Excess sludge phosphorus recovery device

Abstract

The invention relates to the technical field of water treatment, in particular to a residual sludge phosphorus recovery device which comprises a sludge concentration unit, a sludge disintegration unit, a sludge dewatering unit and a phosphorus recovery unit. 10%-20% of concentrated sludge is subjected to cracking treatment through the sludge cracking unit and then returns to the sludge concentration unit; a sludge dewatering liquid output pipe is arranged on the sludge dewatering unit; according to the device, 10%-20% of concentrated sludge is decomposed by adding alkali, and then a carbon source released by the decomposition is used as a carbon source of phosphorus-accumulating microorganisms in the total residual sludge, so that the phosphorus-accumulating microorganisms in the total residual sludge can be recycled, and the phosphorus-accumulating microorganisms in the total residual sludge can be recycled, so that the phosphorus-accumulating microorganisms in the total residual sludge can be recycled, and the phosphorus-accumulating microorganisms in the total residual sludge can be recycled. Anaerobic phosphorus release occurs in an anaerobic environment of the sludge concentration unit, an external carbon source is not needed, and low-cost and efficient phosphorus release and phosphorus recovery of full-amount excess sludge are realized through alkali release phosphorus release of a small amount of concentrated sludge and anaerobic biological phosphorus release of the full-amount excess sludge.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to a residual sludge phosphorus recovery device. Background Art

[0002] To achieve effective recovery of phosphorus in sludge, the phosphorus in the sludge (solid phase) must be released into the liquid phase as much as possible. Efficient release of phosphorus is a key step in phosphorus recovery.

[0003] The existing phosphorus release technologies mainly include:

[0004] ① Physical decomposition method: Use thermal hydrolysis, ultrasound, mechanical ball milling and other methods to break the microbial cells in the sludge and release the phosphorus-containing substances inside and outside the cells into the liquid phase. Sludge thermal hydrolysis needs to be carried out under high temperature and high pressure conditions (150-190℃, 0.7-1.1MPa). It is usually used as a pretreatment process in conjunction with anaerobic digestion process. The equipment is complex, operation and maintenance are difficult, investment and energy consumption are high, and the odorous gas generated is difficult to treat. At present, there are only a few engineering application cases; although ultrasonic decomposition is efficient, the reaction time is short (10-60min), and the equipment is simple, it is currently in the laboratory research stage due to its high power consumption. Actual engineering applications need to overcome the defect of high power consumption.

[0005] ② Chemical decomposition method: Add acid, alkali or H2O2, ozone and other chemical agents to the residual 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 decomposition method has the characteristics of simple process and mature technology, but the existing sludge full-scale acid-base decomposition or H2O2, ozone oxidation and other methods have high drug consumption costs and are still difficult to achieve engineering application.

[0006] ③ Biological phosphorus release method: release phosphorus through anaerobic digestion or enzymatic biological enhanced phosphorus release. Enzymatic biological enhanced phosphorus release technology has high reagent costs and is currently in the laboratory research stage; anaerobic digestion is the most widely used sludge disposal technology in engineering, with the advantages of mature technology and low operating costs, but this method has a slow phosphorus release rate, a long time (the sludge needs to be digested anaerobically for 20 to 30 days), a large reaction device, and high construction investment. If you need to increase the anaerobic phosphorus release rate and shorten the anaerobic phosphorus release time, you need a sufficient carbon source. The available carbon source in the residual sludge discharged from the biochemical system has basically been consumed in the front-end biochemical system, and a large amount of carbon source is needed to meet the requirements.

[0007] ④ Sludge incineration-wet leaching process: After dehydration and drying, the sludge is incinerated into ash, and then acid and alkali are used to leach phosphorus. The phosphorus in the sludge incineration ash mainly exists in the form of combination with metals such as Ca, Mg, Fe, and Al in the ash, which cannot be absorbed and utilized by plants. In addition, the heavy metal substances in the sludge are still retained in the ash after incineration. It is also necessary to separate the phosphorus in the sludge ash from the heavy metals and convert the phosphorus into a form that can be used by plants. The process is complicated and the cost of phosphorus recovery is high.

[0008] ⑤Combination method: Use thermal hydrolysis-acid leaching, acidification-microwave radiation, ultrasound-ozone, ultrasound-alkaline hydrolysis and other combined technologies to destroy the microbial cell structure in the sludge and release the phosphorus-containing substances into the liquid phase. Compared with a single technology, the combination technology can combine the advantages of various technologies and is the trend of technological development in this field.

[0009] Because the existing sludge phosphorus release and phosphorus recovery technologies and equipment are expensive or the systems are complex, sewage treatment plant sludge is mostly disposed of by direct landfill or incineration after concentration and dehydration, and the phosphorus in the sludge is not recycled as a resource.

[0010] In summary, a device with a simplified structure and capable of achieving efficient phosphorus release and 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 residual sludge phosphorus recovery device with a simplified structure and capable of achieving efficient phosphorus release and recovery. The specific technical scheme is as follows:

[0012] A residual sludge phosphorus recovery device, comprising a sludge concentration unit, a sludge decomposition unit, a sludge dehydration unit and a phosphorus recovery unit;

[0013] The sludge concentration unit comprises a first body having a first accommodating chamber, the first body being provided with a residual sludge inlet, a concentrated sludge outlet and a supernatant outlet which are connected to the first accommodating chamber; the residual sludge inlet is connected to a residual sludge conveying pipeline;

[0014] The sludge decomposition unit comprises a first shell, a first stirring assembly, a first sludge inlet pipe and a first sludge outlet pipe, wherein the first stirring assembly is arranged on the first shell for stirring the liquid inside the first shell, the first sludge inlet pipe is connected with the concentrated sludge outlet through a first connecting pipe, and the first sludge outlet pipe is connected with the residual sludge inlet through a second connecting pipe; the 10%-20% concentrated sludge discharged from the concentrated sludge outlet is returned to the sludge concentration unit after being decomposition processed by the sludge decomposition unit;

[0015] The sludge dehydration unit comprises a dehydration treatment body having a dehydration accommodating chamber, the dehydration treatment body is provided with a dehydration treatment mud inlet pipe, a dehydration treatment mud outlet pipe and a sludge dehydration liquid outlet pipe which are connected to the dehydration accommodating chamber, the dehydration treatment mud inlet pipe is connected to the concentrated sludge outlet through a third connecting pipe, and the dehydration treatment mud outlet pipe is used to discharge dry mud;

[0016] The supernatant liquid outlet and the sludge dewatering liquid output pipe are both connected to the phosphorus recovery unit for phosphorus recovery.

