Anaerobic ammonia oxidation float sludge recycling method based on ultrasonic assisted respiration

Abstract

The invention discloses an anaerobic ammonia oxidation float sludge recycling method based on ultrasonic assisted respiration. The anaerobic ammonia oxidation float sludge recycling method comprises the following steps: assisted respiration: taking anaerobic ammonia oxidation float sludge in a three-phase separator of a UASB (Upflow Anaerobic Sludge Blanket) reactor, and putting the anaerobic ammonia oxidation float sludge into a nutrient solution for low-intensity ultrasonic treatment; after the low-intensity ultrasonic treatment is finished, if the float sludge can be completely settled within 5 minutes, a sludge recycling step is carried out, otherwise, the float sludge continues to be subjected to low-intensity ultrasonic treatment in the nutrient solution; sludge recycling: inoculating the settled sludge subjected to low-intensity ultrasonic treatment into a reactor, and when nitrite nitrogen in effluent is gradually reduced to 20 mg L <-1 > or below, increasing the nitrogen load of the inlet water of the reactor; and when the floating rate of the sludge in the reactor reaches 20% or above or the nitrogen removal load per unit volume of the reactor cannot be increased within 5 days, repeating the steps of assisted respiration and sludge reuse until the reactor reaches the required nitrogen removal load per unit volume.

Description

Technical Field

[0001] The present invention relates to the technical field of anaerobic ammonium oxidation sludge treatment, and particularly relates to a method for recycling anaerobic ammonium oxidation floating sludge based on ultrasonic-assisted respiration. Background Art

[0002] Anaerobic ammonium oxidation is a new biological nitrogen removal technology, which has received wide 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 inoculated sludge caused by the long proliferation time of anaerobic ammonium oxidation 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 by the anaerobic ammonium oxidation process, anaerobic ammonium oxidation bacteria will produce a large amount of N2 that cannot be released, trapped inside the granular sludge, resulting in a decrease in the density of the granular sludge and thus floating. The continuously generated floating sludge will not only cause blockage of the three-phase separator, but also cause the floating sludge to rot due to the lack of substrate in the long run, resulting in a decline in the nitrogen removal performance of the reactor, deterioration of the effluent, and even performance collapse. Therefore, these floating sludges are usually collected as excess sludge and discharged from the reactor. Developing a technology for recycling anaerobic ammonium oxidation floating sludge can not only effectively solve the problem of floating sludge disposal, but also shorten the start-up time of high-load anaerobic ammonium oxidation reactors, achieving the dual effects of treating waste with waste and reducing costs and increasing efficiency.

[0004] The current conventional method is to mechanically crush the floating sludge and then return it to the reactor to increase the microbial biomass in the reactor, thereby greatly increasing the nitrogen removal load of the anaerobic ammonium oxidation reactor. However, the regranulation process of the crushed sludge is very long and will seriously affect the effluent quality of the reactor.

[0005] The patent specification with the publication number CN104085983A discloses a method for activating anaerobic ammonium oxidation sludge under low-temperature conditions by ultrasonic waves. The low-temperature conditions refer to the temperature of the anaerobic ammonium oxidation reactor during operation being below 30°C. The method is as follows: add the anaerobic ammonium oxidation sludge to be activated into a reaction vessel, and then perform water bath ultrasonic treatment. The water bath temperature is 31-35°C, and the ultrasonic conditions are: frequency 20 kHz, intensity 0.7-0.9 W cm -2 , and the time is 1.7-2.0 min; after ultrasonic treatment, the activated anaerobic ammonium oxidation sludge is obtained.

