Multistage filter material resourceful treatment system and method for agricultural non-point source nutrient loss

Abstract

The invention discloses a multistage filter material resourceful treatment system for agricultural non-point source nutrient loss, which comprises an oil separation sand setting unit, a hydrolytic acidification unit, at least two contact oxidation units, a secondary precipitation unit, a trickling filtration purification unit, a disinfection unit and a control unit which are arranged in sequence, and each unit is connected with the disinfection unit through a pipeline; and the control unit controls the on-off of the pipeline to realize multi-path selective treatment of the sewage. The oil separation and sand setting unit integrates the functions of sand setting, oil removal and carbon source supplement, the hydrolytic acidification unit decomposes organic pollutants, the contact oxidation unit converts nitrogen and phosphorus forms, the secondary precipitation unit achieves solid-liquid separation, the trickling filtration purification unit deeply removes nitrogen and phosphorus, and the disinfection unit guarantees recycling safety. The system is suitable for distributed scenes through modular design, directional agricultural recycling of raw water, high ammonia nitrogen, high nitrate nitrogen and deeply purified water is achieved through multi-path diversion, the cost is reduced by adopting natural biomass and industrial waste filler, and the system has pollution abatement and nutrient recycling values.

Description

Technical Field

[0001] This invention relates to the field of agricultural non-point source pollution control technology, specifically to a multi-stage filter media resource recovery system and method for treating nutrient loss from agricultural non-point sources. Background Technology

[0002] With the development of the rural economy and the increasing environmental awareness of the people, the treatment of rural domestic sewage has become increasingly important. However, rural sewage treatment faces many challenges. On the one hand, the construction of pipe networks is inadequate, and the phenomenon of combined sewer overflows is common, leading to an imbalance in the carbon-nitrogen ratio of sewage and affecting the treatment effect. On the other hand, sewage discharge is concentrated in certain periods, water quality and quantity fluctuate greatly, and villages are scattered, increasing the difficulty of collection and treatment.

[0003] Currently, most rural wastewater treatment adopts end-of-pipe treatment models copied from urban or industrial practices. Patent publication number CN112374610A describes a biological-ecological coupled rural wastewater treatment device. While this device employs multi-unit staged treatment for low-carbon-nitrogen ratio rural wastewater, using a series of multi-stage hydrolysis tanks, anoxic tanks, and aerobic tanks, along with biological carriers, to achieve nitrogen and phosphorus removal, and is equipped with sludge return pumps, mixed liquor return pumps, and aeration blowers to ensure operation, it has significant shortcomings: First, the cost is too high. The device relies on a series of multi-stage anoxic / aerobic tanks and a sludge return system, requiring multiple power units, resulting in high investment costs and high energy consumption during operation, placing a heavy burden on economically disadvantaged rural areas. Second, resources are not effectively reused. The treatment process focuses only on pollutant removal, failing to convert nutrients such as nitrogen and phosphorus in the wastewater into forms usable by crops, thus failing to achieve wastewater resource reuse and causing resource waste. Third, it has poor adaptability to decentralized rural treatment methods. The equipment structure is relatively complex, requiring professional technicians for maintenance and management, but rural areas lack such technicians, making it difficult to meet their operation and maintenance requirements. At the same time, the installation of multiple power units increases the risk of equipment failure and is not conducive to stable operation in rural decentralized layouts.

[0004] Therefore, how to develop a modular, multi-level resource-based processing system that is low-cost, has high resource utilization, and is suitable for decentralized processing scenarios in rural areas is an urgent problem that needs to be solved. Summary of the Invention

[0005] To address the technical problems existing in the prior art, the first objective of this invention is to provide a multi-stage filter media resource recovery system for agricultural non-point source nutrient loss. Through multi-unit modular integration, graded treatment, and directional diversion, it efficiently removes pollutants such as suspended solids, heavy metals, and organic matter, while converting nitrogen and phosphorus into forms easily absorbed by crops, achieving precise reuse of wastewater nutrients. Simultaneously, it employs natural, low-cost fillers and a gravity flow structure to reduce construction and maintenance costs, making it suitable for rural economic conditions and decentralized treatment needs.

