A method and device for granulating flocculent sludge

Abstract

The invention relates to the technical field of flocculent sludge granulation, and discloses a flocculent sludge granulation method and device, the method comprising sludge inoculation, flow state adjustment, static water replacement, continuous culture, particle formation and particle culture steps; and the device comprises a reactor, the reactor is connected with an inlet system, an outlet system and a flow state regulating loop system, the inlet system is located in the middle and lower part of the reactor, the outlet system is located in the upper part of the reactor, and the flow state regulating loop system is used to adjust the flow state Re value; it uses the Reynolds number as the evaluation index of the flow state, realizes the granulation of flocculent sludge by adjusting the flow state of the fluid, and improves the mass transfer efficiency in the reactor.

Description

Technical Field

[0001] The invention relates to the technical field of flocculent sludge granulation, and in particular to a flocculent sludge granulation method and device. Background Art

[0002] Granular sludge technology has the advantages of traditional flocculent sludge treatment, and has the characteristics of more efficient pollutant removal efficiency, more stable operation, higher load, smaller footprint, more flexible application, lower treatment cost, etc., which can better cope with the complex characteristics of high-concentration wastewater. Due to the difficulty of particle formation and the great difference in the treatment performance of flocculent sludge and granular sludge, there are uncertainties in reactor and process design in actual wastewater treatment applications. In the application of industrial wastewater treatment, sludge granulation is the key to the successful start-up of the reactor. Usually, the method of inoculating granular sludge is adopted to achieve the purpose of rapid start-up. However, granular sludge itself grows slowly, and involves storage, transportation, and recovery of activity. In actual applications, it cannot be guaranteed that there is a sufficient source.

[0003] In the prior art, there is an optimized cultivation method for aerobic granular sludge (authorization announcement number is CN101648746B), which is mainly based on air aeration, and achieves sludge granulation by regulating organic load, sludge settling time, and longer aerobic starvation time, so as to achieve treatment of sewage with lower concentration. Another example is a sludge granulation method based on pure oxygen aeration of urban domestic sewage (authorization announcement number is CN103395881B), which uses high dissolved oxygen and gradient cultivation to shorten the cultivation cycle, increase the particle size, and adapt to high-concentration sewage treatment. However, there has been no systematic study on the relationship between fluid flow morphology and particle formation.

[0004] Although there is no clear conclusion on the mechanism of granulation at present, the description of the particle formation process has been agreed upon by the academic community. That is, first, the particle core is formed by the collision between microorganisms or between microorganisms and solids, and then a microbial aggregate is formed through collision, entanglement, adhesion and the like. After that, the microorganisms in the aggregate grow and reproduce to initially form a particle structure, and finally form tightly structured particles under the action of hydraulic pressure. It is not difficult to see from the description of the particle formation process that hydraulic action and the adhesion and aggregation ability of the microorganisms themselves are important external and internal influencing factors in the particle formation process. Adjustment of hydraulic conditions is generally achieved by changing parameters such as stirring, reactor shape, and residence time. Adjustment of the above parameters will cause changes in the flow pattern of the fluid in the reactor. Therefore, after long-term research on the relationship between fluid flow pattern and particle formation, the applicant provides a flocculent sludge granulation method and device. Summary of the invention

[0005] In view of the deficiencies of the prior art, the purpose of the present invention is to provide a method and device for granulation of flocculent sludge, using the Reynolds number as an evaluation index of the flow regime, and realizing the granulation of flocculent sludge by adjusting the fluid flow regime, and improving the mass transfer efficiency in the reactor.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] A method for granulation of flocculent sludge, characterized by comprising the following steps:

[0008] (1) Sludge inoculation: Inoculate flocculent sludge in the reactor, adopt a sequential batch feeding mode, use laboratory artificial water as the influent, the influent COD concentration is 500 - 3000 mg / L, the nutrient elements COD:N:P = 400 - 600:5:1, and the pH is maintained at 7 - 8;

[0009] (2) Flow regime adjustment: Open the low - level valve of the flow regime adjustment and the variable - frequency pump, adjust the flow velocity to calculate the Re value, so that 2300 < Re < 4000 in the flow regime adjustment loop; at this time, the flocculent sludge entering the loop is in a transitional flow regime;

