A decentralized wastewater treatment system

Abstract

The present application belongs to the technical field of decentralized sewage treatment and water resource recycling, and relates to a decentralized sewage treatment system, which comprises: a grey water internal circulation and recycling system for collecting and pretreating decentralized grey water, and performing biological reinforcement treatment, disinfection, storage and recycling on the grey water to realize internal circulation and recycling of the grey water; and a sewage low-carbon collaborative treatment system for collecting and performing low-carbon collaborative treatment and resource utilization on the excess decentralized grey water and black water. The two-stage coupled system of grey water internal circulation and recycling and sewage low-carbon collaborative treatment is constructed, and the whole process optimization of decentralized sewage from source reduction, efficient treatment to resource utilization is realized.

Description

Technical Field

[0001] This invention belongs to the field of decentralized wastewater treatment and water resource recycling technology, and relates to a wastewater treatment system, particularly a decentralized wastewater treatment system. Background Technology

[0002] Currently, domestic and international treatment technologies for decentralized wastewater in various scenarios such as newly built farmhouses, renovated old houses, scattered homestays, and scenic area rest stops are mainly divided into two categories: centralized treatment and decentralized treatment, which can be broadly categorized into the following modes.

[0003] 1. Centralized sewage pipe network collection, treatment and reuse mode.

[0004] This model mimics urban wastewater treatment systems, constructing a unified wastewater collection network within villages and other areas to transport domestic sewage (usually a combination of black and grey water) from each household to centralized wastewater treatment plants (such as integrated MBR equipment, constructed wetlands, and ecological ponds) for treatment. If the treated effluent meets the corresponding standards, it can be reused through a greywater network for village greening, road washing, or farmland irrigation.

[0005] The core of this model is large-scale collection and treatment. The domestic sewage generated by each household is collected through underground pipe network and transported to the treatment terminal by gravity or lifting pump station. The treatment process mostly adopts a combination of biological and ecological methods to ensure stable effluent. However, its disadvantages or shortcomings are: (1) Extremely high construction cost: The investment in the pipe network system covering the whole village is huge, accounting for about 60%-70% of the total investment of the project. This is particularly prominent in mountainous areas with scattered residences and complex terrain, resulting in great financial pressure. (2) Complex operation and maintenance management: The pipe network is prone to blockage and leakage, making maintenance difficult; centralized treatment facilities require professional operation and maintenance personnel, and the costs of electricity consumption, chemical consumption and sludge disposal continue to occur. In many areas, there is a phenomenon of being able to afford to build, but not being able to afford to use and not being able to manage well. (3) Delayed system start-up: It depends on high occupancy rate and complete pipe network coverage. New villages or areas with low occupancy rate are difficult to achieve benefits and cannot achieve immediate use upon occupancy. (4) Risk of cross-contamination: The combined sewer system mixes the sewage of each household. If a household has pathogens, they may spread through the pipe network. (5) Unable to reduce peak load at the source: The peak water usage of each household overlaps, resulting in drastic fluctuations in the amount and quality of water entering the treatment plant (i.e., water volume peak problem), which has a large impact load on the treatment process and affects stable operation.

[0006] 2. Adopt the model of small-scale integrated sewage treatment equipment for individual or joint households.

[0007] This model involves setting up a small, integrated sewage treatment system near the courtyard of each household or several neighboring households. This system includes a septic tank with an anaerobic biological filter, a solar-powered integrated tank, etc., to treat all domestic sewage generated and discharge it after it meets the standards or for use in courtyard irrigation.

[0008] The equipment in this mode is usually an underground tank, which integrates units such as oil separation, sedimentation, biological contact oxidation, and disinfection to achieve on-site treatment of sewage. Some high-end equipment integrates IoT modules to achieve remote monitoring. However, its disadvantages or shortcomings are: (1) Treatment efficiency is limited by the process: Most equipment adopts the traditional activated sludge process or a modified fixed biofilm, which is poorly adaptable to the typical low carbon-nitrogen ratio and intermittent influent of rural sewage, and the nitrogen and phosphorus removal efficiency is unstable, especially in the low temperature season when the effect drops sharply. (2) Energy consumption and operation and maintenance issues: Aerobic process requires continuous aeration, which consumes a lot of energy; the internal components of the equipment (such as blowers, pumps, membrane components) are easily damaged, and maintenance and replacement are inconvenient and costly. (3) Resource reuse is not achieved: Most of the treated water is directly discharged, which fails to combine with the largest water demand in the household - toilet flushing, and the water resource saving benefits are not fully utilized. (4) All sewage is still treated: Mixing black water with high pollutant concentration and difficult treatment with easily treated gray water increases the treatment load and difficulty, which is not economical.

[0009] 3. Models for greywater reuse systems in residential communities.

[0010] This model is widely used in urban residential communities. An independent greywater collection network is established within the building or community to collect high-quality wastewater from showers, washing, etc., and send it to the community's greywater treatment station. After treatment to meet standards, it is reused in the community for toilet flushing, greening, etc. through a dedicated greywater network.

[0011] This system is a typical greywater collection-centralized treatment-zoned reuse model. It requires the pre-embedding of two sets of drainage pipes (sewage pipes and greywater pipes) and two sets of water supply pipes (tap water pipes and greywater pipes) during the building design and construction phases. However, its disadvantages or shortcomings are: (1) Absolute dependence on centralized pipe network: It requires the construction of a complex greywater collection and greywater reuse pipe network system covering the entire community, which is only suitable for newly built urban communities with high-density residences and is not replicable in rural areas. (2) Huge initial investment: The dual pipe network system greatly increases the construction cost. (3) Risk of cross-infection between households: Greywater is collected and treated in a mixed manner between households, which poses a potential risk of pathogen transmission. (4) Poor system flexibility: It must be designed as a whole and constructed simultaneously, and cannot be used for the renovation of existing rural houses, nor can it achieve independent operation of a single household.

[0012] 4. Adopt a simple greywater recycling device.

[0013] This model uses a simple greywater reuse device, such as directly connecting the washing machine's drainage to a high-level water tank for toilet flushing, or using a simple physical filter canister to filter the greywater before reuse.

[0014] Such devices do not have a biological treatment unit; they only use screens and cloth bags to roughly filter grey water, removing hair and large particles before reuse. However, their disadvantages or shortcomings are: (1) extremely poor treatment effect: they cannot effectively remove dissolved organic matter, detergents, bacteria, viruses, etc., resulting in poor quality recycled water that is prone to odor and discoloration, making hygiene and safety impossible to guarantee. Long-term use may lead to scale buildup and bacterial growth in the toilet. (2) lack of stability and reliability: the filter media is prone to clogging, requiring frequent cleaning or replacement, resulting in a poor user experience. (3) inability to cope with water quality fluctuations: they have no ability to treat chemical agents such as laundry detergent and shower gel, which may damage the flushing valve.

[0015] In summary, existing technologies are either unsuitable for decentralized rural scenarios due to high pipe network and centralized treatment costs, or cannot stably and efficiently treat the special characteristics of rural sewage due to defects in the treatment process, or cannot achieve safe indoor resource recycling due to system complexity.

