In-situ rapid expansion method of granular sludge

Abstract

The present application relates to a kind of in-situ rapid expansion cultivation methods of granular sludge, including fluidized bed reaction system and granular sludge enrichment system, the fluidized bed reaction system includes the reaction zone and feed zone that are interconnected, the feed zone includes water inlet, backflow water inlet, discharge port and dosing port, the reaction zone is located in the feed zone, and the granular sludge enrichment system is arranged in the reaction zone.This method can be used in wastewater decarburization denitrification phosphorus removal treatment, using the crystallization / precipitation of metal cation and phosphate, and the characteristics of metal cation and activated sludge with different charges, respectively as the crystal nucleus of granular sludge agglomeration and the intrinsic driving force of agglomeration growth, cultivate biological granular sludge in-situ rapidly in wastewater treatment process, with higher practicability and industrial value.

Description

A rapid in-situ propagation method for granular sludge Technical Field

[0001] This invention relates to wastewater treatment technology, specifically to an in-situ rapid propagation method for granular sludge. Background Technology

[0002] In recent years, anammox technology has become a promising new biological nitrogen removal process due to its advantages such as low oxygen supply energy consumption, no need for organic carbon sources, high volumetric loading, and low sludge production. However, the long generation cycle and sensitivity to environmental conditions of anammox bacteria greatly limit the widespread adoption of this technology. Granulation of anammox sludge can effectively overcome unfavorable environmental conditions and prevent the loss of anammox microorganisms. Anammox bacteria can aggregate and grow into granular sludge through the secretion of extracellular polymeric substances (EPS) and quorum sensing, but this process is time-consuming, often requiring more than six months. The initially formed sludge particles are not dense enough and easily disintegrate under aeration, stirring, or hydraulic shearing. Sludge particles formed solely by the aggregation of anammox bacteria have low density, and the nitrogen gas produced during anammox and denitrification processes adheres to the surface of the sludge particles, further exacerbating the floating and loss of anammox granular sludge. Summary of the Invention

[0003] The purpose of this invention is to overcome the problems of slow formation and aggregation speed in existing anaerobic ammonia oxidation granular sludge cultivation, and to provide an in-situ rapid expansion cultivation method for granular sludge. By controlling the operating parameters of the granular sludge enrichment unit, the aggregation and enlargement of granular sludge can be controlled. On this basis, the effluent weir is used to discharge water from both sides, reducing the unit width effluent flow rate and avoiding excessive effluent velocity in local areas that would carry away the granular sludge, thus retaining the granular sludge in the system as much as possible.

[0004] The method provided by this invention can simultaneously remove carbon, nitrogen, and phosphorus from wastewater, while utilizing the crystallization / precipitation formed by metal cations and phosphates, and the different charges carried by metal cations and activated sludge, to serve as the crystal nuclei and internal driving force for granular sludge aggregation, thereby forming corresponding types of granular sludge. This achieves the beneficial effect of rapidly cultivating biochemical granular sludge in situ during the wastewater treatment process.

[0005] The specific plan is as follows:

[0006] A method for in-situ rapid expansion and cultivation of granular sludge includes a fluidized bed reaction system and a granular sludge enrichment system. The fluidized bed reaction system includes a reaction zone and a feeding zone that are interconnected. The feeding zone includes an inlet, a return inlet, a discharge outlet, and a dosing outlet. The reaction zone is located above the feeding zone, and the granular sludge enrichment system is set up in the reaction zone.

[0007] The granular sludge enrichment system includes a sludge hopper, a lifting multi-stage agitator, and a geared motor. The sludge hopper is inverted conical with an open top and a granular sludge outlet at the bottom. The lifting multi-stage agitator is located inside the sludge hopper, and its central shaft is connected to the geared motor that drives its rotation. The geared motor operates at a variable frequency to control the upward flow velocity of the water in the sludge hopper at 5-30 mm / s, thereby controlling the agglomeration and enlargement of the granular sludge in the sludge hopper.

[0008] A effluent weir is provided at the top edge of the reaction zone, with the lowest point of the effluent weir being higher than the highest point of the sludge hopper to prevent granular sludge from being lost with the overflow water; an aeration system is also provided at the bottom of the reaction zone, located outside and below the granular sludge enrichment system to prevent the hydraulic turbulence generated by aeration from disrupting the hydraulic flow field within the granular sludge enrichment system.

