A multi-stage conversion and resource treatment process for municipal circulating water

Abstract

The application discloses a kind of municipal circulating water multistage conversion and resource treatment process.The process is under rainfall or flood condition, first in drainage pipeline to incoming water is carried out cyclone-screening coupling separation, obtain low turbidity water and organic sludge;Real-time detection of sludge fertility index, fertile sludge is accurately discharged to planting land and returned to field, barren sludge is discharged into sewage pipe network;Low turbidity water enters subsequent sewage treatment system, by air flotation-magnetic separation, metabolic heat synergic denitrification, membrane distillation-bioreactor, low-temperature multi-effect crystallization Four-stage continuous conversion, simultaneously output recycled water, struvite slow-release fertilizer and recovered heat energy;Meanwhile, use hydraulic residual pressure feedback energy, and through digital twin and energy quality synergistic intelligent control realizes system adaptive operation.The application solves the problem of rainstorm sludge blockage pipe network from source, realizes sludge accurate resource, greatly reduces sewage treatment energy consumption and drug consumption, is applicable to combined sewerage area and urban-rural junction municipal circulating water treatment.

Description

Technical Field

[0001] This invention belongs to the field of municipal wastewater treatment and resource utilization technology, specifically relating to a multi-stage conversion and resource utilization process for municipal circulating water. Background Technology

[0002] The treatment of municipal circulating water (including domestic sewage, stormwater runoff, and combined sewer systems) is transitioning from the traditional "discharge meeting standards" to "resource and energy recovery." Existing technologies include various multi-stage filtration, membrane separation, phosphorus recovery, and wastewater source heat pumps, but they generally suffer from the following drawbacks:

[0003] Severe pipe network blockage occurs during heavy rain or flooding: Rainfall carries large amounts of silt (suspended solids concentration can reach 5000~20000 mg / L) from mountains, farmland, and roads. This silt rapidly deposits in municipal drainage pipes, causing blockages, clogging of pump station screens, and even urban flooding. Traditional intercepting wells or regulating tanks can only buffer water volume and cannot effectively separate silt from the water source.

[0004] Sludge resources are wasted: fertile sludge rich in organic matter, nitrogen, phosphorus and potassium is sent to sewage treatment plants, where it is diluted and biochemically treated to become surplus sludge. A lot of energy is required for dewatering, drying, incineration or landfilling, which not only loses its agricultural value but also increases treatment costs.

[0005] Material morphology and phase separation: Existing multi-stage treatment processes (such as "pretreatment + multi-stage AO + high-efficiency precipitation + deep filtration") have relatively independent functions for each unit, and do not design continuous conversion paths based on the distribution of substances in the liquid, solid, and biological phases.

[0006] Decoupling of energy conversion and material conversion: The chemical energy, thermal energy and biological energy contained in wastewater are not recovered by the system. Even if a heat pump is introduced, heat is only extracted from the outside and internal energy such as metabolic heat and hydraulic residual pressure is not utilized in a coordinated manner.

[0007] Resource recycling exhibits an island effect: phosphorus recycling, nitrogen recycling, and other units operate independently, disrupting the synergistic relationship between carbon, nitrogen, and phosphorus in water purification, and lacking closed-loop adaptive regulation based on water quality fluctuations.

[0008] To address the above problems, this invention provides a multi-stage conversion and resource recovery process for municipal circulating water. Summary of the Invention

[0009] In order to overcome the above-mentioned defects of the prior art, embodiments of the present invention provide a multi-stage conversion and resource utilization process for municipal circulating water to solve the problems mentioned in the background art.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] A multi-stage conversion and resource recovery process for municipal circulating water includes the following steps:

[0012] (1) Set up sludge separation and graded discharge stations in the municipal drainage pipeline to perform cyclone-screening coupling separation on rainwater or floodwater to obtain low turbidity water and organic sludge slurry; detect the fertility index of organic sludge slurry and calculate sludge fertility index SFI. When SFI≥ set threshold, the sludge is discharged to nearby planting area; otherwise, it is discharged into the municipal sewage network; low turbidity water is directly discharged into the municipal sewage pipeline.

