A method and system for urine separation and concentration

Abstract

The application discloses a urine separation and concentration method and system, and belongs to the technical field of sewage resource utilization. The method comprises the following steps: temporarily storing urine in a collecting tank, driving the urine into a membrane separation device through a pressure pump, forming a permeate liquid and a retentate liquid on both sides of the membrane by using the characteristics that urea and ammonia nitrogen can selectively permeate the separation membrane, returning the retentate liquid to the collecting tank through a backwater pipeline for cyclic concentration, and collecting the permeate liquid to a recovery tank through a water outlet pipeline. The system comprises a urine collecting tank, a membrane separation device, a pressure pump, a backwater pipeline, a water outlet pipeline and a water outlet recovery tank which are connected in sequence. The application realizes efficient separation and concentration of nitrogen resources in urine by combining membrane separation with retentate circulation, has the advantages of high separation efficiency, low operation energy consumption, good automation degree and high resource recovery rate, and provides a stable and reliable technical scheme for source treatment of urine and nutrient recovery.

Description

Technical Field

[0001] This invention belongs to the field of wastewater resource utilization technology, and relates to a urine separation and concentration method and system. By using membrane separation and concentration technology under certain pressure, nitrogen-containing urea and ammonia nitrogen in urine are separated and concentrated, ultimately serving agriculture, chemical industry and other fields. Background Technology

[0002] With accelerated urbanization and continuous population growth, the volume of domestic sewage discharge is constantly increasing. Urine, as a key component of sewage, presents an increasingly prominent issue regarding its resource utilization. Although urine discharge accounts for only about 1% of total sewage, it contributes over 80% of the nitrogen load. Its high content of urea and ammonia nitrogen represents both valuable resources and potential environmental pollutants. Direct discharge without effective treatment not only results in a severe waste of nitrogen resources but also leads to environmental problems such as eutrophication and ecological imbalance. Therefore, source separation and efficient treatment of urine have become crucial directions in the fields of sewage treatment and resource recovery.

[0003] Currently, several technical approaches exist for the recovery and treatment of nitrogen in urine, but all have significant limitations. Traditional biological treatment methods, while removing some nitrogen, convert valuable nitrogen resources into nitrogen gas emissions, failing to achieve resource recovery. Methods such as evaporation concentration and chemical precipitation suffer from high energy consumption, complex processes, and the potential for secondary pollution. While membrane separation technology shows some potential for selective separation, it faces challenges such as severe membrane fouling, rapid decline in separation efficiency, and limited concentration when directly treating urine, making long-term stable operation and efficient resource enrichment difficult.

[0004] In summary, current technologies lack a urine treatment solution that can simultaneously achieve high-efficiency separation, deep concentration, long-term stable operation, and low energy consumption. In particular, there is a lack of anti-fouling membrane process designs tailored to the complex composition of urine, as well as integrated systems capable of achieving efficient nitrogen recovery and intelligent process control. Therefore, developing a novel and efficient urine separation and concentration method and system to achieve synergistic nitrogen resource recovery and pollution and carbon reduction is an urgent practical need and has significant application value. Summary of the Invention

[0005] The purpose of this invention is to provide a urine separation and concentration method to solve the problems of low separation efficiency, low resource recovery rate, serious membrane fouling, and unstable system operation in existing urine treatment technologies.

[0006] The first objective of this invention is to provide a method for urine separation and concentration, comprising: S1 Initial Collection and Temporary Storage: The urine to be processed is transported and temporarily stored in a urine collection tank; S2 Pressure Driven Membrane Separation: Urine from the urine collection tank is introduced into the membrane separation device through the inlet pipe, and a pressure pump provides driving force, causing the urine to flow through the separation membrane of the membrane separation device under a set pressure condition; the driving pressure of the pressure pump is controlled within the range of 0.1MPa to 1.5MPa; specifically, when the separation membrane is an ultrafiltration membrane, the pressure is controlled between 0.1MPa and 0.5MPa; when the separation membrane is a nanofiltration membrane, the pressure is controlled between 1.0MPa and 1.5MPa; while using the pressure pump to provide driving force, a DC electric field of 5-50V / cm is also applied to a pair of electrodes integrated in the membrane separation device, so that the electric field force and pressure work together to drive the selective permeation of target ionic nutrients through the separation membrane; utilizing the selective permeation characteristics of urea and ammonia nitrogen molecules through the separation membrane, permeate rich in urea and ammonia nitrogen and retentate rich in retentate are formed on both sides of the membrane, respectively; S3 Retention Fluid Circulation: The retention fluid is returned to the urine collection tank through the return water pipeline; S4 Permeate Collection: Permeate is continuously collected through the effluent pipeline into an effluent recovery tank; S5 Process Monitoring and Regulation: Monitor the operating parameters of the membrane separation unit and / or the water quality of the permeate, and dynamically adjust the operating pressure of the pressure pump and / or the reflux ratio of the return water pipeline based on the monitoring data; dynamic regulation includes: reducing the reflux ratio when the ammonia nitrogen concentration in the influent of the membrane separation unit is lower than a first preset threshold; and / or increasing the reflux ratio and / or the operating pressure when the rate of increase of the transmembrane pressure difference of the membrane separation unit exceeds a preset rate threshold.