[0017] Preferably, the phosphorus recovery unit comprises an outer cylinder, an inner cylinder, a water inlet pipe, a water outlet pipe, a discharge pipe, a perforated plate assembly and an inclined plate assembly; the outer cylinder comprises an outer cylinder body having an opening at the upper end and a movable cover body, and the movable cover body is detachably arranged at the opening; the inner cylinder comprises an inner cylinder body having an opening at the lower end, the inner cylinder body is arranged in the accommodating cavity of the outer cylinder body, and a water outlet channel connected to the water outlet pipe is arranged between the inner wall of the outer cylinder body and the outer wall of the inner cylinder body, and the water outlet channel and the water outlet pipe are both located in the outer cylinder body. The upper part of the main body; a water flow descending channel is formed inside the inner cylinder body, the water inlet pipe is connected with the water flow descending channel and the water outlet end face of the water inlet pipe is higher than the upper end face of the water outlet channel; the perforated plate assembly is arranged in the water flow descending channel; the inner wall of the outer cylinder body, the water outlet channel and the outer wall of the inner cylinder body form a water flow ascending channel, and the inclined plate assembly is arranged in the water flow ascending channel; the accommodating cavity in the outer cylinder body is located below the inner cylinder body to form a crystal gathering area, and the discharge pipe is connected with the crystal gathering area.

[0018] Preferably, along the water flow direction in the water flow descending channel, the perforated plate assembly includes a first perforated single piece, a second perforated single piece and a third perforated single piece arranged in sequence, the first perforated single piece includes one or more first perforated plates arranged at intervals, the second perforated single piece includes one or more second perforated plates arranged at intervals, and the third perforated single piece includes one or more third perforated plates arranged at intervals; the ratio of the total area of ​​through holes to the plate area in the first perforated plate is P1, the ratio of the total area of ​​through holes to the plate area in the second perforated plate is P2, the ratio of the total area of ​​through holes to the plate area in the third perforated plate is P3, and P1<P2<P3; the value of P1 is 2.5% to 3%; the value of P2 is 3.5% to 4.5%; the value of P3 is 5.0% to 6.0%.

[0019] Preferably, the inclined plate assembly is arranged on the inner wall of the outer cylinder body and the outer wall of the inner cylinder body through an inclined plate support frame; the inclined plate assembly includes a plurality of sedimentation inclined plates that are spaced and staggered, and the gaps between the plurality of sedimentation inclined plates form a flow channel.

[0020] Preferably, along the water flow direction, the water inlet pipe includes a horizontal pipe section, an arc-shaped transition pipe section and a vertical pipe section arranged in sequence, and the water outlet end surface of the vertical pipe section is 5-20 cm higher than the upper end surface of the outlet channel.

[0021] Preferably, the first shell includes a first body having a first accommodating cavity, the first mud inlet pipe and the first mud outlet pipe are both arranged on the first body and are both connected to the first accommodating cavity; the first body is provided with a first dosing pipe connected to the first accommodating cavity; the first stirring assembly includes a first driving power source, a first stirring shaft and a first stirring blade, the first driving power source is arranged on the first shell; 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 accommodating cavity and is provided with the first stirring blade.

[0022] Preferably, it further comprises a first pH controller, wherein the first body is provided with a measuring hole connected to the first accommodating cavity, and 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; the first measuring electrode is arranged at the measuring hole and a protective net is arranged on the outer side of the first measuring electrode;

[0023] The inner wall of the first accommodating chamber is also provided with a plurality of protrusions facing the center of the first accommodating chamber; the protrusions are hemispherical protrusions with a radius of 40-80mm; the plurality of protrusions are evenly distributed on the inner wall of the first accommodating chamber; the first stirring shaft is provided with multiple layers of the first stirring blades at intervals along its axial direction; the first body is also provided with a first odor collecting pipe for collecting odor generated in the first accommodating chamber; the first shell also includes an opening connected to the first accommodating chamber, and a first detachable cover is provided at the opening, and the first driving power source, the first dosing pipe, the first pH controller and the first odor collecting pipe are all arranged on the first detachable cover.

[0024] Preferably, it also includes a pH adjustment unit arranged in series with the sludge decomposition unit, and the pH adjustment unit includes a second shell, a second stirring assembly, a second mud inlet pipe and a second mud outlet pipe; the second shell includes a second body having a second accommodating chamber, and the second mud inlet pipe and the second mud outlet pipe are both arranged on the second body and are both connected to the second accommodating chamber; the second body is provided with a second dosing pipe connected to the second accommodating chamber; the second stirring assembly includes a second driving power source, a second stirring shaft and a second stirring blade, and the second driving power source is arranged on the second shell; the connecting end of the second stirring shaft is connected to the output end of the second driving power source, and the free end of the second stirring shaft is arranged in the second accommodating chamber and is provided with the second stirring blade; the first mud outlet pipe is connected to the second mud inlet pipe through a second connecting pipe, and the second mud outlet pipe is connected to the residual sludge inlet through a fourth connecting pipe.

[0025] Preferably, it further comprises a second pH controller, wherein the second body is provided with a measuring hole connected to the second containing cavity, and the second pH controller 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 second pH controller measures the pH value of the sludge through a second measuring electrode; the second measuring electrode is arranged at the measuring hole and a protective net is arranged on the outside of the second measuring electrode;

[0026] The second body is also provided with a second odor collection pipe for collecting odor generated in the second accommodating chamber; the second shell also includes an opening connected to the second accommodating chamber, and a second detachable cover is provided at the opening, and the second driving power source, the second dosing pipe, the second pH controller and the second odor collection pipe are all arranged on the second detachable cover.

[0027] Preferably, the control range of the pH value in the sludge decomposition unit is 10.8-11.5; the control range of the pH value in the pH adjustment unit is 9-10; after the sludge after pH adjustment by the pH adjustment unit intersects with the residual sludge conveying pipeline, the flow time of the mixed sludge from the intersection point to the residual sludge feed inlet outlet is not less than 3 seconds; the control range of the pH value in the phosphorus recovery unit is 9.5-10.

[0028] The application of the technical solution of the present invention has the following beneficial effects:

[0029] 1. The excess sludge phosphorus recovery device of the present invention comprises a sludge concentration unit, a sludge cracking unit, a sludge dehydration unit and a phosphorus recovery unit. The sludge concentration unit comprises a first body having a first accommodating chamber, and the first body is provided with an excess sludge inlet, a concentrated sludge outlet and a supernatant outlet; the sludge cracking unit comprises a first shell, a first stirring assembly, a first sludge inlet pipe and a first sludge outlet pipe, and 10%-20% of the concentrated sludge discharged from the concentrated sludge outlet is returned to the sludge concentration unit after being cracked by the sludge cracking unit; the sludge dehydration unit comprises a second body having a second accommodating chamber, and the second body is provided with a The second mud inlet pipe, the second mud outlet pipe and the sludge dewatering liquid output pipe; the supernatant outlet and the sludge dewatering liquid output pipe are all connected to the phosphorus recovery unit for phosphorus recovery. The overall structure is streamlined. The present invention adds alkali to crack 10% to 20% of the concentrated sludge, and then uses the COD (carbon source) released by the cracking as the carbon source for polyphosphate microorganisms (polyphosphate bacteria) in the whole amount of residual 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 a small amount of concentrated sludge alkali phosphorus interpretation + anaerobic biological phosphorus release of the whole amount of residual sludge realizes low-cost and efficient phosphorus release of the whole amount of residual sludge.

