Operation method of crude glycerol type mainstream short-cut denitrification process

Abstract

The invention discloses an operation method of a crude glycerine type mainstream short-cut denitrification process. The operation method comprises the following steps: quickly enriching crude glycerine nutritional short-cut denitrifying bacteria, stably retaining the crude glycerine nutritional short-cut denitrifying bacteria, optimizing the performance of the crude glycerine type short-cut denitrification process and the like. According to the method disclosed by the invention, more than 90% of nitrate can be removed and more than 50% of nitrite accumulation rate can be kept aiming at the effluent of the nitrification unit under the mainstream condition of urban sewage, and nitrite is stably provided for a subsequent anaerobic ammonia oxidation unit. According to the invention, the cheaper crude glycerol is used as a carbon source, the nitrite is stably provided by optimizing the operation method, and an economical and feasible operation method is provided for a short-range biological denitrification process. The method has the advantages of flexible operation, high efficiency, stability, wide application range and the like.

Description

Technical Field

[0001] The invention relates to the technical field of short-range denitrification, and in particular to an operating method of a crude glycerol type mainstream short-range denitrification process. Background Art

[0002] Anaerobic ammonium oxidation is a new and economical and efficient technology in the field of biological nitrogen removal. It has attracted widespread attention due to its outstanding advantages such as saving aeration energy consumption and reducing the amount of external carbon source added.

[0003] Adequate and stable nitrite supply is a prerequisite and key to anaerobic ammonium oxidation denitrification. At present, there are many obstacles to the stable operation of short-cut nitrification under mainstream conditions of urban sewage. Controlling part of the ammonia nitrogen in urban sewage at the nitrite stage through nitrification-short-cut denitrification can provide a new idea for the acquisition of substrates for anaerobic ammonium oxidation, greatly shortening the carbon source demand and aeration energy consumption required for sewage biological denitrification units.

[0004] Efficient short-term denitrification is affected by many factors, among which the type of carbon source has been proven to play an important role in achieving and maintaining short-term denitrification. Currently, short-term denitrification processes generally use acetic acid or acetic acid-dominated fermentation broth as a carbon source, such as patented technologies such as CN118164613A and CN107265631A.

[0005] The patent specification with publication number CN113603210A discloses a method for taming high-density short-range denitrification granular sludge. The patent technology uses glycerol as the only carbon source and realizes sludge taming in a sequencing batch activated sludge reactor through reactions in two steps: the enrichment start-up phase and the metabolic control phase. The carbon-nitrogen ratio in the metabolic control phase is controlled at about 4.5. In addition, the patent technology does not disclose the specific operating temperature conditions. Therefore, for mainstream process conditions with lower temperatures and complex multi-type mixed carbon sources, the patent technology solution is difficult to apply.

[0006] Compared with methanol, ethanol and acetate from fossil fuel feedstocks, crude glycerol, as a byproduct of biodiesel and oleochemical processes, has been proposed as a cheaper and safer alternative to supplement the carbon source in biological denitrification. However, how to use crude glycerol as a carbon source to quickly enrich short-range denitrifying bacteria and stably provide nitrite is still a major difficulty in economical and efficient biological denitrification technology. Summary of the invention

[0007] In view of the above technical problems, the present invention establishes an operation method of a crude glycerol type mainstream short-range denitrification process. The present invention utilizes cheaper crude glycerol as a carbon source, achieves a stable supply of nitrite by optimizing the operation method, and provides an economically feasible operation method for the biological denitrification process. The method has the advantages of flexible operation, high efficiency and stability, and a wide range of applications.