[0006] The patent specification with the publication number CN104386814A discloses a method for enhancing the start-up efficiency of the anaerobic ammonium oxidation process with ordinary activated sludge as the inoculum by ultrasonic wave. The main body of the ultrasonic generator is placed outside the anaerobic ammonium oxidation start-up reactor, and the ultrasonic vibrator is immersed below the liquid level in the reactor. By irradiating the cultured sludge in the start-up process of the anaerobic ammonium oxidation process with low-intensity ultrasonic waves, the cell membrane permeability, electron transfer rate, and functional enzyme activity of anaerobic ammonium-oxidizing bacteria are improved, thereby enhancing the activity of anaerobic ammonium-oxidizing bacteria and their competitive advantage in the microbial community of the cultured sludge, and thus realizing the rapid start-up of the process.

[0007] Although the above two patent technologies both involve ultrasonic technology, their application objects are not the anaerobic ammonium oxidation floating sludge targeted by the present invention. Further, due to the different objects, the above two patent technologies do not involve the solution to the problem of anaerobic ammonium oxidation sludge floating. Summary of the Invention

[0008] In view of the above technical problems and the deficiencies existing in the art, the present invention provides a method for recycling anaerobic ammonium oxidation floating sludge based on ultrasonic-assisted respiration, which can rapidly reduce the sludge floating rate and retain the macroscopic structure and physical and chemical properties of anaerobic ammonium oxidation granular sludge to the greatest extent, and can rapidly increase the nitrogen removal load per unit volume of the reactor without affecting the effluent water quality, and has the advantages of small loss, quick effect, low cost, simple operation, wide applicability, etc.

[0009] The specific technical solution is as follows:

[0010] A method for recycling anaerobic ammonium oxidation floating sludge based on ultrasonic-assisted respiration, comprising:

[0011] Auxiliary respiration: Taking the anaerobic ammonium oxidation floating sludge in the three-phase separator of an upflow anaerobic sludge bed (UASB) reactor and performing low-intensity ultrasonic treatment in a nutrient solution, the ultrasonic intensity of the low-intensity ultrasonic treatment is 0.2 - 0.4 W / cm -2 (for example, 0.3 W / cm -2 etc.); After the low-intensity ultrasonic treatment is completed, if the floating sludge can completely settle within 5 minutes, the sludge recycling step is carried out, otherwise the floating sludge continues to be subjected to low-intensity ultrasonic treatment in the nutrient solution;

[0012] Sludge recycling: Inoculating the settled sludge after low-intensity ultrasonic treatment into an upflow anaerobic sludge bed reactor, and when the effluent nitrite nitrogen gradually decreases to 20 mg / L -1 or less, increasing the influent nitrogen load of the upflow anaerobic sludge bed reactor;

[0013] When the sludge floating rate in the upflow anaerobic sludge bed reactor reaches more than 20% or the nitrogen removal load per unit volume of the upflow anaerobic sludge bed reactor cannot increase within 5 days (d), repeat the steps of auxiliary respiration and sludge reuse until the upflow anaerobic sludge bed reactor reaches the required nitrogen removal load per unit volume.

[0014] The present invention takes anaerobic ammonium oxidation floating sludge (preferably anaerobic ammonium oxidation granular sludge floating sludge) as the research object, and solves the problem of anaerobic ammonium oxidation sludge floating by low-intensity ultrasonic treatment, so that the floating sludge settles to achieve the purpose of reuse.

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

[0016] In some embodiments, for the method of anaerobic ammonium oxidation floating sludge reuse based on ultrasonic-assisted respiration, the essential components and concentrations of the nutrient solution include: orthophosphate 0.5 - 50 mg P / L -1 、magnesium (II) ion 5 - 500 mg / L -1 、bicarbonate 50 - 2000 mg / L -1 and calcium (II) ion 5 - 500 mg / L -1 , which is beneficial to activating the anaerobic ammonium oxidation bacteria dormant due to starvation inside the anaerobic ammonium oxidation floating sludge.

[0017] In some embodiments, for the method of anaerobic ammonium oxidation floating sludge reuse based on ultrasonic-assisted respiration, among the essential components of the nutrient solution, the orthophosphate can be NaH2PO4, etc., the source of the magnesium (II) ion can be MgSO4·7H2O, etc., the source of the bicarbonate can be NaHCO3, etc., and the source of the calcium (II) ion can be CaCl2, etc.

