A method for collecting, treating and recycling rural sewage by quality separation

Abstract

The application discloses a method suitable for collecting, treating and recycling rural sewage by quality, and belongs to the technical field of sewage treatment and resource utilization, and comprises the following steps: step S1, sewage collection and pre-stage grading detection; step S2, adopting a differential treatment process according to different pollution levels; step S3, matching a corresponding recycling scene according to the water quality level after treatment to realize graded recycling; and step S4, monitoring the whole treatment process through a simple intelligent operation and maintenance system, regularly cleaning and removing sludge generated by each treatment unit and carrying out composting resource disposal. The application realizes the closed-loop operation of 'quality collection-quality treatment-quality recycling' by adopting the method, takes into account the treatment effect, cost control and operation convenience, improves the sewage resource utilization rate, is suitable for centralized rural scenes, and meets the actual management needs of rural areas.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment and resource utilization technology, and in particular to a method for the separate collection, separate treatment, and separate reuse of rural wastewater. Background Technology

[0002] The current rural sewage treatment faces the following prominent problems: First, the treatment model is singular, failing to classify sewage according to its pollution level. Over-treatment leads to cost waste, while incomplete treatment results in substandard discharge. This makes it difficult to adapt to the differentiated characteristics of rural sewage, which ranges from "lightly polluted (high-quality grey water)" to "moderately polluted (grey water)" and "severely polluted (black water)." Second, existing rural sewage collection technologies mostly only achieve simple separation of black water and grey water, or employ high-cost collection methods such as negative pressure and vacuum. They fail to establish a complete closed-loop system encompassing "separate collection - graded treatment - graded reuse - intelligent operation and maintenance - sludge resource utilization," addressing the challenges of fluctuating water quality and weak operational capabilities.

[0003] Existing technologies, such as the "three-chamber septic tank + oxidation pond" model, while having lower costs, suffer from unstable treatment efficiency, with nitrogen and phosphorus removal rates below 70%, and fail to achieve graded reuse. While the "charcoal-bacterial coupling treatment equipment" improves degradation efficiency, its high degree of integration and complex structure, coupled with the limited effectiveness of the "small vegetable garden" ecological model for treating heavily polluted wastewater, necessitate a technology that is easy to operate and maintain, and can achieve graded treatment and precise reuse. Summary of the Invention

[0004] The purpose of this invention is to provide a method for the separate collection, separate treatment, and separate reuse of rural sewage, so as to realize the closed-loop operation of "separate collection-separate treatment-separate reuse", take into account the treatment effect, cost control and operation and maintenance convenience, improve the resource utilization rate of sewage, and meet the actual governance needs of rural areas.

[0005] To achieve the above objectives, the present invention provides a method for the separate collection, separate treatment, and separate reuse of rural sewage, comprising the following steps: Step S1: Construct a three-tiered collection system for rural domestic sewage, separating the source of domestic sewage into grey water and black water. Three independent pipe networks, collection tanks, and transport systems are used for each type of sewage, ensuring they are collected independently without mixing or cross-contamination. High-quality grey water is used for washing and bathing, characterized by low pollution, absence of feces, and ease of treatment; grey water is kitchen wastewater; and black water is used for toilet flushing, characterized by high pollution, presence of feces, and the need for intensive treatment. A multi-household connected drainage system is used to collect high-quality grey water, grey water, and black water. After collection, the wastewater is fed into corresponding equalization tanks. The chemical oxygen demand (COD), suspended solids (SS), and ammonia nitrogen (NH3-N) of each type of wastewater are measured by a water quality testing unit. After preprocessing using a weighted moving average filtering algorithm to remove outliers, the wastewater is input into a fuzzy comprehensive evaluation pollution classification model with seasonal correction to calculate a comprehensive pollution index. The wastewater is classified into three pollution levels: light, moderate, and heavy. High-quality grey water corresponds to light pollution, black water to heavy pollution, and grey water to moderate pollution. Step S2: For different pollution levels and the pollution characteristics of high-quality grey water, grey water, and black water, a rural-adapted "low-power, maintenance-free" differentiated treatment coupling process is adopted. Process parameters are dynamically adjusted through a fuzzy-PID adaptive linkage algorithm. Lightly polluted wastewater (high-quality grey water) uses a gravity multi-stage filtration + biofilm biodegradation + slow-release disinfection combined process. Moderately polluted wastewater (grey water) uses a grid sedimentation + carbon-bacterial coupled composite wetland process, utilizing the wetland ecosystem for stable nitrogen and phosphorus removal. Heavily polluted wastewater (black water) uses a three-compartment septic tank + non-powered A / O ecological infiltration bed process, with no power, solar heating, or low-frequency disturbance components throughout. It relies on gravity flow and ecological degradation for stable operation, does not freeze at low temperatures, and has a failure rate of less than 5%. Step S3: After the treated water quality is judged to meet the standards, if it meets the standards, it will be matched with the corresponding reuse scenarios according to the water quality of high-quality grey water, grey water and black water respectively, so as to realize the closed loop of the whole chain of "separate collection → separate treatment → separate reuse" and "high water high use, low water low use", and achieve full resource utilization of sewage. If it does not meet the standards, it will be returned to step S1 for re-treatment to realize graded closed-loop reuse. Step S4, Intelligent Operation and Maintenance and Sludge Disposal: The IoT intelligent operation and maintenance system monitors water level, water quality and energy consumption coefficient in real time. Based on time series data, it realizes equipment failure prediction and early warning. Compared with the traditional mixed collection mode, this system reduces monitoring-related equipment and costs. The sludge generated by each unit is judged by temperature control-moisture content-C / N coupled composting algorithm and then carried out resource-based composting treatment. It does not need to be transported out and does not generate secondary pollution, realizing the local agricultural use of sludge. This method breaks through the current situation where 99% of rural sewage is collected in a mixed manner. It collects sewage separately from the source, fundamentally reducing the treatment load and improving the reuse rate. Its differentiated treatment method from the source to reuse is not a simple pollution classification, but a combination of non-obvious technologies. It is specifically designed to solve the pain points of rural areas lacking electricity and maintenance personnel, and is a dedicated invention for rural sewage scenarios.