[0009] Furthermore, an internal reflux pipe inlet is provided at the bottom of the reaction zone, below the sludge hopper, and the internal reflux pipe is connected to the feed zone via a reflux pump.

[0010] Furthermore, the aeration system adjusts the aeration rate in the reaction zone to control the dissolved oxygen concentration in the area above the internal return pipe to be between 0.1 and 5.0 mg / L.

[0011] Furthermore, the aeration system controls the dissolved oxygen concentration in the area above the internal return pipe to be between 0.1 and 1.5 mg / L to obtain anaerobic ammonia oxidation granular sludge. The anaerobic granular sludge can be cultivated under non-aeration conditions.

[0012] Furthermore, the aeration system controls the dissolved oxygen concentration in the area above the internal return pipe to be between 1.5 and 5.0 mg / L in order to obtain aerobic granular sludge.

[0013] Furthermore, the reaction zone is connected to a pH meter and linked with a dosing device, thereby controlling the pH value in the reaction zone between 6.5 and 8.5, preferably between 7.5 and 8.0.

[0014] Furthermore, the lifting multi-stage agitator is provided with agitator blades whose length gradually decreases from top to bottom, and the number of agitator blades is two or more, and the central axis of the lifting multi-stage agitator coincides with the axis of symmetry of the mud hopper.

[0015] Furthermore, the bottom of the sludge hopper is circular, preferably with a radius of 5-30 cm, and the bottom is connected to the granular sludge outlet located outside the fluidized bed reaction system.

[0016] Furthermore, the top of the reaction zone is an annular opening, the effluent weir is concentric with the annular opening at the top of the reaction zone, and the orthographic projection of the effluent weir is located inside the mud hopper opening.

[0017] Furthermore, the outlet of the weir is triangular, and water flows out from both sides of the weir channel.

[0018] Beneficial effects:

[0019] In this invention's in-situ rapid expansion method for granular sludge, the type and particle size of the granular sludge can be controlled. A granular sludge hopper divides the traditional fluidized bed into a pollutant removal zone and a granular sludge expansion zone. The pollutant removal zone primarily utilizes activated sludge to remove COD, ammonia nitrogen, and total nitrogen from wastewater, or uses chemical precipitation / crystallization to remove total phosphorus. The removal of COD, ammonia nitrogen, and total nitrogen pollutants with activated sludge causes the activated sludge to proliferate. This proliferated activated sludge rises with the water flow to the granular sludge expansion zone. Under the dual hydraulic conditions of a multi-stage lifting impeller and the fluidized bed's own upward flow velocity, the activated sludge is concentrated in the granular sludge expansion zone. Simultaneously, the readily reacting phosphates in the wastewater with calcium... 2+ Mg 2+ The crystallization properties of metal cations can be utilized to promote the binding, aggregation, and growth of negatively charged activated sludge with these cations by adjusting the pH of the granular sludge expansion zone or by adding trace amounts of metal cations. Adjusting the pH in the expansion zone further promotes the formation of fine crystals from phosphates and cations aggregated by the activated sludge. The positive charge of the metal cations attracts the aggregation of negatively charged activated sludge. The outer ring of these small crystals, formed by cations and activated sludge, is also negatively charged, attracting other cations to aggregate. These charged cations then further attract activated sludge to aggregate, and this process repeats, promoting the aggregation of activated sludge into granular sludge. The initially formed fine crystals act as "nuclei" for activated sludge aggregation, inducing further aggregation and growth of the granular sludge. The crystallization of metal cations and phosphates further optimizes the specific gravity of the particles, improving the settling performance of the sludge particles and preventing them from being too light and being lost with the effluent.

[0020] The layout of peripheral aeration and central effluent effectively promotes the aggregation of activated sludge in the sludge hopper area, creating a favorable hydraulic flow field for sludge aggregation and growth. The internal reflux design of the reaction system further optimizes the dissolved oxygen distribution within the system, providing a good foundation for the removal of COD, ammonia nitrogen, and total nitrogen.

