An apparatus for phosphorus release from excess sludge and phosphorus recovery

Abstract

The present invention relates to the technical field of water treatment, and particularly relates to a device for phosphorus release from excess sludge and phosphorus recovery, which includes a phosphorus release mechanism. The phosphorus release mechanism includes a sludge thickening unit, a sludge cracking assembly, and a sludge dewatering unit. A surplus sludge inlet, a thickened sludge discharge outlet, and a supernatant discharge outlet are provided on the sludge thickening unit; the sludge cracking assembly includes a sludge cracking unit and a pH value adjustment unit arranged in series, and the overall structure is concise. The present invention performs alkali cracking on 10% - 20% of the thickened sludge, and then uses the COD (carbon source) released by its cracking as the carbon source for polyphosphorus microorganisms (polyphosphate-accumulating organisms) in the total amount of surplus sludge entering the thickening tank. Anaerobic phosphorus release occurs in the anaerobic environment of the sludge thickening unit without the need for an external carbon source. Through the new scheme of phosphorus release by alkali hydrolysis of a small amount of thickened sludge + anaerobic biological phosphorus release of the total amount of surplus sludge, low-cost and high-efficiency phosphorus release of the total amount of surplus sludge is achieved, which is beneficial to subsequent efficient phosphorus recovery.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and particularly relates to a device for phosphorus release and phosphorus recovery from excess sludge. Background Art

[0002] At present, to effectively recover phosphorus from sludge, it is necessary to release phosphorus in the sludge (solid phase) into the liquid phase as much as possible. The efficient release of phosphorus is a key step in phosphorus recovery. The existing phosphorus release technologies mainly include:

[0003] ① Physical cracking method: By means of hydrothermal hydrolysis, ultrasonic waves, mechanical ball milling, etc., the microbial cells in the sludge are broken, and the phosphorus-containing substances inside and outside the cells are released into the liquid phase. Sludge hydrothermal hydrolysis needs to be carried out under high temperature and high pressure conditions (150 - 190 °C, 0.7 - 2.6 MPa), and is usually used as a pretreatment process in combination with the anaerobic digestion process. The equipment is complex, the operation and maintenance are difficult, the investment and energy consumption are high, and the treatment of the malodorous gas generated is difficult. At present, there are only a few engineering application cases; although the ultrasonic cracking has high efficiency, short reaction time (10 - 60 min), and simple equipment, due to the too high power consumption, it is mostly in the laboratory research stage at present, and the actual engineering application needs to overcome the defect of too high power consumption.

[0004] ② Chemical cracking method: Adding chemical agents such as acids, alkalis, H 2 O 2 ₂, ozone, etc. to the excess sludge to destroy the microbial cell structure and release the phosphorus-containing substances inside and outside the cells into the liquid phase. The acid-base cracking method has the characteristics of simple process and mature technology, but the existing full-scale acid-base cracking of sludge or methods such as H 2 O 2 ₂, ozone oxidation, etc. have high chemical consumption costs and are still difficult to realize engineering application.

[0005] ③ Biological phosphorus release method: Phosphorus release is carried out through anaerobic digestion or enzyme-promoted biological enhanced phosphorus release. The enzyme-promoted biological enhanced phosphorus release technology has high chemical agent costs and is currently in the laboratory research stage; anaerobic digestion is the most widely used sludge disposal technology in engineering applications at present, with the advantages of mature technology and low operating costs, but this method has a slow phosphorus release rate, a long required time (20 - 30 days of anaerobic digestion of sludge is required), a large volume of the reaction device, high construction investment. If it is necessary to increase the anaerobic phosphorus release rate and shorten the anaerobic phosphorus release time, a sufficient amount of carbon source is required, while the available carbon source in the excess sludge discharged from the biochemical system has basically been consumed in the front-end biochemical system, and a large amount of carbon source needs to be added externally to meet the requirements.

[0006] ④Sludge incineration - wet leaching process: The sludge is dehydrated, dried and then incinerated into ash, and then phosphorus is leached with acid and alkali. Phosphorus in the sludge incineration ash mainly exists in the form of combination with metals such as Ca, Mg, Fe, Al in the ash, which cannot be absorbed and utilized by plants. Moreover, heavy metal substances in the sludge still remain in the ash after incineration. It is also necessary to separate phosphorus from heavy metals in the sludge ash and convert phosphorus into a form that plants can use. The process flow is complex and the cost of phosphorus recovery is high.

[0007] ⑤Combined cracking method: Combined technologies such as hydrothermal hydrolysis - acid leaching, acidification - microwave radiation, ultrasonic - ozone, ultrasonic - alkali hydrolysis are used to destroy the microbial cell structure in the sludge, and the phosphorus - containing substances are released into the liquid phase. Compared with single technologies, the combined technologies can combine the advantages of various technologies, which is the development trend of the technology in this field.

[0008] In the existing sludge phosphorus release methods, a part of the phosphorus released into the liquid phase by physical cracking method, chemical cracking method and some combined cracking processes exists in the form of organic phosphorus - containing compounds (organic phosphorus). Organic phosphorus - containing compounds are difficult to remove by coagulation precipitation method and cannot recover phosphorus by crystallization precipitation method. If it is necessary to improve the recovery rate of phosphorus resources in the sludge, it is also necessary to further increase the content of orthophosphate in the liquid phase of the released phosphorus from the excess sludge.

[0009] Due to the high price or complex system of the existing sludge phosphorus release and phosphorus recovery technologies and equipment, the sludge from the sewage treatment plant after concentration and dewatering treatment is mostly disposed of by direct landfill or incineration, and the phosphorus in the sludge is not recycled resourcefully.

[0010] In summary, a device with a simple structure and capable of realizing efficient phosphorus release and phosphorus recovery is designed to solve the problems existing in the prior art. Summary of the Invention

[0011] The object of the present invention is to provide a device with a simple structure and capable of realizing efficient phosphorus release and phosphorus recovery. The specific technical solutions are as follows:

[0012] An excess sludge phosphorus release and phosphorus recovery device, comprising a phosphorus release mechanism;

[0013] The phosphorus release mechanism includes a sludge concentration unit, a sludge cracking assembly and a sludge dewatering unit. The sludge concentration unit is provided with an excess sludge inlet, a concentrated sludge discharge port and a supernatant discharge port; the sludge cracking assembly includes a sludge cracking unit and a pH value adjustment unit arranged in series;

[0014] The excess sludge enters the sludge thickening unit through the excess sludge feed inlet for thickening treatment; the supernatant after thickening treatment is discharged through the supernatant discharge outlet; the thickened sludge after thickening treatment is discharged through the thickened sludge discharge outlet. A part of the thickened sludge enters the sludge cracking unit through the first pipeline for sludge cracking treatment, and another part of the thickened sludge enters the sludge dewatering unit through the second pipeline for sludge dewatering treatment; the cracked sludge after cracking treatment enters the pH adjustment unit for pH adjustment, and then is transported through the third pipeline to the excess sludge feed inlet and recycled to the sludge thickening unit.

[0015] Preferably, the sludge thickening unit is a gravity thickening tank, and the hydraulic retention time of the sludge in the thickening tank is 6 - 24 h;

[0016] Both the excess sludge feed inlet and the supernatant discharge outlet are arranged at the upper end of the sludge thickening unit, and the thickened sludge discharge outlet is arranged at the bottom of the sludge thickening unit;

[0017] The ratio of the mass or flow rate of the sludge entering the sludge cracking unit through the first pipeline for sludge cracking treatment to the thickened sludge discharged from the thickened sludge discharge outlet is 0.1 - 0.2; the pH control range in the sludge cracking unit is 10.8 - 11.5; the pH control range in the pH adjustment unit is 9 - 10;

[0018] After the sludge is adjusted in pH by the pH adjustment unit and the third pipeline intersects with the excess sludge conveying pipeline, the flow time of the mixed sludge from the intersection point to the outlet of the excess sludge feed inlet is not less than 3 seconds.

[0019] Preferably, the sludge cracking unit includes a first housing, a first stirring assembly, a first sludge inlet pipe, and a first sludge outlet pipe;

[0020] The first housing includes a first body having a first accommodation cavity, and both the first sludge inlet pipe and the first sludge outlet pipe are arranged on the first body and are both communicated with the first accommodation cavity;

[0021] A first chemical addition pipe communicated with the first accommodation cavity is arranged on the first body;

[0022] The first stirring assembly includes a first driving power source, a first stirring shaft, and first stirring blades. The first driving power source is arranged on the first housing; the connecting end of the first stirring shaft is connected to the output end of the first driving power source, and the free end of the first stirring shaft is arranged in the first accommodation cavity and is provided with the first stirring blades thereon;

[0023] The first pipeline is communicated with the first sludge inlet pipe, and the first sludge outlet pipe is communicated with the pH adjustment unit through a fourth pipeline.

