Efficient treatment method and device for phosphorus-containing sludge

Abstract

The invention discloses an efficient treatment method and device for phosphorus-containing sludge. The efficient treatment method comprises the four steps of pretreatment of centrifugation and pH adjustment, release and transfer of phosphorus, recovery of phosphorus in supernate and treatment of recovered wastewater. The centrifugal machine is used for dewatering sludge; the pyrohydrolysis reactor is used for pyrohydrolysis treatment; the anaerobic digester is used for bioelectrochemical treatment; the aeration tank and the clarification tank are used for forming supernate; a BES mode is introduced in the anaerobic digestion process, the phosphorus release efficiency and energy recovery can be remarkably improved, meanwhile, the sludge volume and the treatment cost are reduced, the whole system is improved in environmental benefits and more feasible in economy, meanwhile, biogas generated in the phosphorus extraction process is recycled, and the environment pollution is reduced. And the characteristics of sustainability and environmental protection are realized from each stage of phosphorus extraction.

Description

Technical Field

[0001] The invention belongs to the field of environmental protection and resource recycling, and specifically relates to a high-efficiency treatment method and device for phosphorus-containing sludge. Background Art

[0002] Phosphorus sludge usually comes from the biological phosphorus removal process in wastewater treatment. These sludges are rich in phosphorus, which can be extracted by chemical, physical or biological methods.

[0003] By treating phosphorus-containing sludge, the phosphorus in the sludge can be converted into usable resources, phosphate fertilizer or other phosphorus compounds can be produced, and dependence on natural phosphate rock can be reduced; the phosphorus content in the sludge can be reduced, the risk of secondary pollution to water bodies can be reduced, and eutrophication of water bodies can be prevented; the phosphorus extraction process can reduce the volume and weight of the sludge, and reduce the cost and difficulty of the final disposal of the sludge; removing phosphorus from the sludge can improve the operating performance of the sewage treatment plant and reduce the burden on subsequent treatment units; at the same time, phosphorus is an important fertilizer component in agricultural production, and phosphorus recovery helps to achieve the recycling of resources and promote ecological sustainable development. In short, phosphorus extraction from phosphorus-containing sludge is a technically feasible process with obvious economic and environmental benefits. It can effectively realize resource reuse and pollution control, and has positive significance for environmental protection and economic development.

[0004] However, the traditional treatment methods for phosphorus-containing sludge are mostly single physical methods (landfill incineration, centrifugation, filtration, sedimentation) or chemical methods (pH adjustment, addition of precipitants). Although they have a certain phosphorus extraction effect, the actual phosphorus extraction efficiency is not high, especially for the supernatant, its clarity has not been significantly improved, and the organic matter removal efficiency is not high, which affects the overall phosphorus extraction efficiency. Summary of the invention

[0005] In view of the above defects, the present invention provides an efficient treatment method for phosphorus-containing sludge, comprising the following steps:

[0006] S1, pre-processing stage:

[0007] S1-1, reduce the water content in the sludge stock solution;

[0008] S1-2, adjusting the pH value of the dehydrated sludge;

[0009] S2, Phosphorus release and transfer stage:

[0010] S2-1, eliminating microorganisms in the dewatered sludge after pH adjustment by means of a thermal hydrolysis reactor;

[0011] S2-2, the sludge after thermal hydrolysis treatment is transported to the inside of the anaerobic digester and continuously mixed at 33-55℃;

[0012] S2-3, newly injecting a microbial population into the thermotolerant strains that have not been eliminated by thermal hydrolysis, and providing a low voltage current through a bioelectrochemical reactor to stimulate microbial activity;

[0013] S2-4, the stimulated sludge is input into the aeration tank to complete the degradation of organic matter and phosphorus release, and then passes through the clarification tank to form a supernatant;

[0014] S3, Phosphorus recovery stage:

[0015] A precipitant is added to the supernatant to form insoluble phosphate for separation by a membrane separation device;

[0016] S4. The wastewater after phosphorus recovery is discharged into the wastewater treatment system.

[0017] Furthermore, the biogas generated in step S2-2 is recovered and reused through a gas recovery system.