[0006] The second objective of this invention is to provide a method for the multi-stage filter media resource recovery system for agricultural non-point source nutrient loss, as described above. Through multi-step coordinated operation, the treatment path can be flexibly switched according to the influent water quality, crop nutrient requirements, and reuse scenarios. The system sequentially completes pretreatment, biochemical conversion, nitrogen and phosphorus speciation regulation, solid-liquid separation, deep purification, and disinfection and reuse processes. This ensures that the treatment effect meets the standards and achieves graded recovery and precise matching of nitrogen and phosphorus resources. The process is flexible and simple, with low energy consumption, and is suitable for the diverse sewage treatment and reuse needs in rural areas, making up for the shortcomings of existing technologies that are disconnected from resource recovery.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A multi-stage filter media resource recovery system for agricultural non-point source nutrient loss includes: The oil-water separator and grit removal unit is used to remove suspended solids, grease and heavy metals from wastewater and to replenish the wastewater with carbon sources. The hydrolysis acidification unit, located downstream of the oil-water separation and grit removal unit, is used to receive wastewater pretreated by the oil-water separation and grit removal unit, convert large molecular organic matter in the wastewater into small molecular organic matter, and increase the ammonia nitrogen concentration. At least two contact oxidation units are located downstream of the hydrolysis acidification unit to receive wastewater treated by the hydrolysis acidification unit, decompose organic matter in the wastewater, oxidize ammonia nitrogen to nitrate nitrogen, and convert organic phosphorus to inorganic phosphorus. The secondary sedimentation unit, located downstream of the contact oxidation unit, is used to receive the wastewater treated by the contact oxidation unit, thereby achieving solid-liquid separation and removing suspended solids. The trickling filtration purification unit, located downstream of the secondary sedimentation unit, is used to receive the wastewater separated by the secondary sedimentation unit and to deeply remove nitrogen, phosphorus and residual pollutants from the wastewater. The disinfection unit is used to kill harmful pathogens in wastewater and achieve resource recycling. The control unit is connected to the oil-water separator and sand settling unit, the hydrolysis and acidification unit, the contact oxidation unit, the secondary sedimentation unit, the trickling filtration and purification unit, and the disinfection unit, respectively. The oil-water separation and grit removal unit, the hydrolysis and acidification unit, the secondary sedimentation unit, and the trickling filtration purification unit are all connected to the disinfection unit through pipelines. Under the control of the control unit, the wastewater selectively flows through the oil-water separation and grit removal unit, the hydrolysis and acidification unit, the contact oxidation unit, the secondary sedimentation unit, and the trickling filtration purification unit to form multiple treatment paths before entering the disinfection unit.

[0008] According to one example, the oil-water separation and sand-sinking unit includes a first cylinder, and a vertical partition plate is provided inside the first cylinder to divide the internal space of the first cylinder into a sand-sinking chamber and an oil removal and carbon source replenishment chamber. The vertical partition plate extends downward from the top of the first cylinder for a certain length, so that the lower parts of the sand-sinking chamber and the oil removal and carbon source replenishment chamber are connected. The settling chamber is filled with inclined tube packing material. A first water inlet is formed at the upper part of the settling chamber, and a first sludge discharge outlet is formed at the lower part. The first sludge discharge outlet is connected to a sludge return pump through a pipeline. The oil removal and carbon source replenishment chamber is filled with adsorption packing and carbon source release packing. A first water outlet is formed at the top of the oil removal and carbon source replenishment chamber. The first water outlet is used to discharge the treated wastewater to the hydrolysis acidification unit or the disinfection unit.

[0009] According to one example, the adsorption packing is selected from natural biomass adsorption packing, and the carbon source release packing is selected from natural plant-based carbon source packing.

[0010] According to one example, the hydrolysis acidification unit includes a second cylinder, in which a perforated plate is disposed, and composite filler is packed above the perforated plate; The upper part of the second cylinder has a second water inlet, and the lower part has a second water outlet. The second water outlet is used to discharge the treated wastewater to the contact oxidation unit or the disinfection unit.

[0011] According to one example, the contact oxidation unit includes two first contact oxidation modules and a second contact oxidation module arranged in series; The first contact oxidation module includes a third cylinder, the lower part of which forms a third inlet for receiving wastewater from the hydrolysis acidification unit, and the upper part of which forms a third outlet. The first contact oxidation module is filled with a first fixed curtain-type biological rope packing material, and a first aeration pipe is configured at its bottom. The second contact oxidation module includes a fourth cylinder, a fourth inlet connected to the third outlet is formed in the middle of the fourth cylinder, a fourth outlet is formed at the top of the fourth cylinder, and the second contact oxidation module is filled with a second fixed curtain-type biological rope packing material, and a second aeration pipe is configured at the bottom of the second cylinder. The fourth outlet is used to discharge the treated wastewater to the secondary sedimentation unit.