[0013] (2) Low turbidity water enters the sewage treatment plant and undergoes air flotation-magnetic separation coupling pretreatment to remove suspended solids and pre-enrich phosphorus;

[0014] (3) The pretreated effluent is sent into a multi-stage AO bioreactor to recover the metabolic heat of microorganisms during the denitrification process, and the recovered heat is used to increase the water temperature in the aerobic zone to enhance the denitrification efficiency.

[0015] (4) The effluent from the secondary sedimentation tank enters the membrane distillation bioreactor, and the membrane distillation process is driven by the heat recovered in step (3) to obtain high-purity permeate and nitrogen- and phosphorus-containing concentrate.

[0016] (5) The nitrogen and phosphorus concentrated water is subjected to low-temperature multi-effect crystallization to precipitate struvite and gypsum in sequence. The heat released during the crystallization process is recycled to step (4).

[0017] (6) Collect membrane distillation permeate and struvite products, and recover energy using the hydraulic residual pressure within the system;

[0018] (7) Through online monitoring and digital twin model, the energy and mass flow in steps (2) to (6) is intelligently coordinated and controlled so that the system can automatically switch between "low energy consumption mode" and "high resource recovery mode".

[0019] Preferably, the hydrocyclone-screening coupling separation in step (1) is as follows: first, coarse sand and heavy minerals are separated by a hydrocyclone, and the overflow of the hydrocyclone enters a high-frequency vibrating screen. The material on the screen is organic sludge slurry, and the material under the screen is low turbidity water. When the turbidity of the undersize liquid exceeds 200 mg / L, part of the undersize liquid is returned to the hydrocyclone inlet for secondary separation.

[0020] Preferably, the formula for calculating the sludge fertility index (SFI) in step (1) is:

[0021]

[0022] in , , These are the measured percentage of organic matter by mass, total nitrogen content (mg / g), and total phosphorus content (mg / g), respectively. , , The baseline values ​​for determining fertile silt were 30%, 5 mg / g, and 2 mg / g, respectively. , , The weighting coefficients are set to 0.5, 0.3, and 0.2 respectively; the threshold is set to 0.6.

[0023] Preferably, in step (1), when SFI≥0.6, the system automatically matches the nearest fertilizer-requiring planting site according to the built-in GIS module and opens the corresponding discharge valve, while recording the amount of fertilizer returned to the field for carbon sequestration accounting.

[0024] Preferably, in step (2), when the concentration of suspended solids in the influent is less than 150 mg / L, the flotation unit is automatically stopped and only the magnetic separation unit is operated.

[0025] Preferably, in step (3), a plate heat exchanger is set up in the aerobic zone to extract metabolic heat. The recovered heat is then partially replenished to the influent of the aerobic zone after being upgraded by a heat pump. The total nitrogen in the effluent is monitored in real time. When the total nitrogen concentration exceeds the set value of 15 mg / L, the circulation flow rate of the heat exchanger is automatically increased to raise the water temperature in the aerobic zone.

[0026] Preferably, in step (4), the heat on the hot side of the membrane distillation bioreactor comes entirely from the metabolic heat recovered in step (3), without the need for an external heat source; the concentrated water produced by membrane distillation is directly fed into the crystallizer in step (5) in a superheated state.

[0027] Preferably, in step (5), the dilution heat released during crystallization is recovered through an inter-effect heat exchanger and used to preheat the feed water of the membrane distillation in step (4); the underflow of the crystallizer is classified by swirl flow, and the fine crystals are returned as seed crystals.

[0028] Preferably, in step (6), the potential energy difference between each level of unit is used to convert hydraulic energy into mechanical energy through a micro turbine generator or residual pressure recovery device, which directly drives the agitator, dosing pump or aerator. The turbine generator is linked with the speed control and automatically adjusts the impeller angle when the water volume fluctuates.

[0029] Preferably, the intelligent collaborative regulation in step (7) includes: establishing a digital twin model to calculate the reserves and demand of hydraulic energy, chemical energy, thermal energy and biological energy in real time; using a multi-objective optimization algorithm to output control commands; using variable domain fuzzy PID control for the metabolic heat recovery loop to make the water temperature fluctuation in the aerobic zone ≤0.5℃; and automatically selecting the operating mode with the comprehensive optimization objectives of meeting the effluent water quality standards, minimizing system energy consumption and maximizing resource recovery.