[0006] Preferably, the indicators for lightly polluted wastewater (grey water) in step S1 are COD≤100mg / L, SS≤30mg / L, and NH3-N≤15mg / L; the indicators for moderately polluted wastewater are 100mg / L<COD≤200mg / L, 30mg / L<SS≤60mg / L, and 15mg / L<NH3-N≤30mg / L; and the indicators for heavily polluted wastewater (black water) are COD>200mg / L, SS>60mg / L, and NH3-N>30mg / L.

[0007] Furthermore, the formula for the weighted moving average filtering algorithm with outlier removal in step S1 is as follows: ; ; in, These are the filtered water quality index values; For the first i The raw data collected this time; These are the weighting coefficients; N Number of samples; The standard deviation of the data; The formula for the comprehensive pollution index of the fuzzy comprehensive evaluation pollution classification model with seasonal correction is as follows: ; in, This is a seasonal correction factor for summer. ,winter ; Chemical oxygen demand (COD) is a single pollution index. This refers to the single pollution index of suspended solids; This refers to the single pollution index of ammonia nitrogen. Formula for single-indicator pollution index: ,in, Real-time indicator concentration; This serves as the grading benchmark value; Pollution level determination: Mild; Moderate; It is severe.

[0008] Preferably, the multi-household terraced house mode in step S1 is specifically as follows: High-quality grey water collection: Large-scale high-quality grey water collection ponds are shared by multiple households in a row; Greywater collection: Large greywater collection ponds are shared by multiple households in a row. Blackwater collection: Large blackwater collection ponds are shared by multiple households in a row. The collection pool is equipped with a bentonite waterproof blanket with a thickness of ≥2mm to prevent seepage. High-quality grey water, grey water and black water are respectively collected into their respective collection pools through simple PVC pipe networks laid underground, and then respectively into their respective homogenization pools to ensure that they do not mix or cross over.

[0009] Preferably, in step S1, the water quality testing units are respectively set at the high-quality grey water collection tank, the grey water collection tank outlet, the black water collection tank outlet, and the corresponding homogenization tank outlet. The testing cycle is adaptively adjusted: once every 30 minutes during peak periods and once every 2 hours during off-peak periods. Low-cost portable sensors are used, with a testing accuracy of COD±5mg / L, SS±2mg / L, and NH3-N±0.5mg / L. The testing data is displayed in real time on a simple village-level terminal, which has data layer storage and abnormal alarm functions. No professional personnel are required to operate it. Compared with the traditional mixed collection mode, it reduces the number of monitoring points and monitoring costs.

[0010] Preferably, the lightly polluted wastewater treatment process (grey water, gravity flow + three-stage filtration + slow-release disinfection) in step S2 is as follows: Slightly polluted wastewater flows by gravity into a multi-stage gravity filtration tank, where indigenous nitrifying bacteria and Bacillus are inoculated into the biochar filter layer. The biofilm enables a synergistic effect of biochemical degradation and physical interception, stably degrading COD and ammonia nitrogen. The filtered water is disinfected with sodium hypochlorite using slow-release method, and the water quality after disinfection meets the requirements for reuse. The gravity multi-stage filtration system is filled with three layers of filter media from top to bottom: gravel with a particle size of 5-8 mm and a thickness of 20-30 cm, volcanic rock with a particle size of 2-5 mm and a thickness of 15-25 cm, and iron salt-chitosan modified biochar with a particle size of 0.5-2 mm and a thickness of 10-20 cm; wastewater undergoes gravity-fed filtration with a retention time of 1.5-2.5 hours. Furthermore, the wastewater filtration retention time is adjusted using a fuzzy-PID linkage algorithm, with the following formula: ; in, It is a time variable; This is the retention time adjustment value for gravity filtration of wastewater; This is the proportionality coefficient; The integral coefficient; These are the differential coefficients; This is the integral term for the deviation; This is the combined deviation value of turbidity and pollution index. This is the differential term of the deviation.

[0011] Furthermore, the modified biochar is prepared from rural straw and fruit shells, and then loaded with Bacillus subtilis after high-temperature carbonization.