[0030] 2. The sludge thickening unit in the present invention is a gravity thickening tank, which adopts the conventional gravity thickening tank in the prior art. When it is necessary to recover phosphorus from the residual sludge of an 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), a phosphorus recovery unit and a matching control system, and to make corresponding modifications to the pipelines, so as to economically and conveniently realize efficient phosphorus release from sludge and efficient recovery of phosphorus resources in the existing sewage treatment plant.

[0031] 3. The sludge breaking unit in the present invention comprises a first shell, a first stirring assembly, a first sludge inlet pipe and a first sludge outlet pipe, and has a simple structure. The equipment investment and operating costs (drug consumption, power consumption) of the sludge breaking unit are only equivalent to 10% to 20% of the existing full-volume sludge alkali phosphorus decomposition process, and the equipment footprint can also be saved. The addition of carbon source to the broken 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.

[0032] 4. The phosphorus recovery unit of the present invention comprises an outer cylinder, an inner cylinder, an inlet pipe, an outlet pipe, a discharge pipe, a perforated plate assembly and an inclined plate assembly, and the effects are: ① The phosphorus recovery unit fully utilizes the kinetic energy and potential energy of the wastewater itself to achieve efficient hydraulic vortex crystallization, which is more energy-efficient and has lower operating costs than conventional mechanical mixing crystallization; crystallization and precipitation separation are integrated, the device structure is compact, and the footprint is small; ② An inclined plate assembly is provided in the water flow rising channel B, which increases the precipitation area of ​​fine phosphorus crystal particles in the wastewater and shortens the precipitation time. At the same time, the water flow of the plate changes from a turbulent state to a laminar state, thereby improving the recovery efficiency of phosphorus crystal particles in the wastewater.

[0033] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary 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:

[0035] Figure 1 It is a plan view of the residual sludge phosphorus recovery device in a preferred embodiment of the present invention;

[0036] Figure 2 yes Figure 1 Schematic diagram of the elevation structure;

[0037] Figure 3 yes Figure 2 Schematic diagram of the connection structure between the sludge decomposition unit and the pH value adjustment unit;

[0038] Figure 4 yes Figure 2 Schematic diagram of the structure of the medium phosphorus recovery unit;

[0039] Figure 5 yes Figure 4 A schematic diagram of the structure of the first perforated plate;

[0040] Figure 6 yes Figure 4 A schematic structural diagram of a second perforated plate;

[0041] Figure 7 yes Figure 4 Schematic diagram of the structure of the third perforated plate.

[0042] Among them, 1. Sludge concentration unit, 1.1. Residual sludge inlet, 1.2. Concentrated sludge outlet, 1.3. Supernatant outlet, 1.4. Concentration containing chamber;

[0043] 2. Sludge cracking unit, A1. First shell, A1.1. First accommodating chamber, A1.2. First body, A1.3. Protrusion, A1.4. First detachable cover plate, A2. First stirring assembly, A2.1. First driving power source, A2.2. First stirring shaft, A2.3. First stirring blade, A3. First mud inlet pipe, A4. First mud outlet pipe, A5. First dosing pipe, A6. First pH controller, A6.1. First measuring electrode, A7. First odor collecting pipe;

[0044] 3. Sludge dehydration unit, 3.1. Dehydration containing chamber, 3.2. Dehydration treatment sludge inlet pipe, 3.3. Dehydration treatment sludge outlet pipe, 3.4. Sludge dehydration liquid output pipe;

[0045] 4. Phosphorus recovery unit, 4.1. outer cylinder, 4.1.1. outer cylinder body, 4.1.2. movable cover body; 4.2. inner cylinder, 4.2.1. inner cylinder body; 4.3. water inlet pipe; 4.4. water outlet pipe; 4.5. discharge pipe; 4.6. perforated plate assembly, 4.6.1. first perforated plate, 4.6.2. second perforated plate, 4.6.3. third perforated plate; 4.7. inclined plate assembly; 4.8. water outlet channel; 4.9. support member; 4.10. inclined plate support frame; 4.11. inner cylinder support frame; A. water flow descending channel, B. water flow ascending channel, C. crystal aggregation area, D. through hole;

[0046] 5. pH value adjustment unit, B1. second shell, B1.1. second accommodating chamber, B1.2. second body, B1.3. second detachable cover plate, B2. second stirring assembly, B2.1. second driving power source, B2.2. second stirring shaft, B2.3. second stirring blade, B3. second mud inlet pipe, B4. second mud outlet pipe, B5. second dosing pipe, B6. second pH controller, B6.1. second measuring electrode, B7. second odor collecting pipe;

[0047] 6. Residual sludge transportation pipeline;

[0048] G1, a first connecting pipeline, G2, a second connecting pipeline, G3, a third connecting pipeline, G4, a fourth connecting pipeline;

[0049] 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; L1, first flow meter, L2, second flow meter, L3, third flow meter, L4, fourth flow meter; T, lifting pump; P1, orthophosphate online detector, P2, pH value online detector. DETAILED DESCRIPTION

[0050] The embodiments of the present invention are described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0051] Example:

[0052] See also Figure 1-Figure 2 A residual sludge phosphorus recovery device includes a sludge concentration unit 1, a sludge cracking unit 2, a sludge dehydration unit 3, a phosphorus recovery unit 4 and a pH value adjustment unit 5, and the detailed structure is as follows:

[0053] The sludge concentration unit 1 includes a concentration tank body having a concentration accommodating chamber 1.4, and the concentration tank body is provided with a residual sludge feed port 1.1, a concentrated sludge discharge port 1.2 and a supernatant discharge port 1.3 connected to the concentration accommodating chamber 1.4; the residual sludge feed port 1.1 is connected to the residual sludge conveying pipeline 6. The residual sludge of the urban sewage treatment plant enters the sludge concentration unit 1 from the residual sludge conveying pipeline 6 through the residual sludge feed port 1.1 for sludge concentration treatment. The sludge concentration unit 1 in this embodiment adopts a circular gravity concentration tank in the prior art, and the tank body is constructed of reinforced concrete or steel anti-corrosion equipment. The concentration time of the sludge in the tank (calculated by hydraulic retention time) is 14 to 24 hours. The residual sludge feed port 1.1 is connected to the residual sludge conveying pipeline 6 (a first flowmeter L1 is provided on the pipeline), and the residual sludge conveying pipeline 6 is connected to an external sludge conveying pump. The supernatant discharge port 1.3 is connected to the phosphorus recovery unit 4.

[0054] The sludge breaking unit 2 includes a first shell A1, a first stirring assembly A2, a first sludge inlet pipe A3 and a first sludge outlet pipe A4, see Figure 3 The first stirring component A2 is arranged on the first shell A1 for stirring the liquid inside the first shell, the first mud inlet pipe A3 is connected with the concentrated sludge discharge port 1.2 through the first connecting pipe G1, and the cracked sludge coming out of the first mud outlet pipe A4 enters the pH value adjustment unit 5 through the second connecting pipe G2 for pH value adjustment and then enters the residual sludge feed port 1.1; the 10%-20% concentrated sludge discharged from the concentrated sludge discharge port 1.2 is returned to the sludge concentration unit 1 after being cracked by the sludge cracking unit.

