A sludge resource recovery method based on two-stage sludge hydraulic separation of secondary flow

Abstract

The present application belongs to the technical field of sludge treatment, and particularly relates to a sludge resource utilization method based on two-stage sludge and residue hydraulic separation. The sludge treatment process comprises two relatively independent parts: (1) aeration tank sludge→primary sludge and residue hydraulic separation (primary residue)→residue dewatering→residue external transportation; and (2) secondary sedimentation tank backflow sludge→thickening→wall breaking→sludge and residue secondary flow hydraulic separation fine residue and wall breaking treatment (secondary residue dewatering→residue external transportation)→backflow to an anoxic tank. The primary residue (coarse residue) and the secondary residue (fine residue) are combined, dewatered and externally transported or are externally transported after gravity pressure filtration. The two relatively independent sludge treatment systems, a sewage plant main process system and a phosphorus recovery system jointly constitute the technical system of the present application. Compared with the traditional sludge treatment method which only treats residual sludge, the sludge resource utilization method has a carbon source recovery rate of more than 96%, a sludge reduction rate of about 70-75%, and no sludge is discharged from the sewage plant but only residue is discharged, and is suitable for sewage plants with biological nitrogen and phosphorus removal functions.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sludge treatment, and particularly relates to a sludge resource utilization method based on two-stage sludge and residue hydraulic separation. BACKGROUND

[0002] In sewage treatment, a biological method is very effective and has low treatment cost and is widely applied. In the biological sewage treatment process, microorganisms continuously proliferate to produce a large amount of sludge mainly composed of organic matter. The sludge is difficult to be consumed in the sewage treatment process and becomes residual sludge. The treatment and disposal cost of the residual sludge is high, which has always plagued the sewage treatment industry.

[0003] Traditional residual sludge treatment is mostly based on the basic treatment program of concentration-dewatering-drying, and the residual sludge is finally landfilled or incinerated or used as a building material. The treatment and disposal process consumes a large amount of chemicals and energy, and the treatment cost is high. A sewage plant with a capacity of 100,000 tons of sewage per day often produces tens of tons of wet residual sludge (typical water content is about 80%) per day. The sludge treatment process not only consumes energy and materials, but also generally needs to be transported and disposed outside. The treatment and disposal cost often reaches hundreds of yuan per ton of dry sludge. The high treatment and disposal cost brings a huge economic burden to enterprises. In addition, the existing sewage treatment process needs a large amount of carbon source to maintain the effect of denitrification and phosphorus removal. However, many sewage plants lack carbon sources (especially in the south), and need to purchase carbon sources to make up for the lack of carbon sources in the process. Therefore, if the organic matter in the sludge can be converted into carbon sources, not only can the amount of residual sludge be greatly reduced to achieve sludge reduction, but also the problem of carbon source deficiency in sewage treatment can be solved. Therefore, the sludge treatment method of sludge disintegration to realize carbon source recovery and reduction has extremely important significance. In order to solve this problem, many researchers focus on the combined treatment of sludge by heat and alkali. This method can indeed better realize the recovery of carbon sources in sludge. However, the cost of the heat and alkali method is high, the device is complex to operate, and the economic efficiency is not ideal. Therefore, a sludge resource utilization method based on two-stage sludge and residue hydraulic separation is proposed. SUMMARY

[0004] In order to solve the above problems, the present application is based on the characteristics of the active sludge composition being divided into organic matter and inorganic matter, and a considerable part of the inorganic matter being fine particle sand, and proposes a resource utilization method based on two-stage sludge and residue hydraulic separation. The key technology is to separate the inorganic matter in the process sludge by a suitable method, instead of the traditional residual sludge discharge (equivalent to replacing sludge discharge with residue discharge); the chemical sludge is no longer included in the sludge discharge system and is recycled separately as phosphorus removal sludge; the proliferated active sludge in the system is no longer considered for discharge, but for the organic matter in the sludge, the alkali disintegration is used as the treatment method, and the organic particles and cells in the sludge can be disintegrated into soluble COD, and the particles of organic matter that cannot be completely disintegrated by alkali can be returned to the main process system of the sewage treatment, and after repeated cycle treatment, the organic matter in the sludge can be basically disintegrated and further utilized by denitrification. In this way, the final discharged residue (not including chemical sludge) of the system comes from the residue after the separation of sludge and residue, and the inorganic matter content is high.

