In-situ carbon-sourcing device and method for stripping extracellular polymeric substance of activated sludge

Abstract

The invention discloses an in-situ carbon-sourcing device and method for stripping an extracellular polymeric substance of activated sludge. The device comprises an ultrasonic unit, an emulsification pump and an emulsification box which are sequentially connected through a pipeline, the ultrasonic unit is provided with a feed port, the emulsification box is provided with a discharge port, and the device is further provided with a sludge reflux pump connected with the emulsification box and the emulsification pump. According to the device, activated sludge flocs are scattered by ultrasonic waves, large flocs are changed into a plurality of small flocs, and then activated sludge extracellular polymeric substances are stripped under the action of strong shearing, friction and centrifugal force between a high-speed rotating rotor and a high-speed rotating stator of an emulsification pump; therefore, the purpose of stripping the extracellular polymeric substance to release the carbon source on the premise of not destroying the metabolic activity of the sludge is achieved. The device can be applied to treatment of excess sludge and nitrification liquid return sludge, and can realize continuous treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and more particularly to a method for in-situ carbonization of extracellular polymers of activated sludge by utilizing ultrasound combined with emulsification stripping. Background Art

[0002] Currently, my country's urban sewage treatment plants primarily utilize activated sludge treatment processes. Low carbon-nitrogen ratios in the influent are a common problem, impacting the denitrification efficiency of the biological system. This inadequate carbon source in the influent leads to low total nitrogen removal rates in the biological system, a major challenge facing sewage treatment plants. Currently, my country's urban sewage treatment plants primarily utilize the addition of external carbon sources (glucose, sodium acetate, methanol, and composite carbon sources, among others) to enhance denitrification efficiency, resulting in a significant increase in sewage treatment costs.

[0003] Extracellular polymeric substances (EPPs) are a key component of activated sludge, containing large amounts of organic matter such as proteins and polysaccharides, and possessing high bioavailability potential. Stripping ECPs from the surface of activated sludge can serve as a supplemental carbon source for biological denitrification, offering a new approach to addressing the carbon shortage in wastewater treatment plants. By stripping ECPs from the sludge surface and using them as a carbon source for biological denitrification, while preserving the metabolic activity of the sludge, this approach achieves in-situ carbonization of activated sludge ECPs.

[0004] There are two main methods for applying the in-situ carbonization technology of extracellular polymer stripping in engineering: carbon release by extracellular polymer stripping of excess sludge and carbon release by extracellular polymer stripping of nitrification solution return sludge. The excess sludge stripping carbon release process directly introduces the sludge carbon release process (acting on part or all of the secondary sedimentation tank return sludge) into the biochemical treatment system. The released extracellular polymers and sludge are directly returned to the biochemical reaction tank for utilization. This model is applicable to all types of activated sludge processes with secondary sedimentation tanks.

[0005] Another utilization model involves stripping extracellular polymers (ECPs) from nitrification solution return sludge to release carbon. Specifically, in the nitrification solution return system from the aerobic tank to the anoxic tank in the A / O process, the sludge ECPs are stripped to release organic matter. These organic matter, along with the metabolically active sludge, enter the anoxic tank. Denitrifying bacteria use the organic matter released by the ECPs as electron donors for biological denitrification, achieving in-situ ECP carbon release and online utilization in the mainstream process. This nitrification solution return sludge carbon release model is only applicable to activated sludge processes with a nitrification solution return system, such as A / O or A2 / O processes, and is not applicable to oxidation ditch processes without a nitrification solution return system.