[0055] Preferably in this embodiment, the first shell A1 includes a first main body A1.2 having a first accommodating chamber A1.1, the first mud inlet pipe A3 and the first mud outlet pipe A4 are both arranged on the first main body A1.2 and are both connected to the first accommodating chamber A1.1; the first body A1.2 is provided with a first dosing pipe A5 connected to the first accommodating chamber A1.1; the first stirring assembly A2 includes 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 chamber A1.1 and is provided with the first stirring blade A2.3. The first shell A1 is a cylindrical shell, made of carbon steel anti-corrosion material, and uses sodium hydroxide to break up the sludge. In this embodiment, the pH control range in the sludge breaking component is 10.8-11.5, and the further preferred pH control range is 10.8-11. The reaction time of sludge breaking is 40-60 minutes.

[0056] Preferably, the present embodiment further includes a first pH controller A6, the first body A1.2 is provided with a measuring hole connected to the first accommodating chamber A1.1, 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 first measuring electrode; a plurality of protrusions A1.3 facing the center of the first accommodating chamber are also provided on the inner wall of the first accommodating chamber A1.1; the protrusion A1.3 is a hemispherical protrusion with a radius of 40-80mm; a plurality of protrusions A1.3 are evenly distributed on the inner wall of the first accommodating chamber, wherein the radii of the hemispherical protrusions are all the same, and the plurality of protrusions are evenly distributed on the vertical inner wall of the first accommodating chamber, and the spacing between the edges of two adjacent protrusions is 1.5 times their diameters. The first stirring shaft A2.2 is provided with multiple layers of the first stirring blades A2.3 at intervals along its axial direction (here, preferably two layers of first stirring blades are arranged along the up and down directions, and the stirring blades generate upward thrust when rotating); 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 first removable cover A1.4 is provided at the opening, and 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 first removable cover A1.4.

[0057] The sludge dehydration unit 3 includes a dehydration treatment body having a dehydration accommodating chamber 3.1, and the dehydration treatment body is provided with a dehydration treatment mud inlet pipe 3.2, a dehydration treatment mud outlet pipe 3.3 and a sludge dehydration liquid outlet pipe 3.4 connected to the dehydration accommodating chamber 3.1. The dehydration treatment mud inlet pipe 3.2 is connected to the concentrated sludge outlet 1.2 through a third connecting pipe G3, and the dehydration treatment mud outlet pipe 3.3 is used to discharge dry mud, which can be subsequently transported by a pipeline, a belt conveyor, etc. In this embodiment, the sludge dehydration unit 3 adopts an existing horizontal spiral centrifugal dehydration complete set of equipment.

[0058] The supernatant outlet 1.3 and the sludge dewatering liquid output pipe 3.4 are both connected to the phosphorus recovery unit 4 for phosphorus recovery. The structure of the phosphorus recovery unit 4 is detailed in Figure 4, which includes an outer cylinder 4.1, an inner cylinder 4.2, a water inlet pipe 4.3, a water outlet pipe 4.4, a discharge pipe 4.5, a perforated plate assembly 4.6 and an inclined plate assembly 4.7; the outer cylinder 4.1 includes an outer cylinder body 4.1.1 with an opening at the upper end and a movable cover body 4.1.2, the movable cover body 4.1.2 is detachably arranged at the opening (preferably, the opening is arranged at the top of the outer cylinder body), in this embodiment, the outer cylinder body is composed of a hollow cylindrical vertical cylinder and a hollow cylinder with a width at the top and a narrowness at the bottom. The inner cylinder body 4.2 is composed of a truncated cone cylinder, a hollow truncated cone cylinder is located at the lower end, that is, the bottom of the outer cylinder body is an inverted truncated cone structure; the inner cylinder body 4.2 includes an inner cylinder body 4.2.1 with an opening at the lower end. In this embodiment, the inner cylinder body adopts a hollow cylindrical vertical cylinder, the height of the inner cylinder body is 60% to 80% of the height of the outer cylinder body, and the inner cylinder body is supported by an inner cylinder support frame 4.11 located at the bottom of the outer cylinder body, and the upper end surface of the inner cylinder body can be abutted with the lower surface of the movable cover body on the cover or set in a gap. The inner cylinder body 4.2.1 is arranged in the accommodating cavity of the outer cylinder body 4.1.1, and a water outlet channel 4.8 connected to the water outlet pipe 4.4 is provided between the inner wall of the outer cylinder body 4.1.1 and the outer wall of the inner cylinder body 4.2.1, and the water outlet channel here is a ring-shaped water outlet channel. The outlet channel 4.8 and the outlet pipe 4.4 are both located at the upper part of the outer cylinder body 4.1.1; a water flow descending channel A (forming a crystallization reaction area) is formed inside the inner cylinder body 4.2.1, the water inlet pipe 4.3 is connected to the water flow descending channel A and the outlet end face of the water inlet pipe 4.3 is higher than the upper end face of the outlet channel 4.8; the perforated plate assembly 4.6 is arranged in the water flow descending channel A; the inner wall of the outer cylinder body 4.1.1, the outlet channel 4.8 and the outer wall of the inner cylinder body 4.2.1 form a water flow ascending channel B, and the inclined plate assembly 4.7 is arranged in the water flow ascending channel B; the accommodating cavity in the outer cylinder body 4.1.1 is located below the inner cylinder body 4.2.1 to form a crystal aggregation area C, and the discharge pipe 4.5 is connected to the crystal aggregation area C. In this embodiment, the hollow truncated cone cylinder of the outer cylinder body 4.1.1 is the crystal aggregation area, and the inverted truncated cone structure is conducive to the aggregation and compression precipitation of phosphorus crystal particles. The discharge pipe 4.5 is connected to the crystal aggregation area C. In this embodiment, the discharge pipe 4.5 is connected to the side and lower part of the truncated cone structure. The phosphorus recovery unit 4 is also provided with a pH value online detector P2.