[0018] The present invention also includes an apparatus based on the above-mentioned efficient treatment method of phosphorus-containing sludge, comprising a centrifuge for dewatering the sludge, a thermal hydrolysis reactor for thermal hydrolysis treatment, an anaerobic digester for bioelectrochemical treatment, an aeration tank and a clarification tank for forming a supernatant, a membrane separation device for phosphorus recovery, and a wastewater treatment system for wastewater recovery;

[0019] The interior of the centrifuge is divided into two upper and lower chambers by a material plate, and the two chambers are respectively used for centrifugal dehydration of the sludge raw material and pH adjustment of the dehydrated sludge. The pH adjustment is performed by automatically adding acid and alkali solutions and detecting the internal pH value through a feeding device installed outside the centrifuge;

[0020] A bioelectrochemical reactor for performing bioelectrochemical reaction is installed inside the anaerobic digester.

[0021] Further, the centrifuge includes a kettle body, a motor is installed on the top of the kettle body through a motor frame, a drive shaft is installed on the output end of the motor, the bottom end of the drive shaft passes through the kettle body and extends to the upper chamber and is fixed with a centrifuge drum, the outer ring of the centrifuge drum is installed on load-bearing rods distributed at equal distances, the overflow cylinder sleeved on the outside of the centrifuge drum is penetrated and fixed by each load-bearing rod, and each load-bearing rod is fixed with a scraper plate that fits the inner wall of the kettle body at one end away from the centrifuge drum;

[0022] A transmission rod is installed at the center of the bottom end of the overflow cylinder. The transmission rod passes through the material plate and extends to the interior of the lower chamber and is connected to a differential gear system. The outer side of the differential gear system is fixed to the inner wall of the kettle body by a number of connecting bolts. The number of planetary gears inside the differential gear system is not less than three, and a stirring rod is fixed to the inner ring of each planetary gear.

[0023] Furthermore, a mounting groove is provided at the center of the feed plate, a bearing adapted to the transmission rod is installed at the mounting groove, and a plurality of feed discharge ports are provided at the panel of the feed plate;

[0024] Several water pipes are installed inside the feeding plate, each of which is located between two adjacent feeding ports, and the several water pipes are interconnected through a circular rotating pipe located in the middle of the feeding plate. Several nozzles are installed at the bottom of each water pipe. The nozzles penetrate the inner wall of the feeding plate and are used to spray the acid and alkali solutions input by the feeding device into the lower chamber. The input ends of the two bottle bodies of the feeding device are respectively connected to the water pipe closest to the side through a shunt pipe.

[0025] Furthermore, the inner wall of the lower chamber is provided with equidistantly distributed vibrators, and each vibrator works synchronously through a master control switch;

[0026] The diversion pipe and the water delivery pipe are connected through a hose;

[0027] A rubber pad is additionally provided between the mounting groove and the bearing.

[0028] Furthermore, the bioelectrochemical reactor comprises a cathode and an anode installed inside the anaerobic digester, wherein the cathode and the anode are made of carbon-based materials and are distributed in a plurality of layers or spiral structures.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The centrifuge adopts a dual-chamber design, which performs centrifugation and pH adjustment simultaneously, making the subsequent precipitation and phosphorus extraction more efficient;

[0031] Introducing the BES method in the anaerobic digestion process can significantly improve the phosphorus release efficiency and energy recovery, while reducing the sludge volume and treatment costs, so that the entire system is not only improved in environmental benefits, but also more economically feasible. At the same time, the biogas generated in the phosphorus extraction process is recycled and reused, achieving sustainability and environmental protection at all stages of phosphorus extraction. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the process in the present invention.

[0033] Figure 2 Schematic diagram of the interior of the centrifuge in the present invention.

[0034] Figure 3 It is a bottom view of the feed plate in the present invention.