[0012] Preferably, the moderately polluted wastewater treatment process in step S2 specifically involves: pretreatment of the moderately polluted wastewater by sequentially passing it through a 5mm screen and a 60° inclined tube sedimentation unit, with a sedimentation time of 1.0~1.5h; after pretreatment, the wastewater enters a vertical flow-subsurface flow charcoal-bacterial coupled composite wetland, with the wetland spaced at 5~6m... 2 The design for each household uses a filler material with a volume ratio of gravel:volcanic rock:modified biochar:slow-release calcium-based carrier = 3:2:1:0.5; it is planted with native pollution-tolerant plants such as reeds and calamus, and supplemented with nitrifying bacteria, denitrifying bacteria, and Bacillus; the hydraulic load is controlled at 0.15~0.25m. 3 / (m 2 •d), the residence time is 6~8h; the surface of the wetland is equipped with a straw + polystyrene antifreeze and heat insulation layer, which can operate stably in a low temperature environment of -5℃.

[0013] Preferably, the heavily polluted wastewater treatment process (black water, anaerobic fermentation + solar micro-aeration enhanced treatment) described in step S2 is as follows: the heavily polluted wastewater is first pretreated by anaerobic treatment in a three-compartment septic tank, and then enters a non-powered A / O ecological infiltration bed; the non-powered A / O ecological infiltration bed is filled with modified biochar, volcanic rock and gravel composite filler, and combined with a low-temperature resistant ecological filter layer, which can achieve low-temperature non-freezing, system failure rate of less than 5%, and stable treatment of heavily polluted wastewater to meet standards.

[0014] Furthermore, distributed small photovoltaic modules are installed on the empty space above the ecological infiltration bed and around the septic tank, along with energy storage batteries and low-voltage power distribution control cabinets, for local self-generation and self-use. Photovoltaic energy storage prioritizes supplying solar micro-aeration devices, intermittently supplying oxygen to the surface of the non-powered A / O percolation bed, enhancing the aerobic nitrification reaction of the packing layer; during low-temperature periods, a small amount of power is supplied to support the filter layer antifreeze auxiliary heating components to ensure that the packing filter bed does not freeze at low temperatures and to reduce system failures. The entire aeration and auxiliary heating system relies entirely on photovoltaic power for self-sufficiency, eliminating dependence on municipal power. The photovoltaic surplus electricity is connected to the project's courtyard LED solar street lights and equipment maintenance lighting, covering the septic tank operation area and the percolation bed inspection passage. The photovoltaic power generation and storage is used during the day, and the lighting is automatically turned on at night to meet the lighting needs of operation and maintenance inspections.

[0015] Excess electricity can be stored on-site for backup, and the battery provides backup power on rainy days to ensure continuous operation of micro-aeration and lighting. The entire process is green, low-carbon, and intelligent.

[0016] Preferably, the graded reuse in step S3 specifically refers to the following: lightly polluted wastewater (high-quality grey water) is disinfected and after disinfection, COD ≤ 50 mg / L, SS ≤ 10 mg / L, and NH3-N ≤ 5 mg / L, meeting GB / T 18920-2020 "Water Quality Standard for Urban Miscellaneous Uses", and is used for road sweeping and toilet flushing; moderately polluted wastewater (grey water) is treated and disinfected, and after disinfection, COD ≤ 60 mg / L, SS ≤ 20 mg / L, and NH3-N ≤ 8 mg / L, meeting GB 5084-2021 "Water Quality Standard for Farmland Irrigation", and is used for forest and farmland irrigation; heavily polluted wastewater (black water) is treated and disinfected, and after disinfection, COD ≤ 80 mg / L, SS ≤ 30 mg / L, and NH3-N ≤ 10 mg / L, meeting GB / T 18921-2019 "Water Quality Standard for Urban Wastewater Reuse for Landscape and Environmental Use" is used for farmland irrigation and public green space irrigation. All reuse pipelines are equipped with anti-seamless one-way valves and conspicuous signs, and are physically isolated from drinking water pipelines. Key water quality indicators, including pathogenic bacteria and coliform bacteria content, are tested weekly at the reuse end. If the relevant content exceeds the standard, timely intervention is carried out to stop wastewater reuse, so as to achieve "high water high use, low water low use" and full resource utilization of wastewater.

[0017] Preferably, the simplified intelligent operation and maintenance system described in step S4 is as follows: IoT sensors are set up in each level of the processing unit to monitor water level, COD, SS, and ammonia nitrogen parameters in real time. The data is transmitted to a village-level simplified terminal, which has the functions of audible and visual warning of exceeding limits and fault prediction. Daily inspections and maintenance are carried out by members of the village-level environmental protection cooperative who have received simple training. The operation and maintenance response time is ≤2 hours. The average annual operation and maintenance cost of the system is significantly reduced compared with the traditional decentralized treatment process, which is suitable for the current situation in rural areas where there is a lack of professional operation and maintenance personnel.

[0018] Furthermore, the specific formula for the sludge temperature control-moisture content-C / N coupled decomposition degree algorithm in step S4 is as follows: ; in, The degree of decay is the index. It was determined to be fully decomposed; This is the normalized value for composting temperature; This is the normalized value for moisture content; This is the normalized value for the carbon-to-nitrogen ratio; Preferably, the sludge disposal in step S4 is as follows: the sludge removal cycle of each treatment unit is 3-6 months. After the removed sludge is mixed with straw and sawdust regulators, it is composted. It does not need to be transported out and does not generate secondary pollution. The composting temperature is controlled at 55-65℃ and the composting time is 15-20 days. After it is decomposed, it is used as farm fertilizer. A small amount of sludge that is difficult to decompose is entrusted to the local environmental protection department for unified disposal.