[0024] Preferably, it further includes a first pH controller. A measurement hole communicating with the first accommodation cavity is provided on the first body. The first pH controller is arranged at the measurement hole for measuring the pH value of the sludge. The first pH controller is connected to an external PLC control system, and the first pH controller measures the pH value of the sludge through a first measurement electrode. The first measurement electrode is arranged at the measurement hole and a protective net is provided outside the measurement electrode.

[0025] Preferably, a plurality of protrusions facing the center of the first accommodation cavity are further provided on the inner wall of the first accommodation cavity. The protrusions are hemispherical protrusions with a radius of 40 - 80 mm. The plurality of protrusions are evenly distributed on the inner wall of the first accommodation cavity.

[0026] Preferably, multiple layers of the first stirring blades are provided at intervals along the axial direction of the first stirring shaft.

[0027] A first odor collection pipe for collecting the odor generated in the first accommodation cavity is further provided on the first body. The first housing further includes an opening communicating with the first accommodation cavity. A detachable cover plate is provided at the opening. The first driving power source, the first chemical addition pipe, the first pH controller, and the first odor collection pipe are all arranged on the detachable cover plate.

[0028] Preferably, the pH value adjustment unit includes a second housing, a second stirring assembly, a second sludge inlet pipe, and a second sludge outlet pipe.

[0029] The second housing includes a second body having a second accommodation cavity. The second sludge inlet pipe and the second sludge outlet pipe are both arranged on the second body and both communicate with the second accommodation cavity.

[0030] A second chemical addition pipe communicating with the second accommodation cavity is provided on the second body.

[0031] The second stirring assembly includes a second driving power source, a second stirring shaft, and second stirring blades. The second driving power source is arranged on the second housing. The connecting end of the second stirring shaft is connected to the output end of the second driving power source. The free end of the second stirring shaft is arranged in the second accommodation cavity and the second stirring blades are provided thereon.

[0032] The fourth pipe communicates with the second sludge inlet pipe, and the second sludge outlet pipe communicates with the third pipe.

[0033] Preferably, it further includes a phosphorus recovery mechanism for recovering phosphorus. The phosphorus recovery mechanism communicates with the supernatant discharge port through a fifth pipe. The pH value control range in the phosphorus recovery mechanism is 9.5 - 10.

[0034] The sludge after sludge dewatering treatment by the sludge dewatering unit is transported through a dry sludge conveyor, and the sludge dewatering liquid after sludge dewatering treatment is communicated with the fifth pipeline or the phosphorus recovery mechanism through the sixth pipeline.

[0035] Preferably, the phosphorus recovery mechanism includes an outer shell, a middle shell, an inner shell, a water inlet pipe, a drain pipe, a discharge port, a push-flow stirring assembly, a folded plate eddy current assembly, a modular eddy current assembly, and an inclined plate assembly;

[0036] The outer shell includes a first cylindrical barrel body connected in series from top to bottom and a first conical barrel body with a wider upper part and a narrower lower part and a closed lower end. An a accommodation cavity is arranged in the first cylindrical barrel body, and a b accommodation cavity communicated with the a accommodation cavity is arranged in the first conical barrel body. The discharge port is communicated with the b accommodation cavity; a water collecting tank is arranged at the upper part of the a accommodation cavity;

[0037] The middle shell includes a second cylindrical barrel body connected in series from top to bottom and a second conical barrel body with a wider upper part and a narrower lower part and an opening at the lower end. A c accommodation cavity is arranged in the second cylindrical barrel body, and a d accommodation cavity communicated with the c accommodation cavity is arranged in the second conical barrel body; the upper end of the second conical barrel body is located in the a accommodation cavity and its lower end is located in the b accommodation cavity;

[0038] The inner shell includes a third cylindrical barrel body arranged in the c accommodation cavity, and the third cylindrical barrel body includes an e accommodation cavity with openings at both the upper and lower ends;

[0039] The e accommodation cavity forms a first water flow rising channel; a water flow descending channel is formed between the inner wall of the second cylindrical barrel body and the outer wall of the third cylindrical barrel body. The annular regions between the inner walls of the first cylindrical barrel body and the first conical barrel body, between the outer walls of the second cylindrical barrel body and the second conical barrel body, and the water collecting tank at the upper part of the a accommodation cavity enclose a second water flow rising channel; the push-flow stirring assembly and the folded plate eddy current assembly are arranged in the first water flow rising channel from top to bottom; the modular eddy current assembly is arranged in the water flow descending channel; the inclined plate assembly is arranged in the second water flow rising channel;

[0040] The water inlet pipe penetrates through the side wall of the first cylindrical barrel body and the side wall of the second cylindrical barrel body and is inserted and arranged at the upper part of the first water flow rising channel, and the end of the water outlet of the water inlet pipe is lower than the position of the water collecting tank; the drain pipe is communicated with the water collecting tank.

[0041] Preferably, the push-flow stirring assembly includes a third driving power source, a third stirring shaft, and third stirring blades. The connecting end of the third stirring shaft is connected to the output end of the third driving power source, and the third stirring blades are arranged at the free end of the third stirring shaft; the end of the water outlet of the water inlet pipe is 20-50 cm above the third stirring blades;

[0042] The folded plate eddy current assembly is located directly below the flow-pushing and stirring assembly. The folded plate eddy current assembly includes a first folded plate and a second folded plate arranged in parallel. The first folded plate includes multiple connecting plates connected in sequence, and the included angle α between two adjacent connecting plates is 80°-100°; the first folded plate and the second folded plate are in a mirror image structure;

[0043] The modular eddy current assembly includes multiple eddy current monomers arranged in layers or at intervals. The eddy current monomer is a hollow columnar body enclosed by a first vertical plate, a second vertical plate, an upper arc-shaped outer frame, an upper arc-shaped inner frame, a lower arc-shaped outer frame, and a lower arc-shaped inner frame; an eddy current sheet is installed in the eddy current monomer, and the cross-section of the eddy current sheet is at least one of a triangle, a semi-circle, and a rectangle;

[0044] The inclined plate assembly includes multiple sedimentation inclined plates arranged in parallel. The sedimentation inclined plates are arranged at an angle with the inner wall of the a accommodation cavity; and the inclined plate assembly is located in the middle and lower part of the a accommodation cavity.

[0045] Applying the technical solution of the present invention has the following beneficial effects:

[0046] 1. The device for releasing phosphorus from excess sludge and recovering phosphorus of the present invention includes a phosphorus release mechanism. The phosphorus release mechanism includes a sludge thickening unit, a sludge cracking assembly, and a sludge dewatering unit. The sludge thickening unit is provided with an excess sludge inlet, a thickened sludge discharge port, and a supernatant discharge port; the sludge cracking assembly includes a sludge cracking unit and a pH value adjustment unit connected in series, and the overall structure is concise; the present invention performs alkali cracking on 10% - 20% of the thickened sludge, and then uses the COD (carbon source) released by its cracking as the carbon source for polyphosphorus microorganisms (polyphosphorus bacteria) in the total amount of excess sludge entering the sludge thickening unit. Anaerobic phosphorus release occurs in the anaerobic environment of the sludge thickening unit without adding an external carbon source. Through the new scheme of releasing phosphorus by alkali hydrolysis of a small amount of thickened sludge + anaerobic biological phosphorus release of the total amount of excess sludge, low-cost and high-efficiency phosphorus release of the total amount of excess sludge is achieved.

[0047] 2. The sludge thickening unit in the present invention is a gravity thickening tank, which adopts a conventional gravity thickening tank in the prior art. When recovering phosphorus from the excess sludge of an existing sewage treatment plant, only a sludge cracking assembly (only cracking 10% - 20% of the total amount of thickened sludge), a phosphorus recovery mechanism, and a supporting control system need to be added, and the pipelines are correspondingly transformed to economically and conveniently achieve high-efficiency phosphorus release of sludge and high-efficiency recovery of phosphorus resources in the existing sewage treatment plant.

[0048] 3. In the present invention, the sludge cracking unit includes a first housing, a first stirring assembly, a first sludge inlet pipe, and a first sludge outlet pipe. The structure is concise, and the equipment investment and operating costs (chemical consumption, power consumption) of the sludge cracking unit are only 10% - 20% of those of the existing full-scale sludge alkali hydrolysis phosphorus release process. The occupied area of the equipment can also be saved; the addition of COD (carbon source) in the cracked sludge enables the anaerobic biological phosphorus release time of the excess sludge in the gravity thickening tank to be shortened to 6 hours, which is only 1 / 80 of the time required for the traditional sludge anaerobic digestion process (anaerobic digestion time: 20 - 30 days), greatly reducing the equipment investment and operating costs for sludge phosphorus release and phosphorus recovery.