[0035] In the figure: 1. centrifuge; 11. kettle body; 12. feed plate; 102. feed valve; 103. drive shaft; 104. centrifuge drum; 105. overflow tube; 106. load-bearing rod; 107. scraper plate; 108. differential gear system; 109. fixed rod; 110. stirring rod; 112. vibrator; 113. transmission rod; 114. feeding device; 121. discharge port; 122. rubber pad; 123. bearing; 124. circular rotary pipe; 125. water pipe; 126. nozzle; 3. thermal hydrolysis reactor; 4. anaerobic digester; 5. clarification tank; 6. membrane separation device. DETAILED DESCRIPTION

[0036] In order to facilitate the understanding of the present invention, the device of the present invention will be described more fully below with reference to the relevant drawings. Embodiments of the device are given in the drawings. However, the device can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0037] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "set" should be understood in a broad sense, for example, they can be fixedly connected or set, or detachably connected or set, or integrally connected or set. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] Example

[0039] like Figure 1 As shown, this embodiment provides an efficient treatment method for phosphorus-containing sludge, which specifically includes the following steps:

[0040] S1. Pretreatment stage, including physical and chemical treatment methods:

[0041] Among them, physical treatment (mechanical dehydration) can remove moisture from the sludge through a centrifuge or a filter press, concentrate the sludge and reduce the volume of subsequent treatment, thereby improving the efficiency of subsequent treatment (the following centrifuge is used in this embodiment);

[0042] For chemical agents (such as acid or alkali, determined according to the detected pH value) added to the dewatered sludge to adjust the pH value (i.e. chemical treatment), the adjusted pH environment can improve the efficiency of microbial activity or chemical reactions and promote subsequent phosphorus release;

[0043] S2, Phosphorus release and transfer stage:

[0044] S2-1, firstly, the thermal hydrolysis reactor is set to a high temperature and high pressure environment of 160-180℃ to eliminate most of the microorganisms in the dewatered sludge after pH adjustment, and at the same time, the organic matter is converted into a more degradable form;

[0045] S2-2. The sludge after thermal hydrolysis is then transported to the inside of the anaerobic digester. Although most of the microorganisms are killed during the thermal hydrolysis process, there are still heat-resistant anaerobic bacteria remaining. Therefore, in the environment of 33-55°C inside the anaerobic digester, it is continuously mixed through the mixing mechanism at the bottom. Anaerobic digestion will further decompose organic matter and produce biogas as a by-product, which is recovered in the connected biogas recovery system (such as activated carbon filter, scrubber and dryer, and then stored in a storage tank);

[0046] S2-3, newly injecting microbial populations into the heat-resistant strains that have not been eliminated by thermal hydrolysis, and providing low-voltage current through a bioelectrochemical reactor to stimulate microbial activity (specifically, by applying external current, the activity of anaerobic microorganisms is stimulated to improve the efficiency of organic matter degradation and phosphorus release. The current can promote the microbial electron transfer process, making the decomposition of organic matter more thorough. At the same time, the potential difference generated helps to reduce chemical oxygen demand (COD) and improve the overall energy efficiency of the system);

[0047] By introducing a bioelectrochemical reactor into the anaerobic digestion process, the phosphorus release efficiency and energy recovery can be significantly improved, while reducing the sludge volume and treatment cost. It should be noted that the bioelectrochemical reactor is a device that realizes the function of the bioelectrochemical system (BES). The role of the BES is mainly to stimulate and enhance the metabolic activity of microorganisms through electrochemical means. BES can improve the degradation efficiency of microorganisms and enhance the electron transfer process, thereby accelerating the decomposition of organic matter and the release of phosphorus. It should be noted that BES is not intended to treat anaerobic bacteria that have not been eliminated, but to improve the activity and efficiency of reintroduced or newly grown microbial populations.

[0048] At the same time, the bioelectrochemical reactor is equipped with a control system for monitoring and adjusting current and voltage to ensure the stability of reaction conditions;

[0049] S2-4. Due to the BES treatment, the microbial activity is promoted, the removal efficiency of organic matter is improved, and the concentration of organic matter in the liquid phase is reduced. The treated sludge is then input into the aeration tank to complete the degradation of organic matter and phosphorus release, and finally the supernatant is formed through the clarification tank. Compared with the direct solid-liquid separation method, the BES treatment before solid-liquid separation can form a clearer supernatant;

[0050] It should be noted that the aeration tank is a means of biodegradation, which provides oxygen through aeration to promote the growth of aerobic microorganisms. These microorganisms degrade the organic matter in the sewage and convert it into carbon dioxide, water and new biomass. After aeration treatment, the aforementioned mixed liquid usually enters a secondary sedimentation tank or clarification tank, where the activated sludge settles to the bottom of the tank, and the upper liquid forms a relatively clear supernatant.