[0010] (3) Static water replacement: When the COD removal rate in the reactor reaches 70%, turn off the circulation pump and stop the circulation; let it stand for more than 30 min, open the middle influent valve, and feed water at a flow rate of 0.25 - 2 times the effective volume of the reactor per hour; when the influent volume reaches 70% of the effective volume of the reactor, close the influent valve and stop feeding water;

[0011] (4) Continuous cultivation: Repeat steps (2) and (3), and gradually increase the influent COD concentration to 5000 mg / L; as the concentration of flocculent sludge increases, gradually increase the influent flow rate during the water replacement stage to 2 times the effective volume of the reactor per hour to wash out the suspended sludge with poor sedimentation performance;

[0012] (5) Particle formation: When particles with obvious contours are observed in the flow regime pipeline, close the low - level valve of the flow regime adjustment and open the high - level valve of the flow regime adjustment to switch to high - level circulation, and open the bottom influent valve and close the middle influent valve. The reactor changes to continuous bottom feeding mode for continuous cultivation of particles; during the cultivation process, ensure that the COD removal rate is above 70% and the organic load is not greater than 5 kgCOD / m 3 ·d;

[0013] (6) Particle cultivation: As the particles grow larger, open the high - level valve of the flow regime adjustment for circulation, gradually increase the flow velocity in the flow regime adjustment pipeline by adjusting the variable - frequency pump until Re > 4000, so that the loop is in a turbulent state; at the same time, the reactor adopts continuous bottom feeding. When the particle growth slows down and the size is stable, it indicates that the particle cultivation is completed.

[0014] Among them, the Reynolds number can be calculated from parameters such as the pipeline diameter, fluid viscosity, flow velocity, and fluid density, that is

[0015]

[0016] In the formula: d is the pipeline diameter, u is the flow velocity, ρ is the fluid density, and μ is the kinematic viscosity;

[0017] Therefore, under the condition of a certain pipeline diameter and fluid viscous force, the Re value can be calculated by adjusting the flow velocity.

[0018] By adjusting the fluid flow regime at a low liquid level to make 2300 < Re < 4000, the flocculent sludge is in a transitional flow regime, which increases the probability of collision and entanglement between sludge microorganisms and promotes the agglomeration of microorganisms to form a particle core. At this time, too large or too small Re value is not conducive to the formation of the initial core.

[0019] During the static water replacement stage, when water is introduced in the middle at the initial stage of particle formation, the flocculent sludge with good sedimentation performance can be retained at the bottom of the reactor, and the sludge with poor sedimentation performance can be washed out.

[0020] After observing the formation of particles, as the amount of sludge in the reactor increases, the fluid flow regime is adjusted by combining with the high liquid level to make Re > 4000, so that the sludge microorganisms are in a turbulent flow regime, which is conducive to the formation of granular sludge with a compact structure and stable size.

[0021] Preferably, the sludge concentration of the flocculent sludge inoculated in step (1) is 15 - 30 g / L; the sludge inoculation temperature is set at 35 ± 2 °C.

[0022] A flocculent sludge granulation device includes a reactor, the reactor is connected with a water inlet system, a water outlet system and a flow regime adjustment loop system. The water inlet system is located in the middle and lower part of the reactor, the water outlet system is located in the upper part of the reactor, and the flow regime adjustment loop system is used to adjust the Re value of the flow regime.

[0023] Preferably, the water inlet system includes a bottom water inlet pipeline and a middle water inlet pipeline. The water inlet of the middle water inlet pipeline is located at 30% ± 5% of the effective volume of the reactor, and a bottom water inlet valve and a middle water inlet valve are respectively installed on the bottom water inlet pipeline and the middle water inlet pipeline.

[0024] Preferably, the flow regime adjustment loop system includes a high liquid level outlet pipeline for flow regime adjustment, a low liquid level outlet pipeline for flow regime adjustment and a return pipeline for flow regime adjustment. The high liquid level outlet pipeline for flow regime adjustment and the low liquid level outlet pipeline for flow regime adjustment are arranged in parallel and are both communicated with the return pipeline for flow regime adjustment; the high liquid level outlet pipeline for flow regime adjustment is located at 60% ± 5% of the effective volume of the reactor, the low liquid level outlet pipeline for flow regime adjustment is located at 30% ± 5% of the effective volume of the reactor, and the return pipeline for flow regime adjustment is located at the bottom of the reactor.