[0049] 4. In the present invention, the phosphorus recovery mechanism is composed of an outer housing, a middle housing, and an inner housing nested with each other, forming a circulating flow channel formed by a combination of a first water rising channel, a water falling channel, and a second water rising channel. The push-flow stirring assembly and the folded plate eddy current assembly are arranged from top to bottom in the first water rising channel, and the modular eddy current assembly is arranged in the water falling channel, constituting a mechanical stirring mixing crystallization + hydraulic eddy current crystallization composite system. Due to its special structure, hydraulic classification is achieved during operation, enabling the solution to fully mix the materials and the crystal particles to be fluidized. Self-induced crystallization can be realized without adding external crystal seeds, and the particle size of the crystal particles is larger than that of traditional stirring crystallization; the first water rising channel and the water falling channel form a circulating flow channel that can automatically sort the crystal particles. Larger-sized and heavier particles will automatically break away from the circulating water flow under the action of gravity and be discharged into the crystal aggregation area, while smaller-sized and lighter crystal particles continue to crystallize in the water circulation channel. The crystal particles collected in the crystal aggregation area have a larger particle size and higher purity than those of traditional stirring crystallization, achieving efficient phosphorus recovery. The inclined plate assembly is arranged in the second water rising channel, which can perform secondary separation on the fine crystal particles entrained in the water flow, further improving the recovery efficiency of the phosphorus crystal particles.

[0050] In addition to the purposes, features, and advantages described above, the present invention has other purposes, features, and advantages. The following will refer to the drawings for a further detailed description of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0052] Figure 1 is the floor plan layout of the excess sludge phosphorus release and phosphorus recovery device in the preferred embodiment of the present invention;

[0053] Figure 2 is Figure 1 the elevation structure schematic diagram of

[0054] Figure 3 is Figure 2 the structural schematic diagram of the sludge cracking component in

[0055] Figure 4 is Figure 2 the structural schematic diagram of the phosphorus recovery mechanism in

[0056] Figure 5 is Figure 4 the top view of the installation of the folded plate eddy current component on the inner shell in

[0057] Figure 6 is Figure 5 the M-M sectional view of

[0058] Figure 7 is Figure 4 the structural schematic diagram of the eddy current monomer of the modular eddy current component in

[0059] Figure 8 is Figure 7 the top view of

[0060] Figure 9 is Figure 8 the N-N sectional view of

[0061] Among them, 1. Sludge thickening unit, 1.1. Excess sludge inlet, 1.2. Thickened sludge discharge port, 1.3. Supernatant discharge port; 2. Sludge cracking component, 2.1. Sludge cracking unit, A1. First housing, A1.1. First accommodating cavity, A1.2. First body, A1.3. Protrusion, A1.4. Detachable cover plate, A2. First stirring assembly, A2.1. First driving power source, A2.2. First stirring shaft, A2.3. First stirring blades, A3. First mud inlet pipe, A4. First mud outlet pipe, A5. First chemical addition pipe, A6. First pH controller, A6.1. First measuring electrode, A7. First odor collection pipe; 2.2. pH value adjustment unit, B1. Second housing, B1.1. Second accommodating cavity, B1.2. Second body, B2. Second stirring assembly, B2.1. Second driving power source, B2.2. Second stirring shaft, B2.3. Second stirring blades, B3. Second mud inlet pipe, B4. Second mud outlet pipe, B5. Second chemical addition pipe, B6. Second pH controller, B6.1. Second measuring electrode, B7. Second odor collection pipe; 3. Sludge dewatering unit; 4. First pipeline; 5. Second pipeline; 6. Third pipeline; 7. Fourth pipeline; 8. Phosphorus recovery mechanism, 8.1. Outer housing, 8.1.1. First cylindrical barrel, 8.1.2. First conical barrel, 8.1.3. a accommodating cavity, 8.1.4. b accommodating cavity, 8.2. Middle housing, 8.2.1. Second cylindrical barrel, 8.2.2. Second conical barrel, 8.2.3. c accommodating cavity, 8.2.4. d accommodating cavity, 8.3. Inner housing, 8.3.1. Third cylindrical barrel, 8.3.2. e accommodating cavity, 8.4. Water collecting tank, 8.5. Water inlet pipe, 8.6. Drain pipe, 8.7. Discharge port, 8.8. Pushing and stirring assembly, 8.8.1. Third driving power source, 8.8.2. Third stirring shaft, 8.8.3. Third stirring blades; 8.9. Baffle eddy current assembly, 8.9.1. First baffle, 8.9.2. Second baffle, 8.10. Modular eddy current assembly, 8.10.1. First vertical plate, 8.10.2. Second vertical plate, 8.10.3. Upper arc outer frame, 8.10.4. Upper arc inner frame, 8.10.5. Lower arc outer frame, 8.10.6. Lower arc inner frame, Y. Semi-circular housing eddy current sheet, S. Isosceles right triangle eddy current sheet; 8.11. Inclined plate assembly; A. First water flow rising channel, B. Water flow falling channel, C. Second water flow rising channel, D. Crystal aggregation area; 9. Fifth pipeline; 10. Dry sludge conveyor; 11. Sixth pipeline; 12. Surplus sludge conveying pipeline; 13. Seventh pipeline; H. Pipeline mixer, H1. Magnesium salt dosing pipe, H2. Ammonium salt dosing pipe, H3. Alkali dosing pipe, F1. First electric valve, F2. Second electric valve; K1. First flowmeter, K2. Second flowmeter, K3. Third flowmeter, K4. Fourth flowmeter; C4. Lift pump; P1. Orthophosphate online detector, P2. pH value online detector. Detailed implementation manners

[0062] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways defined and covered by the claims.

[0063] Embodiment

[0064] See Figures 1-2 , a surplus sludge phosphorus release and phosphorus recovery device, including a phosphorus release mechanism and a phosphorus recovery mechanism 8. The surplus sludge of the urban sewage treatment plant is subjected to phosphorus release treatment through the phosphorus release mechanism, and then the phosphorus is recovered through the phosphorus recovery mechanism 8.

[0065] In this embodiment, the phosphorus release mechanism includes a sludge thickening unit 1, a sludge cracking assembly 2 and a sludge dewatering unit 3. The sludge thickening unit 1 is provided with a surplus sludge inlet 1.1, a thickened sludge discharge port 1.2 and a supernatant discharge port 1.3. The surplus sludge inlet 1.1 is communicated with the surplus sludge conveying pipeline 12, and the first flowmeter K1 is arranged on the surplus sludge conveying pipeline 12; the sludge cracking assembly 2 includes a sludge cracking unit 2.1 and a pH value adjusting unit 2.2 arranged in series. The surplus sludge enters the sludge thickening unit 1 through the surplus sludge conveying pipeline 12 and the surplus sludge inlet 1.1 for thickening treatment; the supernatant after thickening treatment is discharged through the supernatant discharge port 1.3; the thickened sludge after thickening treatment is discharged through the thickened sludge discharge port 1.2. A part of the thickened sludge enters the sludge cracking unit 2.1 through the first pipeline 4 (the second flowmeter K2 and the first electric valve F1 are arranged on this pipeline) for sludge cracking treatment, and another part of the thickened sludge enters the sludge dewatering unit 3 through the second pipeline 5 (the third flowmeter K3 and the second electric valve F2 are arranged on this pipeline) for sludge dewatering treatment. The flow ratio of the sludge in the two pipelines can be adjusted by controlling the first electric valve F1 and the second electric valve F2; the cracked sludge after cracking treatment enters the pH value adjusting unit 2.2 for pH value adjustment, and then is lifted by the lift pump C4 and conveyed to the surplus sludge inlet 1.1 through the third pipeline 6 and circulated to the sludge thickening unit 1. The detailed structure is as follows:

[0066] The sludge thickening unit 1 adopts a circular gravity thickening tank in the prior art. In this embodiment, the tank body is built with reinforced concrete or made of a steel anti-corrosion device. The thickening time of the sludge in the tank (calculated by hydraulic retention time) is 14 - 24 h. The excess sludge inlet 1.1 is communicated with the excess sludge conveying pipeline 12, and the excess sludge conveying pipeline 12 is communicated with an external sludge conveying pump. The flow time of the sludge from the intersection point of the excess sludge conveying pipeline 12 and the outlet pipeline of the lift pump C4 (i.e., the third pipeline 6) to the excess sludge inlet 1.1 in the sludge thickening unit 1 is not less than 3 seconds. The supernatant discharge port 1.3 arranged on the upper part of the sludge thickening unit 1 is communicated with the phosphorus recovery mechanism 8 to convey the supernatant to the phosphorus recovery mechanism for phosphorus recovery treatment. The bottom of the sludge thickening unit 1 is provided with a thickened sludge discharge port 1.2, and the thickened sludge discharge port 1.2 is respectively communicated with the sludge cracking assembly 2 and the sludge dewatering unit 3.

