A septic tank excrement resource utilization device and method

Abstract

The application discloses a septic tank excrement and urine resource utilization device, which comprises sequentially connected excrement and urine pumping modules, magnetic flocculation modules, nitrogen and phosphorus recovery modules and discharge modules; the magnetic flocculation modules comprise magnetic flocculation reaction tanks, magnetic excrement and urine separation devices, magnetic seed recovery devices and excrement residue storage tanks; the nitrogen and phosphorus recovery modules comprise magnesium ammonium phosphate reaction tanks, magnesium source-phosphorus source adding systems, mechanical stirring systems and centrifugal separation systems. The magnetic flocculation modules and the nitrogen and phosphorus recovery modules are combined innovatively, the magnetic flocculation technology is adopted, the flocculant consumption and the solid-liquid separation time are reduced, the magnetic seeds can be recycled, there is no flocculant residue in the excrement residue, the solid-liquid separation effect and the resource safety are improved, the supernatant of the solid-liquid separation is used for recovering nitrogen and phosphorus resources by the magnesium ammonium phosphate crystallization method to prepare slow-release fertilizer, and nitrogen and phosphorus resource waste and environmental pollution are avoided.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection and resource utilization, specifically relating to a device and method for the resource utilization of septic tank waste. Background Technology

[0002] Rural areas lack centralized facilities for treating sewage, which is typically reused after natural fermentation in septic tanks. This results in low levels of composting and fertilizer efficiency, and makes sewage recycling difficult. Furthermore, three-chamber septic tanks generally only remove the sludge from the first and second chambers, failing to effectively utilize the nitrogen- and phosphorus-rich effluent from the third chamber, leading to low resource utilization. Therefore, developing in-situ, high-efficiency nitrogen and phosphorus recovery technologies and integrated equipment suitable for rural areas is of great significance for improving the resource utilization level of sewage.

[0003] Solid-liquid separation is a crucial technical method for the resource utilization of septic tank waste, primarily encompassing sedimentation, screening, filtration, centrifugation, hydrocyclone, flotation, membrane filtration, and evaporative sedimentation. Coagulation / flocculation also significantly impacts waste resource utilization; coagulants / flocculators can be combined with most solid-liquid separation technologies to improve separation efficiency. However, in conventional techniques, flocculants often remain in the waste, posing a certain risk to subsequent resource recycling. Therefore, efficient solid-liquid separation of waste and reduced flocculant usage are essential pathways to achieving waste resource utilization and key technical aspects of efficient transportation and treatment. Magnetic flocculation technology is a solid-liquid separation technology developed on the basis of traditional flocculation. It combines the advantages of traditional flocculation and magnetic separation technologies. By adding magnetic seeds and flocculants, the magnetic seeds and particulate matter are combined with the flocculants to form magnetic composite flocs, which are high-density magnetic flocs. These flocs are then rapidly separated from the water by gravity settling or by an external magnetic field. This can shorten the treatment cycle and achieve good separation results. It has advantages such as high flocculation efficiency, fast settling speed, low treatment cost, small footprint, low reagent dosage, and recoverable magnetic seeds, and has broad application prospects.

[0004] In summary, given the practical challenges of numerous and small-sized septic tanks in rural areas, significant pollution, low resource utilization levels, and long solid-liquid separation times, it is necessary to develop efficient solid-liquid separation technologies to reduce flocculant usage and separation time, improve nitrogen and phosphorus recovery rates in manure, thereby enhancing the safety of manure use and achieving the goal of "synergistic efficiency improvement through pollution reduction and carbon reduction". Summary of the Invention

[0005] The first objective of this invention is to address the difficulties in recycling septic tank waste in rural toilets and the safety risks posed by the residues of traditional flocculation technology to the reuse of manure-based fertilizers. This invention provides a septic tank waste resource utilization device that can efficiently, synergistically, and safely recover organic matter and nutrients such as nitrogen and phosphorus from waste in situ, facilitating the long-term operation and maintenance of decentralized septic tanks in rural areas.

[0006] A device for the resource utilization of septic tank waste includes a waste pump suction module, a magnetic flocculation module, a nitrogen and phosphorus recovery module and a discharge module connected in sequence.