[0025] Preferably, the flow state regulating high liquid level outlet pipeline and the flow state regulating low liquid level outlet pipeline are respectively installed with a flow state regulating high liquid level valve and a flow state regulating low liquid level valve; the flow state regulating return water pipeline is installed with a variable frequency pump and a flow meter to control and detect the return water flow.

[0026] Preferably, a reflux system is further included, wherein the reflux system includes a reflux pipe located at the top of the reactor and a reflux pipeline connected to the water inlet system.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The method of the present invention is based on the characteristic that the motion trajectories of each particle in the fluid are disordered in the turbulent state, and uses the Reynolds number as the evaluation index of the flow state. By adjusting the flow state of the fluid, the flocculent sludge microorganisms are placed in the turbulent flow state, thereby increasing the probability of collision and entanglement between the sludge microorganisms, which is conducive to the formation of particle cores and sludge particles, realizing the granulation of flocculent sludge, and improving the mass transfer efficiency in the reactor;

[0029] The method of the present application is used to achieve granulation of flocculent sludge and improve the mass transfer efficiency in the reactor without the need for additional addition of Ca 2+ The process is simpler and the cost of flocculent sludge granulation is reduced by removing metal ions or granulation aids.

[0030] Since the flow adjustment loop and sequencing batch culture are used to wash out the sludge with poor settling properties, the culture process does not need to consider the influence of the rising flow rate and the height-to-diameter ratio in the traditional reactor; and the operation is simple, and it is suitable for the anaerobic sludge granulation of various wastewaters; the flow adjustment loop is simple to set up and can be applied to existing UASB or EGSB reactors to granulate the flocculent sludge in the existing reactor, thereby improving the processing capacity of the existing reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the structure of the flocculent sludge granulation device in this embodiment, which does not include a reflow system.

[0032] Figure 2 It is a schematic diagram of the structure of the flocculent sludge granulation device including the reflow system in this embodiment.

[0033] Figure 3 This is a flowchart of the flocculent sludge granulation process in this embodiment.

[0034] In the accompanying drawings: 10-reactor, 1-water inlet system, 11-bottom water inlet pipeline, 111-bottom water inlet valve, 12-middle water inlet pipeline, 121-middle water inlet valve, 2-water outlet system, 3-gas outlet system, 4-flow state regulation loop system, 41-flow state regulation high liquid level outlet pipeline, 411-flow state regulation high liquid level valve, 42-flow state regulation low liquid level outlet pipeline, 421-flow state regulation low liquid level valve, 43-flow state regulation return water pipeline, 431-frequency conversion pump, 432-flow meter, 433-flow state regulation diversion pipeline, 5-reflux system, 51-reflux tank, 52-reflux pipeline. DETAILED DESCRIPTION

[0035] In order to adjust the flow state in the reactor, the present invention designs a corresponding granulation device. Figure 1-2 As shown, the device includes a reactor 10, which is connected to a water inlet system 1, a water outlet system 2, an air outlet system 3 and a flow state regulating loop system 4. The water inlet system 1 is located in the lower middle part of the reactor 10, the water outlet system 2 is located in the upper part of the reactor 10, and the flow state regulating loop system 4 is used to adjust the flow state Re value.

[0036] The water inlet system 1 includes a bottom water inlet pipeline 11 and a middle water inlet pipeline 12. The water inlet of the middle water inlet pipeline 12 is located at 30%±5% of the effective volume of the reactor 10, and a bottom water inlet valve 111 and a middle water inlet valve 121 are installed on the bottom water inlet pipeline 11 and the middle water inlet pipeline 12 respectively.

[0037] The flow regulation circuit system 4 includes a flow regulation high liquid level outlet pipeline 41 , a flow regulation low liquid level outlet pipeline 42 and a flow regulation return pipeline 43 . The flow regulation high liquid level outlet pipeline 41 and the flow regulation low liquid level outlet pipeline 42 are arranged in parallel and are both connected to the flow regulation return pipeline 43 .