[0059] Preferably, in the present embodiment, along the water flow direction in the water flow descending channel A, the perforated plate assembly 4.6 comprises a first perforated single piece, a second perforated single piece and a third perforated single piece arranged in sequence, the first perforated single piece comprises one or more first perforated plates 4.6.1 arranged at intervals, the second perforated single piece comprises one or more second perforated plates 4.6.2 arranged at intervals, the third perforated single piece comprises one or more third perforated plates 4.6.3 arranged at intervals, the first perforated plate 4.6.1, the second perforated plate 4.6.2 and the third perforated plate 4.6.3 are all detachably arranged by a support member 4.9, wherein the support member is composed of a first plate and a second plate arranged at right angles, the first plate is connected to the perforated plate, and the second plate is connected to the inner wall of the inner cylinder body (i.e., the inner wall forming the water flow descending channel A). The ratio of the total area of ​​through holes D in the first perforated plate to the plate area is P1, the ratio of the total area of ​​through holes D in the second perforated plate to the plate area is P2, the ratio of the total area of ​​through holes D in the third perforated plate to the plate area is P3, and P1<P2<P3. Further preferably, the value of P1 is 2.5%~3%; the value of P2 is 3.5%~4.5%; the value of P3 is 5.0%~6.0%. Further preferably, the support member 4.9 can be a horizontal straight plate and a vertical straight plate arranged at an angle of 90°, the vertical straight plate is used to be fixed to the inner wall of the inner cylinder body 4.2.1, and the horizontal straight plate is used to connect or clamp with the perforated plate in the perforated plate assembly; the first perforated single piece includes two first perforated plates arranged at intervals, the second perforated single piece includes two second perforated plates arranged at intervals, and the third perforated single piece includes two third perforated plates arranged at intervals. In this embodiment, the first perforated plate, the second perforated plate and the third perforated plate are all circular plates, and the diameter of the circular plate is preferably slightly smaller than the inner diameter of the inner cylinder body, such as 20 mm smaller; the first perforated plate, the second perforated plate and the third perforated plate are all provided with circular through holes, and the central axis of the circular through holes is the same as the water flow direction in the water flow descending channel A; P1 is taken as 2.5%, see Figure 5 The first perforated plate is provided with four layers of holes arranged from the center to the periphery, that is, water-passing circular holes with a radius of 15 to 20 mm are opened at equal intervals at the center and three concentric circles (shown as through holes D in the figure); the value of P2 is 4%, see Figure 6 The second perforated plate is provided with five layers of holes arranged from the center to the periphery, that is, water-passing circular holes with a radius of 15 to 20 mm are opened at equal intervals at the center and four concentric circles (shown as through holes D in the figure); the value of P3 is 5.5%, see Figure 7The third perforated plate is provided with six layers of holes arranged from the center to the periphery, that is, water-passing circular holes with a radius of 15 to 20 mm are opened at equal intervals at the center and five concentric circles (shown as through holes D in the figure). The perforated plate assembly with a unique structure can form micro-vortices when the liquid flows through the perforated plate assembly, so that the orthophosphate in the wastewater that has not yet formed crystals and the crystal-forming ions (magnesium ions and ammonium ions) in the reagent are contacted and mixed under the action of the vortex to form magnesium ammonium phosphate crystals.

[0060] In the present embodiment, the inclined plate assembly 4.7 is preferably arranged on the inner wall of the outer cylinder body 4.1.1 and the outer wall of the inner cylinder body 4.2.1 through an inclined plate support frame 4.10; the inclined plate assembly 4.7 includes a plurality of sedimentation inclined plates that are spaced and staggered, and the gaps between the plurality of sedimentation inclined plates form a flow channel. The inclined plate assembly increases the sedimentation area, shortens the sedimentation time, and changes the water flow from a turbulent state to a laminar state, thereby improving the sedimentation efficiency of fine phosphorus crystal particles.

[0061] In this embodiment, the outflow from the upper part of the water flow rising channel B is regulated by the outlet channel 4.8 and then discharged from the outlet pipe 4.4, which can eliminate the short-flow phenomenon of the outflow, is conducive to the stability of the operating state, improves the mud-water separation effect, reduces other pollutants carried in the outflow, and thus improves the pollutant removal rate.

[0062] The structure of the pH value adjustment unit 5 is shown in detail. Figure 3, which includes 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 includes a second body B1.2 having a second accommodating cavity B1.1, and the second shell B1 is a cylindrical shell. 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 chamber B1.1; the second body B1.2 is provided with a second dosing pipe B5 connected to the second accommodating chamber B1.1; the second stirring assembly B2 includes a second driving power source B2.1, a second stirring shaft B2.2 and a second stirring blade B2.3, and 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, and the free end of the second stirring shaft B2.2 is arranged in the second accommodating chamber B1.1 and is provided with the second stirring blade B2.3; the first mud outlet pipe A4 is connected to the second mud inlet pipe B3 through the second connecting pipe G2, and the second mud outlet pipe B4 is connected to the residual sludge feed port 1.1 through the fourth connecting pipe G4. In this embodiment, the control range of the pH value in the pH value adjustment unit is 9 to 10, and the further preferred control range of the pH value is 9 to 9.5. The effective volume of the second containing chamber B1.1 in the pH value adjusting unit is half of the volume of the first containing chamber A1.1 in the sludge breaking unit, and the height of the pH value adjusting unit is lower than the sludge breaking unit, which can ensure that the sludge in the sludge breaking unit flows into the pH value adjusting unit by gravity.

[0063] The preferred pH adjustment unit 5 in this embodiment also includes a second pH controller B6, and the second body B1.2 is provided with a measuring hole connected to the second accommodating chamber B1.1, and the second pH controller is arranged at the measuring hole for measuring the pH value of the sludge; the second pH controller is connected to the external PLC control system, and the second pH controller measures the pH value of the sludge through the second measuring electrode B6.1; the second measuring electrode is arranged at the measuring hole and a protective net is provided on the outside of the second measuring electrode; the second body B1.2 is also provided with a second odor collecting pipe B7 for collecting odor generated in the second accommodating chamber; the second shell B1 also includes an opening connected to the second accommodating chamber B1.1, and a second detachable cover plate B1.3 is provided at the opening, and the second driving power source B2.1, the second dosing pipe B5, the second pH controller B6 and the second odor collecting pipe B7 are all arranged on the second detachable cover plate B1.3.

[0064] Preferably, in this embodiment, the control range of the pH value in the sludge decomposition unit 2 is 10.8-11.5; the control range of the pH value in the pH adjustment unit 5 is 9-10; after the sludge after pH adjustment by the pH adjustment unit 5 intersects with the residual sludge conveying 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; the control range of the pH value in the phosphorus recovery unit 4 is 9.5-10.

[0065] By applying the technical solution of this embodiment, the residual sludge is transported to the residual sludge inlet 1.1 by the residual sludge conveying pipeline 6 and enters the sludge concentration unit 1 for concentration treatment; the supernatant after the concentration treatment is discharged through the supernatant discharge port 1.3 and enters the phosphorus recovery unit 4 for phosphorus recovery; 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 cracking unit 2 through the first connecting pipeline G1 (a second flowmeter L2 and a first electric valve F1 are provided on this pipeline) for sludge cracking treatment, and further passes through the pH value adjustment unit 5 for pH adjustment, and after being lifted by the lifting pump T, it returns to the residual sludge conveying pipeline 6 through the fourth connecting pipeline G4 to be mixed with the residual sludge and then circulated to the sludge concentration unit 1; another part of the concentrated sludge enters the sludge dehydration unit 3 through the third connecting pipeline G3 (a fourth flowmeter L4 and a second electric valve F2 are provided on this pipeline) for sludge dehydration treatment, and 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 supernatant discharged from the supernatant outlet 1.3 and the sludge dehydrated liquid output from the sludge dehydrated liquid output pipe 3.4 are mixed in the pipeline. A third flow meter L3 and a pipeline mixer H are provided on the pipeline. The magnesium salt dosing pipe H1, the ammonium salt dosing pipe H2 and the alkali dosing pipe H3 are all connected to the pipeline mixer H. After mixing, the liquid enters the water inlet pipe 4.3 in the phosphorus recovery unit 4.

