A device and method for in-situ carbonization of exocellular polymer of activated sludge

Abstract

The application discloses a device and a method for stripping active sludge extracellular polymer in-situ carbonization, which comprises an ultrasonic unit, an emulsifying pump and an emulsifying tank connected in sequence through pipelines, wherein the ultrasonic unit is provided with a feeding port, the emulsifying tank is provided with a discharging port, and a sludge backflow pump connected with the emulsifying tank and the emulsifying pump is further arranged. The device firstly disperses active sludge flocs by using ultrasonic waves, and then strips the active sludge extracellular polymer by using the strong shearing, friction and centrifugal force between the rotor and the stator of the high-speed rotating emulsifying pump, so that the purpose of stripping the extracellular polymer to release the carbon source under the premise of not damaging the metabolic activity of the sludge is achieved. The device can be applied to the treatment of residual sludge and nitrification liquid backflow sludge, and continuous treatment can be realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the sewage treatment technical field, more particularly to a method for in-situ carbonization of activated sludge extracellular polymer by ultrasonic combined with emulsification and stripping. BACKGROUND

[0002] At present, the activated sludge treatment process is mainly used in the urban sewage treatment plant in China, and the problem of low carbon-nitrogen ratio in the influent affecting the denitrification effect of the biological system exists in the operation process. The insufficient carbon source in the influent leads to low total nitrogen removal rate of the biological system, which has become the most difficult problem faced by the sewage treatment plant. At present, the urban sewage treatment plant in China mainly uses the method of adding carbon source (glucose, sodium acetate, methanol, and composite carbon source) to improve the denitrification effect of the process, which leads to a sharp increase in the cost of sewage treatment.

[0003] Extracellular polymer is an important component of activated sludge, which contains a large amount of organic matter such as protein and polysaccharide, and has high biological utilization potential. Stripping the extracellular polymer from the surface of activated sludge can be used as a supplementary carbon source for biological denitrification, providing a new idea for solving the problem of insufficient carbon source in the sewage treatment plant. Under the premise that the biological metabolic activity of the sludge is not damaged, the extracellular polymer is stripped from the surface of the sludge as a carbon source for biological denitrification process, realizing the in-situ carbonization of the extracellular polymer of activated sludge.

[0004] There are mainly two ways to apply the extracellular polymer stripping in-situ carbonization technology in engineering, which are the stripping and carbon release of residual sludge extracellular polymer and the stripping and carbon release of nitrification liquid reflux sludge extracellular polymer. The residual sludge stripping and carbon release process is to directly introduce the sludge carbon release process (acting on part or all of the secondary sedimentation tank reflux sludge) into the biochemical treatment system, and the released extracellular polymer and the sludge are directly refluxed into the biochemical reaction tank for utilization. This mode is suitable for various activated sludge processes with a secondary sedimentation tank.

[0005] The nitrification liquid reflux sludge extracellular polymer stripping and carbon release is another utilization mode, which is as follows: in the nitrification liquid reflux system from the aerobic tank to the anoxic tank of the A / O process, the extracellular polymer of the sludge is stripped to release organic matter, and the organic matter and the sludge with undamaged metabolic activity enter the anoxic tank together, and the denitrifying bacteria utilize the organic matter released by the extracellular polymer as an electron donor for biological denitrification reaction, realizing the in-situ carbon release and online utilization of the extracellular polymer of the sludge in the main process. The nitrification liquid reflux sludge carbon release mode is only suitable for the activated sludge process with nitrification liquid reflux system, such as A / O or A2 / O process, and is not suitable for the oxidation ditch process without nitrification liquid reflux system.