[0030] The technical effects and advantages of the multi-stage conversion and resource utilization treatment process for municipal circulating water of this invention are as follows:

[0031] By combining cyclone-sieving coupling separation with online sludge fertility detection algorithms, real-time in-situ separation and precise graded discharge of sludge in municipal drainage pipelines under rainfall or flood conditions are achieved. This effectively solves the problems of traditional interception facilities being unable to separate sludge from water sources, the waste of fertile sludge resources, and frequent pipeline blockages. The introduction of metabolic heat recovery and denitrification efficiency synergistic feedback control analyzes the deterioration effect of microbial metabolic exothermics on nitrification activity during low-temperature periods, improving the system's denitrification stability under conditions of drastic fluctuations in influent carbon-nitrogen ratios and seasonal temperature changes. Through hydraulic residual pressure feedback, crystallization exothermic recovery, and digital twin energy-mass synergistic regulation, closed-loop co-production of water, fertilizer, and heat resources is achieved, significantly reducing external energy consumption and reagent consumption. By comparing the overall energy-mass balance with the preset effluent compliance threshold in real time, the system accurately determines whether to switch to a "low-energy mode" or a "high-resource recovery mode," enhancing the adaptive regulation capability, resource utilization efficiency, and economy of the municipal circulating water treatment process under wide operating conditions. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of a multi-stage conversion and resource utilization treatment process for municipal circulating water according to the present invention; Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1

[0035] like Figure 1 As shown, this invention discloses a multi-stage conversion and resource recovery process for municipal circulating water, comprising the following steps:

[0036] Step (1): Install a sludge separation and grading discharge station in the municipal drainage pipeline. Rainwater or floodwater, after being dissipated by the inlet regulating chamber and large floating objects intercepted by the coarse screen, enters the hydrocyclone-screening coupling separator. The inlet pressure of the hydrocyclone is controlled at 0.2MPa, and the cone angle is 25°; the overflow enters the high-frequency vibrating screen (screen mesh size 100μm, vibration frequency 2200 times / minute). The oversize material obtains organic sludge slurry with a water content of about 75%, which falls into the sludge buffer tank; the undersize material obtains low turbidity water with a suspended solids concentration ≤200mg / L, which is directly discharged into the municipal sewage pipeline. At the outlet of the sludge buffer tank, a near-infrared spectral sensor is used to detect the organic matter content (OM), total nitrogen (TN), and total phosphorus (TP) in real time, and according to... Calculate the silt fertility index. (Measured...) =22%, =4.2mg / g, =1.8mg / g, calculated SFI=0.799≥0.6, determined to be fertile silt, the electric graded gate discharges the silt into the planting area receiving pipeline.

[0037] Step (2): After the low-turbidity water enters the equalization tank of the sewage treatment plant for homogenization, it is added to the effluent. Nanomagnetic seeds (80nm particle size, dosage 35mg / L) and polyaluminum chloride are added. The mixture enters the dissolved air flotation unit to separate hydrophobic suspended solids. The flotation effluent enters a magnetic separator (magnetic field strength 0.35T) to adsorb phosphorus-containing flocs carrying the magnetic seeds. The magnetic seed flocs are recovered through high-frequency desorption and magnetic separation, with a reuse rate of 92%. The recovered suspended solids are sent for anaerobic digestion.

[0038] Step (3): The magnetically separated effluent enters the three-stage AO bioreactor. A plate heat exchanger is embedded in the aerobic zone tank wall to extract metabolic heat, raising the water temperature by 2.0℃. The extracted heat is then used to increase the grade via a heat pump (energy efficiency ratio 4.2), and part of it is returned to the aerobic zone influent. An external carbon source is automatically added to the anoxic zone based on ORP and nitrate concentrations. The total nitrogen in the effluent is monitored in real time (initial value 18 mg / L, exceeding 15 mg / L), and the heat exchanger circulation flow rate is automatically increased. After the water temperature rises to 15℃, the total nitrogen decreases to 13 mg / L. Part of the aerobic mixed liquor enters the side-flow sedimentation tank, and the phosphorus-rich supernatant is sent to the subsequent crystallization unit.