[0066] The phosphorus recovery unit 4 of the application invention has the following working process: the phosphorus in the liquid phase is recovered by using magnesium ammonium phosphate crystals (struvite). In the continuous flow operation, the pH in the phosphorus recovery unit 4 is controlled at 9.5-10. The wastewater containing orthophosphate formed by the supernatant from the supernatant outlet 1.3 of the sludge concentration unit 1 and the sludge dewatering liquid output from the sludge dewatering liquid output pipe 3.4 in the sludge dewatering unit 3 is mixed with the reagent (the reagent is magnesium salt, ammonium salt, alkali) in the pipeline mixer H, and then enters the barrel 4.2 of the phosphorus recovery unit 4 through the water inlet pipe 4.3 (specifically: the overflow from the end of the water inlet pipe 4.3 forms a waterfall and mixes into the upper part of the water flow descending channel A in the inner cavity of the inner barrel body 4.2.1). The orthophosphate in the inlet water and the crystal-forming ions (magnesium ions, ammonium ions) in the reagent are contacted and mixed under the action of the waterfall to form magnesium ammonium phosphate crystals (crystal nuclei). The wastewater passes through the perforated plate group in the water flow descending channel A in sequence under the action of gravity. Component 4.6 reaches the bottom of the water flow descending channel A, and forms micro-vortices at both ends of the circular hole channel when flowing through the perforated plate. The orthophosphate in the wastewater that has not yet formed crystals and the crystal-forming ions (magnesium ions and ammonium ions) in the reagent are contacted and mixed under the action of the vortex to continue to form magnesium ammonium phosphate crystals, and the fine crystals are further enlarged. The water flow and the tiny particle crystals slowly flow upward from the bottom outlet of the water flow descending channel A into the water flow ascending channel B under the action of gravity, and the crystal particles with larger particle size sink into the crystal aggregation area C under the action of gravity; the wastewater flowing into the wastewater ascending channel flows through the inclined plate component 4.7 during the ascending process, and the tiny crystal particles are precipitated on the inclined plate component and sink to the crystal aggregation area C. The clarified wastewater overflows to the outlet channel 4.8 located at the upper part of the outer cylinder body 4.1.1, and then flows out to the next sewage treatment unit through the outlet pipe 4.4. The struvite crystals precipitated in the crystal aggregation area are regularly discharged from the discharge pipe 4.5 to a separate dehydration and separation device.

[0067] The phosphorus recovery unit 4 of this embodiment is applied, and the effects are as follows: ① The present invention fully utilizes the kinetic energy and potential energy of the wastewater itself to realize efficient hydraulic vortex crystallization, which is more energy-efficient and has lower operating costs than conventional mechanical mixing crystallization; crystallization and precipitation separation are integrated into one, the device structure is compact, and the footprint is small; ② An inclined plate assembly is provided in the water flow rising channel B, which increases the precipitation area of ​​fine phosphorus crystal particles in the wastewater and shortens the precipitation time. At the same time, the water flow of the plate changes from a turbulent state to a laminar state, thereby improving the recovery efficiency of phosphorus crystal particles in the wastewater.

[0068] In addition, a control system is also provided in this embodiment, which includes online detection instruments, cables and an electric control cabinet containing a programmable logic controller (PLC). The online detection instruments include a first flow meter L1 arranged on the residual sludge conveying pipeline 6, a second flow meter L2 arranged on the first connecting pipeline G1, a third flow meter L3 arranged on the pipeline connected to the supernatant discharge outlet 1.3, a fourth flow meter L4 arranged on the third connecting pipeline G3, an orthophosphate online detector P1 arranged near the supernatant discharge pipe, an online pH value detector P2 arranged in the phosphorus recovery unit, and a first pH controller A6 and a second pH controller B6 arranged in the sludge decomposition component; the cables and the electric control cabinet containing the programmable logic controller (PLC) all adopt existing mature equipment, which can power the online detection instruments and communicate with the online detection instruments. The PLC controls the operation of external dosing equipment and other equipment according to the data detected by the online monitoring instruments and the preset control logic.

[0069] The technical solution of this embodiment is specifically:

[0070] The phosphorus-rich residual sludge (Q residual, water content 99.2%) discharged from the sewage treatment biochemical system is mixed with the post-breakdown sludge (Q cracked) discharged from the sludge breakage unit 2 and the pH of which is adjusted by the pH adjustment unit 5 through the residual sludge conveying pipeline 6, and then enters the sludge concentration unit 1. The phosphorus-rich residual sludge is concentrated in the sludge concentration unit 1 under the action of the carbon source provided by the post-breakdown sludge, and the anaerobic biological phosphorus release effect occurs at the same time, releasing the phosphorus in the solid phase into the liquid phase. The low-phosphorus sludge after concentration and biological phosphorus release is discharged from the concentration tank from the bottom of the gravity concentration tank. A part of the concentrated sludge (Q cracked) enters the sludge breakage unit 2 through the first connecting pipeline G1 for sludge breakage. The sludge after breakage (Q cracked) enters the pH value adjustment unit 5 for pH adjustment and then returns to the sludge concentration unit 1; the other part of the concentrated sludge (Q dehydrated) is discharged into the sludge dehydration unit 3 through the third connecting pipeline G3 for dehydration treatment. In this embodiment, the flow rate or mass ratio Qdecomposition of the total amount of sludge entering the sludge decomposition unit and the concentrated sludge is: (Qdecomposition + Qdehydration) = 0.2; the high-concentration phosphorus-containing supernatant produced by the sludge concentration unit 1 is discharged into the phosphorus recovery unit 4 to recover phosphorus; the sludge dehydration liquid produced by the sludge dehydration unit is mixed with the supernatant of the sludge concentration unit and discharged together into the phosphorus recovery unit 4 for phosphorus recovery, and the dry sludge is transported out for disposal; the low-phosphorus water discharged from the phosphorus recovery unit can be returned to the biochemical pool at the front end of the sewage treatment system.

[0071] In this embodiment, after the sludge is cracked by alkali, COD (carbon source), ammonia nitrogen, organic nitrogen, orthophosphate, organic phosphorus and other substances are released into the water phase and converted into cracked sludge (Q after cracking). The main component test data of the sludge before concentration (Q remaining) and after cracking (Q after cracking) are shown in Table 1. The mass of the cracked sludge (Q after cracking) is equal to the mass of the concentrated sludge (Q cracking) plus the mass of the alkali and acid reagents added during the cracking process. The cracked sludge (Q after cracking) is discharged into the water inlet of the gravity concentration tank. The sludge cracking step in this embodiment achieves five technical effects at the same time:

[0072] ① The residual phosphorus in the sludge was broken down and released, and orthophosphate was released from the solid phase to the liquid phase, creating conditions for the subsequent phosphorus recovery unit to recover phosphorus;

[0073] ② The high-concentration COD (carbon source) released by sludge cracking is returned to the sludge thickening tank as a carbon source for anaerobic biological phosphorus release of the remaining sludge. No external carbon source is needed, which realizes "waste treatment with waste" and saves the cost of sludge phosphorus release;

[0074] ③ Sludge cracking releases ammonia nitrogen, reducing the amount of ammonium salt (such as ammonium chloride) added to the subsequent phosphorus recovery unit to recover struvite, further saving the cost of phosphorus recovery;

[0075] ④ After the sludge is cracked, the dewatering performance can be improved, and the amount of sludge dewatering agent added in the subsequent sludge dewatering unit can be reduced, which is beneficial to improving the treatment efficiency of the subsequent sludge dewatering unit and reducing the cost of sludge dewatering;

[0076] ⑤ The pH of the cracked sludge is adjusted to 9-9.5 by adding acid in the pH adjustment unit 5, and after being mixed with the remaining sludge (Q remaining), in this scheme, the pH of the mixed sludge entering the sludge thickening tank can be between 8 and 8.5, forming a suitable pH condition for anaerobic biological phosphorus release in the sludge thickening tank.