[0016] Therefore, there is an urgent need for a new type of decentralized wastewater treatment solution that can avoid the above-mentioned shortcomings and integrate high-efficiency treatment, low carbon and energy saving, indoor closed-loop, and immediate use. Summary of the Invention

[0017] To address the problems existing in the prior art, this invention proposes a decentralized wastewater treatment system, which optimizes the entire process of decentralized wastewater treatment from source reduction and efficient treatment to resource utilization by constructing a two-level coupled system of greywater internal recycling and wastewater low-carbon synergistic treatment.

[0018] To achieve the above objectives, the present invention provides the following technical solution:

[0019] A decentralized wastewater treatment system, characterized in that it comprises:

[0020] The greywater internal circulation and reuse system is used to collect decentralized greywater and pre-treat it, perform bio-enhanced treatment, disinfect it, store it and reuse it to achieve greywater internal circulation and reuse.

[0021] The wastewater low-carbon co-treatment system is used to collect excess decentralized greywater and blackwater and to perform low-carbon co-treatment and resource utilization.

[0022] Preferably, the greywater internal circulation and reuse system includes:

[0023] The separate collection subsystem is used to collect ash water by connecting each ash water discharger through ash water collection pipelines;

[0024] An integrated treatment and reuse subsystem is used for pretreatment, bio-enhanced treatment, disinfection, storage and reuse of collected greywater;

[0025] An intelligent control subsystem is used to control the operating cycle of the bio-enhanced treatment, as well as disinfection and reuse, of the integrated processing and reuse subsystem.

[0026] Preferably, the integrated processing and reuse subsystem includes:

[0027] A pretreatment unit is used to pretreat the collected grey water;

[0028] The bio-enhanced tidal filtration unit is filled with HN-AD bacteria immobilized microspheres and operates in a tidal manner to achieve natural oxygenation, organic matter degradation, and nitrogen and phosphorus removal, thereby achieving bio-enhanced treatment of pretreated greywater.

[0029] Disinfection and reclaimed water storage unit, which is used for disinfection and storage of greywater after bio-enhanced treatment;

[0030] The reuse water supply unit is used to reuse the grey water stored in the disinfection and reuse water storage unit at the point of use, so as to realize the internal circulation and reuse of grey water.

[0031] Preferably, the bio-enhanced tidal filtration unit is equipped with an electromagnetic inlet valve and an electromagnetic drain valve at the bottom, an electromagnetic exhaust valve at the top, and a liquid level sensor inside. The electromagnetic inlet valve and the electromagnetic drain valve are each equipped with a flow switch. The intelligent control subsystem includes an embedded microcontroller. The embedded microcontroller is equipped with a time relay, and the electromagnetic inlet valve, the electromagnetic drain valve, the electromagnetic exhaust valve, and the liquid level sensor are all connected to the embedded microcontroller to control the operating cycle of the bio-enhanced treatment of the integrated treatment and reuse subsystem.

[0032] Preferably, the wastewater low-carbon co-treatment system includes:

[0033] A mixed wastewater collection and transfer subsystem is used to collect black water and excess grey water that overflows or does not enter the grey water internal recycling system, and transport it to a low-carbon co-treatment subsystem.

[0034] The low-carbon synergistic treatment subsystem includes a multi-stage dry-wet alternating constructed wetland. Each constructed wetland includes a bottom impermeable layer, a support layer above the impermeable layer, a main filler layer above the support layer, a light-transmitting functional layer above the main filler layer, and a plant layer above the light-transmitting functional layer. The light-transmitting functional layer is filled with HN-AD algae microspheres. The HN-AD algae microspheres are submerged and dried by intermittently introducing water into the multi-stage dry-wet alternating constructed wetland, thereby achieving low-carbon synergistic treatment of the collected black water and residual grey water.

[0035] The resource recycling subsystem is used to recycle and reuse black water and residual grey water after low-carbon co-treatment.

[0036] Preferably, the process of submerging and drying the HN-AD algae microspheres by intermittent water intake is as follows: the HN-AD algae microspheres are submerged for 2 hours and then dried for 4 hours, and this process is repeated.

[0037] Preferably, the HN-AD bacterial and algal microspheres are functional biospheres formed by encapsulating highly efficient heterotrophic nitrifying-aerobic denitrifying bacteria and oxygen-producing microalgae in a polymeric gel matrix.

[0038] Preferably, the highly efficient heterotrophic nitrifying-aerobic denitrifying bacteria is *Pseudomonas schlegelii*, the oxygen-producing microalgae is *Chlorella vulgaris*, and the polymeric gel matrix uses sodium alginate as the embedding framework.

[0039] Preferably, the HN-AD algal microspheres are prepared by the following method:

[0040] S1: HN-AD bacterial culture: Activated *Pseudomonas stearothermiae* were inoculated into sterile LB medium and cultured at 30℃ with shaking at 160 r / min for 24-48 h until the OD600 of the bacterial culture reached 1.0-1.5. After culture, the bacterial cells were collected by centrifugation, washed with sterile physiological saline, and resuspended in sterile water to adjust the bacterial concentration. CFU / mL;

[0041] S2: Microalgae culture: Chlorella was inoculated into BG11 medium under the following conditions: 25℃, light intensity 2000-3000 Lux, light-dark ratio 12 h:12 h, for 7-10 days until the logarithmic growth phase. After culture, algal cells were collected by centrifugation, washed with sterile water, and resuspended in sterile water. The algal density was adjusted to [specific value missing]. cell / mL;

[0042] S3: Preparation of sodium alginate solution: Weigh sodium alginate powder, dissolve it in sterile deionized water, heat to 40-50℃ and stir to dissolve, sterilize at 121℃ for 20 min and cool to room temperature to obtain sodium alginate solution with a mass fraction of 3%;

[0043] S4: Bacterial-algae mixture: The HN-AD bacterial solution prepared in S1 and the microalgae solution prepared in S2 are mixed at a volume ratio of 2:1 to form a bacterial-algae mixture.

[0044] S5: Preparation of embedding precursor solution: The bacterial-algae mixture and the sodium alginate solution are mixed at a volume ratio of 1:3 to form an embedding precursor solution;

[0045] S6: Crosslinking agent preparation: Prepare 4% sterile... Solution as a crosslinking agent;

[0046] S7: Dropping to form microspheres: Under stirring conditions, the embedding precursor liquid is dropped into the crosslinking agent at a constant rate, the dropping height is controlled at 10-20 cm, and the dropping rate is 1-2 mL / min, so as to form microspheres and control the diameter of the formed microspheres to 2-4 mm.

[0047] S8: Cross-linking and curing: This process allows the microspheres to be cured under sterile conditions. Continue cross-linking and curing in the solution for 2-4 hours. After cross-linking and curing are complete, wash with sterile physiological saline to remove excess material from the surface. To obtain the prepared microspheres;

[0048] S9: Activation culture: Place the prepared microspheres in a light incubator and activate them in BG11 medium for 2-3 days, with a light intensity of 2000 Lux and a temperature of 25-28℃.

[0049] Preferably, in step S4, 0.5%-1% of glycerol or trehalose is added as a protective agent; and in step S6, 0.5% of polysorbate-80 is added.