[0006] Extracellular polymeric substances (ECPs) stripping and carbon release technology offers a new approach to addressing the carbon source shortage in the denitrification process of wastewater treatment plants. However, in practical applications, the key to removing ECPs from the sludge surface remains a critical issue. Currently, three main methods for extracting ECPs from activated sludge surfaces exist: physical, chemical, and biological. Physical methods include centrifugation, heating, and ultrasound. Chemical methods include ion exchange resins, NaOH, and EDTA. Biological methods primarily utilize specific enzymes to decompose ECPs and release organic matter. Several combined extraction methods exist, such as ultrasound-heating, hot alkaline extraction, and ultrasonic centrifugation. These methods are primarily used in laboratory research and are suitable only for small-scale, sequencing batch extraction of ECPs from activated sludge. Implementation in continuous-flow systems is challenging and costly. Currently, the only methods for removing ECPs from activated sludge in continuous-flow systems are cyclone or ultrasound-cyclone. However, cyclone operation requires high inlet pressure, making operation and control difficult and resulting in poor sludge carbon release. Summary of the Invention

[0007] In view of this, the present invention provides a method and device for stripping activated sludge using ultrasound combined with emulsification. Ultrasound is first used to break up the activated sludge flocs, turning large flocs into multiple small flocs, and then the strong shear, friction and centrifugal force between the high-speed rotating rotor and stator of the emulsification pump are used to strip the extracellular polymers of the activated sludge, thereby achieving the purpose of stripping the extracellular polymers and releasing the carbon source without destroying the metabolic activity of the sludge.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] First, the present invention provides an in-situ carbonization device for stripping extracellular polymers from activated sludge, comprising an ultrasonic unit, an emulsification pump, and an emulsification tank connected in sequence through pipelines; the ultrasonic unit is provided with a feed inlet, and the emulsification tank is provided with a discharge port.

[0010] Preferably, the device further comprises a sludge return pump, and the sludge return pump is connected to the emulsification tank and the emulsification pump via a pipeline.

[0011] Furthermore, the flow rate of the sludge return pump is 0-3 times the flow rate of the emulsification pump.

[0012] Preferably, the ultrasonic unit adopts a box structure or a pipeline structure;

[0013] The box structure includes a box and an ultrasonic vibration plate placed in the box, wherein the ultrasonic vibration plate is arranged at the bottom of the box and / or on both sides of the box along the water flow direction;

[0014] The pipeline structure includes a pipeline and an ultrasonic vibration rod placed in the pipeline;

[0015] The ultrasonic frequency of the ultrasonic vibration plate or ultrasonic vibration rod is 20-24kHz, and the ultrasonic energy density is 5-30KJ / gMLSS.

[0016] Furthermore, in the box structure, when an ultrasonic vibration plate is arranged alone at the bottom, the depth of the liquid above the ultrasonic vibration plate does not exceed 0.6 meters; when arranged on both sides of the box along the water flow direction, the distance between the two ultrasonic vibration plates is greater than 0.8 meters and does not exceed 1.2 meters.

[0017] Preferably, the emulsification pump is a three-stage emulsification pump.

[0018] Preferably, a stirring device is provided in the emulsification tank, and the sludge retention time in the emulsification tank is 10-20 minutes.

[0019] The present invention also provides a method for stripping extracellular polymers from activated sludge and converting them into in-situ carbon sources using the device described in the above technical solution, wherein the activated sludge is nitrification liquid return sludge, comprising the following steps:

[0020] The nitrification liquid return sludge enters the ultrasonic unit and enters the emulsification pump after ultrasonic treatment, enters the emulsification tank after treatment by the emulsification pump, and then enters the anoxic tank directly after treatment by the emulsification tank.

[0021] The present invention also provides another method for stripping extracellular polymers from activated sludge and in-situ carbonization using the device described in the above technical solution, wherein the activated sludge is excess sludge, comprising the following steps:

[0022] The remaining sludge enters the ultrasonic unit and is then treated by ultrasound before entering the emulsification pump. After being treated by the emulsification pump, it enters the emulsification tank. After being treated in the emulsification tank, it is returned to the emulsification pump through the sludge return pump for treatment, and then enters the emulsification tank again. The finally treated sludge is discharged from the emulsification tank and enters the activated sludge biological reactor.

[0023] Furthermore, when the concentration of suspended solids in residual sludge is 6-10g / L, the flow rate of the sludge return pump is 1-1.5 times the flow rate of the emulsification pump; when the concentration of suspended solids in residual sludge is 10-15g / L, the flow rate of the sludge return pump is 1.5-2.0 times the flow rate of the emulsification pump; when the concentration of suspended solids in residual sludge is greater than 15g / L, the flow rate of the sludge return pump is 3 times the flow rate of the emulsification pump.