[0051] S3, Phosphorus recovery stage:

[0052] A membrane separation device with intelligent control function is used to add a precipitant to the supernatant to form insoluble phosphate for separation, and then the phosphorus can be recovered manually;

[0053] Reverse osmosis membrane equipment is used to separate phosphates from the supernatant, and the intelligent control system uses built-in algorithms to analyze and adjust membrane operating conditions, such as pressure and flow rate, in real time to optimize phosphorus recovery rate and energy efficiency. This not only improves the release and recovery efficiency of phosphorus in sludge, but also optimizes energy consumption and operating costs, which has obvious advantages in terms of environmental protection and economy.

[0054] S4. The wastewater after phosphorus recovery is discharged into the wastewater treatment system, which can be the same as the existing wastewater treatment system, such as passing through the regulating tank, chemical precipitation, biological treatment, filtration, ozone treatment and disinfection processes in sequence, which will not be elaborated here.

[0055] It should be noted that the addition of chemical agents and precipitants can be completed by automatic feeding equipment (automatic selection of dosage type and amount according to pH value).

[0056] like Figure 2-3 As shown, the equipment used in the above-mentioned efficient treatment method for phosphorus-containing sludge specifically includes a centrifuge 1 for dehydrating sludge, a thermal hydrolysis reactor 3 for thermal hydrolysis treatment, an anaerobic digester 4 for bioelectrochemical treatment, an aeration tank 2 and a clarification tank 5 for forming a supernatant, a membrane separation device 6 for phosphorus recovery, and a wastewater treatment system for wastewater recovery;

[0057] The sludge raw material is input through the feed valve 102 at the top of the centrifuge 1. The interior of the centrifuge 1 is divided into two upper and lower chambers by the material plate 12. The two chambers are respectively used for centrifugal dehydration of the sludge raw material and pH adjustment of the dehydrated sludge. The pH adjustment is performed by automatically adding acid and alkali solutions and detecting the internal pH value (the detection function is realized by the acid and alkali sensor 114) through the feeding device 114 installed on the outside of the centrifuge 1, including two bottles for placing acid and alkali solutions respectively;

[0058] In detail, the centrifuge 1 includes a kettle body 11, a motor is installed on the top of the kettle body 11 through a motor frame, a drive shaft 103 is installed on the output end of the motor, the bottom end of the drive shaft 103 passes through the kettle body 11 and extends to the upper chamber and is fixed with a centrifuge drum 104, the outer ring of the centrifuge drum 104 is installed on load-bearing rods 106 distributed at equal distances, and the overflow cylinder 105 sleeved on the outside of the centrifuge drum 104 is penetrated and fixed by each load-bearing rod 106, and each load-bearing rod 106 is fixed at one end away from the centrifuge drum 104 with a scraper plate 107 that fits the inner wall of the kettle body 11;

[0059] The driving shaft 103 drives the centrifuge drum 104 to rotate through the drive of the motor, and the load-bearing rod 106 drives the wall plate 107 to rotate, so as to complete the cleaning of the inner wall of the kettle body 11. At the same time, the overflow tube 105 is limited and fixed by the load-bearing rod 106, and the sludge input into the overflow tube 105 by the feed valve 102 is centrifugally processed, and the filtered sludge is retained in the overflow tube 105 to wait for processing, and the centrifuged sludge flows from the upper chamber into the lower chamber for subsequent processing;

[0060] A transmission rod 113 is installed at the center of the bottom end of the overflow tube 105. The transmission rod 113 passes through the material plate 12 and extends to the inside of the lower chamber and is connected to a differential gear system 108 (specifically connected to the outer shell of the differential gear system 108). The differential gear system 108 is fixed to the inner wall of the kettle body 11 through a plurality of fixing rods 109. The centrifuged sludge can flow down from the fixing rods 109. The outer side of the differential gear system 108 is fixed to the inner wall of the kettle body 11 through a plurality of connecting bolts. The number of planetary gears inside the differential gear system 108 is not less than three, and the inner ring of each planetary gear is fixed with a stirring rod 110. The stirring rod 110 can be in an I-shaped or L-shaped shape, so that a wider range of stirring work can be achieved during stirring.