[0050] Compared with the prior art, the decentralized wastewater treatment system of the present invention has one or more of the following beneficial technical effects:

[0051] (1) Significantly reduce construction and operation and maintenance costs. Completely eliminates the expensive outdoor greywater collection and greywater reuse pipeline network. The equipment is highly integrated, modularly produced, and quick to install. It consumes only a small amount of electricity during operation, requires no chemical agents, and requires no professional on-duty personnel, resulting in extremely low operation and maintenance costs. The overall cost is reduced by more than 50% compared to the traditional model.

[0052] (2) High treatment efficiency and stable operation. The combined filter media synergistic encapsulation technology significantly improves the biomass and activity per unit volume, especially solving the problem of denitrification in wastewater with low carbon-to-nitrogen ratio; the tidal operation ensures long-term high efficiency and stability of the process through natural oxygenation and periodic regeneration, and has strong resistance to water volume and water quality shock loads.

[0053] (3) Achieve safe and reliable indoor resource utilization. Grey water is treated and reused within the water production unit, forming a physical isolation and completely eliminating the risk of cross-infection between units; with the dual protection of biological filtration and disinfection, the effluent water quality meets safety standards and has high user acceptance.

[0054] (4) Excellent low-carbon energy saving and peak shaving effect. The core process does not require an aeration blower, and mainly relies on gravity flow and natural oxygenation, resulting in an energy saving effect of over 90%. The system absorbs grey water in situ, directly reducing the total amount of sewage discharged by the household by about 1 / 3. Through the regulation of the tidal buffer pool, the peak flow rate of the discharged sewage is reduced by more than 50%, effectively reducing the terminal pressure of municipal or village-level pipe networks and the scale requirement of treatment facilities.

[0055] (5) Immediate installation and high adaptability. The system operates independently, enabling water supply upon move-in, without relying on neighbors or overall planning; it is suitable for various scenarios such as newly built farmhouses, renovated old houses, scattered homestays, and scenic area stations, and is especially suitable for remote areas where pipelines cannot cover, making it highly versatile. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the decentralized wastewater treatment system of the present invention;

[0057] Figure 2 This is a schematic diagram of the greywater internal circulation and reuse system of the present invention;

[0058] Figure 3 This is a schematic diagram of the integrated processing and reuse subsystem of the present invention;

[0059] Figure 4 This is a schematic diagram of the wastewater low-carbon co-treatment system of the present invention;

[0060] Figure 5 This is a schematic diagram of the low-carbon collaborative processing subsystem of the present invention. Detailed Implementation

[0061] Before detailing any embodiment of the invention, it should be understood that the invention, in its application, is not limited to the details of the construction and arrangement of the components set forth in the following description or illustrated in the following figures. The invention can have other embodiments and can be practiced or carried out in various ways. Furthermore, it should be understood that the wording and terminology used herein are for descriptive purposes and should not be considered limiting. The use of “comprising” or “having” and variations thereof in this invention is intended to cover the items set forth below and their equivalents, as well as any additional items. Unless otherwise specified or limited, the terms “installation,” “connection,” “support,” and “linkage,” and variations thereof are used broadly and cover both direct and indirect installation, connection, support, and linking. Moreover, “connection” and “linkage” are not limited to physical or mechanical connections or links.

[0062] Furthermore, firstly, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention. Secondly, the term "a" should be understood as "at least one" or "one or more," that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple. The term "a" should not be construed as a limitation on the quantity.

[0063] Figure 1 A schematic diagram of the decentralized wastewater treatment system of the present invention is shown. Figure 1 As shown, the decentralized wastewater treatment system of the present invention includes a greywater internal circulation and reuse system and a wastewater low-carbon co-treatment system.

[0064] The greywater internal circulation and reuse system is used to collect decentralized greywater, such as greywater from greywater drain 1 (e.g., a washbasin), greywater drain 2 (e.g., a washing machine), greywater drain 3 (e.g., a toilet drain valve after a shower), etc., and pre-treats, bio-enhances, disinfects, stores, and reuses it to achieve greywater internal circulation and reuse. For example, the treated greywater can be used to flush toilets, thereby achieving safe and reliable closed-loop reuse of greywater within the generating household, completely eliminating the risk of cross-infection between households, and ensuring that the quality of the reused water meets hygiene standards.

[0065] The wastewater low-carbon co-treatment system is used to collect excess decentralized greywater and blackwater, such as blackwater from blackwater discharger 1 (e.g., a toilet) and blackwater discharger 2 (e.g., a mop pool), and to perform low-carbon co-treatment and resource utilization on it, such as using the low-carbon co-treated blackwater for irrigation of landscapes or farmland.

[0066] This invention innovatively constructs a two-tiered coupled technical architecture of indoor greywater closed-loop reuse and low-carbon treatment of discharged wastewater. The greywater internal recycling system is the core, prioritizing the interception and reuse of greywater within the household, effectively reducing the total amount and peak flow of wastewater entering the low-carbon wastewater co-treatment system at the source. The low-carbon wastewater co-treatment system serves as a supplement and guarantee, treating the remaining wastewater with higher pollutant concentrations. Together, the two systems constitute a complete, tiered, decentralized wastewater low-carbon treatment and resource recovery technology system. This coupling is not a simple parallel connection, but rather prioritizes greywater reuse, achieving the highest value utilization (toilet flushing) and source reduction of high-quality mixed wastewater. The remaining, more difficult-to-treat wastewater is then subjected to targeted low-carbon treatment, achieving optimal efficiency and lowest cost for the system as a whole, embodying the organic combination of "greywater reuse" and "low-carbon treatment of wastewater formed by greywater and blackwater."

[0067] I. Greywater Internal Circulation and Reuse System.

[0068] Figure 2 A schematic diagram of the greywater internal circulation and reuse system of the present invention is shown. Figure 2 As shown, the greywater internal circulation and reuse system includes:

[0069] 1. Separate collection subsystem.

[0070] The separate collection subsystem is used to collect grey water by connecting various grey water dischargers through grey water collection pipelines. Specifically, the separate collection subsystem can consist of independent grey water collection pipelines. The grey water collection pipelines are connected to the drain outlets of washbasins, washing machines, shower drains, etc., to collect high-quality wastewater.

[0071] 2. Integrated processing and reuse subsystem.

[0072] The integrated treatment and reuse subsystem is used for pretreatment, bio-enhanced treatment, disinfection, storage, and reuse of collected greywater. In this invention, the integrated treatment and reuse subsystem can be an indoor greywater treatment and reuse module located in the recessed area of ​​the indoor bathroom or in the equipment room, and the greywater collection pipeline is connected to the inlet of the integrated treatment and reuse subsystem.

[0073] like Figure 3 As shown, the integrated treatment and reuse subsystem integrates a pretreatment unit, a biologically enhanced tidal filtration unit, a disinfection and reuse water storage unit, and a reuse water supply unit, which are used to directly reuse the treated greywater for toilet flushing and other purposes.

[0074] (1) Preprocessing unit.

[0075] The pretreatment unit is used to pretreat the collected grey water. In this invention, a fine screen can be installed inside the pretreatment unit to achieve preliminary filtration of the collected grey water and remove some impurities, such as hair.