[0007] The magnetic flocculation module includes a magnetic flocculation reaction tank, a magnetic-fecal separation device, a magnetic seed recovery device, and a fecal residue storage tank. The inlet of the magnetic flocculation reaction tank is connected to the fecal pump module, and the outlet of the magnetic flocculation reaction tank is connected to the inlet of the magnetic-fecal separation device. The magnetic-fecal separation device includes multiple outlets, wherein the first outlet is connected to the magnetic flocculation reaction tank through the magnetic seed recovery device, the second outlet is connected to the fecal residue storage tank, and the third outlet is connected to the nitrogen and phosphorus recovery module.

[0008] The nitrogen and phosphorus recovery module includes a magnesium ammonium phosphate reaction tank, a magnesium-phosphorus source dosing system, a mechanical stirring system, and a centrifugal separation system. The magnesium-phosphorus source dosing system is connected to the magnesium ammonium phosphate reaction tank via a liquid delivery pipeline. The mechanical stirring system is located inside the magnesium ammonium phosphate reaction tank. The outlet of the magnesium ammonium phosphate reaction tank is connected to the inlet of the centrifugal separation system. The outlet of the centrifugal separation system is connected to the discharge module.

[0009] Magnetic flocculant is replenished into the magnetic flocculation reactor as needed. This magnetic flocculant, or magnetic seed, consists of surface-modified Fe3O4 magnetic particles with a particle size in the nanometer or micrometer range. Recyclable magnetic flocculant (magnetic seed) refers to a process where commercially available carboxylated magnetic Fe3O4 particles (COOH-F3O4) are used as the core, and an amine-based flocculant is coupled to the surface of the magnetic particles through a surface polymerization cross-linking reaction.

[0010] Preferably, the amine-based flocculant is polyethyleneimine (PEI).

[0011] Preferably, the surface polymerization crosslinking reaction employs a two-step grafting method using carbodiimide (EDC) / N-hydroxysuccinimide (NHS). First, COOH-Fe3O4 is mixed with PEI, and 0.01%–0.05% EDC is added to activate the COOH-Fe3O4 for 5–15 minutes. Then, 0.02%–0.1% NHS is added, and the mixture is slowly rotated and mixed at 30–50°C for esterification for 24–48 hours to generate stable amide bonds. After the reaction is complete, the mixture is centrifuged and washed five times with deionized water, then vacuum dried to obtain the recovered magnetic flocculant (magnetic seed), which exhibits superparamagnetism and combines magnetic properties with coagulation / flocculation efficiency.

[0012] Preferably, the amount of magnetic flocculant used is 20-100 mg / L of fecal water, and the flocculation reaction time is 20-60 s.

[0013] Preferably, the septic tank waste resource utilization device further includes a chemical storage and preparation module; the chemical storage and preparation module includes a magnetic seed storage tank, an automatic dosing device, an acid-base chemical storage system, and a dosing device; the outlet of the automatic dosing device is connected to the inlet of the magnetic flocculation reaction tank, and the inlet of the automatic dosing device is connected to the outlet of the magnetic seed storage tank; the outlet of the dosing device is connected to the inlet of the magnesium source-phosphorus source dosing system, and the inlet of the dosing device is connected to the outlet of the acid-base chemical storage system.

[0014] Preferably, the effective volume of the magnetic seed storage tank, automatic dosing device, dosing device, and acid-base storage system is 25-50L.

[0015] Preferably, the sewage pump suction module uses a vacuum pump, and its vacuum level meets the maximum suction lift requirement.

[0016] Preferably, the effective volume of the magnetic flocculation reactor is 1.0-1.5 m³. 3 The magnetic field strength of the magnetic-fecal separation device is 1.0-1.5 Tesla, and the volume of the fecal residue storage tank is 0.6-1.0 m³. 3 .

[0017] Preferably, the nitrogen and phosphorus recovery module is equipped with a liquid level sensor, a pH sensor, a nitrogen content sensor, and a phosphorus content sensor.

[0018] Preferably, the effective volume of the magnesium ammonium phosphate reaction vessel is 1.0-1.5 m³. 3 The maximum rotational speed of the centrifugal separation system is 3600 r / min.