[0021] Furthermore, in the in-situ rapid expansion method for granular sludge of the present invention, after the granular sludge is formed, it will physically stratify according to its particle size. Larger particles will settle at the bottom of the sludge hopper, while smaller particles will be continuously expanded and grown in a fluidized state above the sludge hopper under the lifting action of a multi-stage stirring paddle. Periodically discharging the larger granular sludge particles from the bottom of the sludge hopper can yield superior granular sludge seed material. Attached Figure Description

[0022] To more clearly illustrate the technical solution of the present invention, the accompanying drawings will be briefly described below. Obviously, the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention.

[0023] Figure 1 is a schematic diagram of the device structure provided in one embodiment 1 of the present invention. Detailed Implementation

[0024] Preferred embodiments of the present invention will now be described in more detail. While preferred embodiments of the present 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. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products. In the following embodiments, unless otherwise specified, "%" refers to weight percentage, and "parts" refers to parts by weight.

[0025] Example 1

[0026] As shown in Figure 1, an in-situ rapid expansion method for granular sludge includes a fluidized bed reaction system and a granular sludge enrichment system, with the granular sludge enrichment system located inside the fluidized bed reaction system.

[0027] Specifically, the fluidized bed reaction system includes an interconnected reaction zone and a feed zone. The reaction zone is located above the feed zone. The feed zone includes a water inlet, a reflux water inlet, a discharge port, and a chemical dosing port. The water inlet is the wastewater inlet for the entire system. The chemical dosing port is used to add necessary chemical agents to the system. The reflux water inlet and the discharge port are combined and connected to the feed zone. The reflux water inlet is used to realize the water reflux within the reaction zone. The discharge port is used for staged discharge or emptying of system materials.

[0028] To achieve the above objectives, the dosing port is located on the side wall of the feeding zone, the water inlet is generally located below the feeding zone, and the discharge port is located at the bottom of the feeding zone, with its opening and closing controlled by a valve.

[0029] Wastewater and reagents are mixed in the feeding zone and then enter the reaction zone located above for reaction. In this invention, the main processes are anaerobic ammonia oxidation and struvite crystallization. The reaction process is implemented with reference to "A method for rapidly cultivating anaerobic ammonia oxidation granular sludge" (ZL202211068168.7). For example, the total nitrogen concentration of the raw water influent is controlled at 300-600 mg / L, and reactants that match the anions and cations of the raw water are added, such as magnesium chloride, to form magnesium ammonium phosphate crystals.

[0030] The granular sludge enrichment system includes a sludge hopper, a lifting multi-stage agitator, and a geared motor. The sludge hopper is inverted conical with an open top and a granular sludge outlet connected to the bottom. The lifting multi-stage agitator is located inside the sludge hopper, and its central shaft is connected to the geared motor that drives its rotation. The geared motor operates at a variable frequency to control the upward flow velocity of the water in the sludge hopper at 5-30 mm / s, thereby controlling the agglomeration and enlargement of the granular sludge in the sludge hopper.

[0031] Because the granular sludge enrichment system has an inverted conical sludge hopper built into the central area, acting as a "rectifier" for the rising water flow, the rising water flow rises from the periphery of the fluidized bed. The effluent weir located in the middle causes the water flowing from the periphery of the fluidized bed to converge towards the center of the fluidized bed at the opening of the sludge hopper, thus forming a "peripheral inflow, central outflow" hydraulic field in the fluidized bed. This creates a unique "peripheral inflow, central outflow" hydraulic condition, which causes the activated sludge inside the fluidized bed to fall into the sludge hopper area and form a second fluidization zone under the action of the lifting multi-stage mixer, thereby achieving the concentration of biological sludge. At the same time, with the help of trace amounts of fine struvite crystals (magnesium ammonium phosphate crystals), the activated sludge achieves efficient agglomeration and granulation.

[0032] A effluent weir is provided at the top edge of the reaction zone, with the lowest point of the effluent weir higher than the highest point of the sludge hopper to prevent particulate sludge from being lost with the overflow water. Preferably, the effluent weir has water flowing out from both sides to reduce the unit width of the effluent flow rate, avoid excessive effluent velocity in local areas that would carry sludge out, and retain the sludge in the fluidized bed reaction system as much as possible.