[0076] (2) Bio-enhanced tidal filtration unit.

[0077] The bio-enhanced tidal filtration unit is the core of the integrated treatment and reuse subsystem. It is filled with HN-AD bacteria immobilized microspheres and operates in a tidal manner to achieve natural oxygenation, organic matter degradation, and nitrogen and phosphorus removal, thereby realizing the bio-enhanced treatment of the pretreated greywater.

[0078] The HN-AD bacteria immobilized microspheres are made by immobilizing highly efficient heterotrophic nitrifying-aerobic denitrifying bacteria (Pseudomonas schrenckii) using sodium alginate, and do not contain microalgae. The bio-enhanced tidal filtration unit operates in a "tidal" manner, utilizing the natural reoxygenation of the atmosphere during the dry season to provide dissolved oxygen for the aerobic metabolism of HN-AD bacteria, without the need for light or mechanical aeration.

[0079] In this invention, the HN-AD bacteria immobilized microspheres can be made of sodium alginate. The microspheres were prepared by cross-linking and encapsulation, ultimately yielding pure bacterial microspheres with a particle size of 2-4 mm. The core preparation steps are as follows:

[0080] S1: Preparation of HN-AD bacterial culture.

[0081] First, the bacterial strain was activated. The cryopreserved *Pseudomonas schlegelii* strain was inoculated into LB medium and cultured at 30°C for 24 h. Single colonies were then collected. In this invention, bacteria (*Pseudomonas schlegelii*) with highly efficient heterotrophic nitrification-aerobic denitrification capabilities were selected as the strain. This strain can simultaneously complete nitrification and denitrification processes under aerobic conditions and is particularly adapted to wastewater environments with low C / N ratios.

[0082] Then, liquid expansion was carried out. Single colonies were inoculated into sterile LB liquid medium and cultured at 30°C with shaking at 160 r / min for 24-48 h until the OD600 of the bacterial culture reached 1.0-1.5 (late logarithmic growth phase).

[0083] Next, bacterial cells were collected and washed. The culture medium was centrifuged (8000 r / min, 10 min, 4℃), and the supernatant was discarded. The bacterial precipitate was washed 2-3 times with sterile physiological saline to remove residual culture medium. The washed bacterial cells were resuspended in sterile deionized water, and the bacterial concentration was adjusted to approximately [missing value]. CFU / mL.

[0084] S2: Preparation of the embedding mixture.

[0085] First, prepare the sodium alginate solution. Weigh out sodium alginate powder and dissolve it in sterile deionized water to a concentration of 3% (w / v). Heat to 40-50℃ and stir to dissolve. Sterilize at 121℃ for 20 minutes and cool to room temperature before use.

[0086] Then, the bacterial suspension and sodium alginate were mixed. The HN-AD bacterial suspension prepared in S1 was mixed with the sterilized sodium alginate solution at a volume ratio of 1:3. The final sodium alginate concentration in the system was 2.25%-2.5% (close to 2.5%), and the bacterial density was approximately... CFU / mL. 0.5%-1% glycerol or trehalose can be added as a protectant to improve the survival rate of bacteria within the microspheres. Gently stir with a sterile glass rod or magnetic stirrer until homogeneous, avoiding the formation of air bubbles.

[0087] S3: Microsphere molding (dropping and cross-linking).

[0088] First, prepare the crosslinking agent. Weigh out anhydrous... Dissolve in sterile deionized water to prepare a 4% (w / v) solution. Solution. Adding 0.5% polysorbate-80 can improve the surface properties of the microspheres and prevent adhesion. The crosslinking agent needs to be prepared and sterilized in advance (121℃, 20 min), and used after cooling.

[0089] Then, form droplets into spheres. Load the embedding mixture into a sterile syringe (needle inner diameter 0.5-1.0 mm) or a peristaltic pump tip. Under stirring conditions, drip the mixture at a constant rate. In the cross-linking solution, the dropping height is 10-20 cm (from the liquid surface); the dropping rate is 1-2 mL / min. The diameter of the formed microspheres is controlled at 2-4 mm (adjusted by the needle size and dropping rate).

[0090] Then cross-linking and curing. The microspheres in... Continue cross-linking and curing in the solution for 2-4 hours (it is recommended to perform this at a low temperature of 4℃ to maintain cell activity). During this time, gently stir (using the lowest speed on a magnetic stirrer) to prevent the microspheres from sticking together. After cross-linking is complete, wash the microspheres 2-3 times with sterile physiological saline to remove excess surface material. And uncrosslinked sodium alginate.

[0091] S4: Post-processing and activation.

[0092] First, screening is performed. Damaged, irregular, or excessively large / small microspheres are removed, and finished products with uniform particle size (3±0.5mm) are selected.

[0093] Then, activation culture is performed. The prepared pure bacterial microspheres are placed in sterile nutrient solution or diluted LB medium (e.g., LB medium diluted 10 times with sterile water). The culture conditions are: 30℃, shaking culture (100-120 r / min) for 12-24 h. The purpose is to restore the activity of the HN-AD bacteria embedded inside the sodium alginate gel and allow them to adapt to the microenvironment. No light is required during culture (light avoidance or ordinary indoor light is sufficient).

[0094] Finally, store the microspheres. The activated microspheres can be directly used to fill indoor greywater treatment modules. For short-term storage (1-2 weeks), the microspheres can be soaked in sterile saline or a 0.5% trehalose solution and refrigerated at 4°C. For long-term storage, it is recommended to freeze-dry and seal the microspheres, then rehydrate and activate them before use.

[0095] Meanwhile, in this invention, the bottom of the bio-enhanced tidal filtration unit is equipped with an electromagnetic inlet valve (for water intake, allowing greywater to enter the bio-enhanced tidal filtration unit) and an electromagnetic drain valve (for drainage, allowing greywater to drain from the bio-enhanced tidal filtration unit, facilitating drying); the top is equipped with an electromagnetic exhaust valve (opens during the drying period to prevent air blockage and facilitate air entry into the bio-enhanced tidal filtration unit); and an internal liquid level sensor is equipped with a liquid level sensor (for detecting the water level in the bio-enhanced tidal filtration unit, ensuring that the water level submerges the HN-AD bacteria immobilized microspheres during the flooding period and that the unit is completely emptied during the drying period). The electromagnetic inlet valve and electromagnetic drain valve are respectively equipped with flow switches (for detecting the inlet and outlet flow rates, facilitating the control of inlet and outlet flow).

[0096] (3) Disinfection and reclaimed water storage unit.

[0097] The disinfection and reclaimed water storage unit is used to disinfect and store the bio-enhanced greywater. For example, the disinfection and reclaimed water storage unit includes a reclaimed water tank equipped with an ultraviolet disinfection lamp. The greywater treated by the bio-enhanced tidal filtration unit enters the reclaimed water tank and is disinfected by the ultraviolet disinfection lamp.

[0098] (4) Reuse water supply unit.

[0099] The reuse water supply unit is used to supply the grey water stored in the disinfection and reuse water storage unit to the water use point, so as to realize the internal circulation and reuse of grey water.