[0019] The second objective of this invention is to provide a method for the resource utilization of nitrogen and phosphorus from septic tank waste in rural areas, comprising the following steps:

[0020] S1. Pump the sewage containing fecal particles into the magnetic flocculation reaction tank, and add magnetic seeds as needed to carry out the magnetic flocculation reaction;

[0021] S2. The wastewater after magnetic flocculation is fed into a magnetic-fecal separation device for solid-liquid separation to obtain magnetic seeds, fecal residue and supernatant.

[0022] S3. Pass the supernatant obtained after solid-liquid separation into a magnesium ammonium phosphate reaction tank, add appropriate amounts of magnesium and phosphorus sources for reaction; the magnetic seeds are recycled, and the manure residue is bagged and used as organic fertilizer.

[0023] S4. Centrifuge the reaction product from step S3 to recover magnesium ammonium phosphate.

[0024] Preferably, the wastewater containing fecal particles is the sewage from the third compartment of a three-compartment septic tank, wherein the suspended particulate matter content is 300-1000 mg / L, the dissolved ammonia nitrogen, total nitrogen, and total phosphorus content in the sewage are 80-400 mg / L, 100-500 mg / L, and 25-80 mg / L, respectively, and the fecal particle size ranges from micrometers (70-80%) to millimeters (20-30%).

[0025] Preferably, the reaction conditions for step S3 are: pH 4-9, residence time 1-10 min, stirring GT value 4000-20000; the dosage of magnesium salt and phosphorus source is based on the NH4+ content in the supernatant. + -N and PO4 3- The content is adaptively adjusted to satisfy n(Mg) 2+ ):n(NH4 + -N):n(PO4 3- = (1~1.4):1:(0.8~1).

[0026] The magnetic separation process involves adding a magnetic flocculant (magnetic seed) to the traditional flocculation and sedimentation process. This effectively combines the particulate matter in the sewage mixture with the magnetic seed to form a high-density magnetic particle flocculent. Under the action of a magnetic field, rapid and efficient solid-liquid separation is achieved. After the sewage residue is separated by a shearing machine, the magnetic seed can be separated and recycled using a rare-earth permanent magnet drum and reused in the system. The separated sewage residue is rapidly reduced in volume, and the residual amount of flocculant is less than 1%, allowing for safe and resource-efficient utilization in the future.

[0027] The supernatant of the sewage contains high levels of nitrogen and phosphorus nutrients, but low levels of suspended solids; the nitrogen component is mainly ammonia nitrogen (NH4). + The phosphorus component is mainly composed of orthophosphate (PO4-). 3- (Mainly)

[0028] The magnesium source generally refers to magnesium salts, such as MgCl2 and MgSO4; the phosphorus source generally refers to phosphates, such as KH2PO4, K2HPO4, and Mg3(PO4)2, which react with NH4 under suitable conditions. + -N and PO4 3- Magnesium ammonium phosphate precipitate (MgNH4PO4·6H2O) is formed, which can be quickly removed by centrifugation, with nitrogen and phosphorus recovery rates of over 80% in the supernatant.

[0029] The beneficial effects of this invention are:

[0030] This invention addresses the challenge of recycling fecal waste resources by developing a septic tank waste resource utilization device that integrates in-situ magnetic flocculation solid-liquid separation with magnetic seed recovery and recycling. The invention innovatively combines a magnetic flocculation module with a nitrogen and phosphorus recovery module. The employed magnetic flocculation technology reduces flocculant usage and solid-liquid separation time, allows for magnetic seed recycling, and eliminates flocculant residue in the fecal sludge, thus improving the solid-liquid separation efficiency and resource utilization safety. The supernatant from the solid-liquid separation is used to recover nitrogen and phosphorus resources via magnesium ammonium phosphate crystallization for the preparation of slow-release fertilizer, avoiding waste of nitrogen and phosphorus resources and environmental pollution. The in-situ intelligent integrated design facilitates in-situ recycling of fecal waste resources, improves the operation and maintenance level of rural septic tanks, and solves the problems of large flocculant usage, residue, and safety risks associated with the return of fecal-based fertilizer to the field in current rural three-chamber septic tank wastewater solid-liquid separation for agricultural resource utilization.

