The ultrasonic intensity of the low-intensity ultrasonic treatment was 0.2–0.4 W / cm². -2 (e.g., 0.3W cm) -2 (etc.); If the floating sludge can completely settle within 5 minutes after the low-intensity ultrasonic treatment, the sludge reuse step is carried out; otherwise, the floating sludge continues to undergo low-intensity ultrasonic treatment in the nutrient solution.

[0012] Sludge reuse: Settled sludge treated with low-intensity ultrasonication is inoculated into an upflow anaerobic sludge blanket reactor. When the effluent nitrite nitrogen gradually decreases to 20 mg / L... -1 In the following cases, increase the influent nitrogen load of the upflow anaerobic sludge blanket reactor;

[0013] When the sludge flotation rate in the upflow anaerobic sludge bed reactor reaches 20% or more, or when the nitrogen removal load per unit volume of the upflow anaerobic sludge bed reactor cannot be increased within 5 days (d), repeat the assisted breathing and sludge reuse steps until the upflow anaerobic sludge bed reactor reaches the required nitrogen removal load per unit volume.

[0014] This invention focuses on anaerobic ammonia oxidation (AA) sludge (preferably AA granular sludge) as the research object. It solves the problem of AA sludge floating by low-intensity ultrasonic treatment, allowing the sludge to settle and achieve the purpose of reuse.

[0015] In this invention, the sludge flotation rate can be calculated by the ratio of the volume of floating sludge to the volume of inoculated settled sludge.

[0016] In some embodiments, the anaerobic ammonia oxidation sludge reuse method based on ultrasound-assisted respiration includes the following essential components and concentrations of the nutrient solution: orthophosphate 0.5–50 mg / L. -1 Magnesium(II) ions 5-500 mg / L -1 50-2000 mg / L of bicarbonate -1 5-500 mg / L of calcium(II) ions -1 This is beneficial for activating the anaerobic ammonia-oxidizing bacteria that have become dormant due to starvation inside the anaerobic ammonia-oxidizing sludge.

[0017] In some embodiments, in the anaerobic ammonia oxidation sludge reuse method based on ultrasound-assisted respiration, the essential components of the nutrient solution include, in the case of, the orthophosphate, which may be NaH2PO4, etc.; the magnesium(II) ions, which may be sourced from MgSO4·7H2O, etc.; the bicarbonate ions, which may be sourced from NaHCO3, etc.; and the calcium(II) ions, which may be sourced from CaCl2, etc.

[0018] In some embodiments, the anaerobic ammonia oxidation sludge reuse method based on ultrasound-assisted respiration includes the following essential components and concentrations of the nutrient solution: NaH2PO4 10 mg / L. -1 CaCl2 5.65mg / L -1 NaHCO3 840mg / L -1 And MgSO4·7H2O 58.6mg L -1 .

[0019] In some embodiments, the anaerobic ammonia oxidation sludge reuse method based on ultrasound-assisted respiration has a nutrient solution pH in the range of 7.5 to 8.5, such as 8.0, which is beneficial for activating the anaerobic ammonia oxidation bacteria that are dormant due to starvation inside the anaerobic ammonia oxidation sludge.

[0020] In some embodiments, the anaerobic ammonia oxidation sludge reuse method based on ultrasound-assisted respiration has a nutrient solution with a salinity of less than 2.5 wt%, which is beneficial for activating the anaerobic ammonia oxidation bacteria that are dormant due to starvation inside the anaerobic ammonia oxidation sludge.

[0021] In some embodiments, in the anaerobic ammonia oxidation sludge reuse method based on ultrasound-assisted respiration, the mass concentrations of ammonia nitrogen and nitrite nitrogen in the nutrient solution are independently 0–300 mg N / L. -1 Furthermore, the mass concentration ratio of ammonia nitrogen to nitrite nitrogen in the nutrient solution is 0.7–1.5:1. This is beneficial for activating the anaerobic ammonia-oxidizing bacteria that have become dormant due to starvation inside the anaerobic ammonia-oxidizing sludge.

[0022] In some embodiments, the anaerobic ammonia oxidation sludge reuse method based on ultrasound-assisted respiration, wherein the sludge concentration after mixing the anaerobic ammonia oxidation sludge and nutrient solution in the assisted respiration step ranges from 5 to 30 g-VSS L. -1 For example, 8g-VSSL -1 10g-VSS L -1 wait.

[0023] In some embodiments, the anaerobic ammonia oxidation sludge reuse method based on ultrasound-assisted respiration has a single low-intensity ultrasound treatment time of 1 to 10 minutes.

[0024] In some embodiments, the anaerobic ammonia oxidation sludge reuse method based on ultrasound-assisted respiration has a low-intensity ultrasonic treatment frequency of 20–45 kHz, such as 40 kHz.