[0006] Extracellular polymeric substance (EPS) stripping carbon technology provides a new way to solve the problem of carbon source shortage in the denitrification process of wastewater treatment plant. However, how to strip EPS from the surface of sludge becomes the key to the application of the technology in practical engineering. At present, the methods for extracting EPS from activated sludge mainly include physical method, chemical method and biological method. The physical method includes centrifugation, heating and ultrasonic method, the chemical method mainly includes ion exchange resin method, NaOH method and EDTA method, and the biological method mainly uses specific enzymes to decompose EPS to release organic matter. Meanwhile, there are some combined extraction methods, such as ultrasonic-heating method, hot alkali method and ultrasonic centrifugation method. However, these methods are mainly used for laboratory research and are only suitable for small-scale and sequencing batch extraction of activated sludge EPS. For the continuous operation of practical engineering, the implementation of various methods is difficult and the cost is extremely high. At present, for the continuous flow system of practical engineering, the methods that can be used to strip EPS from activated sludge are only cyclone method or ultrasonic-cyclone method. However, the cyclone requires high inlet operating pressure, and it is difficult to operate and control, and the sludge carbon release effect is poor. SUMMARY

[0007] Therefore, the present application provides a method and device for stripping activated sludge by using ultrasonic combined with emulsification. First, the activated sludge flocs are dispersed into multiple small flocs by ultrasonic waves, and then the EPS is stripped by the strong shearing, friction and centrifugal force between the rotor and stator of the emulsification pump, so as to achieve the purpose of stripping EPS to release carbon source without damaging the metabolic activity of sludge.

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

[0009] Firstly, the present application provides a device for stripping EPS of activated sludge in situ carbon source, which comprises an ultrasonic unit, an emulsification pump and an emulsification tank connected in sequence by pipelines; the ultrasonic unit is provided with a feed inlet, and the emulsification tank is provided with a discharge outlet.

[0010] Preferably, the device further comprises a sludge backflow pump connected with the emulsification tank and the emulsification pump through pipelines.

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

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

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

[0014] The pipeline structure comprises a pipeline and an ultrasonic vibration rod arranged in the pipeline.

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

[0016] Further, in the box structure, when the ultrasonic vibration plate is arranged alone at the bottom, the liquid depth on the ultrasonic vibration plate is not more than 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 not more than 1.2 meters.

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

[0018] Preferably, a stirring device is arranged in the emulsification box, and the sludge residence time in the emulsification box is 10-20 min.

[0019] The application also provides a method for in-situ carbon source of exocellular polymer of activated sludge by using the device, and the activated sludge is nitrification liquid reflux sludge, which comprises the following steps:

[0020] The nitrification liquid reflux sludge enters the ultrasonic unit, is subjected to ultrasonic treatment, enters the emulsification pump, is subjected to treatment by the emulsification pump, enters the emulsification box, is subjected to treatment by the emulsification box, and then directly enters the anoxic tank.

[0021] The application also provides another method for in-situ carbon source of exocellular polymer of activated sludge by using the device, and the activated sludge is residual sludge, which comprises the following steps:

[0022] The residual sludge enters the ultrasonic unit, is subjected to ultrasonic treatment, enters the emulsification pump, is subjected to treatment by the emulsification pump, enters the emulsification box, is subjected to treatment by the emulsification box, is refluxed to the emulsification pump by a sludge reflux pump, then enters the emulsification box again, and finally the treated sludge is discharged from the emulsification box and enters the activated sludge biological reaction tank.

[0023] Further, when the residual sludge suspended solid concentration is 6-10 g / L, the sludge reflux pump flow is 1-1.5 times of the emulsification pump flow; when the residual sludge suspended solid concentration is 10-15 g / L, the sludge reflux pump flow is 1.5-2.0 times of the emulsification pump flow; and when the residual sludge suspended solid concentration is greater than 15 g / L, the sludge reflux pump flow is 3 times of the emulsification pump flow.

[0024] According to the above technical solution, compared with the prior art, the application discloses a device and a method for in-situ carbon source of exocellular polymer of activated sludge, which has the following beneficial effects:

[0025] The present application adopts the mode of ultrasonic combined with emulsification pump to strip the extracellular polymer of activated sludge, is suitable for large-scale sludge treatment of practical engineering, and meanwhile, the method is suitable for continuous flow activated sludge treatment, can realize continuous sludge treatment, and breaks the limitation that the traditional extracellular polymer extraction method can only extract in batches.

