Method for promoting aerobic sludge granulation by combining coagulation sedimentation and two-zone sedimentation tank

Abstract

The application discloses a method for promoting aerobic sludge granulation by combining coagulation sedimentation and a double-zone sedimentation tank, and relates to the technical field of wastewater treatment, which comprises the following steps: sewage is sequentially introduced into a coagulation sedimentation tank and a biochemical tank; effluent from the biochemical tank is introduced into a double-zone sedimentation tank; heavy sludge in the double-zone sedimentation tank is sent back to the biochemical tank; light sludge in the double-zone sedimentation tank is directly discharged; effluent in the double-zone sedimentation tank is discharged after reaching the standard; and the method is beneficial to improving sludge-water separation efficiency by combining the characteristics and defects of the coagulation tank sedimentation process with the advantages of the double-zone sedimentation tank, and is beneficial to strengthening biological denitrification and phosphorus removal by using mechanisms such as simultaneous nitrification and denitrification and biological mineralization.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and more specifically, relates to a method for promoting aerobic sludge granulation by combining coagulation sedimentation and a dual-zone sedimentation tank. Background Technology

[0002] The basic principle of coagulation is to add a coagulant to wastewater. Because the coagulant is an electrolyte, it forms flocs in the wastewater, neutralizing the charge of colloidal substances and causing them to settle. Coagulation and sedimentation can remove not only fine suspended particles from wastewater but also color, oil, microorganisms, nutrients such as nitrogen and phosphorus, heavy metals, and organic matter. When a coagulant is added to wastewater, the colloid's potential decreases or disappears, disrupting the stable state of the particles (called destabilization). The process by which destabilized particles aggregate into larger particles is called coagulation. Undestabilized colloids can also form large particles; this phenomenon is called flocculation. Different chemical agents can cause colloids to destabilize, coagulate, or flocculate in different ways. Based on the mechanism, coagulation can be divided into four types: compression of the electric double layer, adsorption neutralization, adsorption bridging, and precipitate trapping.

[0003] Aerobic granular sludge technology, as one of the most promising biotechnologies in wastewater treatment, offers advantages over traditional activated sludge technology, including compact structure, good settling performance, long biological retention time, tolerance to high organic loads and toxicity, and simultaneous nitrogen and phosphorus removal. Generally, the formation of aerobic granular sludge is a complex process involving physical, chemical, and biological processes. The mainstream view describes this process as bioaggregation caused by microbial self-coagulation under certain hydrodynamic conditions. Conditions proven to significantly contribute to aerobic granular sludge formation include selective pressure, organic load, the addition of metal cations, and the addition of coagulants or inert carriers. However, the long formation time and poor stability of aerobic granular sludge limit its application. Therefore, utilizing the residual coagulants and aggregated particles from the coagulation and sedimentation process to promote aerobic granular sludge formation is of great significance in overcoming the long start-up time of aerobic granular sludge processes and improving effluent quality. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for promoting aerobic sludge granulation by combining coagulation sedimentation and dual-zone sedimentation tanks. This method addresses the characteristics and defects of coagulation sedimentation processes and combines the advantages of dual-zone sedimentation tanks, thereby improving sludge-water separation efficiency and enhancing biological nitrogen and phosphorus removal by utilizing mechanisms such as simultaneous nitrification, denitrification, and biomineralization.

[0005] To achieve the above objectives, the present invention provides a method for promoting aerobic sludge granulation by combining coagulation sedimentation and a dual-zone sedimentation tank, comprising:

[0006] Wastewater enters the coagulation sedimentation tank and the biological treatment tank in sequence;

[0007] The effluent from the biological treatment tank enters a dual-zone sedimentation tank;

[0008] The heavy sludge in the dual-zone sedimentation tank is returned to the biological treatment tank;

[0009] The light sludge in the dual-zone sedimentation tank is discharged directly;

[0010] The effluent from the dual-zone sedimentation tank is discharged after meeting the standards.

[0011] Optionally, the dual-zone sedimentation tank includes a front zone and a rear zone. The bottom of the front zone is provided with a first sludge outlet, which is connected to the biological treatment tank. The bottom of the rear zone is provided with a second sludge outlet. The upper parts of the front zone and the rear zone are connected. The upper part of the rear zone is also provided with a first effluent outlet. The retention time of the front zone is 5-20 minutes, and the retention time of the rear zone is 20-120 minutes.

[0012] Optionally, the first sludge outlet is connected to the front of the biological treatment tank.

[0013] Optionally, the coagulation sedimentation tank includes a stirring zone and a sedimentation zone. The stirring zone is provided with an inlet and a coagulant inlet. The top of the stirring zone is connected to the top of the sedimentation zone, and the second outlet of the sedimentation zone is connected to the inlet of the biological treatment tank.

