CN210764915U - Device for stripping and recycling of extracellular polymers from excess sludge - Google Patents

Abstract

A device for stripping and recycling extracellular polymers of excess sludge, the device comprises a sludge storage tank, the outlet of which is connected with an excess sludge pretreatment unit; the excess sludge pretreatment unit includes a dosing premix tank and hydrocyclone, in which the dosing premix tank is used to add surfactant to the sludge transported from the mud storage tank to separate organic impurities; the hydrocyclone is used for high-speed stirring. Sludge with surfactant; short-path anaerobic fermentation unit, including sludge anaerobic fermentation reactor; excess sludge dewatering unit, including sludge thickening tank and dewatering and drying equipment. The utility model effectively realizes the stripping of the extracellular polymer of the excess sludge while ensuring the microbial activity in the excess sludge; and realizes the conversion of the unusable carbon source in the excess sludge to the easily utilized high-value carbon source.

Description

Device for stripping and recycling of extracellular polymers from excess sludge

technical field

The utility model relates to the technical field of biological treatment of sewage sludge, in particular to a device for stripping and recycling extracellular polymers of excess sludge.

Background technique

A large amount of excess sludge is associated with the sewage treatment process. In the past five years, the average amount of excess sludge produced in the country is about 47.6 million tons per year (80% moisture content), and it is expected to reach nearly 53 million tons in 2020. The treatment and disposal costs usually account for It accounts for 30-40% of the total operating cost of sewage treatment. It is estimated that the national sludge treatment and disposal investment will reach 45-60 billion in 2020. Excess sludge contains a lot of organic matter, of which TCOD is about 780-980mg/gTSS, TN is about 20-60mg/gTSS, and TP is about 2.5-5mg/gTSS, which is a kind of waste that has the potential to be converted into useful resources. The extracellular polymer of excess sludge is the third largest component of microorganisms except cells and water, accounting for 50-90% of the total organic matter of excess sludge. It is mainly composed of proteins, polysaccharides and humic substances. It is divided into TB-EPS, LB-EPS and soluble EPS from the inside out. Except for TB-EPS, which is difficult to peel, the soluble and loosely combined EPS can be easily peeled off by physical and chemical methods.

With the promulgation of the National Pollutant Discharge Standard for Urban Sewage Treatment Plants in 2002, the maximum discharge concentration of total nitrogen has been raised, but most domestic water plants cannot meet the requirements. The key reason is that the C/N ratio of urban sewage in China is generally higher than Low, can not meet the demand of denitrification, generally need to supplement additional carbon source, but this not only increases the CO ₂ emissions of sewage plants but also increases the output of excess sludge. Through anaerobic fermentation, complex carbon sources in sludge can be converted into small molecular short-chain fatty acids, which can be used as efficient denitrifying carbon sources in sewage plants, and effective cracking of extracellular polymeric substances (EPS) in excess sludge. It is the key to improve sludge hydrolysis and subsequent biotransformation. At present, there are problems in sewage treatment plants such as huge output of sludge in sewage treatment plants, low degree of resource utilization, and difficulty in efficient pretreatment of excess sludge.

Utility model content

In view of this, the main purpose of the present invention is to provide a device for stripping and recycling extracellular polymers from excess sludge, in order to at least partially solve at least one of the above technical problems.

In order to achieve the above purpose, the present invention provides a device for stripping and recycling excess sludge extracellular polymer, the device includes a sludge storage tank, an excess sludge pretreatment unit, a short-range anaerobic fermentation unit and a residual sludge unit. Sludge dewatering unit, where:

The sludge storage tank, the outlet of which is connected with the excess sludge pretreatment unit, is used to store the input sludge to be treated;

Excess sludge pretreatment unit, including dosing pre-mixing tank and hydrocyclone, in which the dosing pre-mixing tank is used to add surfactant to the sludge transported from the mud storage tank to separate organic impurities; the hydrocyclone, For high-speed agitation of surfactant-added sludge in the dosing premix tank;

A short-range anaerobic fermentation unit, including a sludge anaerobic fermentation reactor, is used for anaerobic fermentation treatment of the sludge after high-speed separation by the hydrocyclone;

The excess sludge dewatering unit, including a sludge thickening tank and dewatering and drying equipment, is used to concentrate and dry the sludge after fermentation in the short-path anaerobic fermentation unit.