[0039] Step (4): The effluent from the secondary sedimentation tank enters the membrane distillation bioreactor, using a PTFE hydrophobic membrane (pore size 0.3 μm). Hot water (55℃) recovered in step (3) is introduced into the hot side of the membrane, and circulating cooling water (20℃) is introduced into the cold side. Water vapor condenses into high-purity permeate after passing through the membrane, and nitrogen and phosphorus concentrated water (total phosphorus 45 mg / L, ammonia nitrogen 80 mg / L) is obtained on the filtration side and directly sent to the crystallization unit.

[0040] Step (5): The membrane distillation concentrate enters the multi-effect crystallizer, with the first effect at 55℃ and the last effect at 28℃. The pH is controlled at 8.7, and the Mg:N:P molar ratio is 1.1:1:1. Using the fine crystals recovered in this unit as seed crystals, struvite (93% purity) is precipitated. The heat of dilution released during crystallization is recovered through the inter-effect heat exchanger and used to preheat the membrane distillation feed water in step (4). The underflow of the crystallizer is swirled and classified, with the fine crystals returned and the coarse crystals discharged as struvite product.

[0041] Step (6): Collect membrane distillation permeate (meeting GB / T19923-2005 industrial cooling water standard) for backwashing of equipment in the plant area and for external supply; collect struvite products. Install a micro turbine generator on the pipeline from the secondary sedimentation tank to the membrane distillation unit to generate electricity using the potential energy of a 6m height difference. The impeller angle is automatically adjusted by speed control, and the generated electricity directly drives the dosing pump and agitator, with an energy recovery efficiency of 45%.

[0042] Step (7): Online monitoring of influent COD, ammonia nitrogen, total phosphorus, pH, temperature, DO, ORP, membrane flux, and crystal size distribution. Data input is based on a digital twin model using a hybrid modeling approach combining physical mechanisms and neural networks, which calculates the reserves and demands of hydraulic, chemical, thermal, and biological energy in real time. A multi-objective particle swarm optimization algorithm is used to output commands such as aeration rate, reflux ratio, external carbon source dosage, heat recovery pump flow rate, heat pump start / stop, and pH adjuster dosage. With the comprehensive goals of achieving effluent quality standards, minimizing energy consumption, and maximizing resource recovery, the system automatically switches between "low energy consumption mode" and "high resource recovery mode." The metabolic heat recovery loop uses variable domain fuzzy PID control, with aerobic zone water temperature fluctuation ≤0.5℃. In this embodiment, the influent COD fluctuates between 300 and 450 mg / L, and the system automatically adjusts the aeration rate and carbon source dosage, resulting in a power consumption of 0.38 kWh / m³ per ton of water, a 27% reduction compared to traditional processes.

[0043] Further limitations are imposed on the hydrocyclone-screening coupling separation in step (1). The hydrocyclone inlet pressure is 0.15–0.25 MPa, the cone angle is 20°–30°, and the underflow diameter is automatically adjusted according to the sand content of the incoming water. The high-frequency vibrating screen has a mesh size of 50–150 μm and a vibration frequency of 1500–3000 times / minute. When the online monitoring value of the turbidity of the underflow exceeds 200 mg / L, the system automatically opens the reflux valve to return part of the underflow to the hydrocyclone inlet for secondary separation until the turbidity meets the standard.

[0044] The calculation formula and parameters for the silt fertility index (SFI) in step (1) are further defined. The formula is adopted.

[0045] ,

[0046] in =0.5, =0.3, =0.2, baseline value =30%, =5 mg / g, =2 mg / g, threshold set = 0.6. The online fertility detection module adopts a parallel redundant configuration of a near-infrared spectroscopy sensor and an electrical conductivity-organic matter composite sensor, outputting the SFI value every 30 seconds. When SFI ≥ 0.6, it is judged as fertile silt; otherwise, it is infertile silt.

[0047] Add a GIS module to step (1). When SFI ≥ 0.6, the system automatically reads the current GPS coordinates and matches them with the built-in database of soil fertility of surrounding planting areas. Based on the fertilizer requirement priority and distance of each plot, the electric valve of the receiving pipeline of the nearest fertilizer-requiring planting area is automatically opened, and the discharge time, discharge volume and SFI value of this batch of sludge are recorded for subsequent carbon sequestration accounting and fertilization ledger management. If there are no receiving planting areas nearby, the system switches to the transport vehicle loading mode and notifies the dispatch center.