[0014] Optionally, the sedimentation time in the coagulation sedimentation tank is 5-20 minutes.

[0015] Optionally, at least one aeration device is installed in the biological treatment tank, and the organic load is controlled at 0.03-0.15 (kgCOD) / (kgMLVSS*d).

[0016] Optionally, the heavy sludge in the dual-zone sedimentation tank is returned to the biological treatment tank by steam stripping.

[0017] This invention provides a method for promoting aerobic sludge granulation by combining coagulation sedimentation and a dual-zone sedimentation tank, the beneficial effects of which are:

[0018] 1. This method uses the products of front-end coagulation and sedimentation to replace metal cations, and coagulants and inert carriers are used to promote sludge agglomeration and realize waste reuse.

[0019] 2. This method utilizes the biological selective pressure generated by the dual-zone sedimentation tank to separate sludge according to different weights;

[0020] 3. This method utilizes sludge according to its characteristics, recycles heavy sludge, promotes the improvement of sludge quality and granulation in the biological treatment tank, thereby improving sludge-water separation efficiency and enhancing biological nitrogen and phosphorus removal.

[0021] 4. In this method, the sewage passes through a coagulation sedimentation tank, a biological treatment tank, and a dual-zone sedimentation tank in sequence. The only difference is that a heavy sludge return pipe is installed at the front end of the dual-zone sedimentation tank and the biological treatment tank. This method can be achieved with simple modifications to the existing sewage treatment facilities, and the operating cost is low.

[0022] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0023] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the invention.

[0024] Figure 1 A schematic diagram of the apparatus used in a method for promoting aerobic sludge granulation by combining coagulation sedimentation and a dual-zone sedimentation tank according to an embodiment of the present invention is shown.

[0025] Explanation of reference numerals in the attached figures:

[0026] 1. Coagulation sedimentation tank; 2. Biological treatment tank; 3. Dual-zone sedimentation tank; 4. Front zone; 5. Rear zone; 6. First sludge outlet; 7. Second sludge outlet; 8. First effluent outlet; 9. Mixing zone; 10. Sedimentation zone; 11. Inlet; 12. Coagulant inlet; 13. Second effluent outlet. Detailed Implementation

[0027] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0028] This invention provides a method for promoting aerobic sludge granulation by combining coagulation sedimentation and a dual-zone sedimentation tank, comprising:

[0029] Wastewater enters the coagulation sedimentation tank and the biological treatment tank in sequence;

[0030] The effluent from the biological treatment tank enters the dual-zone sedimentation tank;

[0031] Heavy sludge from the dual-zone sedimentation tank is returned to the biological treatment tank;

[0032] Light sludge from the dual-zone sedimentation tank is discharged directly.

[0033] The effluent from the dual-zone sedimentation tank is discharged after meeting the standards.

[0034] Optionally, the settling time in the coagulation sedimentation tank is 5-20 minutes.

[0035] Specifically, this method for promoting aerobic sludge granulation combines the technological characteristics of coagulation sedimentation with the advantages of a dual-zone sedimentation tank. Wastewater is discharged into the coagulation sedimentation tank, and then from there into the biological treatment tank. Because the sedimentation time in the coagulation sedimentation tank is relatively short (5-20 minutes), the effluent after coagulation sedimentation carries more residual coagulant and particulate matter into the biological treatment tank. Sludge is then returned via steam stripping to ensure the integrity of the formed granular sludge, preventing its destruction. Finally, the effluent from the biological treatment tank... Water is discharged into a dual-zone sedimentation tank, where sludge of different weights is separated. The heavier sludge settles and is returned to the biological treatment tank, while the lighter sludge settles and is directly discharged as surplus sludge. The heavier sludge is composed of microorganisms with longer generations. As return sludge, it is beneficial for microbial denitrification, promotes the improvement of sludge quality in the biological treatment tank, and facilitates aerobic sludge granulation. The formation of aerobic granular sludge further improves the efficiency of sludge-water separation and enhances biological nitrogen and phosphorus removal through mechanisms such as simultaneous nitrification, denitrification, and biomineralization.

[0036] In a dual-zone sedimentation tank, sludge of different weights is generally considered to have a median diameter of 220 μm or larger as aerobic granular sludge, and a median diameter of less than 220 μm as flocculent sludge. Cultivating aerobic granular sludge involves gradually growing flocculent sludge into larger aerobic granular sludge particles. Common flocculent sludge typically has a median diameter of 50-80 μm. Generally, larger particle diameters are heavier; however, in this example, sludge weight is a relative concept. The sludge screening process in the dual-zone sedimentation tank is not an absolute separation of sludge particles by size, but rather a division of sludge into relatively heavy and relatively light sludge. Heavy sludge refers to sludge with a median diameter higher than that of the biological treatment tank, while light sludge refers to sludge with a median diameter lower than that of the biological treatment tank.