[0067] The sludge cracking assembly 2 includes a serially arranged sludge cracking unit 2.1 and a pH value adjusting unit 2.2, as detailed in Figure 3 , preferably in this embodiment:

[0068] The sludge cracking unit 2.1 includes a first housing A1, a first stirring assembly A2, a first sludge inlet pipe A3, a first sludge outlet pipe A4, and a first pH controller A6. The first housing A1 includes a first body A1.2 having a first accommodation cavity A1.1. The first sludge inlet pipe A3 and the first sludge outlet pipe A4 are both arranged on the first body A1.2 and are both communicated with the first accommodation cavity A1.1. The first body A1.2 is provided with a first chemical addition pipe A5 communicated with the first accommodation cavity A1.1. The first stirring assembly A2 includes a first driving power source A2.1, a first stirring shaft A2.2, and first stirring blades A2.3. The first driving power source A2.1 is arranged on the first housing A1. The connecting end of the first stirring shaft A2.2 is connected to the output end of the first driving power source A2.1, and the free end of the first stirring shaft A2.2 is arranged in the first accommodation cavity A1.1 and is provided with the first stirring blades A2.3 thereon. The first pipeline 4 is communicated with the first sludge inlet pipe A3, and the first sludge outlet pipe A4 is communicated with the pH value adjusting unit 2.2 through a fourth pipeline 7. The first body A1.2 is provided with a measuring hole communicated with the first accommodation cavity A1.1, and the first pH controller A6 is arranged at the measuring hole for measuring the pH value of the sludge. The first pH controller is connected to an external PLC control system, and the pH controller measures the pH value of the sludge through a first measuring electrode A6.1. The first measuring electrode is arranged at the measuring hole and a protective net is arranged outside the first measuring electrode.

[0069] Further preferably, the first housing A1 is a cylindrical housing, made of carbon steel anti-corrosion material, and uses sodium hydroxide addition to crack sludge under normal temperature and pressure. In this embodiment, the pH control range in the sludge cracking assembly is: 10.8 - 11, and the reaction time for sludge cracking is: 40 - 60 min. A plurality of protrusions A1.3 facing the center of the first accommodation chamber are further provided on the inner wall of the first accommodation chamber A1.1; the protrusions A1.3 are hemispherical protrusions with a radius of 40 - 80 mm; the plurality of protrusions A1.3 are evenly distributed on the inner wall of the first accommodation chamber. Here, the radii of the hemispherical protrusions are the same, and the plurality of protrusions are evenly distributed on the vertical inner side wall of the first accommodation chamber, and the distance between the edges of adjacent two protrusions is 1.5 times their diameter. A plurality of layers of the first stirring blades A2.3 are provided at intervals along the axial direction of the first stirring shaft A2.2 (here, preferably two layers of first stirring blades arranged in the up and down direction, and upward thrust is generated when the stirring blades rotate); a first odor collection pipe A7 for collecting the odor generated in the first accommodation chamber is further provided on the first body A1.2; the first housing A1 further includes an opening communicating with the first accommodation chamber A1.1, and a detachable cover plate A1.4 is provided at the opening, and the first driving power source A2.1, the first chemical addition pipe A5, the first pH controller A6, and the first odor collection pipe A7 are all arranged on the detachable cover plate A1.4.

[0070] In this embodiment, the pH value adjustment unit 2.2 includes a second housing B1, a second stirring assembly B2, a second sludge inlet pipe B3, and a second sludge outlet pipe B4. The second housing B1 includes a second body B1.2 having a second accommodation cavity B1.1. The second sludge inlet pipe B3 and the second sludge outlet pipe B4 are both arranged on the second body B1.2 and are both communicated with the second accommodation cavity B1.1. A second chemical addition pipe B5 communicated with the second accommodation cavity B1.1 is arranged on the second body B1.2. The second stirring assembly B2 includes a second driving power source B2.1, a second stirring shaft B2.2, and second stirring blades B2.3. The second driving power source B2.1 is arranged on the second housing B1. The connecting end of the second stirring shaft B2.2 is connected to the output end of the second driving power source B2.1. The free end of the second stirring shaft B2.2 is arranged in the second accommodation cavity B1.1 and the second stirring blades B2.3 are arranged thereon. The fourth pipeline 7 is communicated with the second sludge inlet pipe B3. The second sludge outlet pipe B4 is communicated with the third pipeline 6. A lift pump C4 is installed on the third pipeline 6. Further preferably, the second housing B1 is a cylindrical housing. In this embodiment, the control range of the pH value in the pH value adjustment unit 2.2 is: 9 to 9.5. The effective volume of the second accommodation cavity B1.1 in the pH value adjustment unit 2.2 is half of the volume of the first accommodation cavity A1.1 in the sludge cracking unit 2.1, and the height of the pH value adjustment unit 2.2 is lower than that of the sludge cracking unit 2.1, which can ensure that the sludge in the sludge cracking unit 2.1 flows into the pH value adjustment unit 2.2 by gravity. The soluble COD of the sludge discharged from the third pipeline 6 is not less than 2000 mg / L and the pH = 9 - 9.5. In addition, a measuring hole communicated with the second accommodation cavity B1.1 is arranged on the second body B1.2. A second pH controller B6 is arranged at the measuring hole for measuring the pH value of the sludge. The second pH controller is connected to an external PLC control system, and the pH controller measures the pH value of the sludge through a second measuring electrode B6.1. The second measuring electrode is arranged at the measuring hole and a protective net is arranged outside the second measuring electrode. A second odor collection pipe B7 for collecting the odor generated in the second accommodation cavity is further arranged on the second body B1.2.

[0071] In this embodiment, the phosphorus recovery mechanism 8 is communicated with the supernatant discharge port 1.3 through a fifth pipeline 9 (a fourth flowmeter K4 is arranged on this pipeline). The sludge after the sludge dewatering unit 3 performs sludge dewatering treatment is conveyed through a dry sludge conveyor 10 (preferably a dry sludge conveying pipe here, and a conveying device such as a conveying belt can also be used). The sludge dewatering liquid after the sludge dewatering treatment is communicated with the fifth pipeline 9 or the phosphorus recovery mechanism through a sixth pipeline 11. Figures 1-2 is schematically shown to enter the phosphorus recovery mechanism 8 after being communicated with the fifth pipeline 9.

[0072] Further preferably, the phosphorus recovery mechanism 8 includes an outer housing 8.1, a middle housing 8.2, an inner housing 8.3, a water inlet pipe 8.5, a drain pipe 8.6, a discharge port 8.7, a flow-pushing and stirring assembly 8.8, a baffle vortex assembly 8.9, a modular vortex assembly 8.10, and an inclined plate assembly 8.11, as shown in Figure 4 , and the detailed structure is as follows:

[0073] The outer housing 8.1 includes a first cylindrical barrel 8.1.1 arranged in series from top to bottom and a first conical barrel 8.1.2 with a wider upper part and a narrower lower part and a closed lower end. An a accommodation cavity 8.1.3 is arranged in the first cylindrical barrel 8.1.1, and a b accommodation cavity 8.1.4 communicated with the a accommodation cavity 8.1.3 is arranged in the first conical barrel 8.1.2. The discharge port 8.7 is communicated with the b accommodation cavity 8.1.4. Figure 4 Specifically, a crystal aggregation area D is formed at the lower part of the b accommodation cavity 8.1.4, and the discharge port 8.7 is communicated with the crystal aggregation area D; a water collecting tank 8.4 is arranged at the upper part of the a accommodation cavity 8.1.3.

[0074] The middle housing 8.2 includes a second cylindrical barrel 8.2.1 arranged in series from top to bottom and a second conical barrel 8.2.2 with a wider upper part and a narrower lower part and an opening at the lower end. A c accommodation cavity 8.2.3 is arranged in the second cylindrical barrel 8.2.1, and a d accommodation cavity 8.2.4 communicated with the c accommodation cavity 8.2.3 is arranged in the second conical barrel 8.2.2; the upper end of the second conical barrel 8.2.2 is located in the a accommodation cavity 8.1.3 and its lower end is located in the b accommodation cavity 8.1.4.

[0075] The inner housing 8.3 includes a third cylindrical barrel 8.3.1 arranged in the c accommodation cavity 8.2.3, and the third cylindrical barrel 8.3.1 includes an e accommodation cavity 8.3.2 with openings at both the upper and lower ends.