[0048] Add a condition judgment to step (2). When the online monitoring value of the suspended solids concentration in the influent is below 150 mg / L, the control system automatically shuts off the air intake and dosing devices of the dissolved air flotation unit, allowing the water to flow directly through the flotation tank (as a flow channel) into the magnetic separation unit, retaining only magnetic separation for phosphorus removal. When the suspended solids concentration rises back to above 150 mg / L, the flotation unit is automatically restarted. Switching is achieved through electric valves and bypass pipelines, with a switching time ≤ 2 minutes.

[0049] Further limitations are imposed on the linkage control of metabolic heat recovery and denitrification in step (3). The plate heat exchanger in the aerobic zone is made of 316L stainless steel, with a heat exchange area configured at 5-10 m² / 100 m³ tank volume. The circulating medium after extracting metabolic heat enters the heat pump evaporator, and the hot water from the heat pump condenser outlet is returned to the inlet of the aerobic zone. The system monitors the total nitrogen concentration of the effluent from the aerobic zone in real time. When the total nitrogen exceeds 15 mg / L twice consecutively (with an interval of 1 hour), the system automatically increases the flow rate of the heat exchanger circulation pump (increasing the rated flow rate by 5% each time, with an upper limit of 120%), raising the water temperature in the aerobic zone by 1-3°C until the total nitrogen returns to below the set value. This feedback adjustment process is recorded for self-learning.

[0050] The heat source for the membrane distillation bioreactor in step (4) is further defined. The heat on the membrane hot side comes entirely from the metabolic heat recovered in step (3), without the need for electric heating or steam-assisted heating. Hot water on the hot side is supplied from the outlet of the heat pump condenser, with a temperature control range of 45–65°C. The concentrate produced by membrane distillation is superheated due to the temperature difference across the membrane (5–8°C lower than the hot side inlet), and is directly piped into the first effect of the multi-effect crystallizer in step (5) without additional preheating. If the amount of hot water provided by the heat recovery system is insufficient to guarantee the design flux of membrane distillation, the system automatically reduces the operating flux of membrane distillation and extends the operating time, still without using an external heat source.

[0051] Further limitations are imposed on the heat recovery and seed crystal circulation in step (5). Plate heat exchangers are installed between the effects of the low-temperature multi-effect crystallizer to recover dilution heat (8–12 kJ / mol struvite). This heat is transferred to the preheating section of the crystallizer via the inter-effect heat exchangers, raising the temperature of the membrane distillation concentrate entering the crystallizer by 3–5 °C. The underflow from the crystallizer is classified by a hydrocyclone, with the particle size controlled at 50–100 μm: fine crystals smaller than 50 μm are returned to the first effect of the crystallizer as seed crystals, while coarse crystals larger than 100 μm are discharged as product, which is then centrifuged, dehydrated, and packaged. The seed crystal circulation ratio is controlled at 3–5 times.

[0052] Further limitations are imposed on the hydraulic energy feedback utilization in step (6). Micro turbine generators or residual pressure recovery turbines are installed at locations with elevation differences between process units within the wastewater treatment plant (including the transition from the equalization tank to the flotation unit, the secondary sedimentation tank to the membrane distillation unit, and the membrane distillation unit to the crystallization unit). A speed controller is installed at the turbine generator outlet to automatically adjust the impeller blade angle based on the instantaneous flow rate to maintain the optimal specific speed, with an energy recovery efficiency target of ≥40%. The recovered electrical energy is rectified and stabilized before being directly connected to the plant's low-voltage power distribution system, prioritizing the driving of dosing pumps, agitators, and small aerators; any shortfall is supplemented by mains power.

[0053] Further detailed limitations are made on the intelligent energy quality coordinated regulation in step (7).

[0054] The online monitoring instruments include: COD online analyzer, ammonia nitrogen ion-selective electrode, total phosphomolybdenum blue method analyzer, pH meter, temperature sensor (accuracy ±0.1℃), dissolved oxygen electrode, ORP electrode, membrane flux sensor (thermal mass flow meter), and crystal particle size distribution online analyzer (laser diffraction method).