[0005] The above-mentioned purposes are achieved by the following method:

[0006] The present application provides a two-stage sludge and residue hydraulic separation based on secondary flow, and the sludge treatment process includes two relatively independent parts: (1) aeration tank sludge→sludge and residue first hydraulic separation (primary residue)→residue dewatering→residue external transport; (2) secondary sedimentation tank return sludge+sedimentation tank A sludge→concentration→wall breaking→sludge and residue secondary flow hydraulic separation fine residue and disintegration treatment (secondary residue dewatering→residue external transport)→return to the anoxic tank, and the primary residue and the secondary residue are combined, dewatered and externally transported or externally transported after gravity pressure filtration. Unlike the traditional sludge treatment which only treats the residual sludge, the process system of the sludge treatment of the present application is integrated into the main process system of the sewage plant, and the two process flows of the sludge treatment and the phosphorus recovery system and the main process system of the sewage treatment system jointly constitute the entire process flow content of the present application.

[0007] The main process system of the sewage treatment includes an anaerobic tank, an anoxic tank, an aerobic tank and a secondary sedimentation tank in sequence (any sewage process with biological denitrification and phosphorus removal function can be used, without being limited to using different structures, such as SBR which can use different timing control); the phosphorus recovery system includes a cation reaction tank (cation additive is PAM), a sedimentation tank A, an iron ion reaction tank (iron ion additive is FeCl3), and a sedimentation tank B (used for recovering iron phosphate, and the effluent of the sedimentation tank B is returned to the main process system); the sludge system includes a sludge and residue separation tank, a concentration tank, a wall breaking tank, a disintegration tank and corresponding dewatering facilities;

[0008] The process of the present application includes the following steps:

[0009] (1) using a sludge separation tank to separate the sludge in the aeration tank, the inorganic particles in the sludge are separated from the organic sludge to form a first sludge (organic sludge) and a first residue (inorganic residue), the first sludge is returned to any tank in the main process system, and the first residue is subjected to mechanical dewatering treatment or gravity pressure filtration dewatering treatment;

[0010] (2) using a concentration tank to concentrate the return sludge of the main process system and the sludge in the sedimentation tank A, the concentrated sludge is subjected to the next step of treatment, and the supernatant of the concentration is returned to the phosphorus recovery system and added into the cation reaction tank for reaction;

[0011] (3) using a wall breaking tank to break the wall of the concentrated sludge, the wall breaking is performed by high-speed mechanical shearing, and the broken sludge is subjected to the next step of treatment;

[0012] (4) using a disintegration tank to hydraulically separate the broken sludge, the mechanism is to separate the fine residue (high density) in the sludge from the disintegrated sludge fragments (low density) under the action of a secondary flow field, and simultaneously perform sludge disintegration and sludge separation, the sludge fragments obtained by the secondary sludge separation are returned to the anoxic tank of the main process system, the residue (second residue) is subjected to dewatering treatment or is returned to the pressure filtration area at the bottom of the sludge separation tank.

[0013] As a further improvement of the above technical solution, the sludge separation tank adopts hydraulic cyclone separation, the diameter-depth ratio is 0.3-0.5, the sludge enters along the tangent direction of the tank wall after entering the sludge separation tank, the flow rate is 0.25-0.40 m / s, and the hydraulic load value is about 25-50 m 3 / (m 2 ·h).

[0014] As a further improvement of the above technical solution, the sludge separation tank is divided into a turbulent zone, a transition zone and a static zone, the Reynolds number of the turbulent zone is greater than 1000, the Reynolds number of the transition zone is 30-2000, and the Reynolds number gradually decreases from the upper part to the lower part, the bottom of the static zone is stacked with sludge in a static state, and the Reynolds number of the water between the sludge gaps is zero.