[0019] Therefore, the present invention employs the above-mentioned method for the separate collection, separate treatment, and separate reuse of rural sewage, and the technical effects are as follows: (1) It solves the adaptability problem of existing technology in “urban technology going to the countryside”. Through the differentiated design of graded processing technology, it achieves a balance between “low cost and high efficiency” and overcomes the defects of high cost and poor processing effect of traditional technology. (2) Simplify intelligent operation and maintenance technology, adapt to the current situation of lack of professional personnel in rural areas, reduce the difficulty of operation and maintenance through simple terminals and early warning functions, and have significant technological breakthroughs.

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0021] Figure 1 This is a flowchart of an embodiment of a method for the separate collection, separate treatment, and separate reuse of rural sewage according to the present invention; Figure 2 This is a schematic diagram of a mild wastewater treatment process according to an embodiment of the present invention, which describes a method for the separate collection, separate treatment, and separate reuse of rural wastewater. Figure 3 This is a schematic diagram of a moderate wastewater treatment process according to an embodiment of the present invention, which describes a method for the separate collection, separate treatment, and separate reuse of rural wastewater. Figure 4 This is a schematic diagram of a heavy wastewater treatment process according to an embodiment of the present invention, which describes a method for the separate collection, separate treatment, and separate reuse of rural wastewater. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "comprising" or "including," as used in this invention, mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. The terms "connected" or "linked," etc., are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect.

[0024] This invention provides a method for the separate collection, treatment, and reuse of rural sewage based on different pollution loads. It constructs a "three-way separate collection" system, separating sewage into high-quality grey water, grey water, and black water at the source, collecting and treating each separately. The treated water quality is then matched to corresponding reuse scenarios. Combined with rural-adapted "low-power, maintenance-free" treatment processes, this achieves synergy between efficient sewage treatment and resource utilization, realizing a closed-loop system of "separate collection - separate treatment - separate reuse." Figure 1 As shown, the specific steps are as follows: Step S1: Wastewater separate collection and pre-classification testing: S1.1 Three-way Separate Collection: A three-way separate collection system for rural domestic sewage is constructed, adopting a multi-household joint collection model. Domestic sewage is separated into high-quality grey water, grey water, and black water, collected independently by three separate pipe networks, collection tanks, and transport systems, ensuring no mixing or cross-contamination. High-quality grey water is used for washing and bathing, characterized by low pollution, no feces, and easy treatment; grey water is kitchen wastewater; and black water is used for toilet flushing, characterized by high pollution, feces content, and the need for intensive treatment.

[0025] The row of farmhouses shares a large-scale high-quality greywater collection pond, a large greywater collection pond, and a large blackwater collection pond. Three independent, simple PVC pipe networks connect the high-quality greywater, greywater, and blackwater to their respective collection ponds. The pipe networks are laid underground to avoid occupying farmland and facilitate future maintenance. All collection ponds are equipped with an impermeable layer (using bentonite waterproof blankets, ≥2mm thick) to prevent sewage leakage and groundwater contamination. After collection, the high-quality greywater, greywater, and blackwater are separately fed into homogenization ponds for homogenization treatment.

[0026] S1.2, Graded Detection: Simple water quality detection units are set up at the outlets of the high-quality grey water collection tank, grey water collection tank, black water collection tank, and their corresponding homogenization tanks. The detection indicators include chemical oxygen demand (COD), suspended solids (SS), and ammonia nitrogen (NH3-N). Low-cost portable sensors are used (detection accuracy: COD±5mg / L, SS±2mg / L, NH3-N±0.5mg / L). The detection cycle is adaptively adjusted: 30min / time during peak periods and 2h / time during off-peak periods. No professional personnel are required to operate it. The detection data is displayed in real time on the village-level simple terminal.

[0027] Based on the test results, and combined with preprocessing using a weighted moving average filtering algorithm with outlier removal and calculation using a fuzzy comprehensive evaluation pollution classification model with seasonal correction, the wastewater is divided into three levels: Slightly polluted wastewater: COD≤100mg / L, SS≤30mg / L, NH3-N≤15mg / L, mainly high-quality grey water with low pollution load; Moderately polluted wastewater: 100mg / L<COD≤200mg / L, 30mg / L<SS≤60mg / L, 15mg / L<NH3-N≤30mg / L, mainly grey water; Severely polluted wastewater: COD > 200 mg / L, SS > 60 mg / L, NH3-N > 30 mg / L, mainly black water, with a small amount of domestic sewage mixed with livestock and poultry breeding wastewater, and high pollution load.