[0055] The digital twin model employs a hybrid modeling approach: the physical mechanism component is based on the activated sludge model ASM2d, the membrane fouling kinetics model, and the crystallization thermodynamics model; the neural network component uses a three-layer BP neural network (the number of input layer nodes equals the number of monitored parameters, the number of hidden layer nodes is 15, and the number of output layer nodes represents the estimated reserves and demands of various energy fields). The model is updated every 15 minutes, calculating in real time hydraulic energy (based on the liquid level and flow rate of each unit), chemical energy (based on COD and nitrogen and phosphorus loads), thermal kinetic energy (based on temperature and heat exchange), and bioenergy (based on microbial respiration rate and methanogenic potential).

[0056] The multi-objective optimization algorithm employs the Non-Dominated Sorting Particle Swarm Optimization (NSPSO) algorithm with an elitist strategy, a population size of 30, and 100 iterations. Decision variables include: aeration rate (0–2.0). Internal reflux ratio (50%–400%), external reflux ratio (30%–100%), external carbon source dosage (0–50 mg) The following parameters were considered: heat recovery circulation pump flow rate (0–100% rated flow), heat pump start / stop (0 / 1) and condensing temperature setpoint, and crystallization pH adjuster dosing rate. The optimization target was: effluent COD ≤ 50. , - ≤5 TN≤15 TP≤0.5 Simultaneously, it minimizes aeration power consumption, heat pump power consumption, and carbon source chemical consumption, while maximizing phosphorus recovery and heat recovery. The optimization results are output as a control command every hour.

[0057] Automatic mode switching logic: When the influent COD / TN ratio is <3.5 and the temperature is below 12℃, the system automatically selects "High Resource Recovery Mode"—prioritizing increasing the heat recovery pump flow rate to raise the water temperature in the aerobic zone, while reducing aeration intensity to reduce carbon source consumption, and increasing the external carbon source dosage if necessary. When the influent COD / TN ratio is >6.0 and the temperature is above 20℃, the system automatically selects "Low Energy Consumption Mode"—reducing the heat recovery pump flow rate, utilizing natural water temperature and high carbon source efficiency for denitrification, and reducing heat pump operating time.

[0058] Temperature control in the metabolic heat recovery loop employs a variable universe of discourse (VOD) fuzzy PID controller. The input variables are the aerobic zone water temperature deviation *e* and the rate of change of deviation *ec*, with the output being the inverter frequency of the heat recovery circulation pump. The VOD adaptively scales according to the magnitude of |e|: it expands for faster response when |e| > 1.5℃ and shrinks for improved steady-state accuracy when |e| < 0.5℃. Testing showed that this controller maintains aerobic zone water temperature fluctuations within ±0.5℃, superior to conventional PID controllers (±1.2℃).

[0059] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters and thresholds in the formulas are set by those skilled in the art according to the actual situation.

[0060] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions or computer programs. When the computer instructions or computer programs are loaded or executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more sets of available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium. The semiconductor medium can be a solid-state drive.

[0061] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0062] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and modules described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0063] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or modules may be electrical, mechanical, or other forms.

[0064] The modules described as separate components may or may not be physically separate. The components shown as modules may or may not be physical modules; they may be located in one place or distributed across multiple network modules. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0065] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0066] If the aforementioned functions are implemented as software functional modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0067] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0068] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multi-stage conversion and resource utilization treatment process for municipal circulating water, characterized in that, Includes the following steps: (1) Set up sludge separation and graded discharge stations in the municipal drainage pipeline to perform cyclone-screening coupling separation on rainwater or floodwater to obtain low turbidity water and organic sludge slurry; detect the fertility index of organic sludge slurry and calculate sludge fertility index SFI. When SFI≥ set threshold, the sludge is discharged to nearby planting area; otherwise, it is discharged into the municipal sewage network; low turbidity water is directly discharged into the municipal sewage pipeline. (2) Low turbidity water enters the sewage treatment plant and undergoes air flotation-magnetic separation coupling pretreatment to remove suspended solids and pre-enrich phosphorus; (3) The pretreated effluent is sent into a multi-stage AO bioreactor to recover the metabolic heat of microorganisms during the denitrification process, and the recovered heat is used to increase the water temperature in the aerobic zone to enhance the denitrification efficiency. (4) The effluent from the secondary sedimentation tank enters the membrane distillation bioreactor, and the membrane distillation process is driven by the heat recovered in step (3) to obtain high-purity permeate and nitrogen- and phosphorus-containing concentrate. (5) The nitrogen and phosphorus concentrated water is subjected to low-temperature multi-effect crystallization to precipitate struvite and gypsum in sequence. The heat released during the crystallization process is recycled to step (4). (6) Collect membrane distillation permeate and struvite products, and recover energy using the hydraulic residual pressure within the system; (7) Through online monitoring and digital twin model, the energy and mass flow in steps (2) to (6) is intelligently coordinated and controlled so that the system can automatically switch between "low energy consumption mode" and "high resource recovery mode".