Wherein, the device further includes a secondary sedimentation tank, the secondary sedimentation tank is used for concentrating and returning activated sludge, and the outlet of the secondary sedimentation tank is connected to the sludge storage tank and the dosing premix tank in the excess sludge pretreatment unit.

Wherein, the top of the dosing premix tank is provided with a dosing port and a stirring device;

Wherein, the bottom of the mud storage tank is connected with the excess sludge dewatering unit.

Wherein, the sludge in the dosing premixing tank is transported into the hydrocyclone by a high-speed centrifugal pump, and the high-speed centrifugal pump and the hydrocyclone are combined to realize a high-speed hydrocyclone process;

Wherein, the top and bottom of the hydrocyclone are respectively connected with the dosing premixing tank, and a control valve is installed to form a backflow, which is used to ensure the required hydrocyclone circulation time.

Wherein, a stirring device is provided at the top of the sludge anaerobic fermentation reactor, and a temperature control kit, a pH sensor and/or a DO sensor are installed in the main body of the sludge anaerobic fermentation reactor.

Based on the above technical solutions, it can be known that the device for stripping and recycling excess sludge extracellular polymers of the present invention has at least one of the following beneficial effects compared to the prior art:

(1) While ensuring the microbial activity in the excess sludge, the stripping of the extracellular polymer in the excess sludge is efficiently achieved;

(2) Effectively reduce the output of excess sludge;

(3) Realize the conversion of difficult-to-use carbon sources in excess sludge to easy-to-use high-value carbon sources;

(4) It is possible to use excess sludge to ferment acid at medium and low temperature;

(5) When the raw water carbon source is insufficient to meet the carbon source demand of the denitrification and denitrification process, the fermentation product can be used as a supplementary carbon source to promote the removal of total nitrogen.

Description of drawings

1 is a schematic structural diagram of a device of the present invention for efficient stripping and recycling of extracellular polymers from excess sludge;

Fig. 2 is the flow chart of the method for efficient stripping and recycling of excess sludge extracellular polymer according to the present invention;

Figure 3 shows the characterization of the changes in the structure and composition of extracellular polymers before and after the pretreatment of excess sludge;

Fig. 4 is the characterization of the change of sludge rheological properties before and after pretreatment of excess sludge;

Fig. 5 is the accumulation characterization of acid production by anaerobic fermentation;

Figure 6 is the characterization of the concentration change of the excess sludge treated by this system.

In the above drawings, the meanings of the reference symbols are as follows:

1. Secondary sedimentation tank 2. Mud storage tank

3. Dosing premix tank 4. High-speed hydrocyclone

5. Sludge anaerobic fermentation reactor 6. Excess sludge dewatering unit

1.1. Secondary sedimentation tank sludge pump 1.2. Sludge inlet valve

2.1. Mixing device 2.2. Feeding mud pump for premixing tank

3.1. Dosing port 3.2. High-speed centrifugal pump

4.1. Cyclone sediment return valve 4.2. Hydrocyclone mud valve

4.4. Swirl sludge return valve

5.1. DO/pH detector 5.2. Sludge valve for anaerobic fermentation reactor

5.3. Heating and heat preservation control kit 5.4. Sludge pump

6.1. Sludge thickening tank feeding pump

Detailed ways

In order to make the purpose, technical solutions and advantages of the present utility model clearer, the present utility model will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

The utility model provides a method for effectively stripping extracellular polymer (EPS) of excess sludge, shortens the time for biological conversion of complex carbon sources in excess sludge, and improves the conversion rate of excess sludge to produce high-value products.