[0076] In the phosphorus recovery mechanism 8: the e accommodation cavity 8.3.2 forms a first water flow rising channel A; a water flow descending channel B is formed between the inner wall of the second columnar cylinder 8.2.1 and the outer wall of the third columnar cylinder 8.3.1. An annular area between the inner wall of the first columnar cylinder 8.1.1 and the first conical cylinder 8.1.2, the outer wall of the second columnar cylinder 8.2.1 and the second conical cylinder 8.2.2, and a water collecting tank 8.4 located above the a accommodation cavity 8.1.3 enclose a second water flow rising channel C; the flow-pushing and stirring assembly 8.8 and the folded plate eddy current assembly 8.9 are arranged from top to bottom in the first water flow rising channel A; the modular eddy current assembly 8.10 is arranged in the water flow descending channel B; the inclined plate assembly 8.11 is arranged in the second water flow rising channel C; the water inlet pipe 8.5 penetrates the side wall of the first columnar cylinder 8.1.1 and the side wall of the second columnar cylinder 8.2.1 and is inserted into the upper part of the first water flow rising channel A, and the end of the water outlet of the water inlet pipe 8.5 is lower than the position of the water collecting tank 8.4; the drain pipe 8.6 is communicated with the water collecting tank 8.4.

[0077] Further preferably, the flow-pushing and stirring assembly 8.8 includes a third driving power source 8.8.1, a third stirring shaft 8.8.2, and third stirring blades 8.8.3. The connecting end of the third stirring shaft 8.8.2 is connected to the output end of the third driving power source 8.8.1, and the third stirring blades 8.8.3 are arranged at the free end of the third stirring shaft 8.8.2; the end of the water outlet of the water inlet pipe 8.5 is 20-50 cm above the third stirring blades 8.8.3. The flow-pushing and stirring assembly 8.8 lifts the liquid and suspended particles in the first water flow rising channel A from its lower section to the upper section and provides a driving force for the water to circulate in the first water flow rising channel A.

[0078] The top of the folded plate eddy current assembly 8.9 is 0.5 m away from the lower edge of the flow-pushing and stirring assembly 8.8 and the lower end is flush with the lower end of the inner shell 8.3; see Figure 5 and Figure 6 , the folded plate eddy current assembly 8.9 includes a first folded plate 8.9.1 and a second folded plate 8.9.2 arranged in parallel. The first folded plate 8.9.1 includes multiple connecting plates connected in sequence, and the included angle α between adjacent two connecting plates is 80°-100°; the first folded plate 8.9.1 and the second folded plate 8.9.2 are mirror structures. The included angle α between adjacent connecting plates in the folded plate eddy current assembly is 90°, the length Q1 of the connecting plate is 20% of the diameter of the inner shell 8.3, the included angle and length of each connecting plate in the same first folded plate or second folded plate are the same, the wave crests and wave troughs of the first folded plate and the second folded plate are horizontally aligned, and the horizontal distance Q2 is equal and is 10% of the diameter of the inner shell 8.3.

[0079] The upper end of the modular eddy current component 8.10 is 0.5 m below the liquid level in the inner cavity of the water flow descending channel B, and the distance from the lower end of the modular eddy current component to the plane where the lower end of the inner housing 8.3 is located is 0.6 m. As Figure 7 , Figure 8 , Figure 9 shown, the outer shape of the modular eddy current component is a sector-ring columnar cube, and its horizontal projection is in the shape of a sector ring, including multiple eddy current monomers arranged in layers or at intervals. The eddy current monomer is a hollow columnar body enclosed by a first vertical plate 8.10.1, a second vertical plate 8.10.2, an upper arc-shaped outer frame 8.10.3, an upper arc-shaped inner frame 8.10.4, a lower arc-shaped outer frame 8.10.5, and a lower arc-shaped inner frame 8.10.6. Eddy current sheets are installed in the eddy current monomer, and the cross-section of the eddy current sheet is at least one of a triangle, a semi-circle, and a rectangle. The columnar body is made of metal or engineering plastic and can bear the weight of the frame itself and the eddy current sheets installed inside.

[0080] In this embodiment, it is further preferred that a semi-circular shell eddy current sheet layer and an isosceles right triangle eddy current sheet layer are provided in the eddy current monomer. A semi-circular shell eddy current sheet Y is provided in the semi-circular shell eddy current sheet layer. The horizontal projection of the semi-circular shell eddy current sheet Y is arc-shaped, and its cross-sectional shape is semi-circular, with a diameter of 30 - 40 mm. The horizontal spacing between each semi-circular shell eddy current sheet Y in the same layer is equal, and the distance between adjacent two semi-circular shell eddy current sheets is 1.3 times its diameter. An isosceles right triangle eddy current sheet S is provided in the isosceles right triangle eddy current sheet layer. The length of the isosceles right triangle eddy current sheet S in the same layer is determined by the radius of the arc of its own horizontal projection and the arc radian corresponding to the horizontal projection of the frame of the eddy current monomer. The horizontal projection of a single isosceles right triangle eddy current sheet is arc-shaped, and its cross-sectional shape is an isosceles right triangle. The height of the triangle is the same as the radius of the semi-circular shell eddy current sheet. The adjacent semi-circular shell eddy current sheet layer and isosceles right triangle eddy current sheet layer are arranged alternately, and the projections of the adjacent semi-circular shell eddy current sheet layer and isosceles right triangle eddy current sheet layer on the horizontal plane do not overlap.

[0081] The inclined plate assembly 8.11 includes multiple precipitation inclined plates arranged in parallel, and the precipitation inclined plates are arranged at an angle with the inner wall of the a accommodation cavity; and the inclined plate assembly 8.11 is located in the middle and lower part of the a accommodation cavity.

[0082] The water inlet pipe 8.5 includes a horizontally arranged pipe section, an arc-shaped transition pipe section, and a vertically arranged pipe section that are connected in series. The horizontally arranged pipe section passes through the upper parts of the outer housing 8.1 and the middle housing 8.2. The arc-shaped transition pipe section is a pipe section bent downward by 90 degrees and extends to the upper part of the inner housing 8.3. The outlet of the vertically arranged pipe section is located at a position 0.4 meters above the third stirring blade 8.8.3 in the flow-pushing and stirring assembly 8.8. A pipeline mixer H is installed on the horizontally arranged pipe section of the water inlet pipe 8.5. The pipeline mixer H is communicated with a magnesium salt dosing pipe H1, an ammonium salt dosing pipe H2, and an alkali dosing pipe H3. The supernatant, sludge dewatering liquid, magnesium salt, ammonium salt, and alkali are mixed evenly and then enter the phosphorus recovery mechanism 8.

[0083] In this embodiment, the sludge dewatering unit 3 adopts an existing horizontal screw centrifugal dewatering complete set of equipment. Its sludge inlet pipe is communicated with the second pipeline 5, and the sludge dewatering liquid discharge pipe is communicated with the phosphorus recovery mechanism 8. During the sludge dewatering process in this embodiment, no agents such as lime, ferric salt, and aluminum salt that can form precipitates with phosphate ions are added. Only a small amount of polyacrylamide agent is added as needed. The dewatered sludge discharged after sludge dewatering is transported out for disposal.

[0084] In addition, a control system is provided in this embodiment. The control system includes on-line detection instruments, cables, and an electric control cabinet containing a programmable logic controller (PLC). The on-line detection instruments include a first flowmeter K1 arranged on the surplus sludge conveying pipeline 12, a second flowmeter K2 arranged on the first pipeline 4, a third flowmeter K3 arranged on the second pipeline 5, a fourth flowmeter K4 arranged on the fifth pipeline 9, an orthophosphate on-line detector P1 arranged near the supernatant discharge pipe, a pH value on-line detector P2 arranged in the phosphorus recovery mechanism 8, a first pH controller A6 and a second pH controller B6 arranged in the sludge cracking assembly; the cables and the electric control cabinet containing a programmable logic controller (PLC) both adopt existing mature equipment, which can supply power to the on-line detection instruments and communicate with the on-line detection instruments. The PLC controls the operation of external dosing equipment and other equipment according to the data detected by the on-line detection instruments and the preset control logic.