[0038] The flow state regulating high liquid level outlet pipeline 41 is located at 60%±5% of the effective volume of the reactor 10, the flow state regulating low liquid level outlet pipeline 42 is located at 30%±5% of the effective volume of the reactor 10, and the flow state regulating return water pipeline 43 is located at the bottom of the reactor 10.

[0039] The flow state regulating high liquid level outlet pipeline 41 and the flow state regulating low liquid level outlet pipeline 42 are respectively installed with a flow state regulating high liquid level valve 411 and a flow state regulating low liquid level valve 421; the flow state regulating return water pipeline 43 is installed with a variable frequency pump 431 and a flow meter 432 to control and detect the return water flow.

[0040] The flow regulating return water pipeline 43 is also provided with a plurality of flow regulating shunt pipelines 433 in front of the variable frequency pump 431 . The plurality of flow regulating shunt pipelines 433 are arranged in parallel to control the return water flow rate and enhance the flow characteristics in the flow regulating loop system 4 .

[0041] According to actual conditions, a reflux system 5 is also included, and the reflux system 5 includes a reflux tank 51 located at the top of the reactor 10 and a reflux pipeline 52 connected to the water inlet system 1 .

[0042] Embodiment 1:

[0043] The method for granulating flocculent sludge using the flocculent sludge granulating device of the present invention comprises the following steps:

[0044] (1) Sludge inoculation: The reactor 10 is inoculated with flocculent sludge at a sludge concentration of 15 g / L and a temperature set at 35 ± 2°C; a sequencing batch water inlet mode is adopted, with laboratory artificial water as the inlet water, an initial inlet COD concentration of 1000 mg / L, nutrient elements COD:N:P=400-600:5:1, and the pH is maintained at 7-8;

[0045] (2) Flow state adjustment: Open the flow state adjustment low liquid level valve 421 and the variable frequency pump 431, adjust the flow rate to calculate the Re value, so that Re=3500 in the flow state adjustment loop, and the flocculent sludge entering the loop is in an excessive flow state;

[0046] (3) Static water replacement: When the COD removal rate in the reactor 10 reaches 70%, the circulation pump is turned off to stop the circulation; after standing for more than 30 minutes, the middle water inlet valve 121 is opened to feed water at a flow rate of 0.25 times the effective volume of the reactor per hour; when the water inflow reaches 70% of the effective volume of the reactor 10, the water inlet valve is closed to stop the water inflow;

[0047] (4) Continuous culture: repeating steps (2) and (3), and gradually increasing the influent COD concentration to 5000 mg / L; as the flocculent sludge concentration increases, gradually increasing the influent flow rate during the water exchange stage to a flow rate of 2 times the effective volume of the reactor per hour to wash out the suspended sludge with poor settling performance;

[0048] (5) Particle formation: When the formation of particles with clear outlines is observed in the flow pipeline, the flow regulating low liquid level valve 421 is closed and the flow regulating high liquid level valve 411 is opened to switch to the high liquid level for circulation, and the bottom water inlet valve 111 is opened and the middle water inlet valve 121 is closed. The reactor 10 uses the bottom continuous water inlet mode to continuously cultivate the particles; the cultivation process ensures that the COD removal rate is above 70% and the organic load is not more than 5 kgCOD / m 3 ·d; After 21 days of continuous cultivation, sludge particles were formed in the reactor;

[0049] (6) Particle cultivation: As the particles become larger, the high liquid level valve 411 for flow regulation is opened for circulation, and the variable frequency pump 431 is adjusted to gradually increase the flow rate in the flow regulation loop to Re = 5000, so that the loop is in a turbulent state; at the same time, the reactor 10 adopts a bottom continuous water inlet method; after 30 days of continuous cultivation, the COD removal rate is stabilized at 79% when Re = 5000 in the flow regulation loop, and granular sludge with a compact structure, a black-gray surface, and a diameter of 2 to 5 mm is produced in the reactor.