[0100] For example, the recycled water supply unit includes a recycled pump located in the recycled water tank, which is connected to the toilet in the house via a water pipe so as to flush the toilet with water from the recycled water tank, thereby realizing the indoor recycling of grey water.

[0101] 3. Intelligent control subsystem.

[0102] The intelligent control subsystem is used to control the operation cycle of the bio-enhanced treatment, as well as disinfection and reuse, of the integrated processing and reuse subsystem.

[0103] Specifically, the intelligent control subsystem includes an embedded microcontroller (such as STM32 or Arduino). The embedded microcontroller is equipped with a time relay (for timing and counting, facilitating submersion and drying at specific times). The electromagnetic inlet valve, electromagnetic drain valve, electromagnetic exhaust valve, level sensor, flow switch, ultraviolet disinfection lamp, and reuse pump are all connected to the embedded microcontroller, enabling control of the bio-enhanced treatment cycle, disinfection, and reuse processes within the integrated processing and reuse subsystem.

[0104] In this invention, the intelligent control subsystem enables the "tidal" operation of the bio-enhanced tidal filtration unit, which is a periodic alternating submersion and drying operation mode. During the submersion period (high water level): wastewater fills the bio-enhanced tidal filtration unit, fully contacting the HN-AD bacteria immobilized microspheres for biodegradation of pollutants. During the drying period (low water level): wastewater is drained from the bio-enhanced tidal filtration unit, exposing the HN-AD bacteria immobilized microspheres to the air. Atmospheric oxygen naturally diffuses into the bio-enhanced tidal filtration unit, achieving natural oxygenation, restoring the activity of the HN-AD bacteria immobilized microspheres, and oxidizing and decomposing residual organic matter.

[0105] In this invention, the "tidal" operation process is as follows: First, flooding begins. The electromagnetic inlet valve is opened, allowing wastewater to enter the biologically enhanced tidal filtration unit. Then, a high-level trigger occurs. The level sensor detects a high water level in the biologically enhanced tidal filtration unit, closes the electromagnetic inlet valve, and starts timing (1.5 hours) via the time relay. Afterward, drying begins. After 1.5 hours, the electromagnetic vent valve is closed, and the electromagnetic drain valve is opened, allowing the wastewater in the biologically enhanced tidal filtration unit to drain. Next, a low-level trigger occurs. The level sensor detects a low water level, closes the electromagnetic drain valve, opens the electromagnetic vent valve, and starts timing (3.5 hours) via the time relay. Drying ends, and the next cycle begins, repeating this cycle. Therefore, it requires no manual intervention, adapts to intermittent greywater discharge, and can enter a standby / dormant mode if there is no continuous water intake.

[0106] The "tidal" operation mode eliminates the need for aeration fans, enabling natural oxygenation, saving electricity, and effectively adapting to the intermittent discharge of greywater, thus buffering water volume fluctuations.

[0107] In this invention, disinfection can be linked to reuse or triggered at set times. For example, the ultraviolet disinfection lamp can be automatically turned on (e.g., 30 seconds in advance) before each start of the reuse pump to achieve linkage. Alternatively, a fixed disinfection cycle can be set (e.g., disinfecting for 10 minutes every 2 hours) to ensure that the water quality in the reuse tank consistently meets standards. Furthermore, if the water level in the reuse tank is too low, disinfection and the start of the reuse pump are prohibited to ensure safety.

[0108] Furthermore, in this invention, to achieve the reuse of greywater, the toilet flush button can be connected to the embedded microcontroller. During reuse, the reuse pump can only be activated when the water level in the reuse tank is higher than the minimum starting water level and the toilet flush button is triggered (via a water pressure switch or remote control signal). The specific operating logic is as follows: the user presses the toilet flush button → the signal is transmitted to the embedded microcontroller → the embedded microcontroller first activates the ultraviolet disinfection lamp → (with delay or immediately) starts the reuse pump → water is supplied to the toilet tank → it stops after reaching the set time or flow rate. Additionally, if the water level in the reuse tank is too low, it automatically switches to tap water for replenishment and issues a warning.

[0109] II. The aforementioned low-carbon co-treatment system for wastewater.

[0110] Figure 4 The diagram shows the configuration of the low-carbon co-treatment system for wastewater according to the present invention. Figure 4 As shown, the wastewater low-carbon co-treatment system includes a mixed wastewater collection and transfer subsystem, a low-carbon co-treatment subsystem, and a resource recovery and reuse subsystem.

[0111] 1. Mixed wastewater collection and transfer subsystem.

[0112] The mixed wastewater collection and transfer subsystem is used to collect black water and excess grey water that overflows or does not enter the grey water internal recycling system, and transport it to the low-carbon co-treatment subsystem.

[0113] Considering that in some scenarios (such as when there is no need for reuse or when there is an excess of grey water), black water and the remaining grey water that has not entered the grey water internal circulation reuse system or has overflowed from the grey water internal circulation reuse system need to be treated together, the mixed wastewater collection and transfer subsystem of the present invention includes a mixed wastewater collection pipeline, which can transport the two to the low-carbon co-treatment subsystem.

[0114] 2. Low-carbon co-processing subsystem.

[0115] The low-carbon co-processing subsystem is a small-scale centralized low-carbon treatment unit that can be set up in courtyards, green spaces, or public areas of villages. It uses a dry-wet alternating artificial wetland based on "light-driven algae microspheres" to deeply treat mixed wastewater (black water and residual grey water). By constructing a synergy between micro-ecological niches and macro-operation strategies, it achieves efficient nitrogen and phosphorus removal from wastewater with a low C / N ratio.

[0116] In this invention, the low-carbon synergistic treatment subsystem includes a multi-stage dry-wet alternating constructed wetland. Taking a three-stage dry-wet alternating constructed wetland as an example, such as... Figure 5 As shown, it comprises three constructed wetlands. The three constructed wetlands have the same structure, and each constructed wetland includes a bottom impermeable layer, a support layer above the impermeable layer, a main filler layer above the support layer, a light-transmitting functional layer above the main filler layer, and a plant layer above the light-transmitting functional layer.

[0117] (1) Impermeable layer.

[0118] The impermeable layer is located at the bottom layer and can be an HDPE membrane or a compacted clay layer. Its purpose is to prevent sewage from seeping into and polluting groundwater.

[0119] (2) Supporting layer.

[0120] The supporting layer is located above the impermeable layer. It can be composed of large-diameter gravel (20-50 mm in diameter) and has a thickness of 100-200 mm. Its purpose is to support the other layers above it so as to facilitate uniform water collection and drainage.

[0121] (3) Main packing layer.

[0122] The main packing layer is located above the support layer. It can be composed of zeolite, ceramsite, crushed stone, etc. (with a diameter of 5-15 mm) and has a thickness of 300-500 mm. Its purpose is to provide a carrier for microbial attachment, filter suspended solids, and adsorb some pollutants.

[0123] (4) Translucent functional layer.