[0085] Applying the technical solution of this embodiment specifically is:

[0086] The phosphorus-rich excess sludge (Q_excess, water content 99.2%) discharged from the sewage treatment biochemical system is mixed with the cracked sludge (Q_cracked) discharged from the sludge cracking unit 2 through the excess sludge transfer pipeline 12 and then enters the sludge thickening unit 1. The phosphorus-rich excess sludge undergoes sludge thickening in the sludge thickening unit 1 under the action of the carbon source provided by the cracked sludge and simultaneously undergoes anaerobic biological phosphorus release, releasing the phosphorus in the solid phase into the liquid phase. The low-phosphorus sludge after thickening and biological phosphorus release is discharged from the bottom of the gravity thickening tank. A part of the thickened sludge (Q_cracked) enters the sludge cracking unit 2.1 in the sludge cracking assembly 2 through the first pipeline 4 for sludge cracking. After cracking, the sludge (Q_cracked) enters the pH adjustment unit 2.2 for pH adjustment and then all returns to the sludge thickening unit 1; another part of the thickened sludge (Q_dewatering) is discharged into the sludge dewatering unit 3 through the second pipeline 5 for dewatering treatment. In this embodiment, the flow rate or mass ratio of the total amount of sludge entering the sludge cracking unit to the thickened sludge is Q_cracked:(Q_cracked + Q_dewatering)=0.2; the high-concentration phosphorus-containing supernatant generated by the sludge thickening unit 1 is discharged into the phosphorus recovery mechanism 8 through the fifth pipeline 9 for phosphorus recovery; the sludge dewatering liquid generated by the sludge dewatering unit is mixed with the supernatant of the sludge thickening unit through the sixth pipeline 11 and then discharged into the phosphorus recovery mechanism 8 for phosphorus recovery. The dried sludge is transported out for disposal through the dried sludge conveyor 10; the low-phosphorus water discharged from the phosphorus recovery mechanism returns to the biochemical pool at the front end of the sewage treatment system through the seventh pipeline 13.

[0087] In this embodiment, after the sludge is cracked with alkali, substances such as COD (carbon source), ammonia nitrogen, organic nitrogen, orthophosphate, and organic phosphorus are released into the aqueous phase and converted into cracked sludge (Q_cracked). The test data of the main components before sludge thickening (Q_excess) and after cracking (Q_cracked) are shown in Table 1. The mass of the cracked sludge (Q_cracked) is equal to the sum of the mass of the thickened sludge (Q_cracked) and the masses of the alkali and acid agents added during the cracking process. The cracked sludge (Q_cracked) is discharged into the inlet of the gravity thickening tank. The sludge cracking step in this embodiment simultaneously achieves five technical effects:

[0088] ① It realizes sludge cracking and phosphorus release for the residual phosphorus in the sludge, releases orthophosphate from the solid phase to the liquid phase, creating conditions for the subsequent phosphorus recovery mechanism to recover phosphorus;

[0089] ② The high-concentration COD (carbon source) released by sludge cracking returns to the sludge thickening tank and serves as the carbon source for anaerobic biological phosphorus release of excess sludge, eliminating the need for external carbon sources, achieving "treating waste with waste", and saving the cost of sludge phosphorus release;

[0090] ③ Sludge cracking releases ammonia nitrogen, reducing the dosage of ammonium salts (such as ammonium chloride) added by the subsequent phosphorus recovery mechanism to recover struvite, further saving the cost of phosphorus recovery;

[0091] ④ After the sludge is cracked, its dewatering performance can be improved, the chemical dosage for sludge dewatering in the subsequent sludge dewatering unit can be reduced, which is conducive to improving the treatment efficiency of the subsequent sludge dewatering unit and reducing the cost of sludge dewatering;

[0092] ⑤ The cracked sludge is adjusted to a pH of 9 - 9.5 by adding acid in the pH adjustment unit 2.2. After being mixed with the surplus sludge (Q_surplus), in this solution, the pH of the mixed sludge entering the sludge thickening tank can be between 8 - 8.5, forming a suitable anaerobic biological phosphorus release pH condition in the sludge thickening tank.

[0093] Table 1 Main components of the sludge before and after thickening

[0094]

[0095] Note: The concentration of the sludge before thickening in the table (Q_surplus, referring to the surplus sludge entering the sludge thickening unit through the surplus sludge conveying pipeline 12) MLSS = 8 g / L, and the concentration of the sludge after cracking (Q_cracked) after sludge thickening is MLSS = 20 g / L. In this embodiment, the volume of the sludge after cracking (Q_cracked) after sludge thickening is only about 8% of the volume of the surplus sludge Q_surplus entering the sludge thickening tank through pipeline 12. The component data of the sludge are all the data measured by centrifuging the sludge and taking the supernatant.

[0096] The surplus sludge before thickening (Q_surplus) and the cracked sludge (Q_cracked) are mixed before entering the sludge thickening unit 1. Compared with the conventional gravity thickening process, in this embodiment, in the sludge thickening unit 1, in addition to realizing the physical thickening effect of the sludge, the following technical effects are also achieved:

[0097] ① The surplus sludge (Q_surplus) and the cracked sludge (Q_cracked) are mixed before entering the sludge thickening unit. The mixing process and the pipeline transportation process can enable the microorganisms in the surplus sludge (Q_surplus) to quickly adsorb the organic components in the cracked sludge (Q_cracked), creating conditions for the microorganisms to further absorb the adsorbed organic matter (carbon source) into the microbial cells in the thickening tank, overcoming the defect of low mass transfer and absorption efficiency between the organic matter and the microbial cells due to small fluid disturbance in the sludge thickening tank, and enabling more organic components in the cracked sludge to enter the microbial cells in the surplus sludge to achieve anaerobic phosphorus release;

[0098] ② The phosphorus-rich microorganisms (such as polyphosphate-accumulating organisms) in the surplus sludge release the phosphorus in the cells into the water (in the form of orthophosphate, PO 4 3- ) under the action of the COD (carbon source) provided by the cracked sludge under anaerobic conditions in the sludge thickening unit 1, realizing anaerobic biological phosphorus release of all surplus sludge. The orthophosphate (PO 4 3-The concentration of phosphorus can reach 50-60 mg / L, which creates conditions for subsequent phosphorus recovery.

[0099] ③ The organic nitrogen and organic phosphorus contained in the sludge are converted into ammonia nitrogen and orthophosphate (PO 4 3- ), the conversion of organic nitrogen into ammonia nitrogen can save the dosage of ammonia nitrogen reagents for the subsequent phosphorus recovery mechanism, and the conversion of organic phosphorus into orthophosphate can further improve the phosphorus recovery efficiency (organic phosphorus cannot be recovered through struvite crystallization). The main component test data before sludge concentration, the water inlet of the sludge concentration unit, and the supernatant of the effluent of the sludge concentration unit are shown in Table 2. The effect of this embodiment on the release of phosphorus from sludge is significant, and most of the phosphorus exists in the form of orthophosphate, which can be recovered by the subsequent phosphorus recovery mechanism 8.

[0100] Table 2 Main components of sludge before thickening, at the inlet of the sludge thickening tank, and at the effluent of the sludge thickening tank

[0101]

[0102] Note: The sludge concentration MLSS in the table before sludge concentration (Qresidual, refers to the residual sludge entering the sludge concentration unit from the residual sludge conveying pipeline 12) is 8g / L. The data before sludge concentration is the data measured by centrifuging the sludge and taking the supernatant; the sludge concentration of the mixed liquor at the inlet of the sludge concentration tank is about 8.8g / L. In this embodiment, the volume of the sludge after concentration is 40% of the volume of the sludge before concentration (Qresidual), the concentrated sludge (Qcracked) entering the cracking unit accounts for 20% of the total volume of the concentrated sludge (Qcracked + Qdewatered), the reagent NaOH added to the sludge cracking unit is added in solid form, the density of the sludge after cracking is similar to that of the sludge before cracking (Qcracked), and the volume of the sludge after cracking (Qcracked) accounts for 8% of the volume of the sludge before concentration (Qresidual); the composition of the mixed liquor at the inlet of the sludge concentration tank is measured by taking the supernatant obtained by centrifuging the mixed liquor.

[0103] The phosphorus recovery mechanism 8 described in this embodiment uses magnesium ammonium phosphate crystals (struvite) to recover phosphorus in the liquid phase. The wastewater containing orthophosphate from the sludge concentration unit 1 and the sludge dehydration unit 3 is mixed with the reagent (the reagent is magnesium chloride, ammonium chloride, and sodium hydroxide) in the pipeline mixer H and then enters the phosphorus recovery mechanism 8. The dosage of magnesium chloride and ammonium chloride reagents is based on Mg:NH 4 + : P=1.3:1.3:1 (molar ratio), the pH of the crystallization reaction is controlled at 9.5-10, the third stirring blade rotates to generate an upward thrust, stirring and mixing the liquid and suspended particles, so that the liquid mixture circulates.