[0028] Step S2, quality and grade processing: Based on the grading results of step S1 and the pollution characteristics of high-quality grey water, grey water, and black water, a rural-adapted "low-power, maintenance-free" differentiated treatment coupling process is adopted. The process parameters are dynamically adjusted through a fuzzy-PID adaptive linkage algorithm. All three differentiated treatment processes follow the principles of "easy operation and maintenance, and local material availability" to avoid complex equipment and high-energy-consuming operations, as detailed below: S2.1, Lightly Polluted Wastewater Treatment Process (High-quality grey water, gravity multi-stage filtration + biofilm biodegradation + slow-release disinfection combined process): Slightly polluted wastewater flows by gravity into a multi-stage gravity filtration tank. The tank is filled with three layers of filter media: from top to bottom, gravel (5-8mm particle size, 20-30cm thickness), volcanic rock (2-5mm particle size, 15-25cm thickness), and modified biochar (0.5-2mm particle size, 10-20cm thickness). The modified biochar is made from rural straw and fruit shells, carbonized at high temperatures, and then loaded with Bacillus subtilis to enhance adsorption and degradation capabilities, reducing costs through locally sourced materials. The wastewater undergoes three stages of filtration by gravity to remove suspended solids, trace amounts of organic matter, and odors, with a filtration retention time of 1.5-2.5 hours. After filtration, the wastewater enters a simple disinfection tank where sodium hypochlorite (5-8mg / L) is used for disinfection, with a retention time of 30-60 minutes. The disinfected water meets reuse standards.

[0029] S2.2, Moderately polluted wastewater treatment process (grid sedimentation + carbon-bacterial coupled composite wetland process): S2.2.1, Grating and Sedimentation: Moderately polluted wastewater is introduced into the pretreatment tank, which is divided into a grating zone and a sedimentation zone. The grating zone is equipped with a simple grating with a 5mm aperture to remove large debris (such as vegetable leaves and plastic bags) from the wastewater and prevent clogging of subsequent treatment units. The sedimentation zone uses inclined tube sedimentation with an inclination angle of 60° and a sedimentation time of 1.0-1.5 hours to remove more than 60% of suspended solids and some organic matter. The sludge after sedimentation is regularly cleaned and composted for use as farm fertilizer, realizing the resource utilization of sludge.

[0030] S2.2.2, Carbon-Biochar Coupling Composite Wetland Treatment: Pretreated wastewater is introduced into a vertical flow-subsurface flow composite wetland. The wetland area is designed according to the treatment volume. The wetland is filled with a composite filler material of gravel:volcanic rock:biochar = 3:2:1, and planted with native aquatic plants such as reeds and calamus. The plant roots and the immobilized microorganisms (Bacillus subtilis and nitrifying bacteria) on the surface of the filler material work synergistically to remove organic matter, nitrogen, phosphorus, and other pollutants from the wastewater through plant absorption, filler adsorption, and microbial degradation. The hydraulic load of the composite wetland is controlled at 0.15-0.25m. 3 / (m 2 •d), with a residence time of 6-8 hours, the COD removal rate is increased by more than 15% compared with a single subsurface flow wetland, and the ammonia nitrogen removal rate is stable at over 90%.

[0031] S2.3, Heavy Pollution Wastewater Treatment Process (Three-Compartment Septic Tank + Non-Powered A / O Ecological Infiltration Bed Process): S2.3.1, Anaerobic Pretreatment in a Three-Compartment Septic Tank: Heavily polluted wastewater is introduced into an enhanced pretreatment tank, first passing through a fine screen with a 3mm aperture to remove small debris; then it enters an anaerobic fermentation tank (volume 2.0-3.0m³). 3 The anaerobic fermentation temperature is controlled at 25-35℃ (using rural solar energy for auxiliary heating to reduce energy consumption), and the fermentation retention time is 24-36 hours. This process degrades large organic molecules in wastewater into smaller organic molecules, while also removing some ammonia nitrogen and phosphorus. The biogas produced during fermentation is collected through a collection pipe and fed into a small biogas tank for use in cooking by farmers, thus achieving energy recovery.

[0032] S2.3.2 Non-powered A / O ecological infiltration bed treatment: The wastewater after anaerobic fermentation is introduced into the non-powered A / O ecological infiltration bed. The non-powered A / O ecological infiltration bed is filled with modified biochar, volcanic rock and gravel composite filler, and is equipped with a low-temperature resistant ecological filter layer, which can achieve low temperature non-freezing, system failure rate of less than 5%, and stable treatment of heavily polluted wastewater to meet standards.

[0033] Step S3, graded and reclaimed: Based on the treatment effects of different levels of wastewater and combined with the actual reuse needs in rural areas, the system achieves "high-quality water for high-use and low-quality water for low-use," with differentiated reuse tailored to corresponding scenarios. The reuse scenarios are strictly matched with water quality standards to avoid reuse risks and achieve full resource utilization of wastewater, as detailed below: Slightly polluted wastewater (high-quality grey water) is treated to have COD≤50mg / L, SS≤10mg / L, and NH3-N≤5mg / L, which meets the requirements of GB / T 18920-2020 "Water Quality Standard for Urban Miscellaneous Water Use". It can be used for road cleaning and toilet flushing, achieving local reuse and reducing tap water consumption.

[0034] After treatment, moderately polluted wastewater (grey water) has the following parameters: COD≤60mg / L, SS≤20mg / L, NH3-N≤8mg / L, which meets the requirements of GB5084-2021 "Standards for Irrigation Water Quality". It can be used for irrigation of forest fields (non-edible crops). The nitrogen and phosphorus in the wastewater can be used as natural fertilizers, reducing the amount of chemical fertilizers used and realizing the "wastewater-farmland" cycle.