[0025] In some embodiments, the anaerobic ammonia oxidation sludge reuse method based on ultrasound-assisted respiration is described, wherein the temperature of the low-intensity ultrasound treatment is 4–25°C, for example, 20°C, 22°C, etc.

[0026] In some embodiments, the anaerobic ammonia oxidation sludge reuse method based on ultrasound-assisted respiration involves increasing the influent nitrogen load of the upflow anaerobic sludge bed reactor by 10% to 25%.

[0027] Compared with the prior art, the beneficial effects of this invention are as follows:

[0028] This invention relates to an anaerobic ammonia oxidation sludge reuse method based on ultrasound-assisted respiration. First, low-intensity ultrasound is used to clear the blocked pores of the anaerobic ammonia oxidation sludge, releasing nitrogen trapped in the internal cavities and drawing in nutrient solution, causing the sludge to settle back into the reactor body. When the granular sludge floats to the surface again due to pore blockage, affecting the reactor's denitrification load, the low-intensity ultrasound treatment is repeated, and the process of exhaling and drawing in liquid is repeated until the dormant anaerobic ammonia oxidizing bacteria inside the granular sludge due to starvation are activated. Based on the reactor effluent conditions, the volumetric nitrogen loading rate of the reactor is continuously increased to achieve the operating load required for a high-load reactor. Attached Figure Description

[0029] Figure 1 This is a comparison chart of nitrogen removal load (NRR) per unit volume between an anaerobic ammonia oxidation reactor (a) started with low-intensity ultrasonic treatment of floating sludge and an anaerobic ammonia oxidation reactor (b) started with untreated floating sludge, as shown in Example 1.

[0030] Figure 2 This is a comparison chart of nitrogen removal load per unit volume between an anaerobic ammonia oxidation reactor (a) started with low-intensity ultrasonic treatment of floating sludge and an anaerobic ammonia oxidation reactor (b) started with untreated floating sludge, as shown in Example 2. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0032] Unless otherwise specified, the operating methods in the following examples are generally performed under conventional conditions or as recommended by the manufacturer.

[0033] In the following examples, the anaerobic ammonia oxidation sludge is granular sludge, and the sludge flotation rate is calculated by the ratio of the volume of floating sludge to the volume of inoculated settled sludge.

[0034] Example 1:

[0035] A method for reusing anaerobic ammonia oxidation sludge based on ultrasound-assisted respiration involves placing anaerobic ammonia oxidation sludge from the three-phase separator of an upflow anaerobic sludge blanket (UASB) reactor into a nutrient solution. The nutrient solution contains 10 mg / L NaH2PO4. -1 CaCl2 5.65mg / L -1 NaHCO3 840mg / L -1 And MgSO4·7H2O 58.6mg L -1 The nutrient solution pH is 8.0, and the sludge concentration after mixing the floating sludge with the nutrient solution is 10 g-VSS L. -1 After 0.3W cm -2Low-intensity ultrasound at 40 kHz for 1 min at 20°C resulted in complete settling of the sludge within 5 min. This ultrasound-treated sludge was then inoculated into a UASB reactor. As the nitrite nitrogen in the effluent gradually decreased to 20 mg / L... -1 When the nitrogen load in the UASB reactor is increased by 25%, the designed nitrogen removal load per unit volume (2.0 kg-N / m³) is reached on the 7th day of operation. -3 d -1 See also Figure 1 a. Meanwhile, the untreated reactor group, which did not undergo low-intensity ultrasonic treatment, only achieved a nitrogen removal load of 1.12 kg-N / m³ per unit volume on day 7. -3 d -1 See Figure 1 b. It takes about 24 days to achieve the designed nitrogen removal load per unit volume.

[0036] Therefore, under the same design load, the start-up time of the floating sludge treated with low intensity according to the present invention is much shorter than that of the control reactor, achieving significant benefits.

[0037] Example 2:

[0038] A method for reusing anaerobic ammonia oxidation sludge based on ultrasound-assisted respiration involves placing anaerobic ammonia oxidation sludge from the three-phase separator of an upflow anaerobic sludge blanket (UASB) reactor into a nutrient solution. The nutrient solution contains 10 mg / L NaH2PO4. -1 CaCl2 5.65mg / L -1 NaHCO3 840mg / L -1 And MgSO4·7H2O 58.6mg L -1 The nutrient solution pH is 8.0, and the sludge concentration after mixing the floating sludge with the nutrient solution is 8 g-VSS L. -1 After 0.3W cm -2 Low-intensity ultrasound at 45 kHz for 1 min at 22°C resulted in complete settling of the sludge within 5 min. This ultrasound-treated sludge was then inoculated into a UASB reactor. As the nitrite nitrogen in the effluent gradually decreased to 20 mg / L... -1 The influent nitrogen load of the UASB reactor was increased by 25% at the following time. After 15 days of operation, the sludge flotation rate in the UASB reactor rebounded to 60% and the volumetric nitrogen removal load remained at 3.2 kg-N / m³. -3 d -1 Therefore, the sludge was removed again and subjected to the aforementioned low-intensity ultrasonic treatment before being reset back into the UASB reactor. After 15 days of operation, the designed nitrogen removal load per unit volume (5.0 kg-N / m³) was achieved. -3 d-1 See also Figure 1 a. Meanwhile, the untreated reactor group, which did not undergo low-intensity ultrasonic treatment, showed a nitrogen removal load of only 2.61 kg-N / m³ per unit volume on day 30. -3 d -1 See Figure 2 b. Based on the increasing trend of nitrogen removal load, it will take approximately 149 days to reach the designed nitrogen removal load per unit volume.

[0039] Therefore, under the same design load, the start-up time of the floating mud after two low-intensity ultrasonic treatments in this embodiment is much shorter than that of the control reactor, and it can reach the operating load required by the high-load reactor, thus achieving more significant benefits.

[0040] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A method for reusing anaerobic ammonia oxidation sludge based on ultrasound-assisted respiration, characterized in that, include: Assisted respiration: Anaerobic ammonia oxidation sludge from the three-phase separator of the upflow anaerobic sludge bed reactor was placed in a nutrient solution and subjected to low-intensity ultrasonic treatment. The ultrasonic intensity of the low-intensity ultrasonic treatment was 0.2–0.4 W / cm². -2 The temperature of the low-intensity ultrasonic treatment is 4–25°C; the essential components and concentration of the nutrient solution include: NaH2PO4 10 mg / L -1 CaCl2 5.65 mg L -1 NaHCO3 840mg / L -1 And MgSO4·7H2O 58.6mg L -1 If the floating sludge can completely settle within 5 minutes after the low-intensity ultrasonic treatment, the sludge reuse step will be carried out; otherwise, the floating sludge will continue to undergo low-intensity ultrasonic treatment in the nutrient solution. Sludge reuse: Settled sludge treated with low-intensity ultrasonication is inoculated into an upflow anaerobic sludge blanket reactor. When the effluent nitrite nitrogen gradually decreases to 20 mg / L... -1 In the following cases, increase the influent nitrogen load of the upflow anaerobic sludge blanket reactor; When the sludge flotation rate in the upflow anaerobic sludge bed reactor reaches 20% or more, or when the nitrogen removal load per unit volume of the upflow anaerobic sludge bed reactor cannot be increased within 5 days, repeat the assisted breathing and sludge reuse steps until the upflow anaerobic sludge bed reactor reaches the required nitrogen removal load per unit volume.

2. The method for anaerobic ammonia oxidation and sludge reuse based on ultrasound-assisted respiration according to claim 1, characterized in that, The pH of the nutrient solution is in the range of 7.5 to 8.

5.

3. The method for anaerobic ammonia oxidation and sludge reuse based on ultrasound-assisted respiration according to claim 1, characterized in that, The salinity of the nutrient solution is less than 2.5 wt%.

4. The method for anaerobic ammonia oxidation and sludge reuse based on ultrasound-assisted respiration according to claim 1, characterized in that, The mass concentrations of ammonia nitrogen and nitrite nitrogen in the nutrient solution are independently 0–300 mg N / L. -1 .

5. The method for anaerobic ammonia oxidation and sludge reuse based on ultrasound-assisted respiration according to claim 4, characterized in that, The mass concentration ratio of ammonia nitrogen to nitrite nitrogen in the nutrient solution is 0.7 to 1.5:

1.

6. The method for anaerobic ammonia oxidation and sludge reuse based on ultrasound-assisted respiration according to claim 1, characterized in that, During the assisted respiration step, the sludge concentration range after mixing the anaerobic ammonia oxidation sludge and nutrient solution is 5–30 g-VSS L. -1 .

7. The method for anaerobic ammonia oxidation and sludge reuse based on ultrasound-assisted respiration according to claim 1, characterized in that, The duration of a single low-intensity ultrasound treatment is 1 to 10 minutes.

8. The method for anaerobic ammonia oxidation and sludge reuse based on ultrasound-assisted respiration according to claim 1, characterized in that, The frequency of the low-intensity ultrasonic treatment is 20–45 kHz.

9. The method for anaerobic ammonia oxidation and sludge reuse based on ultrasound-assisted respiration according to claim 1, characterized in that, The step size for increasing the influent nitrogen load of the upflow anaerobic sludge blanket reactor is 10% to 25%.

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