[0026] Compared with the carbon release method of the cyclone, the present application adopts the mode of ultrasonic combined with emulsification pump, has simple operation control, and has good extracellular polymer stripping and carbon release effect. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the provided drawings.

[0028] Figure 1 Figure 1 is a device structure diagram for stripping the extracellular polymer of activated sludge in situ carbonization by ultrasonic combined with emulsification;

[0029] Figure 2 Figure 2 is a layout structure diagram of the ultrasonic unit;

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

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

[0032] Figure 5 Figure 5 is a layout structure diagram of the ultrasonic unit of the pipeline structure;

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

[0034] The technical solutions of the present application will be described clearly and completely below in connection with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.

[0035] As shown in the accompanying drawings, Figure 1 The device for in-situ carbonization of activated sludge extracellular polymer by ultrasonic emulsion stripping includes an ultrasonic unit 1, an emulsion pump 2 and an emulsion tank 3 connected in sequence by pipelines. The ultrasonic unit 1 is provided with a feed inlet, and the emulsion tank 3 is provided with a discharge outlet. The emulsion pump 2 is a three-stage emulsion pump, and the sludge residence time in the emulsion tank is 10-20 min.

[0036] The device further includes a sludge backflow pump 4 connected with the emulsion tank 3 and the emulsion pump 2 by pipelines. The flow rate of the sludge backflow pump 4 is 0-3 times of that of the emulsion pump 2 (different flow rates are defined according to the source of activated sludge).

[0037] As shown in the accompanying drawings, Figure 2 and 5 The ultrasonic unit 1 adopts a tank structure or a pipeline structure.

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

[0039] The pipeline structure includes a pipeline 15 and an ultrasonic vibration rod 16 arranged in the pipeline. The ultrasonic vibration rod 16 is arranged at the axial line of the pipeline 15 and is powered by an external circuit. The circuit and the pipeline 15 are relatively sealed by a rubber ring or the like to avoid 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 tank structure, when the ultrasonic vibration plate 12 is arranged at the bottom alone, the liquid depth on the ultrasonic vibration plate 12 is not more than 0.6 meters. When the ultrasonic vibration plate 12 is arranged at both sides of the tank 11 along the water flow direction, the distance between the two ultrasonic vibration plates 12 is greater than 0.8 meters and not more than 1.2 meters.

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

[0043] The operating principle of this device is as follows: Excess sludge or nitrification liquor return sludge first enters the ultrasonic unit 1 through the sludge pump integrated into the excess sludge return system or nitrification liquor sludge return system. The cavitation effect of ultrasound breaks down the sludge flocs, breaking large flocs into smaller ones and loosening the floc structure, releasing a small amount of extracellular polymers from the surface of the sludge flocs into the water. Then, the sludge enters the emulsification pump 2, which is a three-stage rotor emulsification pump. The high-speed rotating rotor and stator exert strong shearing, friction, and centrifugal force to peel off and release the extracellular polymers from the surface of the activated sludge, dissolving them in the water. Since the suspended solids concentration of the nitrification liquor return sludge is low, typically 3-5 g / L, the sludge only needs to undergo one emulsification process after ultrasound. After passing through emulsification pump 2, the sludge enters the emulsification tank 3 and then flows out from the outlet. For the excess sludge, due to its high concentration, the sludge return pump 4, connected to the emulsification tank 3, is activated to transport the sludge from the emulsification tank 3 back to the inlet of the emulsification pump 2 for secondary emulsification. The higher the suspended solids concentration of the excess sludge, the greater the sludge return flow rate; the flow rate of the sludge return pump 4 is 1-3 times that of the emulsification pump 3. The core of this method and device is to utilize ultrasound and the emulsification pump to strip the extracellular polymers of activated sludge and release carbon sources. Simultaneously, precise control of the ultrasound intensity and the number of emulsification cycles is crucial to ensure that the metabolic activity of the sludge is not disrupted. Active bacteria in the sludge, along with the released organic matter, enter the anoxic tank. The sludge bacteria utilize the released organic matter as a carbon source for biological carbon and nitrogen processes. Essentially, this is the "self-sustaining" of activated sludge, achieving in-situ carbon source conversion of the extracellular polymers in the activated sludge.