[0015] As a further improvement of the above technical solution, when the sludge separation tank is not provided with a sludge gravity pressure filtration area, the volume ratio of the turbulent zone, the transition zone and the static zone is 2:3:1-2, and the total height of the sludge separation tank is 5-7 m; when the sludge separation tank is provided with a sludge gravity pressure filtration area, the volume ratio of the turbulent zone, the transition zone and the static zone is 2:3:6-7, and the total height of the sludge separation tank is 8-10 m.

[0016] As a further improvement of the above technical solution, gravity concentration is adopted in the concentration tank to increase the sludge concentration to 18000-22000 mg / L, and the HRT is 15-25 h.

[0017] As a further improvement of the above technical solution, the wall-breaking tank adopts a mechanical shearing method for wall breaking.

[0018] As a further improvement of the above technical solution, the wall-breaking tank and the disintegration tank are one structure, and the added medicament in the tank is sodium hydroxide and calcium oxide.

[0019] As a further improvement of the above technical solution, the tank body of the disintegration tank is cylindrical, the disintegration tank adopts hydraulic separation of sludge, and strong alkali is used for disintegrating cells; the disintegration tank maintains the formation of a secondary flow field to separate fine sludge; the sludge enters the tank at an arbitrary flow rate along the tangent direction of the tank wall, a stirring structure is arranged in the tank, the tangent velocity at the edge of the tank is maintained at 0.4-0.7 m / s, the bottom of the disintegration tank is horizontal and smooth, and a sludge storage hopper is arranged at the center position.

[0020] As a further improvement of the above technical solution, the bottom of the sludge separation tank is provided with a sludge gravity pressure filtration area, the secondary sludge is returned to the bottom of the transition area of the sludge separation tank, mixed with the primary sludge, and then enters the sludge gravity pressure filtration area, and the sludge cake after gravity pressure filtration is directly transported out.

[0021] As a further improvement of the above technical solution, the primary sludge and the secondary sludge are mixed and then dewatered, and the dewatered sludge is transported out.

[0022] The technical principle of the present application is that method one, hydraulic separation of coarse sludge:

[0023] The density of inorganic matter in sludge is significantly greater than the density of water, and generally the density of inorganic fine sand reaches 2.5 g / cm 3 , and the density of organic matter in sludge is very close to water, and generally only 1.002-1.003 g / cm 3 . Based on this feature, when the Reynolds number in the separation tank is large, the sedimentation of light sludge is disturbed, and the layered sedimentation of sludge is destroyed, then the fine sand can be separated from the organic matter, and the sludge separation tank is realized according to this principle to realize the hydraulic screening of coarse sludge and organic sludge. Therefore, the sludge separation tank needs to meet the following functional structure characteristics:

[0024] (1) The sludge separation tank needs to have a significant stratification and height, and is divided into a turbulent flow area, a transition area and a static area, the Reynolds number of the turbulent flow area is large enough to destroy the layered sedimentation of sludge, generally greater than 1000, and the typical value is above 20,000; the hydraulic condition of the transition area is provided by the rotational friction of the turbulent flow area, that is, the transition area does not set a stirring measure, and the Reynolds number is preferably controlled between 2000 and 30, and gradually decreases from the upper part to the lower part; the static area has a certain sludge accumulation, so the sludge accumulated at the bottom of the static area is in a state of almost complete static, and the Reynolds number of the water in the sludge gap is zero.

[0025] (2) The volume ratio of turbulent zone, transition zone and static zone can be generally controlled at 2:3:1~2 (without sludge gravity pressure filtration), or 2:3:6~7 (with sludge gravity pressure filtration). Generally, the total height needs to be greater than 5~7 m (without sludge gravity pressure filtration) or 8-10 m (with sludge gravity pressure filtration), and when the hydraulic cyclone is used to realize the circulation in the tank, the diameter-depth ratio should not be too large, which should not be greater than 0.3~0.5.

[0026] (3) In order to reduce the organic matter from crossing the transition zone into the bottom of the static zone, a certain amount of sewage can be introduced into the transition zone, which can promote the upward flow in the transition zone and dilute the organic matter sludge falling from the upper turbulent zone, so as to avoid the organic matter from crossing the transition zone due to the stratified sedimentation.

[0027] (4) The method for maintaining high Reynolds number in the turbulent zone can be water inlet along the tangent direction of the tank wall side, or aeration or stirring.