[0124] The light-transparent functional layer, located above the main filler layer, is the core of the constructed wetland. It is filled with HN-AD algae microspheres (2-4 mm in diameter) with a thickness of 50-100 mm, aiming to achieve light-driven in-situ oxygen production and synergistic nitrogen and phosphorus removal by bacteria and algae. The HN-AD algae microspheres utilize a semi-transparent gel matrix, allowing light to penetrate. Thus, by intermittently introducing water into the multi-stage alternating wet and dry constructed wetland to submerge and dehydrate the HN-AD algae microspheres, low-carbon synergistic treatment of the collected black water and residual grey water is achieved.

[0125] In this invention, the HN-AD bacterial-algae microspheres are functional biospheres formed by co-encapsulating highly efficient heterotrophic nitrifying-aerobic denitrifying bacteria and oxygen-producing microalgae in a polymeric gel matrix. Specifically, the highly efficient heterotrophic nitrifying-aerobic denitrifying bacteria are *Pseudomonas schlegelii*, the oxygen-producing microalgae are *Chlorella vulgaris*, and the polymeric gel matrix uses sodium alginate as the encapsulation framework.

[0126] Specifically, the HN-AD algae microspheres are processed with sodium alginate. It is prepared by cross-linking and embedding method, and the preparation process is as follows:

[0127] S1: HN-AD bacterial culture. Activated HN-AD strain (Pseudomonas schlegelii) was inoculated into sterile LB medium and cultured at 30℃ with shaking at 160 r / min for 24-48 h, until the OD600 reached 1.0-1.5. After culture, the bacterial cells were collected by centrifugation (8000 r / min, 10 min, 4℃), and washed 2-3 times with sterile physiological saline. The cells were then resuspended in sterile water, and the bacterial concentration was adjusted to [value missing]. CFU / mL.

[0128] S2: Microalgae culture. Chlorella was inoculated into BG11 medium and cultured under the following conditions: 25℃, light intensity 2000-3000 Lux, light-dark ratio 12 h:12 h, for 7-10 days until the logarithmic growth phase. After culture, algal cells were collected by centrifugation (5000 r / min, 5 min), washed with sterile water, resuspended in sterile water, and the algal density was adjusted to [specific value missing]. cell / mL.

[0129] S3: Preparation of sodium alginate solution. Weigh sodium alginate powder (analytical grade, viscosity 200±20 mPa·s), dissolve it in sterile deionized water, heat to 40-50℃ and stir to dissolve, sterilize at 121℃ for 20 min and cool to room temperature to obtain sodium alginate solution with a mass fraction of 3%.

[0130] S4: Bacterial-Algae Mixing. The HN-AD bacterial solution prepared in S1 and the microalgae solution prepared in S2 are mixed at a volume ratio of 2:1 and stirred evenly to ensure full contact between the bacteria and algae, thus forming a bacterial-algae mixture. Preferably, 0.5%-1% glycerol or trehalose can be added as a protective agent to improve the survival rate of bacteria within the microspheres.

[0131] S5: Preparation of the embedding precursor solution. The bacterial-algae mixture and the sodium alginate solution are mixed at a volume ratio of 1:3 to form the embedding precursor solution.

[0132] S6: Crosslinking agent preparation. Prepare 4% sterile solution. The solution acts as a crosslinking agent. Preferably, 0.5% polysorbate-80 can be added to improve the surface properties of the microspheres.

[0133] S7: Form the spheres by dripping. Load the embedding precursor solution into a syringe, and under stirring conditions, drip the embedding precursor solution into the spheres at a constant rate. In the crosslinking agent, the dropping height is controlled at 10-20 cm and the dropping speed is 1-2 mL / min, so as to form microspheres and control the diameter of the formed microspheres to 2-4 mm.

[0134] S8: Cross-linking and curing. This allows the microspheres to be cured under sterile conditions. Continue cross-linking and curing in the solution for 2-4 hours, stirring occasionally to prevent sticking. After cross-linking and curing are complete, wash 2-3 times with sterile saline to remove excess material from the surface. To obtain the prepared microspheres.

[0135] S9: Activation Cultivation. For the prepared microspheres, microsphere screening can be performed to remove damaged or irregular microspheres, selecting those with a uniform particle size (3±0.5 mm). Then, the screened microspheres are placed in a light incubator and activated for 2-3 days in BG11 medium or diluted medium (e.g., LB medium diluted 10 times with sterile water) at a light intensity of 2000 Lux and a temperature of 25-28℃ to allow the bacteria and algae to regain activity within the microspheres and establish a symbiotic relationship.

[0136] In this invention, the HN-AD bacterial-algae microspheres and the HN-AD bacterial immobilized microspheres are two different functional materials, applied to different scenarios. Specifically, the bio-enhanced tidal filtration unit (installed indoors, without light) uses the HN-AD bacterial immobilized microspheres (embedding only HN-AD bacteria), relying on atmospheric reoxygenation during tidal operation for oxygen supply; the light-transmitting functional layer (open-air environment, with light) uses the HN-AD bacterial-algae microspheres (embedding both HN-AD bacteria and microalgae), utilizing sunlight to drive in-situ oxygen production through microalgal photosynthesis, achieving zero-energy oxygen supply. Both materials are based on the same HN-AD strain, but the carrier form is designed differently according to the light conditions of the application environment, demonstrating the technical adaptability of this invention to actual working conditions.

[0137] (5) Plant layer.

[0138] The plant layer, located above the light-transmitting functional layer, can be wetland plants such as canna lilies and calamus, with the aim of releasing oxygen through the roots, absorbing nutrients, and beautifying the landscape.

[0139] In this invention, the constructed wetland can be a rectangular or square concrete / brick pond, or a modified natural pit, but its internal structure must be constructed in the layered manner described above. Meanwhile, the HN-AD algae microspheres are only filled in the light-transmitting functional layer (within the submergence range) to ensure that the microalgae receive sufficient light. The main filler layer is not filled with the HN-AD algae microspheres, but a natural biofilm can be attached to it.

[0140] In this invention, the constructed wetland may be equipped with an inlet valve and an inlet pump to allow greywater and blackwater to enter the constructed wetland. Simultaneously, the constructed wetland may be equipped with a drain valve and a drain pump, or a siphon pipe, to allow greywater and blackwater to be discharged from the constructed wetland.

[0141] Furthermore, in this invention, the HN-AD algae microspheres are submerged and dried through intermittent water intake. Specifically, this is achieved through intermittent water intake and rapid drainage, eliminating the need for mechanical aeration and relying primarily on gravity flow or a small lift pump. The specific operating steps for a complete cycle are as follows:

[0142] S1: Flooding period. The inlet valve / pump is opened and the outlet valve / pump is closed, allowing grey water and black water to enter the constructed wetland. The water level in the constructed wetland gradually rises from the bottom of the pool until it completely submerges the HN-AD microspheres (usually the water depth is controlled 10-20 cm above the HN-AD microspheres). The purpose is to ensure that the grey water and black water come into full contact with the microspheres and packing material for adsorption and biodegradation.

[0143] S2: Contact reaction period. The inlet valve / pump is closed to maintain the submerged state and keep the water level high for 1.5 to 2 hours (adjusted according to the design). The purpose is to allow the pollutants to be metabolized and transformed by the bacteria and algae inside the microspheres and the biofilm on the surface of the packing material.