[0007] The second objective of this invention is to provide a urine separation and concentration system, comprising: Urine collection tank, used to receive, mix and temporarily store raw urine and circulating fluid; The membrane separation device has its inlet connected to the outlet of the urine collection tank via an inlet pipe; Pressure pumps are used to provide operating pressure for membrane separation units; The return water pipeline connects the retentate outlet of the membrane separator to the return port of the urine collection tank; The outlet pipe connects to the permeate outlet of the membrane separation unit; The effluent recovery tank is connected to the effluent pipe; The control unit is used to monitor system parameters and dynamically adjust the pressure pump and / or the flow regulating device installed on the return water pipeline.

[0008] The urine separation and concentration method and system provided by this invention have the following significant and beneficial technical effects compared with the prior art: (1) This invention combines membrane separation technology with retentate recycling process to efficiently and selectively separate nitrogenous substances such as urea and ammonia nitrogen from urine, achieving high recovery rate and deep concentration of target components, and greatly enhancing the value of urine as a nitrogen resource. The method operates under optimized pressure parameters, and the separation process is direct and efficient.

[0009] (2) The entire treatment process of this invention has low energy consumption. Through intelligent control, the operating parameters and energy consumption are further optimized, which significantly reduces the treatment cost. At the same time, this process effectively intercepts pollutants in urine at the source, greatly reducing the environmental load of nitrogen and phosphorus emissions on water bodies, and meets the requirements of clean production and environmental protection.

[0010] (3) This invention achieves a high degree of automation and intelligence in the processing. By integrating real-time monitoring, dynamic adjustment and predictive maintenance, it ensures the stability and reliability of the system in long-term operation. The whole set of equipment is easy to operate, has low maintenance costs, strong process continuity, and has good engineering adaptability and prospects for large-scale promotion and application. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a schematic diagram of a urine separation and concentration system according to an embodiment of the present invention; Figure 2 This is a flowchart of a urine separation and concentration method according to an embodiment of the present invention; Figure 3 This is a flowchart of a urine separation and concentration method according to an embodiment of the present invention, which includes pretreatment and solid-liquid separation steps.

[0013] Explanation of reference numerals in the attached drawings: 1-Collection tank; 2-Inlet pipe; 3-Membrane separation device; 4-Outlet pipe; 5-Recovery tank; 6-Pressure pump; 7-Return pipe; 8-Real-time monitoring device. Detailed Implementation

[0014] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid obscuring the invention.

[0015] To fully understand this invention, detailed steps and structures will be presented in the following description to illustrate the technical solution of this invention. Preferred embodiments of the invention are described in detail below; however, in addition to these detailed descriptions, the invention may have other embodiments.

[0016] Example 1 like Figures 1 to 3 In one embodiment of the urine separation and concentration method of the present invention, the method utilizes a membrane separation device to achieve efficient separation and concentration of urea and ammonia nitrogen in urine. See also Figure 1 The process mainly relies on a system consisting of a collection tank 1, an inlet pipe 2, a membrane separation device 3, an outlet pipe 4, a recovery tank 5, a pressure pump 6, a return pipe 7, and a real-time monitoring device 8.

[0017] Step S1: Initial Collection and Temporary Storage The raw urine is transported and temporarily stored in a dedicated collection tank 1. Collection tank 1 must have appropriate volume, good sealing, and necessary stirring function to ensure homogeneity of the urine and prevent odor evaporation and ammonia nitrogen loss. This step achieves centralized and stable storage of the urine, providing stable feeding conditions for subsequent continuous processing and is a prerequisite for ensuring the continuous and stable operation of the entire process.