[0035] After treatment, heavily polluted wastewater (black water) has the following parameters: COD≤80mg / L, SS≤30mg / L, NH3-N≤10mg / L, which meets the requirements of GB / T 18921-2019 "Water Quality Standard for Urban Wastewater Reuse for Landscape and Environmental Use". It can be used for farmland irrigation and public green space irrigation. If it is used for farmland irrigation, it needs to undergo further ultraviolet disinfection treatment (disinfection time 15-20min) to ensure safe reuse.

[0036] All reuse pipelines are clearly marked and strictly separated from drinking water pipelines to avoid cross-contamination. Water quality monitoring points are set up at the end of the reuse process, and key indicators are tested once a week to ensure the safety of reused water quality and achieve "high-quality water for high-use and low-quality water for low-use" as well as the full resource utilization of wastewater.

[0037] Step S4, Intelligent Operation and Maintenance and Sludge Disposal: S4.1 Intelligent Operation and Maintenance: IoT sensors are installed in each treatment unit (high-quality grey water, grey water, black water collection pool, transfer pool, each homogenization pool and each treatment pool) to monitor parameters such as water level, COD, SS, and ammonia nitrogen in real time. The data is transmitted to a simple village-level terminal with an early warning function. When parameters are abnormal (such as filter pool blockage or aeration device failure), an audible and visual warning is issued in a timely manner. Daily inspections and maintenance are carried out by members of the village-level environmental protection cooperative (who can be put to work after simple training). No professional personnel are required, and the operation and maintenance response time is shortened to within 2 hours. The average annual operation and maintenance cost of the system is significantly reduced compared with the traditional decentralized treatment process.

[0038] S4.2 Sludge Disposal: Sludge (sedimented sludge, wetland sediment) generated by each treatment unit is regularly removed every 1-2 months. The sludge is then composted (with the addition of straw, sawdust, and other modifiers, at a composting temperature of 55-65℃ for 30-35 days) and used as farmyard manure to achieve resource utilization of sludge and avoid secondary pollution. For a small amount of sludge that is difficult to compost, it is entrusted to the local environmental protection department for unified disposal to ensure compliance with regulations.

[0039] The specific implementation method is as follows: Example 1: Medium to large-sized villages (multi-household terraced house treatment mode) This embodiment is applicable to suburban villages where farmers live relatively close together, multiple households are connected, sewage is mainly moderately polluted, close to farmland, and the reuse demand is mainly for farmland irrigation.

[0040] Step S1: Large-scale high-quality grey water collection ponds, large-scale grey water collection ponds, and large-scale black water collection ponds are set up for multiple households in a row. The sewage from the high-quality grey water, grey water, and black water collection ponds is fed into the corresponding transfer ponds through three independent pipe networks. Simple detection units are set up at the outlets of the transfer ponds and the homogenization ponds to detect the sewage pollution level in stages.

[0041] Step S2, as follows Figure 2 As shown, lightly polluted wastewater is treated using a combined process of gravity multi-stage filtration + biofilm biodegradation + slow-release disinfection, with a retention time of 2.5 hours, and is reused after disinfection; Figure 3 As shown, moderately polluted wastewater, after pretreatment (grid + inclined tube sedimentation, retention time 1.5h), enters the composite wetland for a retention time of 8h to enhance nitrogen and phosphorus removal; Figure 4 As shown, heavily polluted wastewater, after enhanced pretreatment and a non-powered A / O ecological infiltration bed process, is used for landscape water replenishment.

[0042] Step S3: Lightly treated wastewater is used for road sweeping and toilet flushing; moderately treated wastewater, after passing testing, is used for irrigation of forests and fields through a drip irrigation system; and heavily treated wastewater is used for irrigation of village public green spaces.

[0043] Step S4: The intelligent terminal monitors the parameters. The village-level environmental protection cooperative is responsible for daily operation and maintenance. Every three months, the sludge is cleaned up, composted, and used as fertilizer for farmland to achieve a "sewage-farmland" cycle.

[0044] Implementation results: After treatment, the COD removal rate was 88%, the ammonia nitrogen removal rate was 92%, the farmland irrigation reuse rate was 85%, the groundwater extraction was reduced by 30%, the cotton yield increased by 12%, and the construction cost was reduced by 50% and the operation and maintenance cost was reduced by 40% compared with the traditional centralized treatment mode.

[0045] In summary, the beneficial effects of this application are as follows: (1) Convenient operation and maintenance: All processing technologies use simple equipment, requiring no professional operation and maintenance personnel. Village-level inspection personnel can complete daily maintenance after simple training, solving the problem of "difficult operation and maintenance and high downtime rate" of existing facilities; (2) Local materials: The filter media (biochar, gravel) and wetland plants are all made from local rural materials, which further reduces construction costs and facilitates large-scale promotion in rural areas; (3) Reuse scenarios are tailored to rural needs: Differentiated reuse is suitable for common rural scenarios such as courtyard irrigation, farmland irrigation, and landscape water replenishment, achieving "high water high use and low water low use", improving water resource utilization, while reducing fertilizer use and tap water consumption, which is in line with the actual production and life in rural areas.