[0061] The transmission rod 113 driven synchronously by the overflow tube 105 rotates, which can rotate the revolving gear in the differential gear system 108, and at the same time drive the other meshing planetary gears to rotate, so that the stirring rod 110 connected to the bottom rotates. It should be noted that the bottom of the housing should be open, which will not affect the rotation of the stirring rod 110;

[0062] A mounting groove is provided at the center of the feeding plate 12, and a bearing 123 adapted to the transmission rod 113 is installed at the mounting groove. A plurality of discharge ports 121 for the centrifuged sludge to pass through are provided at the panel of the feeding plate 12.

[0063] A plurality of water pipes 125 are installed inside the feed plate 12, each of which is located between two adjacent feed ports 121, and the plurality of water pipes 125 are interconnected through a circular rotary pipe 124 located in the middle of the feed plate 12, and a plurality of nozzles 126 are installed at the bottom of each water pipe 125, which penetrates the inner wall of the feed plate 12 and is used to spray the acid-base solution input by the feeding device 114 into the lower chamber to complete the acid-base adjustment of the sludge in the lower chamber, and the input ends of the two bottles of the feeding device 114 are respectively connected to the water pipe 125 closest to the side through a shunt pipe;

[0064] In addition, the inner wall of the lower chamber can also be installed with equidistantly distributed vibrators 112, which are coated with anti-corrosion paint. Each vibrator 112 works synchronously through a master control switch. After the vibrator 112 is installed, it is necessary to ensure that the shunt pipe and the water pipe 125 are connected through a hose 115, and a rubber pad 122 is added between the installation groove and the bearing 123 to adapt to small-amplitude vibrations. Its function is to prevent sludge from clogging the discharge port 121.

[0065] A bioelectrochemical reactor for bioelectrochemical reaction is installed inside the anaerobic digester 4. The bioelectrochemical reactor includes a cathode and an anode installed inside the anaerobic digester 4. The cathode and the anode are made of carbon-based materials and are distributed in a layered or spiral structure.

[0066] Grid distribution: Anodes and cathodes are arranged alternately and in parallel in the anaerobic digester 4, forming a grid arrangement, which can provide a large surface area in a small volume;

[0067] Layered distribution: Anodes and cathodes are stacked alternately in several layers with a uniform spacing of 1-3 cm to allow fluid to pass through and ensure good mass transfer;

[0068] Spiral distribution: The anode and cathode are made into a spiral shape and entangled with each other to form a double helix-like structure. This design can provide a maximum surface area in a limited space.

[0069] It should be noted that the membrane separation device 6 is a conventional reverse osmosis membrane, ultrafiltration membrane, nanofiltration membrane or other component, which can be selected according to actual conditions and will not be described in detail here.

[0070] It should be noted that the structure described in the present invention can be implemented in a variety of different forms and is not limited to the described embodiments. Any equivalent transformations made by ordinary technicians in this field using the contents of the present invention description and drawings, or directly or indirectly applied to other related technical fields, such as the loading and unloading of other items, are included in the protection scope of the present invention.

Claims

1. An efficient treatment method for phosphorus-containing sludge, characterized in that: The following steps are involved: S1, pre-processing stage: S1-1, reduce the water content in the sludge stock solution; S1-2, adjusting the pH value of the dehydrated sludge; S2, Phosphorus release and transfer stage: S2-1, eliminating microorganisms in the dewatered sludge after pH adjustment by means of a thermal hydrolysis reactor; S2-2, the sludge after thermal hydrolysis treatment is transported to the inside of the anaerobic digester and continuously mixed at 33-55℃; S2-3, newly injecting a microbial population into the thermotolerant strains that have not been eliminated by thermal hydrolysis, and providing a low voltage current through a bioelectrochemical reactor to stimulate microbial activity; S2-4, the stimulated sludge is input into the aeration tank to complete the degradation of organic matter and phosphorus release, and then passes through the clarification tank to form a supernatant; S3, Phosphorus recovery stage: A precipitant is added to the supernatant to form insoluble phosphate for separation by a membrane separation device; S4. The wastewater after phosphorus recovery is discharged into the wastewater treatment system.