[0024] It can be seen from the above technical solution that, compared with the prior art, the present invention discloses a device and method for in-situ carbonization of extracellular polymers from activated sludge, which has the following beneficial effects:

[0025] The present invention uses ultrasound combined with an emulsification pump to strip extracellular polymers from activated sludge, which is suitable for large-scale sludge treatment in actual engineering projects. At the same time, this method is suitable for the disposal of continuously flowing activated sludge, and can achieve continuous disposal of sludge, breaking the limitation of traditional extracellular polymer extraction methods that can only be extracted in batches.

[0026] This method uses ultrasound combined with an emulsification pump. Compared to cyclone carbon release methods, this method offers simpler operation and control, and achieves superior extracellular polymeric polymer (ECP) removal and carbon release. Furthermore, the method controls the ultrasonic energy input and emulsification times based on the mass of the sludge being treated (rather than the volume of the mixed liquor). This precise control of energy input allows for accurate control of the degree of ECP removal, achieving both ECP removal and sludge cell integrity. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0028] Figure 1 The overall structure diagram of the device for in-situ carbonization of extracellular polymers from activated sludge by ultrasound combined with emulsification.

[0029] Figure 2 FIG1 is a structural diagram of the ultrasonic unit;

[0030] Figure 3 This is a system structure diagram of Example 1;

[0031] Figure 4 This is a system structure diagram of Example 2;

[0032] Figure 5 The ultrasonic unit layout diagram for the pipeline structure;

[0033] In the figure, 1-ultrasonic unit, 11-tank, 12-ultrasonic vibration plate, 2-emulsification pump, 3-emulsification tank, 4-sludge return pump, 5-activated sludge biological reaction tank, 6-secondary sedimentation tank, 7-first sludge return pump, 8-sludge pump, 9-extracellular polymer stripping and carbon release device, 10-anoxic tank, 13-aerobic tank, 14-nitrification liquid return pump, 15-pipeline, 16-ultrasonic vibration rod. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0035] As attached Figure 1 As shown, a device for in-situ carbonization of extracellular polymers of activated sludge by using ultrasound combined with emulsification stripping includes an ultrasonic unit 1, an emulsification pump 2, and an emulsification tank 3 connected in sequence through pipelines; the ultrasonic unit 1 is provided with a feed inlet, the emulsification tank 3 is provided with a discharge port, the emulsification pump 2 is a three-stage emulsification pump, and the sludge residence time in the emulsification tank is 10-20 minutes.

[0036] It also includes a sludge return pump 4, which is connected to the emulsification tank 3 and the emulsification pump 2 through a pipeline. The flow rate of the sludge return pump 4 is 0-3 times the flow rate of the emulsification pump 2 (different flow ratios are defined based on the source of the activated sludge).

[0037] As attached Figure 2 and 5 As shown, the ultrasonic unit 1 adopts a box structure or a pipeline structure;

[0038] The box structure includes a box body 11 and an ultrasonic vibration plate 12 placed in the box body 11. The ultrasonic vibration plate 12 is arranged at the bottom of the box body 11 and / or arranged on both sides of the box body 11 along the water flow direction;

[0039] The pipeline structure includes a pipeline 15 and an ultrasonic vibrating rod 16 placed in the pipeline. The ultrasonic vibrating rod 16 is arranged at the axis of the pipeline 15 and is powered by an external circuit. A rubber ring is used between the circuit and the pipeline 15 to achieve relative sealing to prevent leakage.

[0040] The ultrasonic frequency of the ultrasonic vibration plate 12 or the ultrasonic vibration rod 16 is 20-24 kHz, and the ultrasonic energy density is 5-30 KJ / g MLSS.

[0041] In the box structure, when the ultrasonic vibration plate 12 is arranged alone at the bottom, the depth of the liquid above the ultrasonic vibration plate 12 does not exceed 0.6 meters; when arranged on both sides of the box 11 along the water flow direction, the distance between the two ultrasonic vibration plates 12 is greater than 0.8 meters and does not exceed 1.2 meters.