[0031] After adopting this invention, the solid-liquid separation of septic tank sewage can be completed within 1 minute, which is more than 60% lower than the traditional flocculation sedimentation method; the magnetic seed recycling rate is ≥95%, and the residual amount of flocculant in the manure is low; the nitrogen and phosphorus recovery rate of the three-chamber septic tank is ≥80%, which effectively improves the resource utilization level of rural sewage. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the device structure of the present invention. Detailed Implementation

[0033] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0034] like Figure 1 As shown, the present invention provides a septic tank waste resource utilization device, comprising a waste pump suction module, a magnetic flocculation module, a nitrogen and phosphorus recovery module, and a discharge module connected in sequence.

[0035] The sewage pump suction module uses a vacuum pump, and its vacuum level meets the maximum suction lift requirement.

[0036] The magnetic flocculation module includes a magnetic flocculation reaction tank, a magnetic-fecal separation device, a magnetic seed recovery device, and a fecal residue storage tank. The inlet of the magnetic flocculation reaction tank is connected to the fecal pump module, and the outlet of the magnetic flocculation reaction tank is connected to the inlet of the magnetic-fecal separation device. The magnetic-fecal separation device includes multiple outlets, wherein the first outlet is connected to the magnetic flocculation reaction tank through the magnetic seed recovery device, the second outlet is connected to the fecal residue storage tank, and the third outlet is connected to the nitrogen and phosphorus recovery module. The effective volume of the magnetic flocculation reaction tank is 1.0-1.5 m³. 3 The magnetic field strength of the magnetic-fecal separation device is 1.0-1.5 Tesla, and the volume of the fecal residue storage tank is 0.6-1.0 m³. 3 ;

[0037] The preparation process and conditions of the recyclable magnetic flocculant (magnetic seed) are as follows: commercially available carboxylated magnetic nano Fe3O4 particles (COOH-Fe3O4) are mixed with polyethyleneimine (PEI). First, 0.01%-0.05% EDC is added to activate COOH-Fe3O4 for 5-15 min. Then, 0.02%-0.1% NHS is added. The mixture is slowly rotated and esterified at 30-50℃ for 24-48 h. After centrifugation, the mixture is washed 5 times with deionized water and then vacuum dried.

[0038] The nitrogen and phosphorus recovery module includes a magnesium ammonium phosphate reaction tank, a magnesium-phosphorus source dosing system, a mechanical stirring system, and a centrifugal separation system. The magnesium-phosphorus source dosing system is connected to the magnesium ammonium phosphate reaction tank via a liquid delivery pipeline. The mechanical stirring system is located inside the magnesium ammonium phosphate reaction tank. The outlet of the magnesium ammonium phosphate reaction tank is connected to the inlet of the centrifugal separation system. The centrifugal separation system includes multiple outlets, wherein a first outlet is connected to the nitrogen and phosphorus recovery module, and a second outlet is connected to the discharge module. The effective volume of the magnesium ammonium phosphate reaction tank is 1.0-1.5 m³. 3 The maximum speed of the centrifugal separation system is 3600 r / min.

[0039] The septic tank waste resource utilization device also includes a chemical storage and preparation module; the chemical storage and preparation module includes a magnetic seed storage tank, an automatic dosing device, a magnesium source dosing device, and an acid-base chemical storage system;

[0040] The effective volume of the magnetic seed storage tank, automatic dosing device, magnesium source dosing device, and acid-base storage system is 25-50L.

[0041] A method for the resource utilization of nitrogen and phosphorus waste from rural septic tanks includes the following steps:

[0042] S1. Wastewater containing fecal particles is pumped into a magnetic flocculation reactor using a vacuum pump, and magnetic seeds are added for flocculation. The wastewater containing fecal particles is the sewage from the third compartment of a three-compartment septic tank, with a suspended particulate matter content of 300-1000 mg / L, dissolved ammonia nitrogen, total nitrogen, and total phosphorus content of 80-400 mg / L, 100-500 mg / L, and 25-80 mg / L, respectively, and the fecal particle size range is micrometer (70-80%) and millimeter (20-30%). The magnetic seeds are surface-modified F3O4 magnetic particles with a particle size of nanometer or micrometer. The amount of magnetic seeds used is 20-100 mg / L of sewage, and the flocculation reaction time is 20-60 s.