[0028] Method two, secondary hydraulic separation of fine sludge:

[0029] In the circular reaction tank, the water flow is pushed to circulate in the tank by hydraulic and stirring measures. Since the flow along the boundary is affected by the transverse pressure, it produces a deviation parallel to the boundary. The fluid layer close to the boundary deviates more severely than the fluid layer far from the boundary due to the smaller speed, which leads to the secondary flow superimposed on the main flow. The radial velocity of the secondary flow is small, and the broken organic fragments cannot be precipitated with the secondary flow. Under the action of the secondary flow, the ultra-fine sludge is slowly and gradually pushed to the center of the tank, realizing the re-separation of the ultra-fine sludge and the sludge. According to this principle, the breaking tank needs to meet the following requirements:

[0030] (1) The tank is cylindrical, and there is a certain circular flow in the tank, which can be realized by stirring. The edge flow velocity in the tank should not be too large, otherwise the energy consumption will be too high and it is not conducive to the aggregation of ultra-fine sludge. The edge flow velocity in the tank should not be too low, otherwise the secondary flow will be too weak to promote the centripetal motion of the particles.

[0031] (2) The bottom of the tank is close to horizontal or slightly inclined to the center of the tank, which is conducive to the flow of ultra-fine sludge to the center of the tank.

[0032] (3) The sludge storage hopper is small and located at the center of the tank.

[0033] The beneficial effects of the present application are that: in the present application, the sludge of the main process system is subjected to secondary hydraulic separation, and the inorganic matter coarse residue therein is removed, so that the inorganic matter in the sludge is separated, and the main component (actually, the residue) of the final residual sludge is discharged; the fine residue and sludge fragments in the backflow sludge are separated under the action of the secondary flow field in the disintegration tank; the activated sludge proliferated in the system is no longer considered for discharge, but for the organic matter in the sludge, the alkali disintegration is used as the treatment method, and the organic components such as organic particles and cells in the sludge can be disintegrated into soluble COD, and the particle organic matter which cannot be completely disintegrated by alkali can be backflowed to the main process system of the sewage treatment, and after repeated cycle treatment, the organic matter in the final sludge can be basically disintegrated and further utilized by denitrification. The sludge (excluding chemical sludge) finally discharged from the system comes from the residue after the separation of the sludge and the residue, and the inorganic matter content is high. On the one hand, since the recovered carbon source has met the needs, the sewage plant no longer needs to purchase carbon source, and the cost is saved; on the other hand, the sludge reduction is significant, so the sludge disposal cost is greatly reduced, and the economic benefit is also very significant. The present application is only applicable to sewage plants with biological denitrification and phosphorus removal functions. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 It is the process flow schematic diagram of the embodiment 1 of the present application.

[0035] Figure 2 It is the process flow schematic diagram of the embodiment 2 of the present application. DETAILED DESCRIPTION

[0036] It is necessary to point out here that the following detailed description is only used to further illustrate the present application, and cannot be understood as limiting the protection scope of the present application, and the skilled in the art can make some non-essential improvements and adjustments to the present application according to the above application content.

[0037] The present application provides a two-stage sludge residue hydraulic separation method based on secondary flow, and the sludge treatment process includes two relatively independent parts: (1) aeration tank sludge→sludge residue primary hydraulic separation (primary residue)→residue dewatering→residue external transport; (2) secondary sedimentation tank backflow sludge+sedimentation tank A sludge discharge→concentration→wall breaking→sludge residue secondary flow hydraulic separation fine residue and disintegration treatment (secondary residue dewatering→residue external transport)→backflow to the anoxic tank. The primary residue and the secondary residue are combined, dewatered, and then externally transported or externally transported after gravity pressure filtration. Unlike the traditional sludge treatment which only treats the residual sludge, the process system of the sludge treatment of the present application is integrated into the main process system of the sewage plant, and the two process flows of the sludge treatment and the phosphorus recovery system and the main process system of the sewage treatment system jointly constitute the entire process flow content of the present application.