[0008] A method for operating a crude glycerol type mainstream short-range denitrification process comprises the following steps:

[0009] (1) Rapid enrichment of crude glycerol nutrient-type short-range denitrifying bacteria: The activated sludge was inoculated into a sequencing batch reactor, and the operation mode of delayed water inlet-anaerobic long stirring was adopted. Six to eight typical cycles were operated every day. Any typical cycle included five processes, namely water inlet, anoxic stirring, sedimentation, drainage and standing. The duration of anoxic stirring was more than 75% of the total duration of the typical cycle. In any typical cycle, crude glycerol was slowly added at the same time as water inlet began. The time for adding crude glycerol was longer than the time for water inlet. The COD and NO3 content of glycerol in the crude glycerol in the influent were controlled. - The ratio of -N is 3.0 to 3.5:1, the inlet pH is controlled above 8.0, and the enrichment is successful when the peak value of the nitrite nitrogen accumulation rate in a typical cycle reaches more than 80%;

[0010] (2) Stable retention of crude glycerol nutrient-type short-range denitrifying bacteria: According to the influent nitrate nitrogen concentration, the typical number of cycles and the anoxic stirring time of the sequencing batch reactor in a single day are adjusted so that the volumetric nitrogen load is within the range of 0.15 to 0.30 gN / L / d, and at the same time, the anoxic stirring time is ensured to be more than 75% of the total time of the typical cycle, and the sludge age of the sequencing batch reactor is adjusted so that the sludge concentration in the sequencing batch reactor is within the range of 0.8 to 1.5 gSS / L;

[0011] (3) Optimizing the performance of crude glycerol short-range denitrification process: According to the content of non-glycerol carbon source (such as methanol, etc.) in crude glycerol, the total COD and NO3 in the crude glycerol in the influent were calculated. - The amount of crude glycerol added is adjusted within the range of 2.5 to 4.0:1, and the proportion of anoxic stirring time in a typical cycle is adjusted until the accumulation rate of nitrite nitrogen in the effluent of the sequencing batch reactor reaches more than 50% and the nitrate removal rate is stabilized at more than 90%.

[0012] The method of the present invention uses activated sludge as inoculum and crude glycerol as carbon source. Firstly, the crude glycerol nutrient type short-range denitrifying bacteria are rapidly enriched from the activated sludge by the operation mode of delayed water inlet-anoxic long stirring, combined with the crude glycerol addition ratio and the inlet pH control. The pH value will be reduced during the denitrification process of the crude glycerol inlet. Too low pH value may prevent the short-range denitrification. The present invention requires that the inlet pH value be controlled at above 8.0 to ensure the rapid enrichment of the crude glycerol nutrient type short-range denitrifying bacteria and the effective removal of the crude glycerol. Then, the crude glycerol nutrient type short-range denitrifying bacteria are stably retained based on the reactor volume nitrogen load and the sludge age. Finally, the total COD and NO3 of the crude glycerol are adjusted according to the content of non-glycerol carbon sources such as methanol in the crude glycerol. -The ratio of -N and the anoxic stirring time simultaneously improved the nitrate removal efficiency (NARE) and nitrite accumulation rate (NIAE).

[0013] The substances that can be used as carbon sources in crude glycerol are mainly glycerol, and secondarily include methanol, etc. In some embodiments, in the operation method of the crude glycerol type mainstream short-range denitrification process, the mass percentage concentration of methanol in the crude glycerol is less than 50%.

[0014] In some embodiments, in the operation method of the crude glycerol type mainstream short-cut denitrification process, in step (1), the inoculation amount of activated sludge in the sequencing batch reactor can be 1.5-3.0 gSS / L, for example, 2.0 gSS / L.

[0015] In some embodiments, the operation method of the crude glycerol type mainstream short-range denitrification process is to slowly add crude glycerol so that the concentration of total organic carbon (TOC) in the sequencing batch reactor is maintained within a range of no more than 20 mg / L until the required COD / NO3 is met. - -N ratio.

[0016] The present invention has found that slowly adding crude glycerol and taking longer to add crude glycerol than taking in water is conducive to the rapid enrichment of crude glycerol nutrient-type short-range denitrifying bacteria and the effective removal of crude glycerol. In some embodiments, the operation method of the crude glycerol mainstream short-range denitrification process is that the time for adding crude glycerol is not less than 30 minutes and the time for taking in water is not more than 10 minutes.