[0043] S2. The flocculated wastewater is fed into a magnetic-fecal separation device for solid-liquid separation to obtain magnetic seeds, fecal residue and supernatant; the magnetic seeds are then fed back into the magnetic flocculation reaction tank via a magnetic seed recovery device; the fecal residue is fed into a fecal residue storage tank for easy collection and discharge for agricultural use.

[0044] S3. Pass the supernatant obtained after solid-liquid separation into a magnesium ammonium phosphate reaction vessel, add appropriate amounts of magnesium and phosphorus sources, and react for 1-10 minutes under conditions of pH 4-9 and stirring GT value of 4000-20000; the nitrogen content and phosphorus content of the magnesium source, supernatant, and phosphorus source satisfy n(Mg) 2+ ): n(NH4) + -N): n(PO4) 3- ) = (1~1.4): 1: (0.8~1);

[0045] S4. Centrifuge the reaction product from step S3 to recover magnesium ammonium phosphate precipitate for agricultural use.

[0046] Application Example 1

[0047] A septic tank wastewater resource utilization device was used to perform solid-liquid separation and nitrogen and phosphorus resource recovery treatment on the sewage from a three-compartment septic tank in a rural public toilet. The pollutant indicators of the sewage were: suspended solids content 500 mg / L, dissolved ammonia nitrogen, total nitrogen, and total phosphorus content 260 mg / L, 300 mg / L, and 60 mg / L, respectively.

[0048] The septic tank waste resource utilization device used includes modules such as a waste pump suction module, a chemical storage and dosing module, a magnetic flocculation module, and a nitrogen and phosphorus recovery module. (See attached image) Figure 1 The effective volume of the magnetic flocculation reactor is 1.0 m³. 3 The magnetic field strength of the magnetic-fecal separation device is 1.0 Tesla, and the volume of the fecal residue storage tank is 0.6 m³. 3 The effective volume of the magnesium ammonium phosphate reaction vessel is 1.0 m³. 3 .

[0049] The preparation process and conditions of the recycled magnetic flocculant (magnetic seed) used are as follows: commercially available carboxylated magnetic nano Fe3O4 particles (COOH-Fe3O4) are mixed with polyethyleneimine (PEI). First, 0.05% EDC is added to activate COOH-F3O4 for 10 min. Then, 0.05% NHS is added. The mixture is slowly rotated and mixed overnight at 35°C for esterification (24 h). After centrifugation, the mixture is washed 5 times with deionized water and then vacuum dried.

[0050] The dosage of magnetic flocculant (magnetic seed) is 60 mg / L of fecal water. After flocculation reaction for 45 seconds, magnetic centrifugation is performed, and the fecal residue recovery rate reaches more than 96%. After separation by a high-pressure shearing machine, more than 98% of the magnetic seed can be recycled and reused.

[0051] After magnetic separation, the suspended solids content in the supernatant decreased significantly to below 50 mg / L. Online monitoring data showed that the ammonia nitrogen and total phosphorus contents were 196 mg / L and 48 mg / L, respectively, with a pH of 6.7. Subsequently, the supernatant entered the magnesium ammonium phosphate reaction tank, with magnesium and phosphorus sources reacted in a ratio of n(Mg) 2+ ):n(NH4 + -N):n(PO4 3- The ammonium magnesium phosphate was added adaptively at a ratio of 1.2:1:1, mechanically stirred for 5 minutes at 20 RPM, and then centrifuged at 2000 RPM to obtain the precipitate. At this point, the recovery rates of ammonia nitrogen and total phosphorus reached 96% and 100%, respectively, achieving efficient resource utilization.

[0052] Application Example 2

[0053] A septic tank wastewater resource utilization device was used to perform solid-liquid separation and nitrogen and phosphorus resource recovery treatment on the wastewater from the decentralized three-chamber septic tanks of multiple farmers in a village. The pollutant indicators of the wastewater were: suspended solids content 400-700 mg / L, dissolved ammonia nitrogen, total nitrogen, and total phosphorus content 165-342 mg / L, 186-385 mg / L, and 28-74 mg / L, respectively.