[0018] In some embodiments, for the method of anaerobic ammonium oxidation floating sludge reuse based on ultrasonic-assisted respiration, the essential components and concentrations of the nutrient solution include: NaH2PO4 10 mg / L -1 、CaCl2 5.65 mg / L -1 、NaHCO3 840 mg / L -1 and MgSO4·7H2O 58.6 mg / L -1 .

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

[0020] In some embodiments, in the anaerobic ammonium oxidation floc reuse method based on ultrasonic-assisted respiration, the salinity of the nutrient solution is lower than 2.5 wt%, which is beneficial to activating the anaerobic ammonium-oxidizing bacteria that are dormant due to starvation inside the anaerobic ammonium oxidation flocs.

[0021] In some embodiments, in the anaerobic ammonium oxidation floc reuse method based on ultrasonic-assisted respiration, the mass concentrations of ammonia nitrogen and nitrite nitrogen in the nutrient solution are independently 0 - 300 mgN / L -1 . Further, the mass concentration ratio of ammonia nitrogen to nitrite nitrogen in the nutrient solution is 0.7 - 1.5:1. This is beneficial to activating the anaerobic ammonium-oxidizing bacteria that are dormant due to starvation inside the anaerobic ammonium oxidation flocs.

[0022] In some embodiments, in the anaerobic ammonium oxidation floc reuse method based on ultrasonic-assisted respiration, during the auxiliary respiration step, the sludge concentration range after mixing the anaerobic ammonium oxidation flocs and the nutrient solution is 5 - 30 g-VSS / L -1 , such as 8 g-VSS / L -1 、10 g-VSS / L -1 etc.

[0023] In some embodiments, in the anaerobic ammonium oxidation floc reuse method based on ultrasonic-assisted respiration, the time for single low-intensity ultrasonic treatment is 1 - 10 min.

[0024] In some embodiments, in the anaerobic ammonium oxidation floc reuse method based on ultrasonic-assisted respiration, the frequency of the low-intensity ultrasonic treatment is 20 - 45 kHz, such as 40 kHz, etc.

[0025] In some embodiments, in the anaerobic ammonium oxidation floc reuse method based on ultrasonic-assisted respiration, the temperature of the low-intensity ultrasonic treatment is 4 - 25 °C, such as 20 °C, 22 °C, etc.

[0026] In some embodiments, in the anaerobic ammonium oxidation floc reuse method based on ultrasonic-assisted respiration, the step size for increasing the influent nitrogen load of the upflow anaerobic sludge bed reactor is 10% - 25%.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] The anaerobic ammonium oxidation floating sludge recycling method based on ultrasonic-assisted respiration first uses low-intensity ultrasound to dredge the blocked pores of the anaerobic ammonium oxidation floating sludge, release the nitrogen retained in the internal cavity and inhale the nutrient solution, so that the floating sludge settles back into the reactor main body. When the granular sludge floats up again due to pore blockage and affects the nitrogen removal load of the reactor, repeat the low-intensity ultrasonic treatment, exhale and inhale the liquid repeatedly for many times until the anaerobic ammonium oxidation bacteria dormant due to starvation inside the granular sludge are activated, and continuously increase the reactor volume nitrogen load rate according to the reactor effluent situation to reach the operating load required by the high-load reactor. Description of the Drawings

[0029] Figure 1 Comparison chart of the nitrogen removal load per unit volume (NRR) of the anaerobic ammonium oxidation reactor (a) started with floating sludge treated by low-intensity ultrasound and the anaerobic ammonium oxidation reactor (b) started with untreated floating sludge in Example 1.