[0044] Example 1

[0045] As attached Figure 3 As shown, the activated sludge is excess sludge. 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 excess sludge to the device described in Example 1 (the extracellular polymer stripping and carbon release device 9 in the figure). The excess sludge enters the ultrasonic unit 1 and is ultrasonically treated before entering the emulsification pump 2. After being treated by the emulsification pump 2, it enters the emulsification tank 3. After being treated by the emulsification tank 3, it is returned to the emulsification pump 2 by the sludge return pump 4 and then enters the emulsification tank 3 again. Finally, the treated sludge is discharged from the emulsification tank 3 and enters the activated sludge biological reactor 5.

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

[0047] Example 2

[0048] As attached Figure 4 As shown, the activated sludge is nitrified liquor return sludge. 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 nitrified liquor return pump 14 transports the nitrified liquor return sludge to the device described in Example 1 (the extracellular polymer stripping and carbon release device 9 in the figure). The nitrified liquor return sludge enters the ultrasonic unit 1 and is ultrasonically treated before entering the emulsification pump 2. 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 its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0050] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those 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 invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for in-situ carbon source conversion of extracellular polymers in activated sludge, characterized in that, The process utilizes an in-situ carbon source conversion device for the exogenous polymers of stripped activated sludge. The device comprises an ultrasonic unit, an emulsification pump, and an emulsification tank connected in sequence via pipelines. The ultrasonic unit is provided with an inlet, and the emulsification tank is provided with an outlet. The device also includes a sludge return pump, which is connected to the emulsification tank and the emulsification pump via a pipeline; The activated sludge is excess sludge. The method for in-situ carbon source removal of extracellular polymers from activated sludge includes the following steps: The remaining sludge enters the ultrasonic unit and is treated by ultrasound before entering the emulsification pump. After being treated by the emulsification pump, it enters the emulsification tank. After being treated by the emulsification tank, it is returned to the emulsification pump by the sludge return pump, and then enters the emulsification tank again. Finally, the treated sludge is discharged from the emulsification tank and enters the activated sludge biological reactor. Specifically, when the suspended solids concentration of the residual sludge is 6-10 g / L, the flow rate of the sludge return pump is 1-1.5 times that of the emulsification pump; when the suspended solids concentration of the residual sludge is 10-15 g / L, the flow rate of the sludge return pump is 1.5-2.0 times that of the emulsification pump; and when the suspended solids concentration of the residual sludge is greater than 15 g / L, the flow rate of the sludge return pump is 3 times that of the emulsification pump.

2. The method for in-situ carbon source conversion of extracellular polymers in activated sludge according to claim 1, characterized in that, The ultrasonic unit adopts a box structure or a pipe 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 arranged on both sides of the box along the water flow direction; The pipeline structure includes a pipeline and an ultrasonic vibrating rod placed inside the pipeline; The ultrasonic frequency of the ultrasonic vibrating plate or ultrasonic vibrating rod is 20-24kHz, and the ultrasonic energy density is 5-30 KJ / gMLSS.

3. The method for in-situ carbon source conversion of extracellular polymers in activated sludge according to claim 2, characterized in that, In the aforementioned box structure, when an ultrasonic vibration plate is arranged at the bottom alone, the liquid depth 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.

4. The method for in-situ carbon source conversion of extracellular polymers in activated sludge according to claim 1, wherein the emulsifying pump is a three-stage emulsifying pump.

5. The method for in-situ carbon source conversion of extracellular polymers in activated sludge according to claim 1, characterized in that, The emulsification tank is equipped with a stirring device, and the sludge retention time in the emulsification tank is 10-20 minutes.

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