[0017] Taking a typical cycle with a total duration of 3 hours as an example, the water inlet time can be 5 minutes, the anoxic stirring time can be 150 minutes, the sedimentation time can be 10 minutes, the drainage time can be 5 minutes, and the standing time can be 10 minutes. As another example, when the total duration of a typical cycle is 4 hours, the anoxic stirring time can be set to 210 minutes, and the duration of the remaining stages can be consistent with the corresponding stages in the above-mentioned typical cycle with a total duration of 3 hours. Here is another example of a typical cycle with a total duration of 4 hours, the water inlet time can be 5 minutes, the anoxic stirring time can be 180 minutes, the sedimentation time can be 40 minutes, the drainage time can be 5 minutes, and the standing time can be 10 minutes.

[0018] In the present invention, the pH of the inlet water of the sequencing batch reactor can be adjusted and controlled by adding sodium bicarbonate and / or sodium hydroxide. In some embodiments, in the operation method of the crude glycerol type mainstream short-range denitrification process, the pH of the inlet water of the sequencing batch reactor is controlled at 8.0-8.5.

[0019] In the operation method of the crude glycerol type mainstream short-range denitrification process, anoxic means that the dissolved oxygen concentration is below 0.5 mg / L. In the present invention, the anoxic stirring process can be placed in the required anoxic condition by controlling the stirring speed.

[0020] The present invention as a whole is based on the operation mode of delayed water inlet-anaerobic long stirring. In step (2), the typical number of cycles of the sequencing batch reactor in a single day is adjusted based on the range of volumetric nitrogen load. In this process, the duration of anaerobic stirring still needs to be maintained at more than 75% of the total duration of its typical cycle.

[0021] In some embodiments, in the method for operating the crude glycerol-based mainstream short-cut denitrification process, in step (2), the typical number of cycles of the sequencing batch reactor in a single day is 6 to 12 times.

[0022] In some embodiments, in the operation method of the crude glycerol type mainstream short-cut denitrification process, in step (2), the sludge age of the sequencing batch reactor is 5 to 15 days, such as 10 days.

[0023] In some embodiments, in the operation method of the crude glycerol type mainstream short-range denitrification process, in step (3), the total COD of crude glycerol = (mass of glycerol in the added crude glycerol / glycerol density × 1533 + mass of methanol in the added crude glycerol / methanol density × 1188) × 10, wherein: the total COD of crude glycerol is in mg / L, the mass of glycerol in the added crude glycerol is in g, the density of glycerol is in g / L, the mass of methanol in the added crude glycerol is in g, and the density of methanol is in g / L.

[0024] In some embodiments, in the method for operating the crude glycerol-based mainstream short-range denitrification process, in step (3), the proportion of anoxic stirring time in a typical cycle is 75% to 85%.

[0025] In some embodiments, the method for operating the crude glycerol type mainstream short-range denitrification process, in step (3), adjusts the proportion of anoxic stirring time in a typical cycle without changing the typical number of cycles of the sequencing batch reactor in a single day, that is, continues the typical number of cycles of the sequencing batch reactor in a single day in step (2).

[0026] In some embodiments, in the operation method of the crude glycerol type mainstream short-range denitrification process, in step (3), the proportion of the anoxic stirring time in a typical cycle can be adjusted by adjusting the anoxic stirring time and the sedimentation time.

[0027] In some embodiments, the operation method of the crude glycerol type mainstream short-range denitrification process, the operating temperature of the sequencing batch reactor is in the range of 15 to 25°C, and the influent NO3 -The -N concentration ranges from 20 to 70 mg / L (e.g., 55 to 65 mg / L, etc.), which is consistent with the operating characteristics and conditions of the mainstream short-range denitrification process.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The method of the present invention is aimed at the effluent of the nitrification unit under the mainstream condition of urban sewage, and can remove more than 90% of nitrate and maintain more than 50% of nitrite accumulation rate, so as to stably provide nitrite for the subsequent anaerobic ammonium oxidation unit.

[0030] The present invention utilizes cheaper crude glycerol as a carbon source, achieves stable supply of nitrite by optimizing the operation method, and provides an economically feasible operation method for a short-range biological denitrification process. The method has the advantages of flexible operation, high efficiency and stability, and a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The graphs show the results of the nitrogen concentration in the inlet and outlet water of the denitrification reactor (a), the nitrate removal rate, and the nitrite accumulation rate (b) of Example 1.