[0046] (4) A closed-loop model of “separate collection-separate treatment-separate reuse” is proposed to break the limitations of the existing technology of “unified treatment and single reuse”. The treatment process and reuse scenario are accurately matched according to the degree of sewage pollution to avoid over-treatment or under-treatment. (5) By coupling modified biochar (rural straw preparation) with functional microorganisms and combining it with solar micro-power aeration technology, a high-efficiency graded treatment system is constructed, which is different from the traditional single ecological treatment mode and also different from the complex integrated treatment equipment. (6) Construct a supporting system of “village-level simple intelligent operation and maintenance + sludge resource utilization” to simplify the operation and maintenance process, realize the dual resource utilization of sewage and sludge, and break through the bottleneck of existing technology that “emphasizes treatment, neglects operation and maintenance, and neglects resource utilization”.

[0047] Therefore, the present invention adopts the above-mentioned method for the separate collection, separate treatment and separate reuse of rural sewage to realize the closed-loop operation of "separate collection-separate treatment-separate reuse", which takes into account the treatment effect, cost control and operation and maintenance convenience, improves the resource utilization rate of sewage, adapts to centralized rural scenarios and meets the actual governance needs of rural areas.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for the separate collection, separate treatment, and separate reuse of rural sewage, characterized in that, Includes the following steps: Step S1: Construct a three-tiered collection system for rural domestic sewage, separating the source of domestic sewage into high-quality grey water, grey water, and black water. Each type of sewage is collected independently using three separate pipe networks, collection tanks, and transport systems. High-quality grey water is used for washing and bathing; grey water is used for kitchen wastewater; and black water is used for toilet flushing. A multi-household connected drainage system is used to collect high-quality grey water, grey water, and black water. After collection, the wastewater is fed into corresponding equalization tanks. The chemical oxygen demand (COD), suspended solids (SS), and ammonia nitrogen (NH3-N) of each type of wastewater are measured by a water quality testing unit. After preprocessing using a weighted moving average filtering algorithm to remove outliers, the wastewater is input into a fuzzy comprehensive evaluation pollution classification model with seasonal correction to calculate a comprehensive pollution index. The wastewater is classified into three pollution levels: light, moderate, and heavy. High-quality grey water corresponds to light pollution, black water to heavy pollution, and grey water to moderate pollution. Step S2: Lightly polluted wastewater adopts a combined process of gravity multi-stage filtration + biofilm biodegradation + slow-release disinfection; moderately polluted wastewater adopts a combined wetland process of grid sedimentation + carbon-bacterial coupling; heavily polluted wastewater adopts a three-compartment septic tank + non-powered A / O ecological infiltration bed process, relying on gravity flow and ecological degradation for stable operation. Step S3: After the treated water quality is judged to meet the standards, if it meets the standards, it will be matched with the corresponding reuse scenarios according to the water quality of high-quality grey water, grey water and black water respectively. If it does not meet the standards, it will be returned to step S1 for re-treatment to achieve graded closed-loop reuse. Step S4, Intelligent Operation and Maintenance and Sludge Disposal: The IoT intelligent operation and maintenance system monitors water level, water quality and energy consumption coefficient in real time, and realizes equipment failure prediction and early warning based on time series data. The sludge generated by each unit is subjected to resource-based composting disposal after being judged by the temperature control-moisture content-C / N coupled maturity algorithm, so as to realize the local agricultural use of sludge.

2. The method for separate collection, separate treatment, and separate reuse of rural sewage according to claim 1, characterized in that, The indicators for lightly polluted wastewater mentioned in step S1 are COD≤100mg / L, SS≤30mg / L, and NH3-N≤15mg / L; the indicators for moderately polluted wastewater are 100mg / L<COD≤200mg / L, 30mg / L<SS≤60mg / L, and 15mg / L<NH3-N≤30mg / L; and the indicators for heavily polluted wastewater are COD>200mg / L, SS>60mg / L, and NH3-N>30mg / L. The formula for the weighted moving average filtering algorithm with outlier removal in step S1 is as follows: ； ； in, These are the filtered water quality index values; For the first i The raw data collected this time; These are the weighting coefficients; N Number of samples; The standard deviation of the data; The formula for the comprehensive pollution index of the fuzzy comprehensive evaluation pollution classification model with seasonal correction is as follows: ； in, This is a seasonal correction factor for summer. ,winter ; Chemical oxygen demand (COD) is a single pollution index. This refers to the single pollution index of suspended solids; This refers to the single pollution index of ammonia nitrogen. Formula for single-indicator pollution index: ,in, Real-time indicator concentration; This serves as the grading benchmark value; Pollution level determination: Mild; Moderate; It is severe.

3. The method for separate collection, separate treatment, and separate reuse of rural sewage according to claim 1, characterized in that, The multi-household terraced house model mentioned in step S1 is specifically as follows: High-quality grey water collection: Large-scale high-quality grey water collection ponds are shared by multiple households in a row; Greywater collection: Large greywater collection ponds are shared by multiple households in a row. Blackwater collection: Large blackwater collection ponds are shared by multiple households in a row. The collection pool is equipped with a bentonite waterproof blanket with a thickness of ≥2mm to prevent seepage. High-quality grey water, grey water and black water are respectively collected into the corresponding collection pool through simple PVC pipe networks laid underground, and then respectively into the corresponding homogenization pool.