[0018] Step S2: Pressure-driven membrane separation Urine from collection tank 1 is introduced into membrane separation device 3 through inlet pipe 2. Pressure pump 6 is started to provide a stable transmembrane driving force for the system. The driving pressure of pressure pump 6 is controlled within the range of 0.1 MPa to 1.5 MPa. Driven by pressure pump 6, urine flows through the separation membrane surface in membrane separation device 3 at a set pressure. The separation membrane is an ultrafiltration membrane or a nanofiltration membrane. When membrane separation device 3 is an ultrafiltration membrane separation device, the driving pressure of pressure pump 6 is preferably controlled between 0.1 MPa and 0.5 MPa; when it is a nanofiltration membrane separation device, the driving pressure of pressure pump 6 is preferably controlled between 1.0 MPa and 1.5 MPa.

[0019] In one specific embodiment, the membrane separation device 3 integrates an electric field auxiliary unit. Specifically, a pair of corrosion-resistant electrodes, which can be a titanium-coated ruthenium anode and a stainless steel cathode, are arranged parallel to each other on both sides of the separation membrane inside the membrane housing. The electrodes are separated from the separation membrane by insulating gaskets and connected to an external DC power supply. While the pressure pump 6 provides driving force, a DC electric field of 5-50V / cm is applied to the pair of electrodes. The direction of the electric field force is set to promote the migration of target ionic nutrients, such as NH4+, to the permeate side. +The synergistic effect of this electric field and pressure enhances the selective permeation efficiency of small molecules such as urea and ammonia nitrogen. Utilizing the small molecular size and enhanced migration ability of urea and ammonia nitrogen under the synergistic effect of the electric field, target nutrients can selectively permeate through the separation membrane, resulting in the formation of a permeate rich in urea and ammonia nitrogen, and a retentate containing macromolecular organic matter, colloids, and other impurities on either side of the membrane. This process achieves efficient and clean separation of the target nutrients.

[0020] In one specific embodiment, after step S1 and before S2, a pretreatment and solid-liquid separation step S1a is included. This step specifically involves: first, adding an alkaline regulator, preferably sodium hydroxide solution, to the urine in collection tank 1 to precisely adjust the urine pH to a strongly alkaline range of 9.5-11.5. Under these conditions, phosphate ions in the urine react with free calcium, magnesium, and ammonium ions to generate a microcrystalline precipitate mainly composed of magnesium ammonium phosphate (commonly known as struvite). Simultaneously, a low-intensity advanced oxidation or electrochemical treatment can be applied to the urine to alter the surface charge, hydrophilicity, and hydrophobicity of colloidal and macromolecular organic matter in the urine, making them more prone to coagulation. Subsequently, solid-liquid separation is performed through precipitation, centrifugation, or filtration to effectively separate the generated microcrystalline precipitate from the urine.

[0021] The pretreatment step offers multiple benefits. First, by generating struvite precipitate, it achieves preliminary recovery of phosphorus resources, turning waste into treasure. Second, by removing easily fouling ions such as calcium and some organic matter, it significantly reduces the risk of fouling and organic pollution in the subsequent membrane separation unit 3, improving membrane flux stability. Third, advanced oxidation or electrochemical processes can alter the stability of colloids, reducing their adhesion to the membrane, further protecting the membrane module and extending the cleaning cycle.

[0022] Step S3: Retained solution circulation: The retentate, consisting of unpermeated material discharged from the retentate side of the membrane separation unit 3, is guided back to the collection tank 1 via the return water pipe 7. A flow meter and regulating valve can be installed on the return water pipe 7 to precisely control the reflux ratio. By returning the retentate to the front end of the system, mixing it with fresh urine, and then separating it, the target substance in the urine can be continuously circulated and enriched within the system, improving the recovery concentration and recovery rate of the resource.

[0023] Step S4: Permeate collection: The permeate produced by the separation of the membrane in the membrane separation device 3 is continuously drawn out through the outlet pipe 4 and transported to a dedicated outlet recovery tank 5 for collection and storage. This step yields the main product of the present invention, namely, permeate rich in urea and ammonia nitrogen. This product can be used as liquid nitrogen fertilizer or chemical raw material, realizing the direct production of urine resource utilization.