[0032] Figure 2 The graphs are the results of the nitrogen concentration in the inlet and outlet water of the denitrification reactor in Example 2 (a), the nitrate removal rate, and the nitrite accumulation rate (b).

[0033] Figure 3 The graphs show the nitrogen concentration in the inlet and outlet water of the denitrification reactor (a), the nitrate removal rate, and the nitrite accumulation rate (b) of Example 3. DETAILED DESCRIPTION

[0034] 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 are not used to limit the scope of the present invention.

[0035] The operating methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturers.

[0036] In the following embodiments:

[0037] Anoxic means that the dissolved oxygen concentration is below 0.5 mg / L. Specifically, the anoxic stirring process can be kept under the required anoxic conditions by controlling the stirring speed.

[0038] Total COD of crude glycerol = (mass of glycerol in crude glycerol added / glycerol density × 1533 + mass of methanol in crude glycerol added / methanol density × 1188) × 10, wherein: the unit of total COD of crude glycerol is mg / L, the unit of mass of glycerol in crude glycerol added is g, the unit of glycerol density is g / L, the unit of mass of methanol in crude glycerol added is g, and the unit of methanol density is g / L.

[0039] Embodiment 1:

[0040] The invention discloses an operation method of a crude glycerol type mainstream short-range denitrification process. The method comprises the following steps: a sequencing batch reactor is used at 25°C, crude glycerol with a glycerol content of 99% is used as a carbon source, the influent nitrate nitrogen concentration is 55-65 mgN / L, the ratio of glycerol COD and nitrate nitrogen in the influent crude glycerol is controlled to be 3.0:1, the influent pH is adjusted to 8.0 by NaHCO3, 8 typical cycles are operated every day, each typical cycle includes five processes of influent, anoxic stirring, sedimentation, drainage and standing in sequence, wherein the influent (nitrogen source) is quickly pumped in for 5 minutes, the carbon source crude glycerol is added for 30 minutes at the beginning of influent, the anoxic stirring time is 150 minutes, the sedimentation time is 10 minutes, the drainage time is 5 minutes, the standing time is 10 minutes, the sequencing batch reactor is inoculated with 2.0 gSS / L of activated sludge, and the initial sludge age is 20 days (d). After 10 days of operation, the peak value of the nitrite nitrogen accumulation rate in a typical cycle reaches 80%, and the sludge concentration reaches 3.0 gSS / L. Subsequently, the typical daily cycle number of the reactor was adjusted to 6 cycles, and the anoxic stirring time in each typical cycle was changed to 210 minutes, and the time for the other stages remained unchanged. The sludge age was 10 days, and the volumetric nitrogen load was 0.18gN / L / d, so that the sludge concentration of the reactor was 1.1gSS / L. The ratio of total COD and nitrate nitrogen in the influent crude glycerol was adjusted to 3.5:1, the anoxic long stirring time was 180 minutes, the typical daily cycle number of the reactor was still 6 cycles, the sedimentation time was changed to 40 minutes, and the time for the other stages remained unchanged. After a period of operation, stable nitrite accumulation was obtained, achieving efficient short-range denitrification performance. Figure 1 As shown, the nitrate removal rate reached 94% ± 3%, and the nitrite accumulation rate also reached 53% ± 5%.

[0041] Embodiment 2:

[0042] The invention discloses an operation method of a crude glycerol type mainstream short-range denitrification process. The method comprises the following steps: adopting a sequencing batch reactor at 25°C, taking crude glycerol with a glycerol content of 60% as a carbon source, and controlling an influent nitrate nitrogen concentration of 55-65 mgN / L. The ratio of glycerol COD and nitrate nitrogen in the influent crude glycerol is controlled to be 3.0:1. The influent pH is adjusted to 8.0 by using NaHCO3, and the inoculated activated sludge concentration is 2.0 gSS / L. Eight typical cycles were run every day, and the typical cycle time was 3 hours. Each typical cycle included five processes, namely, water inlet, anoxic stirring, sedimentation, drainage and standing. The water inlet (nitrogen source) was pumped in quickly for 5 minutes, and the carbon source crude glycerol was added for 30 minutes at the beginning of water inlet. The anoxic stirring time was 150 minutes, the sedimentation time was 10 minutes, the drainage time was 5 minutes, and the standing time was 10 minutes. After 10 days of operation, the sludge concentration reached 3.0 gSS / L, and the peak value of the typical cycle nitrite nitrogen accumulation rate reached 80%, and the crude glycerol nutrient short-range denitrifying bacteria were successfully enriched. Subsequently, the sludge age was gradually adjusted to 10 days, the number of daily cycles was adjusted to 6 cycles, the anoxic stirring time in each typical cycle was changed to 210 minutes, and the time for the other stages remained unchanged, so that the sludge concentration in the reactor was 0.9 gSS / L, the volumetric nitrogen load was 0.19 gN / L / d, and the crude glycerol nutrient short-range denitrifying bacteria were stably retained. Finally, the crude glycerol dosage was adjusted so that the ratio of crude glycerol COD concentration to nitrate nitrogen concentration was 3.0:1, the anoxic long stirring time was shortened to 180 min, the typical number of cycles per day in the reactor was still 6 cycles, the precipitation time was changed to 40 min, and the time for the other stages remained unchanged. After a period of operation, stable nitrite accumulation was obtained, achieving efficient short-range denitrification performance. Figure 2 As shown, the nitrate removal efficiency (NARE) reached 96%±4%, and the nitrite accumulation efficiency (NIAE) also reached 55%±4%.

[0043] Embodiment 3:

[0044] The invention discloses an operation method of a crude glycerol type mainstream short-range denitrification process. Under the condition of 25°C, a sequencing batch reactor is used, crude glycerol with a glycerol content of 80% is used as a carbon source, the influent nitrate nitrogen concentration is 55-65 mgN / L, the ratio of glycerol COD and nitrate nitrogen in the influent crude glycerol is controlled to be 3.0:1, the influent pH is adjusted to 8.0 by NaHCO3, and 3.0 gSS / L of activated sludge is inoculated. The number of cycles per day is 8 cycles, and a typical cycle time is 3 hours. Each typical cycle includes five processes of water inlet, anoxic stirring, sedimentation, drainage and standing in sequence, wherein the water inlet (nitrogen source) is quickly pumped in for 5 minutes, the carbon source crude glycerol is added for 30 minutes at the beginning of water inlet, the anoxic stirring time is 150 minutes, the sedimentation time is 10 minutes, the drainage time is 5 minutes, the standing time is 10 minutes, and the initial sludge age is 20 days. After 25 days of operation, the sludge concentration reaches 3.0 gSS / L, and the peak value of the typical cycle nitrite nitrogen accumulation rate reaches 80%. Then, by gradually adjusting the sludge age to 10 days, the number of cycles per day was 6 cycles, the anoxic stirring time in each typical cycle was changed to 210 minutes, and the time for the other stages remained unchanged, so that the sludge concentration in the reactor was 1.1gSS / L, the volumetric nitrogen load was 0.19gN / L / d, and the nutrient short-term denitrifying bacteria of crude glycerol were stably retained. Finally, the crude glycerol dosage was adjusted until the COD concentration and nitrate nitrogen concentration of crude glycerol were 3.0:1, the anoxic long stirring time was shortened to 150 minutes, the typical number of cycles per day in the reactor was still 6 cycles, the sedimentation time was changed to 40 minutes, and the time for the other stages remained unchanged. After a period of operation, stable nitrite accumulation was obtained, achieving efficient short-term denitrification performance. Figure 3 As shown, the nitrate removal rate reached 91%±6%, and the nitrite accumulation rate also reached 50%±3%.