[0104] The orthophosphate in the influent water and the crystal-forming ions (magnesium ions, ammonium ions) in the reagent are contacted and mixed under the mechanical stirring condition of the third stirring blade to form tiny magnesium ammonium phosphate crystals (crystal nuclei). The tiny crystals circulate in the first water flow ascending channel A and the water flow descending channel B along with the water flow. When passing through the folded plate vortex component 8.9 and the modular vortex component 8.10, the crystal-forming ions in the wastewater are further contacted and mixed under the action of a large number of micro-vortices generated by the vortex component, and the tiny crystal particles are fluidized. The tiny crystals and the crystal nuclei and the crystal-forming ions fully collide and contact with each other under the action of the micro-vortices. , secondary nucleation occurs, and self-induced crystallization is achieved without the need for external seed crystals. The particle size of the crystal particles gradually increases. When the particle size and mass of the crystal particles increase to a certain extent, under the action of gravity, the large-particle crystals gradually automatically detach from the circulating water flow and flow into the crystal gathering area D. After the crystallization is completed, the water flow enters the annular solid-liquid separation area. The fine crystal particles entrained in the water flow are further separated from the solid and liquid under the action of gravity and the inclined plate assembly. After the crystal particles are precipitated, they slide to the crystal gathering area D under the action of gravity. The supernatant after precipitation is collected upward to the water collection tank 8.4 and discharged from the phosphorus recovery mechanism 8 through the drain pipe 8.6. The struvite crystals accumulated in the crystal gathering area D are regularly discharged to the dehydration and separation equipment set separately through the discharge port 8.7. In this embodiment, the recovery rate of orthophosphate by the phosphorus recovery mechanism is greater than 80%, and the recovered product is struvite.

[0105] The low-phosphorus liquid discharged from the phosphorus recovery mechanism is returned to the biochemical pool at the front end of the sewage treatment system through the seventh pipeline 13.

[0106] Applying the technical solution of this embodiment has the following beneficial effects:

[0107] 1. Existing sludge decomposition and phosphorus release technologies all use the method of decomposing the entire amount of excess sludge. In this embodiment, only 10% to 20% of the concentrated sludge needs to be decomposed by adding alkali, and the COD (carbon source) released by the decomposition is used as the carbon source for the polyphosphate microorganisms (polyphosphate bacteria) in the entire amount of excess sludge entering the thickening tank. Anaerobic phosphorus release occurs in the anaerobic environment of the sludge thickening tank without the need for an external carbon source. The new scheme of alkaline phosphorus release of a small amount of concentrated sludge + anaerobic biological phosphorus release of the entire amount of excess sludge achieves low-cost and efficient phosphorus release from the entire amount of excess sludge. In this embodiment, the equipment investment and operating costs (drug consumption, electricity consumption) of the sludge breakdown unit are only equivalent to 10% to 20% of the existing full-volume sludge alkaline phosphorus decomposition process, and the equipment footprint can also be saved; the addition of carbon source to the cracked sludge shortens the anaerobic biological phosphorus release time of the sludge in the gravity thickening tank to 6 hours, which is only 1 / 80 of the time required for the traditional sludge anaerobic digestion process (anaerobic digestion time 20 to 30 days), greatly reducing the equipment investment and operating costs of sludge phosphorus release and phosphorus recovery.

[0108] 2. Some of the phosphorus and nitrogen elements released into the liquid phase by existing physical dephosphorization (ultrasound, thermal hydrolysis, mechanical ball milling) and chemical dephosphorization (acid, alkali) technologies exist in the form of organic phosphorus and organic nitrogen, and organic phosphorus is difficult to recycle. In this embodiment, the sludge after chemical dephosphorization is returned to the concentration tank. The organic phosphorus and organic nitrogen released during the dephosphorization process are converted into orthophosphate and ammonia nitrogen that can be recovered by the subsequent phosphorus recovery unit under the action of the anaerobic environment of the concentration tank and anaerobic bacteria in the remaining sludge, which can further improve the phosphorus recovery rate and reduce the cost of adding ammonia nitrogen to the phosphorus recovery unit.

[0109] 3. At present, most of the domestic urban sewage treatment plants adopt the technical route of sludge gravity concentration + sludge dewatering for the treatment of residual sludge, and have built sludge concentration tanks and sludge dewatering facilities. In this embodiment, the gravity concentration tank adopts the existing conventional gravity concentration tank. When it is necessary to recover phosphorus from the residual sludge of the existing sewage treatment plant, it is only necessary to add a sludge breaking component (only 10% to 20% of the total concentrated sludge needs to be broken, and there is no need to break the entire amount of concentrated sludge), a sludge phosphorus recovery device, and a control system. The corresponding modification of the pipeline can realize the economical and convenient recovery of sludge phosphorus resources in the existing sewage treatment plant.

[0110] 4. In this embodiment, the phosphorus recovery mechanism adopts an outer shell, a middle shell, and an inner shell to form a three-layer shell arrangement, forming a circulating flow channel formed by a first water flow rising channel, a water flow descending channel, and a second water flow rising channel. The plug flow stirring component and the folded plate vortex component are arranged from top to bottom in the first water flow rising channel, and the modular vortex component is arranged in the water flow descending channel, forming a mechanical stirring mixed crystallization + hydraulic vortex crystallization composite system. Due to its special structure, hydraulic classification is realized during operation, so that the solution is fully mixed with materials and the crystal particles are fluidized, and self-induction is realized without the need for external crystal seeds. The crystal particles are larger in size and purity than those in traditional stirred crystallization. The first water flow ascending channel and the water flow descending channel form a water flow circulation channel to automatically sort the crystal particles. Particles with large size and mass will automatically separate from the circulating water flow and be discharged into the crystal gathering area under the action of gravity, while crystal particles with small size and mass continue to crystallize in the water flow circulation channel. The crystal particles collected in the crystal gathering area are larger in size and higher in purity than those in traditional stirred crystallization. The inclined plate assembly is arranged in the second water flow ascending channel to perform secondary separation on the fine crystal particles entrained in the water flow, thereby further improving the recovery efficiency of the phosphorus crystal particles.

[0111] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A device for releasing phosphorus from excess sludge and recovering phosphorus, characterized in that: Includes phosphorus release mechanism; The phosphorus release mechanism comprises a sludge concentration unit (1), a sludge decomposition component (2) and a sludge dehydration unit (3); the sludge concentration unit (1) is provided with a residual sludge inlet (1.1), a concentrated sludge outlet (1.2) and a supernatant outlet (1.3); the sludge decomposition component (2) comprises a sludge decomposition unit (2.1) and a pH value adjustment unit (2.2) which are arranged in series; The residual sludge enters the sludge concentration unit (1) through the residual sludge inlet (1.1) for concentration treatment; the supernatant after the concentration treatment is discharged through the supernatant discharge outlet (1.3); The concentrated sludge after the concentration treatment is discharged through the concentrated sludge discharge port (1.2), a part of the concentrated sludge enters the sludge decomposition unit (2.1) through the first pipeline (4) for sludge decomposition treatment, and another part of the concentrated sludge enters the sludge dehydration unit (3) through the second pipeline (5) for sludge dehydration treatment; the decomposition sludge after the decomposition treatment enters the pH value adjustment unit (2.2) for pH value adjustment, and then is transported to the residual sludge inlet (1.1) through the third pipeline (6) and circulated to the sludge concentration unit (1); The ratio of the mass or flow rate of the sludge entering the sludge decomposition unit (2.1) through the first pipeline (4) for sludge decomposition treatment to the concentrated sludge discharged from the concentrated sludge discharge port (1.2) is 0.1 to 0.2; The control range of the pH value in the sludge decomposition unit (2.1) is 10.8 to 11.5; the control range of the pH value in the pH value adjustment unit (2.2) is 9 to 10; After the sludge whose pH value has been adjusted by the pH adjusting unit (2.2) intersects with the residual sludge conveying pipeline (12) through the third pipeline (6), the flow time of the mixed sludge from the intersection point to the outlet of the residual sludge feed inlet (1.1) is not less than 3 seconds.

2. The excess sludge phosphorus release and phosphorus recovery device according to claim 1, characterized in that: The sludge concentration unit (1) is a gravity concentration tank; The excess sludge inlet (1.1) and the supernatant liquid outlet (1.3) are both arranged at the upper end of the sludge concentration unit (1), and the concentrated sludge outlet (1.2) is arranged at the bottom of the sludge concentration unit (1).

3. The excess sludge phosphorus release and phosphorus recovery device according to claim 1 is characterized in that: The sludge decomposition unit (2.1) comprises a first shell (A1), a first stirring assembly (A2), a first sludge inlet pipe (A3) and a first sludge outlet pipe (A4); The first shell (A1) comprises a first body (A1.2) having a first accommodating cavity (A1.1); the first mud inlet pipe (A3) and the first mud outlet pipe (A4) are both arranged on the first body (A1.2) and are both connected to the first accommodating cavity (A1.1); The first body (A1.2) is provided with a first drug adding pipe (A5) which is in communication with the first containing cavity (A1.1); The first stirring component (A2) comprises a first driving power source (A2.1), a first stirring shaft (A2.2) and a first stirring blade (A2.3); the first driving power source (A2.1) is arranged on the first shell (A1); the connecting end of the first stirring shaft (A2.2) is connected to the output end of the first driving power source (A2.1); the free end of the first stirring shaft (A2.2) is arranged in the first accommodating cavity (A1.1) and the first stirring blade (A2.3) is arranged on the free end; The first pipeline (4) is in communication with the first mud inlet pipe (A3), and the first mud outlet pipe (A4) is in communication with the pH value adjustment unit (2.2) via a fourth pipeline (7).