[0144] S3: Rapid Drying Period. The drain valve / pump or siphon is opened to quickly empty the wastewater in the constructed wetland (completed within minutes), causing the water level to drop rapidly to the bottom of the pool. The microspheres are fully exposed to the air, which aims to: ① Atmospheric reoxygenation: oxygen directly enters the pores of the microspheres and packing material; ② Microalgae photosynthesis: continuously producing oxygen using sunlight; ③ Wash away trapped material and prevent clogging.

[0145] S4: Drying and Idle Period. The drain valve / pump is opened or intermittently slightly opened, with no water intake, allowing a small amount of water to accumulate at the bottom of the constructed wetland or to dry out completely for 3-4 hours. The purpose is to allow wet aerobic microorganisms to deeply degrade residual organic matter and restore the permeability of the filter media.

[0146] In practical implementation, multiple constructed wetlands can be operated in rotation (taking a three-stage alternating constructed wetland as an example): the timing of each constructed wetland is staggered. For example, constructed wetland one: 2 hours of water intake → 4 hours of drying; constructed wetland two: start after a 2-hour delay, also 2 hours of water intake → 4 hours of drying, alternating with constructed wetland one; constructed wetland three: start after another 2-hour delay, also 2 hours of water intake → 4 hours of drying. This achieves continuous treatment (there is always one constructed wetland receiving water), while each constructed wetland experiences alternating wet and dry conditions.

[0147] Therefore, this invention constructs an artificial wetland that alternates between wet and dry operation. Through intermittent water inflow, the wetland bed is periodically submerged and dried, ensuring sufficient contact between wastewater and the packing material while promoting atmospheric reoxygenation and guaranteeing an aerobic environment in the deeper layers of the wetland. Simultaneously, sunlight can be used to drive microalgae to perform photosynthesis and produce oxygen in situ, creating an oxygen-rich microenvironment inside and around the microspheres, precisely meeting the dissolved oxygen requirements of HN-AD bacteria for aerobic metabolism, without the need for external aeration.

[0148] Through the aforementioned multi-stage alternating wet and dry constructed wetlands, the following can be achieved: ① Enhanced denitrification. Metabolic feedback between microalgae and bacteria (microalgae provide oxygen, bacteria decompose organic matter and release oxygen) (Providing for microalgal photosynthesis) significantly enhances heterotrophic nitrification and aerobic denitrification processes, achieving highly efficient removal of total nitrogen. ② Enhanced phosphorus removal. The photosynthetic carbon fixation of microalgae induces local... Increased dissolved oxygen levels promote the chemical precipitation of phosphorus; simultaneously, the assimilation and absorption by bacteria and algae further reduce the phosphorus concentration in the effluent. ③ Micro-interface regulation. The dissolved oxygen gradient formed inside the bacterial and algal microspheres creates diverse ecological niches for microorganisms with different metabolic types, thereby improving the overall biofilm activity and pollutant degradation efficiency.

[0149] Therefore, the wastewater low-carbon co-treatment system can serve as a complement to the grey water internal circulation and reuse system, and can perform low-cost and high-efficiency deep treatment on the mixed wastewater with higher pollutant concentration remaining after source reduction. The effluent can be stably discharged in compliance with standards or used for landscaping and agricultural irrigation.

[0150] 3. Resource recycling subsystem.

[0151] The resource recycling subsystem is used to recycle and reuse black water and residual grey water after low-carbon co-treatment.

[0152] For example, the black water and residual grey water after low-carbon co-treatment can be used for landscaping and agricultural irrigation through the drainage valve / pump, thereby achieving resource recycling.

[0153] The core operation flow of the decentralized wastewater treatment system of this invention is as follows (with priority given to indoor greywater reuse): First, greywater is treated and reused. After being subjected to "tidal biological enhanced filtration" (cycle: 1.5 hours of flooding, 3.5 hours of drying) and disinfection, the greywater is stored and reused for toilet flushing. Then, overflow and mixing treatment is carried out. When the treatment capacity is saturated or reuse is not required, excess greywater can enter the mixed wastewater pipeline through the overflow pipe, while black water directly enters the pipeline. The mixed wastewater undergoes deep low-carbon treatment to achieve standard discharge or resource utilization.

[0154] As can be seen from the above introduction, the key technical points and innovations of this invention are reflected in:

[0155] 1. For indoor environments without light, the indoor module, namely the bio-enhanced tidal filtration unit, uses HN-AD bacteria immobilized microspheres without microalgae, and oxygen supply relies entirely on tidal atmospheric reoxygenation; while the outdoor module, namely the artificial wetland, uses bacteria and algae microspheres to achieve light-driven in-situ oxygen production. The two differ in materials, but both are based on the enhanced biological treatment principle of HN-AD bacteria.

[0156] 2. Adopting a "tidal" biological high-efficiency filtration process based on water quality and quantity balance, combined with combined filter media and biological enhancement methods, it realizes the separate collection and treatment of grey water and black water (forming an internal circulation of drainage system of "grey water treatment - toilet flushing reuse", reducing water volume fluctuation peaks), reducing construction and operation and maintenance costs, improving treatment efficiency, realizing efficient purification of black water and recycling of grey water, and achieving the goals of in-situ treatment and low carbon of rural domestic sewage.

[0157] 3. System-level Innovation – Coupling of Treatment and Reuse Systems. An innovative two-tiered technical architecture was constructed, linking an indoor greywater recycling system with an outdoor low-carbon wastewater treatment system. This coupling is not a simple parallel process, but rather prioritizes greywater reuse, maximizing the utilization of high-quality wastewater (for toilet flushing) and reducing wastewater at the source. The remaining, more difficult-to-treat wastewater is then treated with targeted low-carbon solutions, achieving optimal efficiency and lowest cost across the entire system.

[0158] 4. Process-level Innovation – Scenario-specific Applications of Bioaugmentation and Ecological Coupling Technologies. Indoor Treatment Process Innovation: Applying HN-AD bacterial immobilization technology to small indoor equipment. For indoor environments without light, pure bacteria immobilized microspheres without microalgae are used. Oxygen supply relies entirely on natural atmospheric reoxygenation during tidal operation, requiring no light or mechanical aeration, achieving low-carbon, low-cost indoor greywater treatment and reuse. Outdoor Deep Treatment Process Innovation: For outdoor open-air scenarios, a light-driven bacterial-algae microsphere-based constructed wetland improvement technology is creatively proposed. Utilizing in-situ oxygen production through microalgae photosynthesis, an aerobic microenvironment is created for HN-AD bacteria, achieving zero aeration energy consumption in the deep denitrification process. This technology not only retains the low-energy consumption and ecological advantages of traditional constructed wetlands but also revolutionarily solves the bottleneck problems of low treatment efficiency, high temperature susceptibility, and easy clogging in constructed wetlands through the synergy of microscopic functional materials (bacterial-algae microspheres) and macroscopic operating strategies (alternating dry and wet conditions). Its core features include: light-driven in-situ oxygen supply, using microalgal photosynthesis to replace mechanical aeration, achieving zero energy consumption in the deep denitrification process; mutual feedback of bacterial and algal metabolism, constructing a micro-ecosystem, which enhances the transformation and removal of pollutants at the micro-interface; and precise microenvironment regulation, which simultaneously achieves nitrification and denitrification through the oxygen gradient within the microspheres, especially improving the denitrification efficiency of wastewater with low C / N ratios.