[0045] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A method for operating a crude glycerol type mainstream short-range denitrification process, characterized in that: Includes steps: (1) Rapid enrichment of crude glycerol nutrient-type short-range denitrifying bacteria: The activated sludge was inoculated into a sequencing batch reactor, and the operation mode of delayed water inlet-anaerobic long stirring was adopted. Six to eight typical cycles were operated every day. Any typical cycle included five processes, namely water inlet, anoxic stirring, sedimentation, drainage and standing. The duration of anoxic stirring was more than 75% of the total duration of the typical cycle. In any typical cycle, crude glycerol was slowly added at the same time as water inlet began. The time for adding crude glycerol was longer than the time for water inlet. The COD and NO3 content of glycerol in the crude glycerol in the influent were controlled. - The ratio of -N is 3.0 to 3.5:1, the inlet pH is controlled above 8.0, and the enrichment is successful when the peak value of the nitrite nitrogen accumulation rate in a typical cycle reaches more than 80%; (2) Stable retention of crude glycerol nutrient-type short-range denitrifying bacteria: According to the influent nitrate nitrogen concentration, the typical number of cycles and the anoxic stirring time of the sequencing batch reactor in a single day are adjusted so that the volumetric nitrogen load is within the range of 0.15 to 0.30 gN / L / d, and at the same time, the anoxic stirring time is ensured to be more than 75% of the total time of the typical cycle, and the sludge age of the sequencing batch reactor is adjusted so that the sludge concentration in the sequencing batch reactor is within the range of 0.8 to 1.5 gSS / L; (3) Optimizing the performance of crude glycerol short-range denitrification process: According to the non-glycerol carbon source content in crude glycerol, the total COD and NO3 in the crude glycerol in the influent were calculated. - The amount of crude glycerol added is adjusted within the range of 2.5 to 4.0:1, and the proportion of anoxic stirring time in a typical cycle is adjusted until the accumulation rate of nitrite nitrogen in the effluent of the sequencing batch reactor reaches more than 50% and the nitrate removal rate is stabilized at more than 90%.

2. The operation method of the crude glycerol type mainstream short-range denitrification process according to claim 1, characterized in that: The methanol mass percentage concentration in the crude glycerol is lower than 50%.

3. The operation method of the crude glycerol type mainstream short-range denitrification process according to claim 1, characterized in that: In step (1), the inoculum amount of activated sludge in the sequencing batch reactor is 1.5-3.0 gSS / L.

4. The operation method of the crude glycerol type mainstream short-range denitrification process according to claim 1, characterized in that: Slowly add crude glycerol to maintain the concentration of total organic carbon in the sequencing batch reactor within the range of no more than 20 mg / L until the required COD / NO3 is met. - -N ratio.

5. The operation method of the crude glycerol type mainstream short-range denitrification process according to claim 1, characterized in that: The pH of the inlet water to the sequencing batch reactor was controlled at 8.0-8.

5.

6. The operation method of the crude glycerol type mainstream short-range denitrification process according to claim 1, characterized in that: Hypoxia refers to a dissolved oxygen concentration below 0.5 mg / L.

7. The operation method of the crude glycerol type mainstream short-range denitrification process according to claim 1, characterized in that: In step (2), the typical number of cycles of the sequencing batch reactor in a single day is 6 to 12 times, and the sludge age of the sequencing batch reactor is 5 to 15 days.

8. The operation method of the crude glycerol type mainstream short-range denitrification process according to claim 1, characterized in that: In step (3), the total COD of crude glycerol = (mass of glycerol in the crude glycerol added / glycerol density × 1533 + mass of methanol in the crude glycerol added / methanol density × 1188) × 10, wherein: the unit of total COD of crude glycerol is mg / L, the unit of mass of glycerol in the crude glycerol added is g, the unit of glycerol density is g / L, the unit of mass of methanol in the crude glycerol added is g, and the unit of methanol density is g / L.

9. The method for operating the crude glycerol type mainstream short-range denitrification process according to claim 1, characterized in that: In step (3): the proportion of anoxic stirring time in a typical cycle is adjusted without changing the typical number of cycles in a single day of operation of the sequencing batch reactor; the proportion of anoxic stirring time in a typical cycle is 75% to 85%.

10. The method for operating the crude glycerol type mainstream short-range denitrification process according to claim 1, characterized in that: The operating temperature of the sequencing batch reactor is in the range of 15-25°C, and the influent NO3 - The -N concentration ranges from 20 to 70 mg / L.

Images