[0024] Step S5, Process Monitoring and Adjustment: The operating parameters of the membrane separation unit 3 and the quality of the permeate are monitored in real time and continuously by a real-time monitoring device 8 installed at key nodes. The monitoring device 8 includes an online water quality analyzer, a pressure sensor, and a flow meter. Based on the data obtained from the monitoring, the control system dynamically adjusts the key operating parameters of the system, including the operating pressure of the pressure pump 6 and the reflux ratio controlled by the regulating valve on the return water pipe 7.

[0025] The dynamic adjustment specifically includes the following intelligent logic: When the real-time monitoring device 8 detects that the ammonia nitrogen concentration at the inlet of the membrane separation device 3 is lower than the first preset threshold, it indicates that the system is not in the optimal ammonia nitrogen recovery and enrichment operation state. At this time, the reflux ratio of the return water pipe 7 is automatically reduced to reduce the circulation treatment of low-concentration materials and promote the system to adjust to a more efficient resource recovery state. When the rate of increase of the transmembrane pressure difference of the membrane separation device 3 exceeds the preset rate threshold, it indicates that membrane fouling is occurring rapidly. At this time, the reflux ratio of the return water pipe 7 is automatically increased and / or the operating pressure of the pressure pump 6 is appropriately increased. Increasing the reflux ratio can increase the membrane surface velocity and enhance the shear scouring effect to alleviate fouling; increasing the operating pressure can temporarily compensate for the decrease in flux caused by fouling. The combination of online monitoring and the above dynamic adjustment logic realizes the intelligent and adaptive optimization of the process. It can respond in real time to fluctuations in influent water quality and membrane fouling status, maintain optimal separation performance by adjusting parameters, ensure stable product water quality, and provide early warning of faults, which is the guarantee for the long-term stable, efficient, and automatic operation of the system.

[0026] In one specific embodiment, to achieve deep resource recovery and pollutant detoxification, the membrane separation device 3 can be configured as a multi-stage fractional treatment process. The membrane separation device is configured as two stages in series: the first membrane separation device uses a nanofiltration membrane NF1 with a molecular weight cutoff (MWCO) of 500 Da and an operating pressure of 1.0 MPa; the second membrane separation device uses a nanofiltration membrane NF2 with a MWCO of 150 Da and an operating pressure of 1.5 MPa. The retentate pipeline of the first membrane separation device is branched to an advanced oxidation unit, such as a UV / persulfate reactor. The pretreated urine supernatant first enters NF1, which allows small molecules such as inorganic salts and urea to permeate, but effectively retains large organic molecules such as humic acid, pigments, and drug residues. The resulting first concentrate has a pollutant concentration concentrated 5-10 times and is then introduced into the advanced oxidation unit for complete mineralization. The first permeate enters NF2, which has a high rejection rate for divalent ions and urea, but a low rejection rate for monovalent ions. Therefore, the second concentrate is enriched with the vast majority of nitrogen, phosphorus, and potassium nutrients, becoming a high-quality liquid fertilizer; the second permeate is mainly composed of monovalent salts and water, suitable for reuse. This solution achieves precise grading and separation. The first stage selectively separates and destroys recalcitrant organic pollutants, ensuring environmental safety; the second stage selectively enriches key nutrients, producing high-value fertilizer while simultaneously recovering water resources, forming a closed-loop recycling system that maximizes resource recovery and completely renders pollutants harmless.

[0027] In one specific embodiment, step S5 further includes a separation efficiency assessment and cleaning triggering mechanism. Specifically, data acquired by the real-time monitoring device 8 is used to calculate and compare the total nitrogen content in the permeate with the total nitrogen content of the initial urine entering the system, thereby assessing the nitrogen recovery and separation efficiency of the entire system in real time. When the calculated separation efficiency is lower than a preset threshold, it is determined that the membrane performance has deteriorated, resulting in insufficient separation. The system will automatically generate an alarm and trigger the cleaning procedure. Introducing an efficiency assessment method based on the law of conservation of mass provides a more realistic and comprehensive reflection of the degradation of membrane separation performance than simply monitoring a single parameter. Using this as the basis for cleaning triggering is more scientific and accurate, avoiding the problems of over-cleaning or untimely cleaning, and optimizing maintenance costs while ensuring treatment effectiveness.