[0054] The septic tank waste resource utilization device used includes modules such as a waste pump suction module, a chemical storage and dosing module, a magnetic flocculation module, and a nitrogen and phosphorus recovery module. (See attached image) Figure 1 The effective volume of the magnetic flocculation reactor is 1.0 m³. 3 The magnetic field strength of the magnetic-fecal separation device is 1.0 Tesla, and the volume of the fecal residue storage tank is 0.6 m³. 3 The effective volume of the magnesium ammonium phosphate reaction vessel is 1.0 m³. 3 .

[0055] The preparation process and conditions of the recycled magnetic flocculant (magnetic seed) used are as follows: commercially available carboxylated magnetic nano Fe3O4 particles (COOH-Fe3O4) are mixed with polyethyleneimine (PEI). First, 0.02% EDC is added to activate COOH-Fe3O4 for 15 min. Then, 0.1% NHS is added. The mixture is slowly rotated and mixed overnight at 50°C for esterification (30 h). After centrifugation, the mixture is washed 5 times with deionized water and then vacuum dried.

[0056] The dosage of magnetic flocculant (magnetic seed) is 35-100 mg / L of fecal water, the flocculation reaction time is in the range of 30-60 s, followed by solid-liquid separation, the fecal residue recovery rate is between 90.5-97.8%, and after separation by a high-strength shear machine, the magnetic seed recovery rate reaches more than 95%.

[0057] After magnetic separation, the suspended solids content in the supernatant decreased significantly to between 32-65 mg / L. Online monitoring data showed that the ammonia nitrogen and total phosphorus contents were 143-308 mg / L and 15-68 mg / L, respectively, with a pH range of 4.6-8.3. Subsequently, the supernatant entered the magnesium ammonium phosphate reaction tank, with magnesium and phosphorus sources reacted in a ratio of n(Mg) 2+ ):n(NH4 + -N):n(PO4 3- The ammonium magnesium phosphate was added adaptively at a ratio of 1.4:1:0.8, and mechanically stirred for 3-8 minutes at 20 RPM. Then, it was centrifuged at 2000 RPM to obtain magnesium ammonium phosphate precipitate. At this point, the recovery rates of ammonia nitrogen and total phosphorus reached 84-92% and 93-99%, respectively, achieving efficient resource utilization.

[0058] The above embodiments are not intended to limit the present invention, and the present invention is not limited to the above embodiments. Any embodiment that meets the requirements of the present invention is within the protection scope of the present invention.

Claims

1. A device for the resource utilization of septic tank waste, characterized in that, It includes a sewage pump suction module, a magnetic flocculation module, a nitrogen and phosphorus recovery module, and a discharge module connected in sequence; The magnetic flocculation module includes a magnetic flocculation reaction tank, a magnetic-fecal separation device, a magnetic seed recovery device, and a fecal residue storage tank. The inlet of the magnetic flocculation reaction tank is connected to the fecal pump module, and the outlet of the magnetic flocculation reaction tank is connected to the inlet of the magnetic-fecal separation device. The magnetic-fecal separation device includes multiple outlets, wherein the first outlet is connected to the magnetic flocculation reaction tank through the magnetic seed recovery device, the second outlet is connected to the fecal residue storage tank, and the third outlet is connected to the nitrogen and phosphorus recovery module. The nitrogen and phosphorus recovery module includes a magnesium ammonium phosphate reaction tank, a magnesium-phosphorus source dosing system, a mechanical stirring system, and a centrifugal separation system. The magnesium-phosphorus source dosing system is connected to the magnesium ammonium phosphate reaction tank via a liquid delivery pipeline. The mechanical stirring system is located inside the magnesium ammonium phosphate reaction tank. The outlet of the magnesium ammonium phosphate reaction tank is connected to the inlet of the centrifugal separation system. The outlet of the centrifugal separation system is connected to the discharge module. The magnetic flocculation reactor is replenished with recoverable magnetic flocculant at appropriate times. This recoverable magnetic flocculant uses carboxylated magnetic Fe3O4 particles (COOH-Fe3O4) as its core, and is obtained by coupling an amine-based flocculant to the surface of COOH-Fe3O4 through a surface polymerization crosslinking reaction. The amine-based flocculant is polyethyleneimine (PEI). The surface polymerization crosslinking reaction employs a two-step grafting method using carbodiimide (EDC) and N-hydroxysuccinimide (NHS), specifically as follows: First, COOH-Fe3O4 and PEI are mixed, and 0.01-0.05% EDC is added to activate COOH-Fe3O4 for 5-15 min. Then, 0.02-0.1% NHS is added, and the mixture is mixed at 30-50℃ for esterification for 24-48 h. After the reaction is completed, the mixture is centrifuged and washed multiple times with deionized water, and then vacuum dried to obtain the recovered magnetic flocculant.