[0042] In some specific improved technical solutions, a stirring device is provided in the emulsification tank.

[0043] The operating principle of this device is as follows: excess sludge or nitrification liquid return sludge first enters ultrasonic unit 1 through the sludge pump provided by the excess sludge return system or the nitrification liquid sludge return system. The cavitation effect of ultrasound breaks up the sludge flocs, breaking large particles into smaller flocs while loosening the floc structure and releasing a small amount of extracellular polymeric substances (ECPs) on the surface of the sludge flocs into the water. The sludge then enters emulsification pump 2, which utilizes a three-stage rotor emulsification pump. The intense shear, friction, and centrifugal force between the high-speed rotating rotor and stator exfoliates the ECPs from the activated sludge surface, releasing them and dissolving them into the water. Because the suspended solids concentration of the nitrification liquid return sludge is relatively low, typically 3-5 g / L, the sludge only needs to undergo a single emulsification process after ultrasonic treatment. After passing through emulsification pump 2, the sludge enters emulsification tank 3 and flows out through the outlet. For the residual sludge, due to the high sludge concentration, the sludge return pump 4 connected to the emulsification tank 3 is started to transport the sludge from the emulsification tank 3 to the inlet of the emulsification pump 2 for secondary emulsification. The higher the concentration of suspended solids in the residual sludge, the greater the sludge return volume, and the flow rate of the sludge return pump 4 is 1-3 times the flow rate of the emulsification pump 3. The core of this method and device is to use ultrasound and an emulsification pump to strip the extracellular polymers of the activated sludge to release the carbon source. At the same time, the ultrasound intensity and the number of emulsifications must be precisely controlled to ensure that the sludge metabolic activity is not broken. The active bacteria in the sludge enter the anoxic tank together with the organic matter released by the stripping. The sludge bacteria use the organic matter released by themselves as a carbon source to carry out the biological carbon and nitrogen process. Its essence is to "cut meat for food" of the activated sludge, realizing the in situ carbon source conversion of the extracellular polymers of the activated sludge.

[0044] Example 1

[0045] As attached Figure 3 As shown, the activated sludge is residual sludge, and the treatment system includes an activated sludge biological reactor 5 and a secondary sedimentation tank 6 connected in sequence by pipelines. The secondary sedimentation tank 6 is connected to a first sludge return pump 7 and a sludge pump 8. The first sludge return pump 7 transports part of the residual sludge to the device described in Example 1 (the figure is an extracellular polymer stripping and carbon release device 9). The residual sludge enters the ultrasonic unit 1 and enters the emulsification pump 2 after ultrasonic treatment. After being treated by the emulsification pump 2, it enters the emulsification tank 3, and then after being treated in the emulsification tank 3, it is returned to the emulsification pump 2 through the sludge return pump 4 for treatment, and then enters the emulsification tank 3. Finally, the treated sludge is discharged from the emulsification tank 3 and enters the activated sludge biological reactor 5.

[0046] Among them, the rules for determining the return flow rate are as follows: when the concentration of residual sludge suspended solids is 6-10g / L, the flow rate of the sludge return pump 4 is 1-1.5 times the flow rate of the emulsification pump 2; when the concentration of residual sludge suspended solids is 10-15g / L, the flow rate of the sludge return pump 4 is 1.5-2.0 times the flow rate of the emulsification pump 2; when the concentration of residual sludge suspended solids is greater than 15g / L, the flow rate of the sludge return pump 4 is 3 times the flow rate of the emulsification pump 2.

[0047] Example 2

[0048] As attached Figure 4 As shown, the activated sludge is nitrification liquid return sludge, and the treatment system includes an anoxic tank 10, an aerobic tank 13, and a secondary sedimentation tank 6 connected in sequence by pipelines. The secondary sedimentation tank 6 is connected to a first sludge return pump 7 and a sludge pump 8. The first sludge return pump 7 returns part of the sludge, and the nitrification liquid return pump 14 transports the nitrification liquid return sludge to the device described in Example 1 (the figure is the extracellular polymer stripping and carbon release device 9). The nitrification liquid return sludge enters the ultrasonic unit 1 and enters the emulsification pump 2 after ultrasonic treatment. After being treated by the emulsification pump 2, it enters the emulsification tank 3, and then directly enters the anoxic tank 10 after being treated by the emulsification tank 3.