[0028] In one specific embodiment, the method further includes an online cleaning step. When the system determines that the separation efficiency has decreased or the transmembrane pressure differential is persistently high, the online cleaning program is automatically or manually initiated. Cleaning operations include physical cleaning and / or chemical cleaning. Physical cleaning primarily involves backflushing. Chemical cleaning can be selected based on the type of fouling: one option is to inject an alkaline cleaning solution, such as sodium hydroxide solution, to adjust the pH of the cleaning environment within the membrane system to above 10.5. In this strongly alkaline environment, residual urea will accelerate hydrolysis to generate ammonia and carbonate ions, which helps to break down and remove the organic fouling layer; another option is to inject a cleaning solution containing persulfate or hydrogen peroxide, utilizing its strong oxidizing properties to catalytically oxidize and decompose organic pollutants on the membrane surface. For inorganic fouling, specific acidic cleaning solutions, such as diluted citric acid or hydrochloric acid, can also be used for dissolution and removal. A systematic online cleaning solution can effectively restore membrane flux and ensure long-term operation. Alkaline cleaning utilizes the components of urine itself in the reaction, making it more targeted and environmentally friendly. Oxidative cleaning can efficiently degrade stubborn organic matter. Acid washing can remove inorganic scale. The combination of multiple cleaning methods enables comprehensive cleaning of complex contaminants, significantly extending the service life of membrane modules.

[0029] Example 2 This embodiment provides a urine separation and concentration system for implementing the method described in Embodiment 1. See also Figure 1 Specifically, it includes: Urine collection tank 1 is used to receive, mix, and temporarily store raw urine and circulating fluid; Membrane separation device 3 has a built-in selective separation membrane; Pressure pump 6 provides a stable pressure drive source for the membrane separation process; Water inlet pipe 2 connects the outlet of collection tank 1 to the inlet of membrane separation device 3, forming a feeding channel; The return water pipe 7 connects the retentate outlet of the membrane separation device 3 to the return port of the collection tank 1, forming a concentrated liquid circulation channel. The water outlet pipe 4 is connected to the permeate outlet of the membrane separation device 3, serving as the product liquid outflow channel; The effluent recovery tank 5 is connected to the effluent pipe 4 and is used to store the final obtained permeate product. The real-time monitoring device 8, including water quality sensors, pressure sensors, flow meters, etc., is installed at key nodes such as the inlet pipe 2, membrane separation device 3, outlet pipe 4, and recovery tank 5 for full-process monitoring.

[0030] The system has constructed a complete process of collection, separation, circulation, recycling, and monitoring. It has a reasonable layout, clear functions, and all components work together to achieve the process goal of urine separation and concentration efficiently and continuously, providing a reliable equipment foundation for the industrial application of the method.

[0031] In one specific embodiment, the membrane separation device 3 uses an ultrafiltration membrane or a nanofiltration membrane. Specifically, the ultrafiltration membrane has a nominal molecular weight cutoff or pore size of 0.01 μm and is mainly used to separate large organic molecules, colloids, and microorganisms. The nanofiltration membrane has a pore size of 0.001 μm and can effectively separate small molecules such as urea and ammonia nitrogen from divalent salts and larger molecules. The choice between the 0.01 μm ultrafiltration membrane and the 0.001 μm nanofiltration membrane corresponds to different separation accuracies and application scenarios.

[0032] In one specific embodiment, to further improve the selective permeation performance of the separation membrane for urea and ammonia nitrogen, and to endow it with antifouling or adaptive capabilities, the separation membrane is a composite functional membrane. A polyamide nanofiltration membrane with an average pore size of 0.001 μm is used as the base membrane. 2-Acrylamido-2-methylpropanesulfonic acid (AMPS) monomer, N-isopropylacrylamide (NIPAM) monomer, and crosslinking agent N,N'-methylenebisacrylamide (MBA) are dissolved in deionized water to form a prepolymer solution. The nanofiltration membrane is immersed in this prepolymer solution, and under nitrogen protection, gamma-ray radiation graft polymerization is initiated using a 60Co source to form a smart hydrogel network layer with a thickness of approximately 50-200 nm on the membrane surface and within the pores. When the pH environment is close to that of urine, the sulfonic acid groups within this hydrogel layer exhibit weak ionic interactions with ammonia nitrogen molecules, promoting ammonia nitrogen adsorption and surface diffusion, thereby achieving a higher ammonia nitrogen permeation flux than ordinary nanofiltration membranes under pressure. Experiments show that, under the same operating pressure, such as 1.2 MPa, when treating simulated urine with the same ammonia nitrogen concentration, the composite membrane reduces the ammonia nitrogen rejection rate by about 15-25% compared to the unmodified nanofiltration membrane, while the rejection rate of total organic carbon (TOC) remains basically unchanged, significantly improving the separation selectivity of the target analyte.