[0050] Embodiment 2:

[0051] The method for realizing flocculent sludge granulation by using the flocculent sludge granulation device of the present invention is different from that of Example 1 in that: in step (2), the flow state regulating low liquid level valve 421 and the variable frequency pump 431 are opened, and the flow rate is adjusted to calculate the Re value, so that Re in the flow state regulating loop is 2400;

[0052] In step (6), the flow state regulating high liquid level valve 411 is opened for circulation, and the variable frequency pump 431 is adjusted to gradually increase the flow rate in the flow state regulating loop to Re=4200;

[0053] After 25 days of batch culture, sludge particles were formed in the reactor; after 36 days of continuous culture, the COD removal rate was stabilized at 75% when Re=4200 in the flow regulation loop, and granular sludge with a compact structure, black-gray surface and a diameter of 2 to 5 mm was produced in the reactor.

[0054] Embodiment 3:

[0055] The method for realizing flocculent sludge granulation by using the flocculent sludge granulation device of the present invention is different from that of Example 1 in that: in step (2), the flow state regulating low liquid level valve 421 and the variable frequency pump 431 are opened, and the flow rate is adjusted to calculate the Re value, so that Re=3900 in the flow state regulating loop;

[0056] In step (6), the flow state regulating high liquid level valve 411 is opened for circulation, and the variable frequency pump 431 is adjusted to gradually increase the flow rate in the flow state regulating loop to Re=6000;

[0057] After 23 days of batch culture, sludge particles were formed in the reactor; after 37 days of continuous culture, the COD removal rate was stabilized at 77% when Re=6000 in the flow regulation loop, and granular sludge with a compact structure, black-gray surface and a diameter of 2 to 5 mm was produced in the reactor.

[0058] Meanwhile, in other embodiments, the influent COD concentration is controlled within 500-3000 mg / L, and by adjusting the fluid flow pattern, through batch culture and continuous culture, granular sludge with a compact structure, a black-gray surface, and a diameter of 2 to 5 mm can be produced in the reactor.

[0059] Comparative Example 1:

[0060] The method for granulating flocculent sludge by using the flocculent sludge granulation device of the present invention is different from that of Example 1 in that: in step (2), the low liquid level valve 421 for flow state regulation and the variable frequency pump 431 are opened, the flow velocity is adjusted to calculate the Re value, so that Re = 2000 in the flow state regulation loop; after 40 days of cultivation, no particle formation was observed.

[0061] Comparative Example 2:

[0062] The method for granulating flocculent sludge by using the flocculent sludge granulation device of the present invention is different from that of Example 1 in that: in step (2), the low liquid level valve 421 for flow state regulation and the variable frequency pump 431 are opened, the flow velocity is adjusted to calculate the Re value, so that Re = 4000 in the flow state regulation loop; after 40 days of cultivation, no particle formation was observed.

[0063] It can be seen from the above Examples 1-3 and Comparative Examples 1-2 that: based on the characteristic that the movement trajectories of each particle inside the fluid are disordered in the turbulent state, the fluid flow state is adjusted by the low liquid level to make 2300 < Re < 4000, and the flocculent sludge is in the transitional flow state to increase the probability of collision and entanglement between sludge microorganisms and promote the agglomeration of microorganisms to form the particle core. At this time, too large or too small Re value is not conducive to the formation of the initial core; after static water replacement and continuous cultivation, when particle formation is observed, as the sludge volume in the reactor increases, the fluid flow state is adjusted by the high liquid level to make Re > 4000, so that the sludge microorganisms are in the turbulent flow state, which is conducive to the formation of granular sludge with a compact structure and stable size.