[0030] Figure 2 Comparison chart of the nitrogen removal load per unit volume of the anaerobic ammonium oxidation reactor (a) started with floating sludge treated by low-intensity ultrasound and the anaerobic ammonium oxidation reactor (b) started with untreated floating sludge in Example 2. Detailed Embodiments

[0031] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0032] For the operation methods without specific conditions noted in the following embodiments, they are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer.

[0033] The anaerobic ammonium oxidation sludge in the following embodiments is all granular sludge, and the sludge floating rate is calculated by the ratio of the floating sludge volume to the volume of the inoculated settled sludge.

[0034] Example 1:

[0035] For an anaerobic ammonium oxidation floating sludge recycling method based on ultrasonic-assisted respiration, take the anaerobic ammonium oxidation floating sludge in the three-phase separator of an upflow anaerobic sludge bed (UASB) reactor and place it in a nutrient solution. The nutrient composition in the nutrient solution is NaH2PO4 10 mg / L -1 、CaCl2 5.65 mg / L -1 、NaHCO3 840 mg / L -1 and MgSO4·7H2O 58.6 mg / L -1 , the pH of the nutrient solution is 8.0, and the sludge concentration after mixing the floating sludge and the nutrient solution is 10 g-VSS / L -1 , and it is treated with 0.3 W / cm -2, The low-intensity ultrasound at 40 kHz is applied for 1 min at 20 °C. The floating sludge after the low-intensity ultrasound treatment can be completely settled within 5 min. The settled sludge after this low-intensity ultrasound treatment is inoculated into the UASB reactor. When the effluent nitrite nitrogen gradually decreases to 20 mg / L -1 or less, the influent nitrogen load of the UASB reactor is increased by 25%. On the 7th day of operation, the designed nitrogen removal load per unit volume (2.0 kg-N / m -3 d -1 ) is reached, see Figure 1 a. For the untreated group reactor where the floating sludge is not treated with low-intensity ultrasound, the nitrogen removal load per unit volume on the 7th day is only 1.12 kg-N / m -3 d -1 , see Figure 1 b. It takes about 24 days to reach 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 ultrasound according to the present invention is much less than that of the control reactor, achieving significant benefits.

[0037] Example 2:

[0038] An anaerobic ammonium oxidation floating sludge recycling method based on ultrasound-assisted respiration. The anaerobic ammonium oxidation floating sludge in the three-phase separator of an upflow anaerobic sludge bed (UASB) reactor is placed in a nutrient solution. The nutrient composition in the nutrient solution is NaH2PO4 10 mg / L -1 , CaCl2 5.65 mg / L -1 , NaHCO3 840 mg / L -1 and MgSO4·7H2O 58.6 mg / L -1 . The pH of the nutrient solution is 8.0, and the sludge concentration after mixing the floating sludge and the nutrient solution is 8 g-VSS / L -1 . It is treated with low-intensity ultrasound at 0.3 W / cm -2 and 45 kHz for 1 min at 22 °C. The floating sludge after the low-intensity ultrasound treatment can be completely settled within 5 min. The settled sludge after this low-intensity ultrasound treatment is inoculated into the UASB reactor. When the effluent nitrite nitrogen gradually decreases to 20 mg / L -1 or less, the influent nitrogen load of the UASB reactor is increased by 25%. After 15 days of operation, the sludge floating rate in the UASB reactor rebounds to 60% and the volumetric nitrogen removal load stays at about 3.2 kg-N / m -3 d -1 . Therefore, the sludge is taken out again for the aforementioned low-intensity ultrasound treatment and then reset back into the UASB reactor. After continuing to operate for 15 days, the designed nitrogen removal load per unit volume (5.0 kg-N / m -3 d-1 ) See Figure 1 a. The untreated reactor with floating sludge without low-intensity ultrasonic treatment had a nitrogen removal load per unit volume of only 2.61 kg-N m on the 30th day -3 d -1 , see Figure 2 b. According to the increasing trend of nitrogen removal load, it would take about 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 sludge after two low-intensity ultrasonic treatments in this embodiment is much less than that of the control reactor and can reach the operating load required by the high-load reactor, achieving more significant benefits.