2. The method for efficiently treating phosphorus-containing sludge according to claim 1, characterized in that: The biogas generated in step S2-2 is recovered and reused through a gas recovery system.

3. An efficient treatment device for phosphorus-containing sludge, used in the efficient treatment method for phosphorus-containing sludge according to claim 1, characterized in that: It includes a centrifuge for dewatering sludge, a thermal hydrolysis reactor for thermal hydrolysis treatment, an anaerobic digester for bio-electrochemical treatment, an aeration tank and a clarifier for forming a supernatant, a membrane separation device for phosphorus recovery, and a wastewater treatment system for wastewater recovery; The interior of the centrifuge is divided into two upper and lower chambers by a material plate, and the two chambers are respectively used for centrifugal dehydration of the sludge raw material and pH adjustment of the dehydrated sludge. The pH adjustment is performed by automatically adding acid and alkali solutions and detecting the internal pH value through a feeding device installed outside the centrifuge; A bioelectrochemical reactor for performing bioelectrochemical reaction is installed inside the anaerobic digester.

4. The high-efficiency treatment device for phosphorus-containing sludge according to claim 3, characterized in that: The centrifuge comprises a kettle body, a motor is installed on the top of the kettle body through a motor frame, a drive shaft is installed on the output end of the motor, the bottom end of the drive shaft passes through the kettle body and extends to the upper chamber and is fixed with a centrifuge drum, the outer ring of the centrifuge drum is installed on load-bearing rods distributed at equal distances, the overflow cylinder sleeved on the outside of the centrifuge drum is penetrated and fixed by each load-bearing rod, and each load-bearing rod is fixed with a scraper plate that fits the inner wall of the kettle body at one end away from the centrifuge drum; A transmission rod is installed at the center of the bottom end of the overflow cylinder. The transmission rod passes through the material plate and extends to the interior of the lower chamber and is connected to a differential gear system. The outer side of the differential gear system is fixed to the inner wall of the kettle body by a number of connecting bolts. The number of planetary gears inside the differential gear system is not less than three, and a stirring rod is fixed to the inner ring of each planetary gear.

5. The high-efficiency treatment device for phosphorus-containing sludge according to claim 4, characterized in that: A mounting groove is provided at the center of the feeding plate, a bearing adapted to the transmission rod is installed at the mounting groove, and a plurality of feeding ports are provided at the panel of the feeding plate; Several water pipes are installed inside the feeding plate, each of which is located between two adjacent feeding ports, and the several water pipes are interconnected through a circular rotating pipe located in the middle of the feeding plate. Several nozzles are installed at the bottom of each water pipe. The nozzles penetrate the inner wall of the feeding plate and are used to spray the acid and alkali solutions input by the feeding device into the lower chamber. The input ends of the two bottle bodies of the feeding device are respectively connected to the water pipe closest to the side through a shunt pipe.

6. The high-efficiency treatment device for phosphorus-containing sludge according to claim 5, characterized in that: The inner wall of the lower chamber is provided with vibrators which are equidistantly distributed, and each vibrator works synchronously through a master control switch; The diversion pipe and the water delivery pipe are connected through a hose; A rubber pad is additionally provided between the mounting groove and the bearing.

7. The high-efficiency treatment device for phosphorus-containing sludge according to claim 3, characterized in that: The bio-electrochemical reactor comprises a cathode and an anode installed inside the anaerobic digester. The cathode and the anode are made of carbon-based materials and are distributed in a plurality of layers or spiral structures. The anode and cathode are alternately arranged in parallel in the anaerobic digester to form a grid arrangement. The anode and cathode are alternately stacked into several layers with a uniform spacing value of 1-3 cm.

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