4. The excess sludge phosphorus release and phosphorus recovery device according to claim 3 is characterized in that: It also includes a first pH controller (A6); a measuring hole connected to the first containing cavity (A1.1) is provided on the first body (A1.2); the first pH controller is arranged at the measuring hole for measuring the pH value of the sludge; the first pH controller is connected to an external PLC control system, and the first pH controller measures the pH value of the sludge through a first measuring electrode (A6.1); the first measuring electrode is arranged at the measuring hole and a protective net is provided on the outer side of the measuring electrode.

5. The excess sludge phosphorus release and phosphorus recovery device according to claim 3 is characterized in that: The inner wall of the first accommodating cavity (A1.1) is also provided with a plurality of protrusions (A1.3) facing the center of the first accommodating cavity; the protrusions (A1.3) are hemispherical protrusions with a radius of 40-80 mm; the plurality of protrusions (A1.3) are evenly distributed on the inner wall of the first accommodating cavity.

6. The excess sludge phosphorus release and phosphorus recovery device according to claim 3 is characterized in that: The first stirring shaft (A2.2) is provided with multiple layers of the first stirring blades (A2.3) at intervals along its axial direction; The first body (A1.2) is also provided with a first odor collecting pipe (A7) for collecting odor generated in the first accommodating chamber; the first shell (A1) also includes an opening connected to the first accommodating chamber (A1.1), and a detachable cover (A1.4) is provided at the opening; the first driving power source (A2.1), the first dosing pipe (A5), the first pH controller (A6) and the first odor collecting pipe (A7) are all arranged on the detachable cover (A1.4).

7. The excess sludge phosphorus release and phosphorus recovery device according to claim 3 is characterized in that: The pH value adjustment unit (2.2) comprises a second shell (B1), a second stirring assembly (B2), a second mud inlet pipe (B3) and a second mud outlet pipe (B4); The second shell (B1) comprises a second body (B1.2) having a second accommodating cavity (B1.1); the second mud inlet pipe (B3) and the second mud outlet pipe (B4) are both arranged on the second body (B1.2) and are both connected to the second accommodating cavity (B1.1); The second body (B1.2) is provided with a second drug adding pipe (B5) communicating with the second accommodating cavity (B1.1); The second stirring component (B2) comprises a second driving power source (B2.1), a second stirring shaft (B2.2) and a second stirring blade (B2.3); the second driving power source (B2.1) is arranged on the second shell (B1); the connecting end of the second stirring shaft (B2.2) is connected to the output end of the second driving power source (B2.1); the free end of the second stirring shaft (B2.2) is arranged in the second accommodating cavity (B1.1) and the second stirring blade (B2.3) is arranged thereon; The fourth pipeline (7) is in communication with the second mud inlet pipe (B3), and the second mud outlet pipe (B4) is in communication with the third pipeline (6).

8. The excess sludge phosphorus release and phosphorus recovery device according to any one of claims 1 to 7, characterized in that: It also includes a phosphorus recovery mechanism (8) for recovering phosphorus, the phosphorus recovery mechanism being connected to the supernatant discharge port (1.3) via a fifth pipeline (9); the control range of the pH value in the phosphorus recovery mechanism (8) is 9.5 to 10; The sludge after the sludge dehydration treatment by the sludge dehydration unit (3) is transported through the dry sludge transporting member (10), and the sludge dehydration liquid after the sludge dehydration treatment is connected to the fifth pipeline (9) or the phosphorus recovery mechanism (8) through the sixth pipeline (11).

9. The excess sludge phosphorus release and phosphorus recovery device according to claim 8, characterized in that: The phosphorus recovery mechanism (8) comprises an outer shell (8.1), a middle shell (8.2), an inner shell (8.3), a water inlet pipe (8.5), a drain pipe (8.6), a discharge port (8.7), a plug-flow stirring assembly (8.8), a folded plate vortex assembly (8.9), a modular vortex assembly (8.10) and an inclined plate assembly (8.11); The outer shell (8.1) comprises a first cylindrical body (8.1.1) and a first conical body (8.1.2) which is wide at the top and narrow at the bottom and closed at the bottom. The first cylindrical body (8.1.1) is provided with an a accommodating chamber (8.1.3), and the first conical body (8.1.2) is provided with a b accommodating chamber (8.1.3) which is connected to the a accommodating chamber (8.1.3). 8.1.4), the discharge port (8.7) is connected to the b accommodating chamber (8.1.4); a water collecting tank (8.4) is provided on the upper part of the a accommodating chamber (8.1.3); The middle shell (8.2) comprises a second cylindrical body (8.2.1) and a second conical body (8.2.2) which is wide at the top and narrow at the bottom and has an opening at the lower end. A c accommodating chamber (8.2.3) is arranged in the second cylindrical body (8.2.1), and a d accommodating chamber (8.2.4) which is connected to the c accommodating chamber (8.2.3) is arranged in the second conical body (8.2.2); the upper end of the second conical body (8.2.2) is located in the a accommodating chamber (8.1.3) and the lower end thereof is located in the b accommodating chamber (8.1.4); The inner shell (8.3) comprises a third cylindrical body (8.3.1) arranged in the c accommodating chamber (8.2.3), and the third cylindrical body (8.3.1) comprises an e accommodating chamber (8.3.2) with openings at both upper and lower ends; The e accommodating chamber (8.3.2) forms a first water flow ascending channel (A); a water flow descending channel (B) is formed between the inner wall of the second columnar cylinder (8.2.1) and the outer wall of the third columnar cylinder (8.3.1); the annular area between the inner wall of the first columnar cylinder (8.1.1) and the first conical cylinder (8.1.2), the outer wall of the second columnar cylinder (8.2.1) and the second conical cylinder (8.2.2), and the water collecting tank (8.4) form a second water flow ascending channel (C); the plug-flow stirring assembly (8.8) and the folded plate vortex assembly (8.9) are arranged from top to bottom in the first water flow ascending channel (A); the modular vortex assembly (8.10) is arranged in the water flow descending channel (B); the inclined plate assembly (8.11) is arranged in the second water flow ascending channel (C); The water inlet pipe (8.5) penetrates the side wall of the first columnar barrel (8.1.1) and the side wall of the second columnar barrel (8.2.1) and is inserted into the upper part of the first water flow rising channel (A), and the water outlet end of the water inlet pipe (8.5) is lower than the water collecting tank (8.4); the drainage pipe (8.6) is connected to the water collecting tank (8.4).

10. The excess sludge phosphorus release and phosphorus recovery device according to claim 9, characterized in that: The plug-flow stirring assembly (8.8) comprises a third driving power source (8.8.1), a third stirring shaft (8.8.2) and a third stirring blade (8.8.3); the connection end of the third stirring shaft (8.8.2) is connected to the output end of the third driving power source (8.8.1), and the third stirring blade (8.8.3) is arranged on the free end of the third stirring shaft (8.8.2); the water outlet end of the water inlet pipe (8.5) is located 20-50 cm above the third stirring blade (8.8.3); The folded plate vortex component (8.9) is located directly below the plug-flow stirring component (8.8), and the folded plate vortex component (8.9) comprises a first folded plate (8.9.1) and a second folded plate (8.9.2) arranged in parallel, the first folded plate (8.9.1) comprises a plurality of connecting plates connected in sequence, and the angle α between two adjacent connecting plates is 80°-100°; the first folded plate (8.9.1) and the second folded plate (8.9.2) are in a mirror image structure; The modular vortex assembly (8.10) comprises a plurality of vortex monomers stacked or spaced apart, wherein the vortex monomer is a hollow columnar body formed by a first vertical plate (8.10.1), a second vertical plate (8.10.2), an upper arc-shaped outer frame (8.10.3), an upper arc-shaped inner frame (8.10.4), a lower arc-shaped outer frame (8.10.5) and a lower arc-shaped inner frame (8.10.6); a vortex sheet is installed in the vortex monomer, and the cross-section of the vortex sheet is at least one of a triangle, a semicircle and a rectangle; The inclined plate assembly (8.11) comprises a plurality of settling inclined plates arranged in parallel, the settling inclined plates being arranged at an angle to the inner wall of the a accommodating chamber; and the inclined plate assembly (8.11) is located in the middle and lower part of the a accommodating chamber.

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