Specifically, a device for stripping and recycling excess sludge extracellular polymers, the device includes a sludge storage tank, an excess sludge pretreatment unit, a short-range anaerobic fermentation unit and an excess sludge dewatering unit, wherein:

The sludge storage tank, the outlet of which is connected with the excess sludge pretreatment unit, is used to store the input sludge to be treated;

Excess sludge pretreatment unit, including dosing pre-mixing tank and hydrocyclone, in which the dosing pre-mixing tank is used to add surfactant to the sludge transported from the mud storage tank to separate organic impurities; the hydrocyclone, For high-speed agitation of surfactant-added sludge in the dosing premix tank;

A short-range anaerobic fermentation unit, including a sludge anaerobic fermentation reactor, is used for anaerobic fermentation treatment of the sludge after high-speed separation by the hydrocyclone;

The excess sludge dewatering unit, including a sludge thickening tank and dewatering and drying equipment, is used to concentrate and dry the sludge after fermentation in the short-path anaerobic fermentation unit.

Wherein, the device further includes a secondary sedimentation tank, the secondary sedimentation tank is used for concentrating and returning activated sludge, and the outlet of the secondary sedimentation tank is connected to the sludge storage tank and the dosing premix tank in the excess sludge pretreatment unit.

Wherein, the top of the dosing premix tank is provided with a dosing port and a stirring device;

Preferably, the bottom of the mud storage tank is connected with the excess sludge dewatering unit.

Wherein, the sludge in the dosing premixing tank is transported into the hydrocyclone by a high-speed centrifugal pump, and the high-speed centrifugal pump and the hydrocyclone are combined to realize a high-speed hydrocyclone process;

Preferably, the top and bottom of the hydrocyclone are respectively connected to the dosing premix tank and a control valve is installed to form a backflow, so as to ensure the required hydrocyclone circulation time.

Wherein, a stirring device is provided at the top of the sludge anaerobic fermentation reactor, and a temperature control kit, a pH sensor and/or a DO sensor are installed in the main body of the sludge anaerobic fermentation reactor.

The technical solutions of the present utility model will be described in further detail below with reference to the accompanying drawings and embodiments.

As shown in Figure 1, the present invention provides a device for efficient stripping and recycling of extracellular polymers from excess sludge, the device includes a secondary sedimentation tank 1, a mud storage tank 2, a dosing premix tank 3, High-speed centrifugal pump 3.2, hydrocyclone 4, sludge anaerobic fermentation reactor 5, excess sludge dewatering unit 6. Among them, an excess sludge pretreatment unit and a short-range anaerobic fermentation unit are added between the sludge storage tank 2 and the excess sludge dewatering unit 6. The sludge pretreatment unit consists of a dosing premix tank 3, a high-speed centrifugal pump 3.2 and a hydrocyclone. The sludge storage tank 2 is connected with the dosing premixing tank 3 and the residual sludge dewatering unit 6 respectively. The chemical dosing premixing tank 3 is connected with the high-speed hydrocyclone 4, the residual sludge anaerobic device through the high-speed centrifugal pump 3.2 The fermentation reactor 5 and the excess sludge dewatering unit 6 are connected in sequence. The top of the dosing premixing tank 3 is provided with a dosing port 3.1 and a stirring device. The dosing premixing tank 3 is connected to the mud storage tank 2 through the mud feeding pump 2.2, and is connected to the secondary sedimentation tank through the mud feeding valve 1.2 and the water inlet pipe. It is connected to the hydrocyclone 4 through a high-speed centrifugal pump 3.2. The high-speed hydrocyclone process is realized by the combination of the high-speed centrifugal pump 3.2 and the hydrocyclone 4. The top and bottom of the hydrocyclone 4 are respectively connected with the dosing premixing tank 3, and control valves 4.1 and 4.4 are installed to form backflow to ensure all The required hydrocyclone circulation time, the hydrocyclone 4 is respectively connected with the dosing premix tank 3 and the sludge anaerobic fermentation reactor 5 through a high-speed centrifugal pump 3.2 and a sludge discharge pipe valve 4.2. The top of the sludge anaerobic fermentation reactor 5 is provided with a stirring device, the main body of the reactor is equipped with the temperature control kit 5.3, the reactor is equipped with pH and DO sensors 5.1, and the bottom of the reactor is equipped with a sludge discharge valve 5.2 and a thickening tank feeding pump 5.4 and the remaining The sludge dewatering unit 6 is connected.