[0033] A 0.01 μm pore size polyvinylidene fluoride (PVDF) ultrafiltration membrane was selected as the base membrane. A brush-like polymer layer of poly(dimethylaminoethyl methacrylate) (PDMAEMA) was grafted onto the membrane surface using surface-initiated atom transfer radical polymerization (SI-ATRP). This polymer layer exhibits pH-responsive characteristics: when the system detects an increase in the feed pH, the protonation degree of the polymer chains decreases, and the chain conformation shrinks, slightly increasing the actual pore size of the membrane surface, which helps to operate at higher fluxes and mitigate fouling; when the feed pH returns to normal, the polymer chains swell, the pore size recovers, and a high rejection rate for colloidal and other contaminants is maintained. This smart membrane, through its dynamic fine-tuning of pore size, achieves self-adaptation to operating conditions, and in long-term operation, the average transmembrane pressure gradient rise rate is reduced by more than 30% compared to conventional membranes.

[0034] A ceramic ultrafiltration membrane or a polyethersulfone ultrafiltration membrane with an average pore size of 50 nm was used as the porous base membrane. First, the base membrane was pretreated to enhance its surface activity. Then, using an in-situ hydrothermal growth method, the pretreated base membrane was immersed in a mixed aqueous solution composed of zinc salt and 2-methylimidazole ligand, where the zinc ion concentration was 0.05 mol / L and the 2-methylimidazole concentration was 0.2 mol / L. After standing at 25°C for a certain period, a layer of zeolite imidazole ester framework material ZIF-8 crystals was uniformly grown on the surface and within the pores of the base membrane, forming a metal-organic framework material functional layer with a thickness of approximately 100-500 nm. ZIF-8 possesses a regular microporous structure and abundant nitrogen heterocyclic sites. During urine separation, its pore size, between that of urea molecules and hydrated ammonium ions, can produce a precise size sieving effect. More importantly, the nitrogen atoms on its pore surface have strong hydrogen bonding and dipole-dipole interactions with ammonia nitrogen molecules in urine, which can preferentially adsorb and promote the passage of ammonia nitrogen molecules through the membrane layer, while showing a higher rejection rate for organic pollutants and colloids with larger molecular sizes in urine.

[0035] In one specific embodiment, the system further includes a phosphorus recovery unit, which specifically comprises a reaction crystallization device, a dosing device, and a solid-liquid separation device. The inlet of the reaction crystallization device is connected to the effluent recovery tank 5 or the effluent pipe 4 to receive the permeate rich in ammonium nitrogen and residual phosphate. The dosing device is used to precisely add a magnesium source and a pH adjuster to the reaction crystallization device. The magnesium source can be magnesium chloride, and the pH adjuster can be sodium hydroxide. The solid-liquid separation device is used to separate the high-purity struvite precipitate generated after reaction crystallization from the liquid phase to obtain a solid phosphate fertilizer product. By adding the phosphorus recovery unit, the system is expanded from single nitrogen recovery to synergistic nitrogen and phosphorus recovery, enabling further extraction of residual phosphorus from the permeate to produce high-value-added struvite fertilizer, maximizing the utilization of urine resources, and improving the overall economic and environmental benefits of the process.

[0036] In one embodiment, the system further includes a central control unit and a sensor network electrically connected thereto. The sensor network includes at least: A first concentration sensor is installed in the inlet of the membrane separation device 3 or in the collection tank 1 to monitor the ammonia nitrogen concentration in the inlet liquid in real time; Pressure sensor used to monitor the pressure difference across the membrane in membrane separation unit 3; A second concentration sensor is installed in the outlet pipe 4 or the recovery tank 5 to monitor the water quality of the permeate.

[0037] Based on real-time signals from the first concentration sensor, pressure sensor, and second concentration sensor, and according to a preset algorithm model, the central control unit dynamically controls the opening of the regulating valve on the return water pipe 7 to adjust the reflux ratio, and / or controls the motor power of the pressure pump 6 to adjust the operating pressure. The central control unit and sensor network enable closed-loop intelligent control of the system. The sensor network provides sensing, the central control unit makes decisions and issues execution commands, giving the system the ability to adaptively optimize operation, significantly reducing the need for manual intervention, and improving the stability, accuracy, and energy efficiency of the processing.