[0049] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0050] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A device for in-situ carbonization of extracellular polymers from activated sludge, characterized in that: The method comprises an ultrasonic unit, an emulsification pump and an emulsification box which are sequentially connected through pipelines; the ultrasonic unit is provided with a feed inlet, and the emulsification box is provided with a discharge outlet.

2. The device for in-situ carbonization of extracellular polymers removed from activated sludge according to claim 1, characterized in that: The device further comprises a sludge return pump, which is connected to the emulsification tank and the emulsification pump via a pipeline.

3. The device for in-situ carbonization of extracellular polymers removed from activated sludge according to claim 2, characterized in that: The flow rate of the sludge return pump is 0-3 times the flow rate of the emulsification pump.

4. The device for in-situ carbonization of extracellular polymers removed from activated sludge according to claim 1, characterized in that: The ultrasonic unit adopts a box structure or a pipeline structure; The box structure includes a box and an ultrasonic vibration plate placed in the box, wherein the ultrasonic vibration plate is arranged at the bottom of the box and / or on both sides of the box along the water flow direction; The pipeline structure includes a pipeline and an ultrasonic vibration rod placed in the pipeline; The ultrasonic frequency of the ultrasonic vibration plate or ultrasonic vibration rod is 20-24 kHz, and the ultrasonic energy density is 5-30 KJ / g MLSS.

5. The device for in-situ carbonization of extracellular polymers removed from activated sludge according to claim 4, characterized in that: In the box structure, when the ultrasonic vibration plate is arranged alone at the bottom, the depth of the liquid above the ultrasonic vibration plate does not exceed 0.6 meters; when arranged on both sides of the box along the water flow direction, the distance between the two ultrasonic vibration plates is greater than 0.8 meters and does not exceed 1.2 meters.

6. The device for in-situ carbonization of extracellular polymers removed from activated sludge according to claim 1, characterized in that: The emulsification pump is a three-stage emulsification pump.

7. The device for in-situ carbonization of extracellular polymers removed from activated sludge according to claim 1, characterized in that: A stirring device is provided in the emulsification tank, and the sludge retention time in the emulsification tank is 10-20 minutes.

8. A method for in-situ carbonization of extracellular polymers stripped from activated sludge using the device according to any one of claims 1 to 7, characterized in that: The activated sludge is nitrification liquid return sludge, comprising the following steps: The nitrification liquid return sludge enters the ultrasonic unit and enters the emulsification pump after ultrasonic treatment, enters the emulsification tank after treatment by the emulsification pump, and then enters the anoxic tank directly after treatment by the emulsification tank.

9. A method for in-situ carbonization of extracellular polymers stripped from activated sludge using the device according to any one of claims 1 to 7, characterized in that: The activated sludge is excess sludge, comprising the following steps: The remaining sludge enters the ultrasonic unit and is then treated by ultrasound before entering the emulsification pump. After being treated by the emulsification pump, it enters the emulsification tank. After being treated in the emulsification tank, it is returned to the emulsification pump through the sludge return pump for treatment, and then enters the emulsification tank again. The finally treated sludge is discharged from the emulsification tank and enters the activated sludge biological reactor.

10. The method according to claim 9, characterized in that When the concentration of suspended solids in residual sludge is 6-10g / L, the flow rate of the sludge return pump is 1-1.5 times the flow rate of the emulsification pump; when the concentration of suspended solids in residual sludge is 10-15g / L, the flow rate of the sludge return pump is 1.5-2.0 times the flow rate of the emulsification pump; when the concentration of suspended solids in residual sludge is greater than 15g / L, the flow rate of the sludge return pump is 3 times the flow rate of the emulsification pump.

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