[0038] The sludge system includes a sludge residue separation tank, a concentration tank, a wall breaking tank, a disintegration tank, and a dewatering treatment;

[0039] The main sewage process system sequentially comprises an anaerobic tank, an anoxic tank, an aerobic tank and a secondary sedimentation tank, the untreated sewage (mud-water mixture) is sequentially treated in the anaerobic tank, the anoxic tank and the aerobic tank after pretreatment, a part of sludge is backflowed to the anoxic tank, and the remaining mud-water mixture is fed into the secondary sedimentation tank, wherein a part of the sludge is backflowed to the anaerobic tank, and a part of the backflowed sludge is fed into the thickening tank of the sludge system, and the supernatant of the secondary sedimentation tank is directly discharged or subjected to advanced treatment;

[0040] The phosphorus recovery system sequentially comprises a cation reaction tank (the cation additive is PAM), a sedimentation tank A, an iron ion reaction tank (the iron ion additive is FeCl3), and a sedimentation tank B (for recovering iron phosphate, and the effluent of the sedimentation tank B is backflowed to the main process system);

[0041] The process of the present application comprises the following steps:

[0042] (1) The sludge in the aeration tank is subjected to primary sludge separation by using a sludge separation tank, the inorganic particles in the sludge are separated from the organic sludge to form primary sludge (organic sludge) and primary sludge (inorganic sludge), the primary sludge is backflowed to any tank of the main process system, and the primary sludge is subjected to dewatering treatment or gravity pressure filtration treatment;

[0043] (2) The backflowed sludge of the main process system and the sludge of the sedimentation tank A are concentrated by using a thickening tank, the concentrated sludge is subjected to next step treatment, and the supernatant of the concentration is backflowed to the phosphorus recovery system and fed into the cation reaction tank to add PAM for reaction;

[0044] (3) The concentrated sludge is subjected to wall breaking treatment by using a wall breaking tank, the wall breaking treatment is carried out by using high-speed mechanical shearing method, and the wall broken sludge is subjected to next step treatment;

[0045] (4) The wall broken sludge is subjected to hydraulic separation by using a disintegration tank, the separation is based on the action of a secondary flow field, and is mainly used for separating fine sludge, the disintegration tank is used for sludge separation and sludge disintegration, and the sludge fragments obtained by secondary sludge separation are backflowed to the anoxic tank of the main process system, and the sludge (secondary sludge) is subjected to dewatering treatment or backflowed to the sludge separation tank.

[0046] According to the results of the small-scale test, the organic matter content in the sludge (a mixture of primary and secondary sludge) is as low as 5-8%. For a wastewater treatment plant with a dry sludge discharge rate of 10 t / d, and an organic matter content of 50%, the organic matter discharge rate would be 5 t / d. If the technology of this invention is used, the mass of inorganic sludge recovered in the form of phosphorus recovery is approximately 1.8-2.0 t / d, and the final sludge discharge rate is only 2.0-2.5 t / d, of which the organic matter discharge rate is <0.16 t / d. Therefore, the actual carbon source recovery rate is >96%, and the sludge reduction rate is at least 70% (approximately 70-75%), demonstrating significant technological advantages. Since the recovered carbon source already meets the needs, the wastewater treatment plant no longer needs to purchase carbon sources, and the sludge disposal cost is significantly reduced, resulting in substantial economic benefits. However, this invention is only applicable to wastewater treatment plants with biological nitrogen and phosphorus removal functions. For wastewater treatment plants without biological nitrogen and phosphorus removal functions, its economic viability is significantly reduced.

[0047] Example 1

[0048] like Figure 1 The diagram shows a two-stage hydraulic separation process for sludge and sludge in a sludge separation tank, including gravity filtration. This embodiment describes a sludge resource utilization method based on two-stage hydraulic separation of sludge and sludge in a secondary flow. The sludge treatment process is as follows: (1) Sludge from aeration tank → primary hydraulic separation of sludge and sludge (primary sludge) → gravity filtration → sludge cake transportation; (2) sludge return from the main process + sludge discharge from sedimentation tank A → thickening → mechanical wall breaking → secondary hydraulic separation of sludge and sludge, with fine sludge treatment (secondary sludge returned to the gravity filtration zone) → returned to the anoxic tank. The primary and secondary sludge produced are then transported after gravity filtration. The process includes the following steps:

[0049] (1) A sludge separation tank is used to perform primary sludge separation on the sludge from the aeration tank. The inorganic particulate sludge is separated from the organic sludge. The separated organic sludge is returned to the main process system and can be returned to any structure. The primary sludge from the primary sludge separation is subjected to gravity filter press treatment. The sludge separation tank adopts a hydraulic cyclone separation with a diameter-to-depth ratio of 0.3-0.5. After entering the sludge separation tank, it enters along the tangential direction of the tank wall with a flow velocity of 0.25-0.40 m / s and a hydraulic load of approximately 25-50 m. 3 / (m 2 ·h).

[0050] The density of inorganic matter in sludge is significantly greater than that of water; generally, the specific gravity of inorganic fine sand reaches 2.5 g / cm³. 3 The density of organic matter in sludge is very close to that of water, with a specific gravity of only 1.002–1.003 g / cm³ under normal circumstances. 3Based on this feature, when the Reynolds number in the separation tank is large, the settling of the disturbed light sludge is disturbed, and the sludge layering settling is destroyed, then the fine sand can be separated from the organic matter, and the sludge separation tank realizes the hydraulic screening of the coarse slag and the organic sludge according to this principle. Therefore, the sludge separation tank needs to meet the following functional structure characteristics:

[0051] (a) The sludge separation tank needs to have significant stratification and height, which is divided into a turbulent zone, a transition zone and a static zone. The Reynolds number in the turbulent zone is large enough to destroy the layered settling of the sludge, which is generally greater than 1000, and the typical value is above 20,000. The hydraulic conditions in the transition zone can be provided by the rotational friction of the turbulent zone, that is, the transition zone does not need to be provided with stirring measures, and the Reynolds number should be controlled between 2000 and 30, and the Reynolds number decreases gradually from the upper part to the lower part. The bottom of the static zone has a certain amount of sludge accumulation, so the sludge at the bottom of the static zone is in a state of almost complete static state, and the Reynolds number of the water between the sludge gaps is zero.

[0052] (b) The volume ratio of the turbulent zone, the transition zone and the static zone can be controlled at 2:3:6-7 (set up sludge gravity pressure filtration), generally, the total height needs to be greater than 8-10 m (set up sludge gravity pressure filtration), and when the hydraulic cyclone method is used to realize the circulation in the tank, the diameter-depth ratio should not be too large, which should not be greater than 0.3-0.5.

[0053] (c) In order to reduce the organic matter from passing through the transition zone into the bottom static zone, a certain amount of sewage can be added to the transition zone, which can promote the upward flow in the transition zone, and dilute the organic matter sludge falling from the upper turbulent zone, so as to avoid the organic matter from passing through the transition zone due to the layered settling.

[0054] (d) The method for maintaining a high Reynolds number in the turbulent zone can be water inlet along the tangent direction of the tank wall side, or aeration or stirring.

[0055] (2) The return sludge is concentrated in the concentration tank, and the concentrated sludge enters the next step of treatment, and the concentrated sewage (supernatant) is returned to the phosphorus recovery system; gravity concentration is used in the concentration tank to increase the sludge concentration to 18,000-22,000 mg / L, and the HRT is 15-25 h.

[0056] (3) The concentrated sludge is subjected to wall breaking treatment in the wall breaking tank, and the wall breaking adopts high-speed mechanical shearing method, and the wall broken sludge enters the next step of treatment. The reagent added in the wall breaking tank is sodium hydroxide and calcium oxide.

[0057] (4) The broken sludge is subjected to secondary hydraulic separation in the breaking tank to separate the sludge and break the sludge, and the sludge separated by the secondary sludge separation is returned to the anoxic tank of the main process system, and the sludge (secondary sludge) is returned to the primary sludge separation tank. The secondary sludge is returned to the bottom of the transition zone of the sludge separation tank, mixed with the primary sludge, and then enters the sludge gravity filter zone. After gravity filtration, the sludge cake is directly transported out.