As shown in Figure 2, the present utility model simultaneously provides the operation process of applying the method for realizing the efficient stripping and recycling of extracellular polymers of excess sludge:

(1) Inject the remaining sludge in the secondary sedimentation tank into the sludge storage tank for temporary storage, the temporary storage time is 1-3 days, open the sludge inlet valve and sludge inlet pump, and transfer the sludge in the sludge storage tank and the sludge imported from the secondary sedimentation tank. Injected into the dosing pre-mixing tank according to the proportion, and mixed evenly by stirring; in this step, the residual sludge in the dosing tank is mixed by the temporarily stored sludge in the mud storage tank and the imported sludge in the secondary sedimentation tank according to the ratio of 1:1 made. The sludge in the sludge storage tank of a municipal sewage treatment plant in the north is mixed with the sludge imported from the secondary sedimentation tank to form a surplus sludge head of 15-18g/L, which is added to the pre-mixing tank for dosing, and the stirring device and dissolved oxygen control are turned on to adjust the dissolved oxygen to Between 0.05-1.0mg/L and pH 6.5-8.0.

(2) According to the sludge concentration of the excess sludge mixed in proportion in the dosing tank, add the surfactant, and fully stir it evenly; in this step, according to the proportion of the excess sludge mixed in the dosing tank Sludge concentration, add 0.005-0.1 g/g TSS of the surfactant. Use the concentration of 23-25% rhamnolipid as the surface active agent, the dosage is 0.34 ~ 6.8g/L, turn on the stirring device to adjust the speed, and mix the sludge with the rhamnosus under the premise of producing as few bubbles as possible. The sugar and fat are mixed well.

(3) Open the high-speed centrifugal pump, the swirl sludge return valve, and the swirl sludge return valve, so that the excess sludge treated with the biosurfactant enters the hydrocyclone at a high speed and continues to swirl for multiple cycles; in this step In the process, the excess sludge treated with biosurfactant enters the hydrocyclone at high speed and continues to circulate for multiple cycles, lasting 0.5 to 20 minutes. The main principle is to use the physical action of high-speed hydrocyclone to make the biological Surfactant-solubilized extracellular polymers of excess sludge are quickly stripped from excess sludge cells and sludge flocs, and converted into dissolved organic matter that is more easily utilized by fermentation and acid-producing bacteria.

(4) Open the sludge discharge valve of the hydrocyclone, then close the cyclone sludge return valve and the cyclone sediment return valve, inject the pretreated excess sludge into the excess sludge anaerobic fermentation reactor, and pass The temperature control kit and pH and DO sensors monitor and control the operating conditions and parameters of the fermentation system; in step (4), inject the pretreated excess sludge into the excess sludge anaerobic fermentation reactor, and ferment for 2- 10d, and monitor and control the temperature and other parameters of the fermentation system through the temperature control kit and pH and DO sensors, wherein the temperature is controlled at 25-40°C, the pH is 6.5-8.0, and the DO is 0.05-1.0;

(5) Open the sludge discharge valve and sludge discharge pump of the anaerobic fermentation reactor, and discharge the fermentation sludge in the anaerobic fermentation reactor while leaving the seed sludge to prepare for the sequencing batch sludge anaerobic fermentation.

The fermentation time was adjusted by measuring the production of short-chain fatty acids during the anaerobic fermentation of sludge. Taking the residual sludge of a city sewage treatment plant in the north treated by the system of the utility model as an example, the optimum fermentation time is controlled at 3d.

The specific implementation cases are as follows:

The residual sludge used in the specific experiment is the residual sludge of municipal sewage treatment in a sewage treatment plant in the north (TCOD=780-980mg/gTSS, TN=20-60mg/gTSS, TP=2.5-5mg/gTSS). The effective volume is 60L, the power of the high-speed centrifugal pump is 50HZ, the speed is 3000r/min, the effective volume of the anaerobic fermentation reactor is 30L, and the excess sludge is fermented by sequencing batch, inoculated with 10-15% anaerobic activated sludge , the SRT in the fermentation system is 3-5d. The specific operation process and operation effect are as follows:

(1) Inject the remaining sludge from the secondary sedimentation tank into the sludge storage tank for temporary storage for 1 to 3 days, open the sludge inlet valve and the sludge inlet pump, and mix the sludge in the sludge storage tank and the secondary sedimentation tank inlet sludge at a ratio of 1:1. The residual sludge head of about 17000mg/L is mixed and mixed in proportion to add the dosing pre-mixing tank, turn on the stirring device and the dissolved oxygen control, and adjust the dissolved oxygen to about 0.3 mg/L and the pH of about 6.8.