2. The process according to claim 1, characterized in that, The hydrocyclone-screening coupling separation in step (1) is as follows: first, coarse sand and heavy minerals are separated by a hydrocyclone, and the overflow of the hydrocyclone enters a high-frequency vibrating screen. The material on the screen is organic sludge slurry, and the material under the screen is low turbidity water. When the turbidity of the undersize liquid exceeds 200 mg / L, part of the undersize liquid is returned to the hydrocyclone inlet for secondary separation.

3. The process according to claim 1, characterized in that, The formula for calculating the sludge fertility index (SFI) in step (1) is as follows: ;in , , These are the measured percentage of organic matter by mass, total nitrogen content (mg / g), and total phosphorus content (mg / g), respectively. , , The baseline values ​​for determining fertile silt were 30%, 5 mg / g, and 2 mg / g, respectively. , , The weighting coefficients are set to 0.5, 0.3, and 0.2 respectively; the threshold is set to 0.

6.

4. The process according to claim 1, characterized in that, In step (1), when SFI≥0.6, the system automatically matches the nearest fertilizer-requiring planting site according to the built-in GIS module and opens the corresponding discharge valve, while recording the amount of fertilizer returned to the field for carbon sequestration accounting.

5. The process according to claim 1, characterized in that, In step (2), when the concentration of suspended solids in the influent is below 150 mg / L, the flotation unit is automatically shut down and only the magnetic separation unit is operated.

6. The process according to claim 1, characterized in that, In step (3), a plate heat exchanger is set up in the aerobic zone to extract metabolic heat. The recovered heat is then partially replenished to the influent of the aerobic zone after being upgraded by a heat pump. The total nitrogen in the effluent is monitored in real time. When the total nitrogen concentration exceeds the set value of 15 mg / L, the circulation flow rate of the heat exchanger is automatically increased to raise the water temperature in the aerobic zone.

7. The process according to claim 1, characterized in that, In step (4), the heat on the hot side of the membrane distillation bioreactor comes entirely from the metabolic heat recovered in step (3), without the need for an external heat source; the concentrated water produced by membrane distillation is directly fed into the crystallizer in step (5) in a superheated state.

8. The process according to claim 1, characterized in that, In step (5), the dilution heat released during crystallization is recovered through an inter-effect heat exchanger and used to preheat the feed water of membrane distillation in step (4); the underflow of the crystallizer is classified by swirl flow, and the fine crystals are returned as seed crystals.

9. The process according to claim 1, characterized in that, In step (6), the potential energy difference between the units at each level is used to convert the hydraulic energy into mechanical energy through a micro turbine generator or residual pressure recovery device, which directly drives the agitator, dosing pump or aerator. The turbine generator is linked with the speed control and automatically adjusts the impeller angle when the water volume fluctuates.

10. The process according to claim 1, characterized in that, The intelligent collaborative regulation described in step (7) includes: establishing a digital twin model to calculate the reserves and demand of hydraulic energy, chemical energy, thermal energy and biological energy in real time; using a multi-objective optimization algorithm to output control commands; using variable domain fuzzy PID control for the metabolic heat recovery loop to ensure that the water temperature fluctuation in the aerobic zone is ≤0.5℃; and automatically selecting the operating mode with the comprehensive optimization objectives of achieving the effluent water quality standard, minimizing system energy consumption and maximizing resource recovery.

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