[0058] In the breaking tank, the water flow is driven to flow in a ring shape in the tank by hydraulic force and stirring measures. Due to the effect of the transverse pressure, the flow along the boundary generates a deviation parallel to the boundary. Then, the fluid layer close to the boundary deviates more severely than the fluid layer far from the boundary due to the smaller speed, which leads to a secondary flow superimposed on the main flow. The radial velocity of the secondary flow is small, and the broken organic fragments cannot be precipitated with the secondary flow. Instead, the fine sludge is gradually pushed to the center of the tank under the action of the secondary flow, so as to realize the separation of the fine sludge and the sludge again. According to this principle, the breaking tank needs to meet the following requirements:

[0059] (a) The tank is cylindrical, and a ring-shaped flow with a certain flow rate is formed in the tank, which can be achieved by stirring. The flow rate at the edge of the tank should not be too large, otherwise the energy consumption will be too high. The flow rate at the edge of the tank should not be too low, otherwise the secondary flow will be too weak to drive the particles to move towards the center.

[0060] (b) The bottom of the tank is close to horizontal or slightly inclined towards the center of the tank, which is beneficial to the flow of fine sludge to the center of the tank.

[0061] (c) The sludge storage hopper is small and located at the center of the tank.

[0062] Example 2

[0063] As shown in FIG. 2, it is a process flow diagram of the two-stage hydraulic separation of sludge and sludge in the sludge separation tank without gravity filtration. Compared with Example 1, the difference is that the sludge separation tank does not contain gravity filtration, and the process includes the following steps: Figure 2 (1) The primary sludge separation of the sludge in the aeration tank is performed by using the sludge separation tank, and the inorganic particles in the residual sludge are separated from the organic sludge. The separated organic sludge is returned to the main process system, and can be returned to any structure. The primary sludge separated by the primary sludge separation is subjected to dewatering treatment. Since the sludge separation tank does not have a sludge gravity filtration zone, the volume ratio of the turbulent zone, the transition zone and the static zone is 2:3:1-2, and the total height of the sludge separation tank is 5-7 m.

[0064] (2) The return sludge of the main process system and the sludge of the sedimentation tank A are concentrated by using the concentration tank, and the concentrated sludge enters the next step of treatment. The concentrated wastewater is returned to the phosphorus recovery system.

[0065]

[0066] ​(3) The concentrated sludge is subjected to wall breaking treatment in a wall breaking tank. The wall breaking treatment is performed by high-speed mechanical shearing. The wall broken sludge is subjected to the next step.

[0067] (4) The wall broken sludge is subjected to secondary hydraulic separation in a disintegration tank to separate the sludge and disintegrate the sludge. The sludge obtained by the secondary sludge separation is returned to the anoxic tank of the main process system. The sludge (secondary sludge) is directly subjected to dewatering treatment and then is externally transported.

[0068] The small-scale test is performed in the manner of Example 2. The primary sludge separation is performed in the cyclone reactor. The primary sludge mainly comprises large particles with a particle size greater than 0.05 mm. The organic matter content in the sludge is 5-8%. The secondary separation is performed in the cylindrical barrel. The secondary sludge comprises various particles with different particle sizes, and the fine particles are the majority. According to the different control of the hydraulic conditions, the minimum particle size can be less than 0.015 mm. The organic matter content in the sludge is 9-16%. According to the principle of the present application, the primary sludge is controlled to be the main sludge (more than 95%) and the secondary sludge is controlled to be the secondary sludge (less than 5%). The two sludges are independently operated, and the amount of each sludge is controlled by the flow rate into the reactor. The average organic matter content of the total sludge is less than 8% after weighting, and the sludge is efficiently utilized.

[0069] The above-described examples only express several embodiments of the present application, and the description is relatively specific and detailed. However, it should not be understood as a limitation on the scope of the present application. It should be pointed out that, for ordinary skilled persons in the art, several improvements can be made without departing from the concept of the present application, and these improvements are within the protection scope of the present application.