Claims

1. A method for granulating flocculent sludge, characterized in that: It includes the following steps: (1) Sludge inoculation: Flocculent sludge is inoculated in the reactor. The sequential batch influent mode is adopted, and the laboratory artificial water is used as the influent. The influent COD concentration is 500 - 3000 mg / L, the nutrient element COD:N:P = 400 - 600:5:1, and the pH is maintained at 7 - 8. (2) Flow regime adjustment: Open the low-level valve of the flow regime adjustment and the variable-frequency pump, adjust the flow velocity to calculate the Re value, so that 2300 < Re < 4000 in the flow regime adjustment loop; at this time, the flocculent sludge entering the loop is in a transitional flow regime. (3) Static water replacement: When the COD removal rate in the reactor reaches 70%, turn off the circulation pump and stop the circulation; let it stand for more than 30 minutes, then open the middle influent valve, and the influent velocity is 0.25 - 2 times the effective volume of the reactor per hour; when the influent volume reaches 70% of the effective volume of the reactor, close the influent valve and stop the influent. (4) Continuous cultivation: Repeat steps (2) and (3), and gradually increase the influent COD concentration to 5000 mg / L; as the concentration of flocculent sludge increases, gradually increase the influent velocity during the water replacement stage to 2 times the effective volume of the reactor per hour to wash out the suspended sludge with poor sedimentation performance. (5) Particle formation: When the formation of particles with clear outlines is observed in the flow pipeline, the low liquid level valve of the flow regulation is closed and the high liquid level valve of the flow regulation is opened to switch to the high liquid level for circulation, and the bottom water inlet valve is opened and the middle water inlet valve is closed. The reactor uses the bottom continuous water inlet mode to continuously cultivate the particles; the cultivation process ensures that the COD removal rate is above 70% and the organic load is not more than 5kgCOD / m 3 ·d; (6) Granule cultivation: As the granules become larger, open the high-level valve of the flow regime adjustment for circulation, adjust the variable-frequency pump to gradually increase the flow velocity in the flow regime adjustment pipeline to Re > 4000, so that the loop is in a turbulent state; at the same time, the reactor adopts the bottom continuous influent method. When the granule growth slows down and the size is stable, it indicates that the granule cultivation is completed.

2. The method for granulating flocculent sludge according to claim 1, characterized in that: The concentration of the flocculent sludge inoculated in step (1) is 15 - 30 g / L; the sludge inoculation temperature is set at 35 ± 2 °C.

3. A flocculent sludge granulation device, comprising a reactor, characterized in that: Adopt a method for granulation of flocculent sludge according to claim 1 or 2, wherein the reactor is connected with an influent system, an effluent system, an air outlet system and a flow regime adjustment loop system. The influent system is located in the middle and lower part of the reactor, the effluent system is located in the upper part of the reactor, and the flow regime adjustment loop system is used to adjust the Re value of the flow regime.

4. The flocculent sludge granulation device according to claim 3, characterized in that: The influent system includes a bottom influent pipeline and a middle influent pipeline. The water inlet of the middle influent pipeline is located at 30% ± 5% of the effective volume of the reactor, and a bottom influent valve and a middle influent valve are respectively installed on the bottom influent pipeline and the middle influent pipeline.

5. The flocculent sludge granulation device according to claim 3, characterized in that: The flow regime adjustment loop system includes a high-level outlet pipeline for flow regime adjustment, a low-level outlet pipeline for flow regime adjustment and a return pipeline for flow regime adjustment. The high-level outlet pipeline for flow regime adjustment and the low-level outlet pipeline for flow regime adjustment are arranged in parallel and are both connected to the return pipeline for flow regime adjustment.

6. The flocculent sludge granulation device according to claim 5, characterized in that: The high-level outlet pipeline for flow regime adjustment is located at 60% ± 5% of the effective volume of the reactor, the low-level outlet pipeline for flow regime adjustment is located at 30% ± 5% of the effective volume of the reactor, and the return pipeline for flow regime adjustment is located at the bottom of the reactor.

7. The flocculent sludge granulation device according to claim 6, characterized in that: A high-level valve for flow regime adjustment and a low-level valve for flow regime adjustment are respectively installed on the high-level outlet pipeline for flow regime adjustment and the low-level outlet pipeline for flow regime adjustment.

8. The flocculent sludge granulation device according to claim 6, characterized in that: A variable-frequency pump and a flowmeter are installed on the return pipeline for flow regime adjustment to control and detect the return water flow.

9. The flocculent sludge granulation device according to claim 8, characterized in that: The flow pattern regulating return water pipeline is also provided with a plurality of flow pattern regulating shunt pipelines in front of the variable frequency pump. The plurality of flow pattern regulating shunt pipelines are arranged in parallel to control the return water flow rate.

10. A flocculent sludge granulation device according to any one of claims 3 to 9, characterized in that: The invention also comprises a reflux system, wherein the reflux system comprises a reflux tank located at the top of the reactor and a reflux pipeline connected with the water inlet system.

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