[0038] In one specific embodiment, the system further includes an adaptive intelligent control system. This system is the core of achieving intelligent operation and specifically includes: A sensor network, deployed at key nodes of the system, is used to acquire physicochemical parameters characterizing the process state in real time and in multiple dimensions. This network includes at least: a first pressure sensor and a first water quality sensor installed on the inlet pipe of membrane separation unit 3, for monitoring inlet pressure, conductivity, pH, or ammonia nitrogen concentration; a second pressure sensor installed on the retentate outlet pipe of membrane separation unit 3, for calculating the transmembrane pressure difference TMP in conjunction with the inlet pressure; and a flow meter and a second water quality sensor installed on the permeate outlet pipe, for monitoring product water flux J and permeate water quality. The data acquisition and processing module is electrically connected to the sensor network. It is responsible for receiving the raw signals from each sensor in real time, performing preprocessing such as filtering, calibration, and unit conversion, and sending the processed standardized data to the decision module. The intelligent decision-making module incorporates an advanced membrane fouling prediction model and process optimization algorithm. The membrane fouling prediction model is built upon dynamic parameters such as the rate of change of transmembrane pressure and the rate of change of permeate flux. Its core definition is: F = α × (d(TMP) / dt) + β × (d(J) / dt) + γ × f (influent TDS, pH). Here, TMP is the real-time transmembrane pressure, J is the real-time permeate flux, α, β, and γ are weighting coefficients trained based on historical data, and f is a function nonlinearly corrected based on the influent total dissolved solids (TDS) and pH value. This model can comprehensively reflect the combined effects of hydrodynamic and chemical fouling. When the calculated F value exceeds a preset threshold, the module generates a membrane cleaning trigger command in advance, achieving predictive maintenance. The process optimization algorithm dynamically calculates and outputs the optimal combination of operating parameters based on the influent water quality parameters and the real-time permeate flux J, adjusting the optimal operating pressure setpoint of pressure pump 6 and the optimal reflux ratio setpoint of return pipe 7.

[0039] The actuator control module is connected to the intelligent decision module, pressure pump 6, and cleaning device. This module receives control commands from the decision module and precisely adjusts the power or frequency of pressure pump 6 to change the operating pressure, adjusts the opening of the valve on the return water pipe 7 to change the reflux ratio, or automatically starts and stops the chemical cleaning program.

[0040] The introduction of the adaptive intelligent control system elevates this system from automation to intelligence. Its technical benefits are significant: First, the F-model, based on the fouling index, can provide early warnings and trigger cleaning before membrane performance deteriorates significantly, greatly reducing unplanned downtime and extending membrane life. Second, the process optimization algorithm enables the system to adaptively adjust to the most energy-efficient and effective operating point based on real-time influent water quality, achieving precise control. Third, it forms a complete closed loop of perception, analysis, decision-making, and execution, significantly reducing reliance on operator experience and ensuring high stability of treatment results and optimized system energy efficiency.

[0041] The preferred embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, nor is it limited to urine separation and concentration methods and systems. Devices and structures not described in detail herein should be understood as being implemented in a manner common to the art. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. This does not affect the essential content of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for separating and concentrating urine, characterized in that, Includes the following steps: S1 Initial Collection and Temporary Storage: The urine to be processed is transported and temporarily stored in a urine collection tank; S2 Pressure Driven Membrane Separation: Urine from the urine collection tank is introduced into the membrane separation device through the inlet pipe, and a pressure pump provides driving force, causing the urine to flow through the separation membrane of the membrane separation device under a set pressure condition; the driving pressure of the pressure pump is controlled within the range of 0.1MPa to 1.5MPa; specifically, when the separation membrane is an ultrafiltration membrane, the pressure is controlled between 0.1MPa and 0.5MPa; when the separation membrane is a nanofiltration membrane, the pressure is controlled between 1.0MPa and 1.5MPa; while using the pressure pump to provide driving force, a DC electric field of 5-50V / cm is also applied to a pair of electrodes integrated in the membrane separation device, so that the electric field force and pressure work together to drive the selective permeation of target ionic nutrients through the separation membrane; utilizing the selective permeation characteristics of urea and ammonia nitrogen molecules through the separation membrane, permeate rich in urea and ammonia nitrogen and retentate rich in retentate are formed on both sides of the membrane, respectively; S3 Retention Fluid Circulation: The retention fluid is returned to the urine collection tank through the return water pipeline; S4 Permeate Collection: Permeate is continuously collected through the effluent pipeline into an effluent recovery tank; S5 Process Monitoring and Regulation: Monitor the operating parameters of the membrane separation unit and / or the water quality of the permeate, and dynamically adjust the operating pressure of the pressure pump and / or the reflux ratio of the return water pipeline based on the monitoring data; dynamic regulation includes: reducing the reflux ratio when the ammonia nitrogen concentration in the influent of the membrane separation unit is lower than a first preset threshold; and / or increasing the reflux ratio and / or the operating pressure when the rate of increase of the transmembrane pressure difference of the membrane separation unit exceeds a preset rate threshold.