[0037] Optionally, the dual-zone sedimentation tank includes a front zone and a rear zone. The bottom of the front zone is provided with a first sludge outlet, which is connected to the biological treatment tank. The bottom of the rear zone is provided with a second sludge outlet. The upper parts of the front zone and the rear zone are connected. The upper part of the rear zone is also provided with a first effluent outlet. The retention time in the front zone is 5-20 minutes, and the retention time in the rear zone is 20-120 minutes.

[0038] Specifically, the dual-zone sedimentation tank is divided into a front zone and a rear zone, with the tops of the two zones interconnected. The residence time in the front zone is set at 5-20 minutes, and the residence time in the rear zone is set at 20-120 minutes. When the effluent from the biological tank enters the front zone, a preliminary sedimentation stage is achieved. A first sludge outlet is set at the bottom of the front zone. The heavier sludge formed after the preliminary sedimentation accumulates at the bottom of the front zone and is discharged back to the biological tank through the first sludge outlet. This is conducive to the formation of aerobic sludge granules in the biological tank. The effluent after sedimentation in the front zone enters the rear zone, where it continues to settle and decompose. The supernatant after sedimentation is discharged from the first outlet. In this way, the effluent from the first outlet meets the discharge standards after two sedimentation processes.

[0039] Optionally, the first sludge outlet is connected to the front of the biological treatment tank.

[0040] Specifically, the heavier sludge separated from the sedimentation in the front zone is returned to the biological treatment tank. The returned sludge enters the area near the inlet of the biological treatment tank, where it reacts with the effluent after coagulation and sedimentation. This utilizes the products of the front-end coagulation and sedimentation to replace metal cations, coagulants, and inert carriers to promote sludge aggregation, thereby achieving waste reuse. This eliminates the need for chemical dosing during the start-up phase of aerobic granular sludge technology. At the same time, the dual-zone sedimentation tank creates a "biological selective pressure" mechanism to promote the formation of aerobic granular sludge, achieving efficient wastewater treatment.

[0041] Optionally, the coagulation sedimentation tank includes a stirring zone and a sedimentation zone. The stirring zone is provided with an inlet and a coagulant inlet. The top of the stirring zone is connected to the top of the sedimentation zone, and the second outlet of the sedimentation zone is connected to the inlet of the biological treatment tank.

[0042] Specifically, the coagulant introduced into the mixing zone can be aluminum salts, iron salts, polymeric salts, etc., including but not limited to aluminum sulfate, ferrous sulfate, polyaluminum chloride, and polyaluminum sulfate.

[0043] Optionally, at least one aeration device is installed in the biological treatment tank, and the organic load is controlled at 0.03-0.15 (kgCOD) / (kgMLVSS*d).

[0044] Optionally, the heavy sludge in the dual-zone sedimentation tank is returned to the biological treatment tank by steam stripping.

[0045] Specifically, the sludge is returned by steam stripping to ensure the integrity of the resulting granular sludge. After the returned sludge enters the front end of the biological treatment tank, it is conducive to the denitrification of microorganisms, promotes the improvement of sludge quality in the biological treatment tank, and facilitates the granulation of aerobic sludge.

[0046] Example

[0047] like Figure 1 As shown, this invention provides a method for promoting aerobic sludge granulation by combining coagulation sedimentation and a dual-zone sedimentation tank, comprising:

[0048] Wastewater sequentially enters coagulation sedimentation tank 1 and biological treatment tank 2;

[0049] The effluent from biological treatment tank 2 enters dual-zone sedimentation tank 3;

[0050] The heavy sludge in the dual-zone sedimentation tank 3 is returned to the biological treatment tank 2;

[0051] The light sludge in the dual-zone sedimentation tank 2 is discharged directly;

[0052] The effluent from the dual-zone sedimentation tank 2 is discharged after meeting the standards.

[0053] In this embodiment, the dual-zone sedimentation tank 2 includes a front zone 4 and a rear zone 5. The bottom of the front zone 4 is provided with a first sludge outlet 6, which is connected to the biological treatment tank 2. The bottom of the rear zone 5 is provided with a second sludge outlet 7. The upper parts of the front zone 4 and the rear zone 5 are connected. The upper part of the rear zone 5 is also provided with a first effluent outlet 8. The retention time of the front zone 4 is 5-20 minutes, and the retention time of the rear zone 5 is 20-120 minutes.

[0054] In this embodiment, the first sludge outlet 6 is connected to the front of the biological treatment tank 2.