[0077] Table 1 Main components of sludge before and after sludge concentration

[0078]

[0079] Note: In the table, the concentration of sludge before concentration (Qresidual, referring to the residual sludge entering the sludge concentration unit from the residual sludge conveying pipeline 6) is MLSS=8g / L, and the concentration of sludge after concentration and decomposition (Qdecomposition) is MLSS=20g / L. In this embodiment, the volume of sludge after concentration and decomposition (Qdecomposition) is only about 8% of the volume of residual sludge Qresidual entering the sludge concentration tank. The composition data of the sludge are all measured by centrifuging the sludge and taking the supernatant.

[0080] The excess sludge before concentration (Q excess) and the sludge after cracking (Q cracked) are mixed before entering the sludge concentration unit 1 and then enter the sludge concentration unit 1. Compared with the conventional gravity concentration process, this embodiment not only realizes the physical concentration of sludge in the sludge concentration unit 1, but also realizes the following technical effects:

[0081] ① The excess sludge (Q excess) and the cracked sludge (Q cracked) are mixed before entering the sludge thickening unit. The mixing process and pipeline transportation process allow the microorganisms in the excess sludge (Q excess) to quickly adsorb the organic components in the cracked sludge (Q cracked), creating conditions for the microorganisms to further absorb the adsorbed organic matter into the microbial cells in the thickening tank, overcoming the defect of low mass transfer efficiency between organic matter and microbial cells caused by small fluid disturbance in the sludge thickening tank, allowing more organic components in the cracked sludge to enter the microbial cells in the excess sludge to achieve anaerobic phosphorus release;

[0082] ② Phosphorus-rich microorganisms (such as polyphosphate bacteria) in the residual sludge release the phosphorus in the cells into the water (in the form of orthophosphate, PO4) under the action of COD (carbon source) provided by the decomposition sludge under the anaerobic conditions in the sludge concentration unit 1. 3- The anaerobic biological phosphorus release of the entire amount of excess sludge was achieved, and the orthophosphate (PO4 3- The concentration of phosphorus can reach 50-60 mg / L, which creates conditions for subsequent phosphorus recovery.

[0083] ③ The organic nitrogen and organic phosphorus contained in the sludge are converted into ammonia nitrogen and orthophosphate (PO4 3- ), the conversion of organic nitrogen into ammonia nitrogen can save the dosage of ammonia nitrogen in the subsequent phosphorus recovery unit, and the conversion of organic phosphorus into orthophosphate can further improve the phosphorus recovery efficiency (organic phosphorus cannot be recovered through struvite crystallization).

[0084] The test data of the main components of the supernatant before sludge concentration, at the water inlet of the sludge concentration unit, and at the effluent of the sludge concentration unit are shown in Table 2. This embodiment has a significant effect on phosphorus release from sludge, and most of the phosphorus exists in the form of orthophosphate, which can be recovered by the subsequent phosphorus recovery unit 4.

[0085] Table 2 Main components of sludge before sludge thickening, sludge thickening tank inlet, and sludge thickening tank effluent

[0086]

[0087] 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 6) 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 (Qdecomposition) entering the decomposition unit accounts for 20% of the total volume of the concentrated sludge (Qdecomposition + Qdehydration), the reagent NaOH added to the sludge decomposition unit is added in solid form, the density of the sludge after decomposition is similar to that of the sludge before decomposition (Qdecomposition), and the volume of the sludge after decomposition (Qdecomposition) 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.

[0088] The phosphorus recovery unit 4 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 unit 4. 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. In this embodiment, the recovery rate of the phosphorus recovery unit for orthophosphate is greater than 80%, and the recovered product is struvite. The low-phosphorus liquid discharged from the phosphorus recovery unit can be returned to the biochemical pool at the front end of the sewage treatment system.

[0089] Applying the technical solution of this embodiment has the following beneficial effects:

[0090] 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 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.

[0091] 2. The phosphorus and nitrogen elements released into the liquid phase by the existing physical dephosphorization (ultrasound, thermal hydrolysis, mechanical ball milling) and chemical dephosphorization (acid, alkali) technologies are partially in the form of organic phosphorus and organic nitrogen, and the 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 the anaerobic bacteria in the residual sludge, which can further improve the phosphorus recovery rate and reduce the cost of adding ammonia nitrogen to the phosphorus recovery unit.

[0092] 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 sludge concentration unit 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 decomposition unit, a pH adjustment unit, a phosphorus recovery unit, and a control system, and carry out corresponding modifications to the pipelines to economically and conveniently realize the recovery of sludge phosphorus resources in the existing sewage treatment plant.

[0093] Fourth, the phosphorus recovery unit in this embodiment includes an outer cylinder, an inner cylinder, an inlet pipe, an outlet pipe, a discharge pipe, a perforated plate assembly and an inclined plate assembly, and the effects are: ①, the phosphorus recovery unit fully utilizes the kinetic energy and potential energy of the wastewater itself to achieve efficient hydraulic vortex crystallization, which is more energy-saving and has lower operating costs than conventional mechanical stirring crystallization; crystallization and precipitation are integrated, the device structure is compact, and the footprint is small; ②, a multi-layer perforated plate assembly with different porosities is arranged in the water flow descending channel A, and the perforated plates with different porosities can form micro-vortices of different intensities when the wastewater flows through, so that the wastewater is hydraulically graded during the flow process, so that the orthophosphate in the solution and the crystal-forming ions (Mg 2+ NH4 + ions) fully contact and mix and make the crystal particles fluidized, without the need for external seed crystals to achieve self-induced crystallization; ③, an inclined plate assembly is provided in the water flow rising channel B, which increases the precipitation area of ​​fine phosphorus crystal particles in the wastewater and shortens the precipitation time. At the same time, the water flow of the plate is changed from a turbulent state to a laminar state, thereby improving the recovery efficiency of phosphorus crystal particles in the wastewater.