[0033] Preferably, the top of the reaction zone is an annular opening, the effluent weir is concentric with the annular opening at the top of the reaction zone, and the center projection of the effluent weir is located inside the mud hopper opening. The outlet of the effluent weir is triangular, resulting in optimal water discharge.

[0034] An aeration system is also installed at the bottom of the reaction zone, located in the area below and outside the granular sludge enrichment system. Aeration provides oxygen to the activated sludge and creates the hydraulic conditions for complete mixing to rapidly adjust the pH value.

[0035] Example 2

[0036] This embodiment, based on Embodiment 1, controls the dissolved oxygen concentration in the area above the internal return intake by adjusting the aeration system. Different types of microorganisms have different dissolved oxygen requirements; therefore, different types of granular sludge can be selectively cultivated by adjusting the aeration rate. Specifically:

[0037] If it is an expansion of anaerobic granular sludge, aeration is not required at all; simply follow the operating conditions of the UASB. If it is an expansion of anaerobic ammonia oxidation sludge, the dissolved oxygen concentration needs to be controlled between 0.1-1.5 mg / L. If it is an expansion of aerobic granular sludge, the dissolved oxygen concentration needs to be controlled between 1.5-5.0 mg / L.

[0038] Example 3

[0039] This embodiment improves the dosing scheme based on Embodiment 1. An internal reflux pipeline is installed at the bottom of the reaction zone, below the sludge hopper. The internal reflux pipeline is connected to the feed zone via a reflux pump. The water below the reaction zone is partially intercepted through the internal reflux pipeline and transported to the feed zone to mix with the raw water. This achieves internal reflux in the fluidized bed reaction system, promoting rapid mixing and reaction of the reagents.

[0040] Typically, when wastewater with high phosphorus content enters the system of this invention, a large amount of struvite (or calcium phosphate, or magnesium phosphate) crystals will form in the area below the intake of the internal return pipe. Some small crystals, due to their small particle size, will rise (i.e., escape and be lost). These small crystals will become the "nuclei" for activated sludge granulation, promoting sludge granulation. However, some chemical wastewater has a simple composition and few impurities, allowing small crystals to quickly aggregate and grow. Therefore, there may not be any small crystals reaching the granular sludge expansion area, resulting in a decrease in the sludge aggregation rate.

[0041] In response to the above situation, it is necessary to add appropriate reactants. Specifically, in the area above the water intake of the internal return pipeline in the reaction zone, reactants that match the cations and anions of the wastewater itself, such as aluminum salts, iron salts, magnesium salts, calcium salts, and other metal cations, are added to promote the formation of crystals in the fluidized bed area above the internal return water intake. This allows the sludge and crystals to grow together, thereby accelerating the granulation of activated sludge.

[0042] Example 4

[0043] Based on Example 1, this embodiment studies the control conditions of a granular sludge enrichment system, which includes a sludge hopper, a lifting multi-stage stirring paddle, and a geared motor.

[0044] The bottom of the sludge hopper is circular with a radius of 5-30cm. The bottom sludge hopper is connected to a granular sludge outlet located outside the fluidized bed reaction system via a pipe. Once the granular sludge has grown to the required size and strength, it is discharged through pipes and valves or transported to other projects that require inoculation.

[0045] The lifting multi-stage agitator has agitator blades whose length gradually decreases from top to bottom, and the central axis of the lifting multi-stage agitator coincides with the axis of symmetry of the sludge hopper. Through the cooperation of the sludge hopper and the lifting multi-stage agitator, the stable operation of the granular sludge enrichment system is achieved.

[0046] Based on the above, the operating frequency of the lifting multi-stage agitator is appropriately adjusted according to the sludge concentration and particle size (variable frequency control; the lower the frequency, the lower the motor output power): when the sludge concentration is low and the particle size is small, a low operating frequency can reduce the upward flow velocity of the water, thus preventing the loss of a large amount of granular sludge that is still in the growth stage; conversely, a high operating frequency can increase the upward flow velocity of the water and granular sludge, thus preventing too much granular sludge from settling to the bottom and being unable to continue growing.