2. The method for urine separation and concentration according to claim 1, characterized in that: After step S1 and before step S2, the process also includes step S1a, which involves pretreatment and solid-liquid separation. Adjust the pH of the urine in the urine collection tank to 9.5-11.5 to promote the formation of microcrystalline precipitates, mainly composed of magnesium ammonium phosphate, by reacting phosphate ions with calcium, magnesium, and ammonium ions in the urine. Then, perform solid-liquid separation to remove the precipitates. This involves applying low-intensity advanced oxidation or electrochemical action to the urine during or after pH adjustment.

3. The method for urine separation and concentration according to claim 1, characterized in that: The membrane separation device includes a first membrane separation device and a second membrane separation device connected in series; the first membrane separation device is used to retain macromolecular organic matter and obtain a first permeate; the first permeate enters the second membrane separation device to enrich nitrogen, phosphorus and potassium nutrients and obtain a second concentrate and a second permeate; the first concentrate retained by the first membrane separation device is led to an advanced oxidation unit for treatment.

4. The method for urine separation and concentration according to claim 1, characterized in that, Step S5 also includes: The separation efficiency was evaluated by calculating and comparing the total nitrogen content in the osmotic fluid with the total nitrogen content in the initial urine. When the separation efficiency is lower than a preset threshold, the cleaning of the membrane separation device is triggered.

5. The method for urine separation and concentration according to claim 4, characterized in that, Cleaning operations include physical cleaning and / or chemical cleaning; Chemical cleaning includes: adjusting the pH of the cleaning environment to above 10.5 using an alkaline cleaning solution, and / or using a cleaning solution containing persulfate, hydrogen peroxide, or an acidic solution.

6. A urine separation and concentration system for carrying out the method as described in any one of claims 1-5, characterized in that, include: Urine collection tank, used to receive, mix and temporarily store raw urine and circulating fluid; The membrane separation device has its inlet connected to the outlet of the urine collection tank via an inlet pipe; Pressure pumps are used to provide operating pressure for membrane separation units; The return water pipeline connects the retentate outlet of the membrane separator to the return port of the urine collection tank; The outlet pipe connects to the permeate outlet of the membrane separation unit; The effluent recovery tank is connected to the effluent pipe; The control unit is used to monitor system parameters and dynamically adjust the pressure pump and / or the flow regulating device installed on the return water pipeline.

7. The system according to claim 6, characterized in that, The separation membrane in the membrane separation device is a composite functional membrane, which includes: Porous base membrane; and, A functional layer coated or composited onto at least one surface of a porous base membrane, wherein the functional layer comprises a material that has a specific adsorption or transport-promoting effect on ammonia nitrogen molecules; The functional layer includes at least one of a hydrogel layer, a metal-organic framework material layer, or a pH-responsive polymer layer.

8. The system according to claim 6, characterized in that, It also includes a phosphorus recovery unit, which comprises: The reaction crystallization apparatus has its inlet connected to the water recovery tank or water outlet pipeline; A dosing device is used to add a magnesium source and a pH adjuster to the reaction crystallization apparatus; A solid-liquid separation device is used to separate the struvite precipitate generated during the reaction.

9. The system according to claim 6, characterized in that: The membrane separation device also integrates a pair of electrodes electrically connected to a DC power supply; the control unit is connected to the DC power supply to regulate the field strength of the DC electric field.

10. The system according to claim 6, characterized in that: The control unit is connected to a sensor network, which includes a first sensor for monitoring the influent concentration, a pressure sensor for monitoring the transmembrane pressure difference, and a second sensor for monitoring the permeate quality. The control unit executes dynamic adjustment logic based on the sensor signals.

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