Claims

1. A sludge resource recovery method based on two-stage sludge hydraulic separation of secondary flow, characterized in that, The main process system, the phosphorus recovery system and the sludge separation system, the main process system comprises an anaerobic tank, an anoxic tank, an aerobic tank and a secondary sedimentation tank in sequence, the phosphorus recovery system comprises a cation reaction tank, a sedimentation tank A, an iron ion reaction tank and a sedimentation tank B in sequence, and the sludge system comprises a sludge residue separation tank, a concentration tank, a wall-breaking tank, a breaking tank and a dehydration facility; The method comprises the following steps: (1) the sludge in the aeration tank is put into a sludge separation tank for primary sludge separation, to obtain primary residue and primary sludge, the primary sludge is all returned to any tank in the main process system, and the primary residue is subjected to dewatering treatment; the sludge separation tank adopts hydrocyclone separation, the diameter-depth ratio is 0.3-0.5, the sludge enters the sludge separation tank along the tangent direction of the tank wall at a flow rate of 0.25-0.40 m / s, and the hydraulic load value is 25-50 m 3 / (m 2 ·h); the sludge separation tank is divided into a turbulent zone, a transition zone and a static zone, the Reynolds number of the turbulent zone is greater than 1000, the Reynolds number of the transition zone is 30-2000, and the Reynolds number gradually decreases from the upper part to the lower part, the bottom of the static zone is stacked with sludge in a static state, and the Reynolds number of the water between the sludge gaps is close to zero; (2) the sludge in the main process system and the sludge in the sedimentation tank A are put into the concentration tank for concentration, the concentrated sludge is subjected to the next treatment, and the supernatant of the concentration is returned to the cation reaction tank of the phosphorus recovery system; (3) the concentrated sludge is subjected to wall-breaking treatment, the wall-breaking is performed by using a high-speed mechanical shearing method, and the wall-broken sludge is subjected to the next treatment; (4) the wall-broken sludge is put into the breaking tank for secondary hydraulic separation, sludge residue separation and sludge breaking, the secondary sludge obtained by the secondary sludge residue separation is returned to the anoxic tank of the main process system, and the secondary residue is subjected to dehydration treatment or is returned to the sludge residue separation tank; the tank body of the breaking tank is cylindrical, the breaking tank uses hydraulic separation sludge residue, maintains a secondary flow field in the radial direction of the tank, and uses strong alkali to break cells; the sludge is put into the tank at an arbitrary flow rate along the tangent direction of the tank wall, a stirring structure is arranged in the tank, the tangent velocity at the edge of the tank is maintained at 0.4-0.7 m / s, the bottom of the breaking tank is horizontal and smooth, and a residue storage hopper is arranged at the center position.

2. The two-stage sludge dewatering hydraulic separation method based on the secondary flow according to claim 1, characterized in that, When the sludge residue separation tank is not provided with a sludge gravity filter area, the volume ratio of the turbulent zone, the transition zone and the static zone is 2:3:1-2, and the total height of the sludge residue separation tank is 5-7 m; when the sludge residue separation tank is provided with a sludge gravity filter area, the volume ratio of the turbulent zone, the transition zone and the static zone is 2:3:6-7, and the total height of the sludge residue separation tank is 8-10 m.

3. The method according to claim 1, wherein the method is characterized in that, Gravity concentration is used in the concentration tank to increase the sludge concentration to 18000-22000 mg / L, and the HRT is 15-25 h.

4. The method according to claim 1, wherein the method is characterized by, The medicament added in the wall-breaking tank is sodium hydroxide and calcium oxide.

5. The two-stage sludge dewatering hydraulic separation method based on the secondary flow according to claim 1, characterized in that, The bottom of the sludge residue separation tank is provided with a sludge gravity filter area, the secondary residue is returned to the bottom of the transition zone of the sludge residue separation tank, is mixed with the primary residue, and then enters the sludge gravity filter area, and the residue cake is directly transported out after gravity filtration.

6. The two-stage sludge dewatering hydraulic separation method based on the secondary flow according to claim 1, characterized in that, The primary residue and the secondary residue are mixed and subjected to dehydration, the dehydration is performed by using mechanical dehydration, and the residue is transported out after dehydration.

7. The two-stage sludge dewatering hydraulic separation method based on the secondary flow according to claim 1, characterized in that, The inorganic matter in the sludge has a density greater than that of water, and is mainly composed of inorganic fine sand with a density of 2.5 g / cm 3 The organic matter in the sludge has a density close to that of water, i.e. 1.002-1.003 g / cm 3 .

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