4. A method for the separate collection, separate treatment, and separate reuse of rural sewage according to claim 1, characterized in that, In step S1, water quality testing units are installed at the outlets of the high-quality grey water collection tank, grey water collection tank, black water collection tank, and their corresponding homogenization tank. The testing cycle is adaptively adjusted: once every 30 minutes during peak periods and once every 2 hours during off-peak periods. The sensor detection accuracy is COD±5mg / L, SS±2mg / L, and NH3-N±0.5mg / L. The test data is displayed in real time on a simple village-level terminal without the need for professional personnel to operate it.

5. A method for the separate collection, separate treatment, and separate reuse of rural sewage according to claim 1, characterized in that, The specific process for treating lightly polluted wastewater in step S2 is as follows: lightly polluted wastewater flows into a gravity multi-stage filtration tank by gravity, and indigenous nitrifying bacteria and Bacillus are inoculated in the biochar filter layer; the filtered water is disinfected with sodium hypochlorite using slow-release disinfection, and the water quality after disinfection meets the requirements for reuse. The gravity multi-stage filtration tank is filled with three levels of filter media from top to bottom: gravel with a particle size of 5-8mm and a thickness of 20-30cm, volcanic rock with a particle size of 2-5mm and a thickness of 15-25cm, and iron salt-chitosan modified biochar with a particle size of 0.5-2mm and a thickness of 10-20cm; the wastewater is filtered by gravity with a retention time of 1.5-2.5h. The wastewater filtration retention time is adjusted using a fuzzy-PID linkage algorithm, and the formula is as follows: ； in, It is a time variable; This is the retention time adjustment value for gravity filtration of wastewater; This is the proportionality coefficient; The integral coefficient; These are the differential coefficients; This is the integral term for the deviation; This is the combined deviation value of turbidity and pollution index. This is the differential term of the deviation.

6. A method for the separate collection, separate treatment, and separate reuse of rural sewage according to claim 1, characterized in that, The specific process for treating moderately polluted wastewater in step S2 is as follows: Moderately polluted wastewater is pretreated sequentially by a 5mm screen and a 60° inclined tube sedimentation unit, with a sedimentation time of 1.0–1.5 hours. After pretreatment, the wastewater enters a vertical flow-subsurface flow biochar-bacterial coupled composite wetland. The filler material volume ratio is gravel:volcanic rock:modified biochar:slow-release calcium-based carrier = 3:2:1:0.

5. Native pollution-tolerant plants such as reeds and calamus are planted, and nitrifying bacteria, denitrifying bacteria, and Bacillus are added. The hydraulic load is controlled at 0.15–0.25 m³. 3 / (m 2 •d), stay time 6~8h; straw + polystyrene antifreeze and heat insulation layer is set on the surface of wetland.

7. A method for the separate collection, separate treatment, and separate reuse of rural sewage according to claim 1, characterized in that, The specific process for treating heavily polluted wastewater in step S2 is as follows: Heavily polluted wastewater is first pretreated anaerobically in a three-compartment septic tank before entering a non-powered A / O ecological infiltration bed. The non-powered A / O ecological infiltration bed is filled with a composite filler of modified biochar, volcanic rock, and gravel, and is equipped with a low-temperature resistant ecological filter layer.

8. A method for the separate collection, separate treatment, and separate reuse of rural sewage according to claim 1, characterized in that, The graded reuse described in step S3 is as follows: lightly polluted wastewater is treated and disinfected before being used for road sweeping and toilet flushing; moderately polluted wastewater is treated and disinfected before being used for forest and field irrigation; heavily polluted wastewater is treated and disinfected before being used for public green space irrigation; all reuse pipelines are equipped with anti-seamless one-way valves and conspicuous signs, and are physically isolated from drinking water pipelines; key water quality indicators are tested weekly at the end of the reuse pipeline, including the content of pathogenic bacteria and coliform bacteria.

9. A method for the separate collection, separate treatment, and separate reuse of rural sewage according to claim 1, characterized in that, The intelligent operation and maintenance system described in step S4 is as follows: IoT sensors are set up in each level of processing unit to monitor water level, COD, SS and ammonia nitrogen parameters in real time. The data is transmitted to a village-level simple terminal, which is inspected daily by village-level environmental protection cooperative personnel. The operation and maintenance response time is ≤2 hours.

10. A method for the separate collection, separate treatment, and separate reuse of rural sewage according to claim 1, characterized in that, The specific formula for the sludge temperature control-moisture content-C / N coupled decomposition degree algorithm in step S4 is as follows: ； in, The degree of decay is the index. It was determined to be fully decomposed; This is the normalized value for composting temperature; This is the normalized value for moisture content; This is the normalized value for the carbon-to-nitrogen ratio; The sludge disposal process is as follows: the sludge removal cycle of each treatment unit is 1-2 months. After the sludge is removed, straw and sawdust are added as a conditioner and then composted. The composting temperature is controlled at 55-65℃ and the composting time is 30-35 days. After it is fully decomposed, it is used as farmyard manure.

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