[0094] 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 residual sludge phosphorus recovery device, characterized in that: It comprises a sludge concentration unit (1), a sludge decomposition unit (2), a sludge dehydration unit (3) and a phosphorus recovery unit (4); The sludge concentration unit (1) comprises a concentration tank body having a concentration accommodating chamber (1.4); the concentration tank body is provided with a residual sludge inlet (1.1), a concentrated sludge outlet (1.2) and a supernatant outlet (1.3) which are connected to the concentration accommodating chamber (1.4); the residual sludge inlet (1.1) is connected to a residual sludge conveying pipeline (6); The sludge decomposition unit (2) comprises a first shell (A1), a first stirring component (A2), a first sludge inlet pipe (A3) and a first sludge outlet pipe (A4); the first stirring component (A2) is arranged on the first shell (A1) for stirring the liquid inside the first shell; the first sludge inlet pipe (A3) is connected to the concentrated sludge outlet (1.2) through a first connecting pipe (G1); the first sludge outlet pipe (A4) is connected to the residual sludge inlet (1.1) through a second connecting pipe (G2); the 10%-20% concentrated sludge discharged from the concentrated sludge outlet (1.2) is returned to the sludge concentration unit (1) after being decomposition processed by the sludge decomposition unit; The sludge dehydration unit (3) comprises a dehydration treatment body having a dehydration accommodating chamber (3.1), the dehydration treatment body being provided with a dehydration treatment mud inlet pipe (3.2), a dehydration treatment mud outlet pipe (3.3) and a sludge dehydration liquid outlet pipe (3.4) which are connected to the dehydration accommodating chamber (3.1), the dehydration treatment mud inlet pipe (3.2) being connected to the concentrated sludge outlet (1.2) via a third connecting pipe (G3), and the dehydration treatment mud outlet pipe (3.3) being used for discharging dry mud; The supernatant liquid outlet (1.3) and the sludge dewatering liquid output pipe (3.4) are both connected to the phosphorus recovery unit (4) for phosphorus recovery.

2. The excess sludge phosphorus recovery device according to claim 1, characterized in that: The phosphorus recovery unit (4) comprises an outer cylinder (4.1), an inner cylinder (4.2), a water inlet pipe (4.3), a water outlet pipe (4.4), a discharge pipe (4.5), a perforated plate assembly (4.6) and an inclined plate assembly (4.7); The outer cylinder (4.1) comprises an outer cylinder body (4.1.1) having an opening at the upper end and a movable cover (4.1.2), wherein the movable cover (4.1.2) is detachably arranged at the opening; The inner cylinder body (4.2) comprises an inner cylinder body (4.2.1) having an opening at the lower end, the inner cylinder body (4.2.1) being arranged in the accommodating cavity of the outer cylinder body (4.1.1), and a water outlet channel (4.8) communicating with the water outlet pipe (4.4) being arranged between the inner wall of the outer cylinder body (4.1.1) and the outer wall of the inner cylinder body (4.2.1), the water outlet channel (4.8) and the water outlet pipe (4.4) being both located in the outer cylinder body ( 4.1.1); a water flow descending channel (A) is formed inside the inner cylinder body (4.2.1); the water inlet pipe (4.3) is connected to the water flow descending channel (A), and the water outlet end surface of the water inlet pipe (4.3) is higher than the upper end surface of the water outlet channel (4.8); the perforated plate assembly (4.6) is arranged in the water flow descending channel (A); The inner wall of the outer cylinder body (4.1.1), the water outlet channel (4.8) and the outer wall of the inner cylinder body (4.2.1) enclose a water flow rising channel (B), and the inclined plate assembly (4.7) is arranged in the water flow rising channel (B); The accommodating cavity in the outer cylinder body (4.1.1) is located below the inner cylinder body (4.2.1) to form a crystal gathering area (C), and the discharge pipe (4.5) is connected to the crystal gathering area (C).

3. The excess sludge phosphorus recovery device according to claim 2, characterized in that: Along the water flow direction in the water flow descending channel (A), the perforated plate assembly (4.6) comprises a first perforated single piece, a second perforated single piece and a third perforated single piece arranged in sequence, the first perforated single piece comprises one or more first perforated plates (4.6.1) arranged at intervals, the second perforated single piece comprises one or more second perforated plates (4.6.2) arranged at intervals, and the third perforated single piece comprises one or more third perforated plates (4.6.3) arranged at intervals; The ratio of the total area of ​​through holes in the first perforated plate to the plate area is P1, the ratio of the total area of ​​through holes in the second perforated plate to the plate area is P2, the ratio of the total area of ​​through holes in the third perforated plate to the plate area is P3, and P1<P2<P3; The value of P1 is 2.5% to 3%; the value of P2 is 3.5% to 4.5%; the value of P3 is 5.0% to 6.0%.

4. The excess sludge phosphorus recovery device according to claim 2, characterized in that: The inclined plate assembly (4.7) is arranged on the inner wall of the outer cylinder body (4.1.1) and the outer wall of the inner cylinder body (4.2.1) through an inclined plate support frame (4.10); the inclined plate assembly (4.7) comprises a plurality of sedimentation inclined plates that are spaced and staggered, and the gaps between the plurality of sedimentation inclined plates form a flow channel.

5. The excess sludge phosphorus recovery device according to claim 2, characterized in that: Along the water flow direction, the water inlet pipe (4.3) comprises a horizontal pipe section, an arc-shaped transition pipe section and a vertical pipe section which are arranged in sequence, and the water outlet end surface of the vertical pipe section is 5-20 cm higher than the upper end surface of the water outlet channel (4.8).

6. The excess sludge phosphorus recovery device according to any one of claims 1 to 5, characterized in that: 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) includes 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), and 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 thereon.

7. The excess sludge phosphorus recovery device according to claim 6, characterized in that: It also includes a first pH controller (A6), wherein the first body (A1.2) is provided with a measuring hole connected to the first containing cavity (A1.1), and 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 arranged on the outer side of the first measuring electrode; 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; 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 first 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 first detachable cover (A1.4).

8. The excess sludge phosphorus recovery device according to claim 6, characterized in that: It also includes a pH value adjustment unit (5) arranged in series with the sludge decomposition unit (2), and the pH value adjustment unit (5) includes a second shell (B1), a second stirring component (B2), a second sludge inlet pipe (B3) and a second sludge 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 first mud outlet pipe (A4) is connected to the second mud inlet pipe (B3) via a second connecting pipe (G2), and the second mud outlet pipe (B4) is connected to the residual sludge inlet (1.1) via a fourth connecting pipe (G4).

9. The excess sludge phosphorus recovery device according to claim 8, characterized in that: It also includes a second pH controller (B6), the second body (B1.2) is provided with a measuring hole connected to the second containing cavity (B1.1), the second pH controller 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 second 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 provided on the outer side of the second measuring electrode; The second body (B1.2) is also provided with a second odor collecting pipe (B7) for collecting odor generated in the second accommodating chamber; the second shell (B1) also includes an opening connected to the second accommodating chamber (B1.1), and a second detachable cover (B1.3) is provided at the opening; the second driving power source (B2.1), the second dosing pipe (B5), the second pH controller (B6) and the second odor collecting pipe (B7) are all arranged on the second detachable cover (B1.3).

10. The excess sludge phosphorus recovery device according to claim 6, characterized in that: The control range of the pH value in the sludge decomposition unit (2) is 10.8 to 11.5; the control range of the pH value in the pH adjustment unit (5) is 9 to 10; After the sludge after pH adjustment by the pH adjustment unit (5) intersects with the excess sludge conveying pipeline (6), the flow time of the mixed sludge from the intersection point to the outlet of the excess sludge feed inlet (1.1) is not less than 3 seconds; The control range of the pH value in the phosphorus recovery unit (4) is 9.5-10.

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