[0159] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Those skilled in the art can modify or make equivalent substitutions to the technical solutions of the present invention based on the concept of the present invention, without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A decentralized wastewater treatment system, characterized in that, include: The greywater internal circulation and reuse system is used to collect decentralized greywater and pre-treat it, perform bio-enhanced treatment, disinfect it, store it and reuse it to achieve greywater internal circulation and reuse. The wastewater low-carbon co-treatment system is used to collect excess decentralized greywater and blackwater and to perform low-carbon co-treatment and resource utilization.

2. The decentralized wastewater treatment system according to claim 1, characterized in that, The greywater internal circulation and reuse system includes: The separate collection subsystem is used to collect ash water by connecting each ash water discharger through ash water collection pipelines; An integrated treatment and reuse subsystem is used for pretreatment, bio-enhanced treatment, disinfection, storage and reuse of collected greywater; An intelligent control subsystem is used to control the operating cycle of the bio-enhanced treatment, as well as disinfection and reuse, of the integrated processing and reuse subsystem.

3. The decentralized wastewater treatment system according to claim 2, characterized in that, The integrated processing and reuse subsystem includes: A pretreatment unit is used to pretreat the collected grey water; The bio-enhanced tidal filtration unit is filled with HN-AD bacteria immobilized microspheres and operates in a tidal manner to achieve natural oxygenation, organic matter degradation, and nitrogen and phosphorus removal, thereby achieving bio-enhanced treatment of pretreated greywater. Disinfection and reclaimed water storage unit, which is used for disinfection and storage of greywater after bio-enhanced treatment; The reuse water supply unit is used to supply the grey water stored in the disinfection and reuse water storage unit to the water use point, so as to realize the internal circulation and reuse of grey water.

4. The decentralized wastewater treatment system according to claim 3, characterized in that, The bio-enhanced tidal filtration unit is equipped with an electromagnetic inlet valve and an electromagnetic drain valve at the bottom, an electromagnetic exhaust valve at the top, and a liquid level sensor inside. The electromagnetic inlet valve and the electromagnetic drain valve are each equipped with a flow switch. The intelligent control subsystem includes an embedded microcontroller. The embedded microcontroller is equipped with a time relay, and the electromagnetic inlet valve, electromagnetic drain valve, electromagnetic exhaust valve, liquid level sensor, and flow switch are all connected to the embedded microcontroller to control the operating cycle of the bio-enhanced treatment of the integrated treatment and reuse subsystem.

5. The decentralized wastewater treatment system according to claim 1, characterized in that, The wastewater low-carbon co-treatment system includes: A mixed wastewater collection and transfer subsystem is used to collect black water and excess grey water that overflows or does not enter the grey water internal recycling system, and transport it to a low-carbon co-treatment subsystem. The low-carbon synergistic treatment subsystem includes a multi-stage dry-wet alternating constructed wetland. Each constructed wetland includes a bottom impermeable layer, a support layer above the impermeable layer, a main filler layer above the support layer, a light-transmitting functional layer above the main filler layer, and a plant layer above the light-transmitting functional layer. The light-transmitting functional layer is filled with HN-AD algae microspheres. The HN-AD algae microspheres are submerged and dried by intermittently introducing water into the multi-stage dry-wet alternating constructed wetland, thereby achieving low-carbon synergistic treatment of the collected black water and residual grey water. The resource recycling subsystem is used to recycle and reuse black water and residual grey water after low-carbon co-treatment.

6. The decentralized wastewater treatment system according to claim 5, characterized in that, The process of submerging and drying the HN-AD algae microspheres by intermittent water intake is as follows: the HN-AD algae microspheres are submerged for 2 hours and then dried for 4 hours, and this process is repeated.

7. The decentralized wastewater treatment system according to claim 6, characterized in that, The HN-AD bacterial and algal microspheres are functional biospheres formed by encapsulating highly efficient heterotrophic nitrifying-aerobic denitrifying bacteria and oxygen-producing microalgae in a polymer gel matrix.

8. The decentralized wastewater treatment system according to claim 7, characterized in that, The highly efficient heterotrophic nitrifying-aerobic denitrifying bacteria are *Pseudomonas schlegelii*, the oxygen-producing microalgae are *Chlorella vulgaris*, and the polymeric gel matrix uses sodium alginate as the embedding framework.

9. The decentralized wastewater treatment system according to claim 8, characterized in that, The HN-AD algal microspheres were prepared by the following method: S1: HN-AD bacterial culture: Activated *Pseudomonas stearothermiae* were inoculated into sterile LB medium and cultured at 30℃ with shaking at 160 r / min for 24-48 h until the OD600 of the bacterial culture reached 1.0-1.

5. After culture, the bacterial cells were collected by centrifugation, washed with sterile physiological saline, and resuspended in sterile water to adjust the bacterial concentration. CFU / mL; S2: Microalgae culture: Chlorella was inoculated into BG11 medium under the following conditions: 25℃, light intensity 2000-3000 Lux, light-dark ratio 12 h:12 h, for 7-10 days until the logarithmic growth phase. After culture, algal cells were collected by centrifugation, washed with sterile water, and resuspended in sterile water. The algal density was adjusted to [specific value missing]. cell / mL; S3: Preparation of sodium alginate solution: Weigh sodium alginate powder, dissolve it in sterile deionized water, heat to 40-50℃ and stir to dissolve, sterilize at 121℃ for 20 min and cool to room temperature to obtain sodium alginate solution with a mass fraction of 3%; S4: Bacterial-algae mixture: The HN-AD bacterial solution prepared in S1 and the microalgae solution prepared in S2 are mixed at a volume ratio of 2:1 to form a bacterial-algae mixture. S5: Preparation of embedding precursor solution: The bacterial-algae mixture and the sodium alginate solution are mixed at a volume ratio of 1:3 to form an embedding precursor solution; S6: Crosslinking agent preparation: Prepare 4% sterile... Solution as a crosslinking agent; S7: Dropping to form microspheres: Under stirring conditions, the embedding precursor liquid is dropped into the crosslinking agent at a constant rate, the dropping height is controlled at 10-20cm, and the dropping rate is 1-2 mL / min, so as to form microspheres and control the diameter of the formed microspheres to 2-4mm. S8: Cross-linking and curing: This process allows the microspheres to be cured under sterile conditions. Continue cross-linking and curing in the solution for 2-4 hours. After cross-linking and curing are complete, wash with sterile physiological saline to remove excess material from the surface. To obtain the prepared microspheres; S9: Activation culture: Place the prepared microspheres in a light incubator and activate them in BG11 medium for 2-3 days, with a light intensity of 2000 Lux and a temperature of 25-28℃.

10. The decentralized wastewater treatment system according to claim 9, characterized in that, In step S4, 0.5%-1% of glycerol or trehalose is added as a protective agent; and in step S6, 0.5% of polysorbate-80 is added.

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