(2) According to the sludge concentration of the excess sludge mixed in proportion in the dosing tank, add rhamnolipid with a concentration of 0.34-6.8 g/L. Turn on the stirring device to adjust the speed, and fully stir the mixed sludge and rhamnolipid under the premise of generating as few bubbles as possible.

(3) Open the high-speed centrifugal pump, swirling sludge return valve, and swirl sediment return valve, so that the excess sludge treated with biosurfactant enters the hydrocyclone at a high speed and continues to swirl for 0.5 to 20 minutes.

(4) Open the sludge discharge valve of the hydrocyclone, then close the cyclone sludge return valve and the cyclone sediment return valve, and inject the pretreated excess sludge into the excess sludge anaerobic fermentation reactor for fermentation for 3 days, The operating conditions and parameters of the fermentation system are monitored and controlled through the temperature control kit and pH and DO sensors: the temperature is controlled at about 35 °C, the pH is about 6.8, and the DO is about 0.3 mg/L;

(5) Open the sludge discharge valve and sludge discharge pump of the anaerobic fermentation reactor, discharge the fermentation sludge in the anaerobic fermentation reactor while leaving the seed sludge, enter the sludge dewatering unit through the sludge discharge pipe, and pass the concentration filter press The fermentation broth is recovered to extract short-chain fatty acids, or the press filtrate is directly returned to the denitrification process of sewage treatment as a carbon source for denitrification of sewage.

The utility model is used to treat the surplus sludge of the urban sewage treatment plant, the pretreated sludge has an accumulation concentration of 2500mg/L of short-chain fatty acids through anaerobic fermentation, and the conversion rate is 240mg/gVSS; then the fermented sludge is passed through the sewage treatment plant. In the dewatering unit, the TSS of the excess sludge decreased by about 17%, and the recovery rate of short-chain fatty acids was about 3100 mg/L.

The technical principle of the present utility model is as follows:

The extracellular polymer of excess sludge is the third largest component of microorganisms except cells and water, accounting for about 70% of the total organic matter of excess sludge, mainly composed of protein, polysaccharide and humus. In terms of spatial structure, it is divided into tightly bound extracellular polymer (TB-EPS), loosely bound extracellular polymer (LB-EPS) and soluble extracellular polymer (Soluble EPS), except TB-EPS. In addition to being more difficult to peel, the soluble and loosely bound EPS can be easily peeled off by physical and chemical methods. Biosurfactant and high-speed hydrocyclone can effectively realize the cracking and dissolving of extracellular polymers, and will not cause a lot of rupture damage to active microbial cells within the range of conditions set in the present utility model, and the biological activity is ensured while stripping EPS. , which is beneficial to the biomass maintenance in the subsequent fermentation process. During the pretreatment process, the structure and composition of EPS changed, as shown in Table 1 and Figure 3. Figure 3 shows the TEM images of excess sludge before and after biosurfactant treatment coupled with high-speed hydrocyclone pretreatment. It shows that the pretreatment process can effectively strip the extracellular polymer of the excess sludge (indicated by the arrow in the figure). Among them, a, c are the original residual sludge; b, d are the residual sludge after pretreatment. Under the solubilization effect of biosurfactants and the physical separation of hydrocyclone, more loose EPS was exfoliated to become soluble EPS and converted into dissolved organic matter (DOM). , the rheological properties of the pretreated excess sludge in the present invention are significantly improved, and the sludge viscosity and viscoelasticity parameters show a significant downward trend, as shown in Figure 4. Figure 4 shows the changes in the rheological properties of excess sludge before and after pretreatment, which significantly shows that the pretreatment method coupled with biosurfactants and high-speed hydrocyclone improves the rheology of excess sludge: reduces viscosity and viscoelasticity. Among them, (a, b) is the viscosity change curve, (c, d) is the viscoelasticity change curve; (a, c) is the original residual sludge, (b, d) is the residual sludge after pretreatment. This is not only conducive to the further stripping of extracellular polymers from sludge, but also to the mass transfer process during anaerobic fermentation.