2. The septic tank waste resource utilization device according to claim 1, characterized in that, The dosage of the recyclable magnetic flocculant is 20~100 mg / L of fecal water.

3. The septic tank waste resource utilization device according to claim 1, characterized in that, The septic tank waste resource utilization device also includes a chemical storage and preparation module; the chemical storage and preparation module includes a magnetic seed storage tank, an automatic dosing device, an acid-base chemical storage system, and a dosing device; the outlet of the automatic dosing device is connected to the inlet of the magnetic flocculation reaction tank, and the inlet of the automatic dosing device is connected to the outlet of the magnetic seed storage tank; the outlet of the dosing device is connected to the inlet of the magnesium source-phosphorus source dosing system, and the inlet of the dosing device is connected to the outlet of the acid-base chemical storage system.

4. The septic tank waste resource utilization device according to claim 1, characterized in that, The nitrogen and phosphorus recovery module is equipped with a liquid level sensor, a pH sensor, a nitrogen content sensor, and a phosphorus content sensor.

5. The septic tank waste resource utilization device according to claim 1, characterized in that, The effective volume of the magnetic flocculation reactor is 1.0~1.5 m³. 3 The magnetic field strength of the magnetic-fecal separation device is 1.0~1.5 Tesla, and the volume of the fecal residue storage tank is 0.6~1.0 m³. 3 The effective volume of the magnesium ammonium phosphate reaction vessel is 1.0-1.5 m³. 3 The maximum rotational speed of the centrifugal separation system is 3600 r / min.

6. A method for the resource utilization of nitrogen and phosphorus from rural septic tank waste, characterized in that, Includes the following steps: S1. Activate the septic tank waste resource utilization device according to any one of claims 1-5, pump wastewater containing waste particles into the magnetic flocculation reaction tank, and add magnetic seeds in a timely manner to carry out magnetic flocculation reaction. S2. The wastewater after magnetic flocculation is fed into a magnetic-fecal separation device for solid-liquid separation to obtain magnetic seeds, fecal residue and supernatant. S3. Pass the supernatant obtained after solid-liquid separation into a magnesium ammonium phosphate reaction tank, add appropriate amounts of magnesium and phosphorus sources for reaction; the magnetic seeds are recycled, and the manure residue is bagged and used as organic fertilizer. S4. Centrifuge the reaction product from step S3 to recover magnesium ammonium phosphate.

7. The method for resource utilization of nitrogen and phosphorus from rural septic tank waste according to claim 6, characterized in that, The wastewater containing fecal particles is the sewage from the third compartment of a three-compartment septic tank, wherein the suspended particulate matter content is 300-1000 mg / L, the dissolved ammonia nitrogen, total nitrogen, and total phosphorus content in the sewage are 80-400 mg / L, 100-500 mg / L, and 25-80 mg / L, respectively, and the fecal particle size ranges from micrometers to millimeters.

8. The method for resource utilization of nitrogen and phosphorus from rural septic tank waste according to claim 7, characterized in that, In step S3, the amounts of magnesium and phosphorus sources added are based on the NH4+ content in the supernatant. + -N and PO4 3- Content adjustment to meet requirements n (Mg 2+ ): n (NH4 + -N): n (PO4 3- ) = (1~1.4) : 1 : (0.8~1).

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