[0055] In this embodiment, the coagulation sedimentation tank 1 includes a stirring zone 9 and a sedimentation zone 10. The stirring zone 9 is provided with an inlet 11 and a coagulant inlet 12. The top of the stirring zone 9 is connected to the top of the sedimentation zone 10. The second outlet 13 of the sedimentation zone 10 is connected to the inlet of the biological treatment tank 2.

[0056] In one embodiment, the sedimentation time in the coagulation sedimentation tank 1 is 5-20 minutes.

[0057] In one embodiment, at least one aeration device is installed in the biological tank 2, and the organic load is controlled at 0.03-0.15 (kgCOD) / (kgMLVSS*d).

[0058] In one embodiment, the heavy sludge in the dual-zone sedimentation tank 3 is returned to the biological treatment tank 2 by air stripping.

[0059] In summary, this method, which combines coagulation sedimentation and a dual-zone sedimentation tank to promote aerobic sludge granulation, involves sequentially feeding wastewater into coagulation sedimentation tank 1 and biological treatment tank 2. The influent COD, ammonia nitrogen, total nitrogen, and total phosphorus concentrations are 600 mg / L, 40 mg / L, 50 mg / L, and 7 mg / L, respectively. Polyaluminum chloride is added as a coagulant in coagulation sedimentation tank 1, and the sedimentation time is set to 10-15 minutes. Additionally, an aeration device is added to the biological treatment tank, and the aeration rate is controlled at 0.05-0.08 (kg COD) / (kg MLVSS*d). The wastewater then undergoes sludge-water separation in the dual-zone sedimentation tank 2, with a retention time of 8-10 minutes in the initial zone and 40-50 minutes in the subsequent zone. Due to the effective coagulation sedimentation process... The sedimentation time in tank 1 is very short, so the water discharged from the second outlet 13 carries more residual coagulant and particulate matter. The cultivated aerobic sludge has a particle size (d50) greater than 220μm, which has a good denitrification and phosphorus removal effect. It mixes and reacts with the heavy sedimented sludge returned from the front zone 4, which promotes the improvement of sludge quality and facilitates the granulation of aerobic sludge in the biological treatment tank. In this way, the water discharged from the biological treatment tank 2 enters the dual-zone sedimentation tank 3, which can improve the sludge-water separation efficiency of the dual-zone sedimentation tank 3. By utilizing its simultaneous nitrification, denitrification, and biomineralization mechanisms, the effect of biological denitrification and phosphorus removal of wastewater is enhanced. This can ensure that the COD, ammonia nitrogen, total nitrogen, and total phosphorus of the effluent are 30mg / L, 0.5mg / L, 11mg / L, and 0.2mg / L, respectively.

[0060] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for promoting aerobic sludge granulation by combining coagulation sedimentation and a dual-zone sedimentation tank, characterized in that, The method includes: Wastewater enters the coagulation sedimentation tank and the biological treatment tank in sequence; The effluent from the biological treatment tank enters a dual-zone sedimentation tank; The heavy sludge in the dual-zone sedimentation tank is returned to the biological treatment tank; The light sludge in the dual-zone sedimentation tank is discharged directly; The effluent from the dual-zone sedimentation tank is discharged after meeting the standards. The dual-zone sedimentation tank includes a front zone and a rear zone. The bottom of the front zone is provided with a first sludge outlet, which is connected to the biological treatment tank. The bottom of the rear zone is provided with a second sludge outlet. The upper parts of the front zone and the rear zone are connected. The upper part of the rear zone is also provided with a first effluent outlet. The retention time of the front zone is 5-20 minutes, and the retention time of the rear zone is 20-120 minutes. The first sludge outlet is connected to the front of the biological treatment tank; The coagulation sedimentation tank includes a stirring zone and a sedimentation zone. The stirring zone is provided with an inlet and a coagulant inlet. The top of the stirring zone is connected to the top of the sedimentation zone. The second outlet of the sedimentation zone is connected to the inlet of the biological treatment tank.

2. The method for promoting aerobic sludge granulation by combining coagulation sedimentation and a dual-zone sedimentation tank according to claim 1, characterized in that, The sedimentation time in the coagulation sedimentation tank is 5-20 minutes.

3. The method for promoting aerobic sludge granulation by combining coagulation sedimentation and a dual-zone sedimentation tank according to claim 1, characterized in that, At least one aeration device is installed in the biochemical tank, and the organic load is controlled at 0.03-0.15 (kgCOD) / (kgMLVSS*d).

4. The method for promoting aerobic sludge granulation by combining coagulation sedimentation and a dual-zone sedimentation tank according to claim 1, characterized in that, The heavy sludge in the dual-zone sedimentation tank is returned to the biological treatment tank by steam stripping.

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