After the extracellular polymer is stripped, the excess sludge enters the anaerobic fermentation reactor for acid-producing fermentation, which is mainly the process of metabolizing complex macromolecular organic matter into small-molecule organic matter by anaerobic fermentation acid-producing bacteria. The exfoliation and dissolution of the exopolymer effectively enhanced the microbial transformation. By controlling pH, DO, temperature and other conditions, the environment is conducive to the reproduction of fermentative acid-producing bacteria and inhibits the growth of methanogenic bacteria, which can promote acid-producing accumulation. The results of acid-producing fermentation using the utility model are shown in Figure 5. Figure 5 shows that a large amount of short-chain fatty acids accumulated in the process of pretreatment and anaerobic fermentation of excess sludge, and the highest acid-producing accumulation of anaerobic fermentation after extracellular polymer stripping was more than 3 times that of the original excess sludge. . Among them, O: original residual sludge, P: pretreated residual sludge, F: anaerobic fermentation sludge. After the excess sludge has undergone the pretreatment and anaerobic fermentation, the organic matter itself is more fully utilized and converted into small molecular organic compounds such as short-chain fatty acids that are more easily utilized by microorganisms, so the utility model can effectively reduce the amount of sludge. , the results are shown in Figure 6. Figure 6 shows that the extracellular polymer stripping of excess sludge can effectively reduce the amount of sludge. Among them, B3S1, BSS2, B3S3, and B3S4 are marked as residual sludge pretreatment methods.

Table 1. Changes in the structural composition of extracellular polymers after pretreatment of excess sludge to exfoliation and anaerobic fermentation

The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present utility model should be included within the protection scope of the present utility model.

Claims (7)

1. The device for stripping and recycling the extracellular polymers in the excess sludge is characterized by comprising a sludge storage tank, an excess sludge pretreatment unit, a short-range anaerobic fermentation unit and an excess sludge dehydration unit, wherein:

the outlet of the sludge storage tank is connected with the residual sludge pretreatment unit and is used for storing the input sludge to be treated;

the residual sludge pretreatment unit comprises a dosing premixing tank and a hydrocyclone, wherein the dosing premixing tank is used for adding a surfactant to sludge conveyed from the sludge storage tank and separating organic impurities; the hydrocyclone is used for stirring the sludge added with the surfactant in the dosing premixing tank at a high speed;

the short-distance anaerobic fermentation unit comprises a sludge anaerobic fermentation reactor and is used for carrying out anaerobic fermentation treatment on the sludge subjected to high-speed separation treatment by the hydrocyclone;

and the residual sludge dewatering unit comprises a sludge concentration tank and a dewatering and drying device and is used for concentrating and drying the sludge after the short-range anaerobic fermentation unit performs fermentation treatment.

2. The apparatus according to claim 1, further comprising a secondary sedimentation tank for concentrating and refluxing the activated sludge, wherein an outlet of the secondary sedimentation tank is connected with the sludge storage tank and the dosing premixing tank in the residual sludge pretreatment unit.

3. The device of claim 1, wherein a dosing port and a stirring device are arranged at the top of the dosing premixing tank.

4. The apparatus according to claim 1, wherein the bottom of the sludge storage tank is connected to a residual sludge dewatering unit.

5. The device of claim 1, wherein the sludge in the dosing premix tank is delivered to a hydrocyclone by a high-speed centrifugal pump, and the high-speed centrifugal pump and the hydrocyclone are combined to realize a high-speed hydrocyclone process.

6. The apparatus of claim 1, wherein the top and bottom of the hydrocyclone are connected to a dosing premix tank and a control valve is added to form a backflow for ensuring a desired hydrocyclone cycle time.

7. The device of claim 1, wherein a stirring device is arranged at the top of the anaerobic sludge fermentation reactor, and a temperature control kit, a pH sensor and/or a DO sensor are/is additionally arranged in the main body of the anaerobic sludge fermentation reactor.

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