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

Claims

1. An anaerobic ammonium oxidation floating sludge recycling method based on ultrasonic-assisted respiration, characterized in that, Including: Auxiliary respiration: Anaerobic ammonium oxidation floating sludge in the three-phase separator of an upflow anaerobic sludge bed reactor is placed in a nutrient solution for low-intensity ultrasonic treatment. The ultrasonic intensity of the low-intensity ultrasonic treatment is 0.2 - 0.4 W / cm -2 ; After the low-intensity ultrasonic treatment, if the floating sludge can completely settle within 5 minutes, the sludge recycling step is carried out; otherwise, the floating sludge continues to be subjected to low-intensity ultrasonic treatment in the nutrient solution; Sludge reuse: The sedimentation sludge after low-intensity ultrasonic treatment was inoculated into an upflow anaerobic sludge bed reactor. When the nitrite nitrogen in the effluent gradually decreased to 20 mg / L -1 or less, the influent nitrogen load of the upflow anaerobic sludge bed reactor was increased; When the sludge floating rate in the upflow anaerobic sludge bed reactor reaches more than 20% or the nitrogen removal load per unit volume of the upflow anaerobic sludge bed reactor cannot increase within 5 days, repeat the auxiliary respiration and sludge recycling steps until the upflow anaerobic sludge bed reactor reaches the required nitrogen removal load per unit volume.

2. The anaerobic ammonium oxidation floating sludge recycling method based on ultrasonic-assisted respiration according to claim 1, wherein The essential components and concentrations of the nutrient solution include: orthophosphate 0.5 - 50 mg P / L -1 , magnesium (II) ion 5 - 500 mg / L -1 , bicarbonate 50 - 2000 mg / L -1 and calcium (II) ion 5 - 500 mg / L -1 .

3. The method for recycling anaerobic ammonium oxidation floating sludge based on ultrasonic-assisted respiration according to claim 1, wherein, The pH of the nutrient solution is in the range of 7.5 - 8.

5.

4. The anaerobic ammonium oxidation floating sludge reuse method based on ultrasonic-assisted respiration according to claim 1, characterized in that, The salinity of the nutrient solution is lower than 2.5 wt%.

5. The anaerobic ammonium oxidation floating sludge reuse method based on ultrasonic-assisted respiration according to claim 1, wherein The mass concentrations of ammonia nitrogen and nitrite nitrogen in the nutrient solution are independently 0 to 300 mgN / L respectively -1 .

6. The anaerobic ammonium oxidation floating sludge recycling method based on ultrasonic-assisted respiration according to claim 5, characterized in that The mass concentration ratio of ammonia nitrogen to nitrite nitrogen in the nutrient solution is 0.7 - 1.5:

1.

7. The method for recycling anaerobic ammonium oxidation floating sludge based on ultrasonic-assisted respiration according to claim 1, wherein In the auxiliary respiration step, the sludge concentration range after the mixing of anammox floating sludge and nutrient solution is 5 - 30 g-VSS / L -1 .

8. The anaerobic ammonium oxidation floating sludge recycling method based on ultrasonic-assisted respiration according to claim 1, characterized in that, The time of single low-intensity ultrasonic treatment is 1 - 10 min.

9. The anaerobic ammonium oxidation floating sludge recycling method based on ultrasonic-assisted respiration according to claim 1, wherein The frequency of the low-intensity ultrasonic treatment is 20 - 45 kHz; The temperature of the low-intensity ultrasonic treatment is 4 - 25 °C.

10. The anaerobic ammonium oxidation floating sludge reuse method based on ultrasonic-assisted respiration according to claim 1, characterized in that, The step of increasing the influent nitrogen load of the upflow anaerobic sludge bed reactor is 10% - 25%.

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