[0047] The upward flow velocity of the water is closely related to the particle size of the granular sludge. Through repeated experiments, it was found that an upward flow velocity of 5-30 mm / s can effectively control the agglomeration and enlargement of sludge in the sludge hopper, producing sludge with a suitable particle size. When the upward flow velocity is below 5 mm / s, the sludge will settle to the bottom and fail to grow. When the upward flow velocity is above 30 mm / s, sludge loss will occur.

[0048] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0049] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0050] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for in-situ rapid propagation of granular sludge, characterized in that: A fluidized bed reaction system and a granular sludge enrichment system are employed. The fluidized bed reaction system includes an interconnected reaction zone and a feed zone. The feed zone includes an inlet, a return inlet, a discharge port, and a chemical dosing port. The reaction zone is located above the feed zone, and the granular sludge enrichment system is installed within the reaction zone. The granular sludge enrichment system includes a sludge hopper, a lifting multi-stage agitator, and a geared motor. The sludge hopper is inverted conical in shape, open at the top, and connected to the granular sludge outlet at the bottom. The lifting multi-stage agitator is located within the... Inside the sludge hopper, the central shaft of the lifting multi-stage stirring paddle is connected to the geared motor that drives its rotation. The geared motor operates at a variable frequency to control the upward flow velocity of the water in the sludge hopper at 5-30 mm / s, thereby controlling the agglomeration and enlargement of the granular sludge in the sludge hopper. An outlet weir is provided at the top of the reaction zone, with the lowest point of the outlet weir being higher than the highest point of the sludge hopper to prevent the granular sludge from being lost with the overflow water. An aeration system is also provided at the bottom of the reaction zone, located below the granular sludge enrichment system.

2. The in-situ rapid propagation method for granular sludge according to claim 1, characterized in that: An internal reflux pipe inlet is provided at the bottom of the reaction zone, below the mud hopper. The internal reflux pipe is connected to the feed zone via a reflux pump.

3. The in-situ rapid propagation method for granular sludge according to claim 2, characterized in that: The aeration system adjusts the aeration rate in the reaction zone to control the dissolved oxygen concentration in the area above the internal return pipe to be between 0 and 5.0 mg / L.

4. The in-situ rapid propagation method for granular sludge according to claim 3, characterized in that: The aeration system controls the dissolved oxygen concentration in the area above the internal return pipe to be between 0.1 and 1.5 mg / L to obtain anaerobic ammonia oxidation granular sludge; or the aeration system can operate in a non-aeration mode to expand the anaerobic granular sludge.

5. The in-situ rapid propagation method for granular sludge according to claim 3, characterized in that: The aeration system controls the dissolved oxygen concentration in the area above the internal return pipe to be between 1.5 and 5.0 mg / L in order to obtain aerobic granular sludge.

6. The in-situ rapid propagation method for granular sludge according to claim 1, characterized in that: The reaction zone is connected to a pH meter and linked to a dosing device, thereby controlling the pH value in the reaction zone between 6.5 and 8.

5.

7. The in-situ rapid propagation method for granular sludge according to claim 6, characterized in that: The pH value in the reaction zone is controlled between 7.5 and 8.

0.

8. The in-situ rapid propagation method for granular sludge according to claim 1, characterized in that: The lifting multi-stage agitator has agitator blades whose length gradually decreases from top to bottom, and the number of agitator blades is two or more. The central axis of the lifting multi-stage agitator coincides with the axis of symmetry of the mud hopper.

9. The in-situ rapid propagation method for granular sludge according to claim 8, characterized in that: The bottom of the sludge hopper is circular with a radius of 5-30 cm, and the bottom of the sludge hopper is connected to the granular sludge outlet located outside the fluidized bed reaction system.

10. The in-situ rapid propagation method for granular sludge according to claim 1, characterized in that: The top of the reaction zone has an annular opening, the effluent weir is concentric with the annular opening at the top of the reaction zone, and the projection of the effluent weir is located inside the mud hopper opening.

11. The in-situ rapid propagation method for granular sludge according to claim 10, characterized in that: The outlet of the weir is triangular, and water flows out from both sides of the weir channel.

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