[0012] According to one example, the secondary sedimentation unit includes a fifth cylinder filled with inclined tube packing, a fifth inlet formed at the top for receiving wastewater from the contact oxidation unit, a fifth outlet formed in the middle, and a second sludge discharge outlet formed at the bottom. The fifth outlet is used to discharge the treated wastewater to the trickling filter purification unit or the disinfection unit, and the second sludge discharge port is connected to the sludge return pump through a pipeline.

[0013] According to one example, the trickling filtration purification unit includes a sixth cylinder filled with nitrogen removal packing and phosphorus removal packing arranged vertically, and a water distributor positioned above the nitrogen removal packing. The upper part of the sixth cylinder has a sixth inlet for receiving wastewater from the secondary sedimentation unit, and the lower part has a sixth outlet for discharging the treated wastewater to the disinfection unit.

[0014] According to one example, both the denitrification packing and the dephosphorization packing are synthesized from industrial waste as raw materials, the particle size of the denitrification packing is 50-100 mm, and the particle size of the dephosphorization packing is 30-80 mm.

[0015] According to one example, the disinfection unit includes a tank body with at least one ultraviolet irradiation lamp disposed on the upper part of the tank body, and a seventh inlet and a seventh outlet formed on its side wall, the seventh inlet being used to receive wastewater from the oil-water separation and grit removal unit, the hydrolysis acidification unit, the secondary sedimentation unit or the trickling filtration purification unit.

[0016] A method for utilizing the above-mentioned multi-stage filter media resource recovery system for agricultural non-point source nutrient loss includes the following steps: Wastewater is treated by the oil-water separation and grit removal unit to remove suspended solids, grease and heavy metals, and a carbon source is added. The pretreated wastewater is then selectively discharged into the hydrolysis acidification unit or the disinfection unit. Wastewater pretreated by the oil-water separation and grit removal unit is discharged into the hydrolysis and acidification unit to convert macromolecular organic matter and increase ammonia nitrogen concentration. High ammonia nitrogen wastewater is selectively discharged into the contact oxidation unit or the disinfection unit. The wastewater treated by the hydrolysis acidification unit flows through the contact oxidation unit, where organic matter is decomposed and ammonia nitrogen is converted into nitrate nitrogen and organic phosphorus is converted into inorganic phosphorus. Then, solid-liquid separation is carried out in the secondary sedimentation unit, and high-nitrate nitrogen wastewater is selectively discharged into the trickling filtration purification unit or the disinfection unit. The wastewater treated by the secondary sedimentation unit is discharged into the trickling filtration purification unit, where nitrogen, phosphorus and residual pollutants are deeply removed before being discharged into the disinfection unit. After being disinfected, the wastewater discharged into the disinfection unit is directed to different agricultural irrigation scenarios according to the reuse needs.

[0017] The present invention has the following advantages: This invention presents a multi-stage filter media resource recovery system for agricultural non-point source nutrient loss. Through the coordinated operation of multiple units, it removes pollutants while simultaneously converting nitrogen and phosphorus into forms easily absorbed by crops. This allows for the targeted reuse of water bodies with high ammonia nitrogen levels in farmland, achieving the resource recovery of wastewater nutrients. Existing technologies, however, only address wastewater purification and do not involve the recovery and utilization of nitrogen and phosphorus resources.

[0018] Using natural, low-cost fillers such as pine bark and corn cobs, the trickling filtration purification unit employs a gravity flow structure, reducing the need for power equipment and lowering construction and maintenance costs. Furthermore, the fillers can be replaced as needed, adapting to rural economic conditions and maintenance capabilities. Existing technologies rely on multiple power devices, resulting in high equipment investment and energy consumption costs, making them difficult to promote in rural areas.

[0019] This system constructs four wastewater treatment pathways, which can be adjusted according to water quality and reuse requirements. Each unit uses replaceable, compounded, segmented filling materials, enhancing the targeted treatment and system adaptability. Existing technologies do not have this design, making it more suitable for decentralized treatment scenarios in rural areas with diverse water needs and large fluctuations in water quality. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the multi-stage filter media resource recovery system for agricultural non-point source nutrient loss according to the present invention.

[0021] Figure 2 This is a schematic diagram of the structural process of the multi-stage filter media resource recovery system for agricultural non-point source nutrient loss according to the present invention.

[0022] Figure 3 This is a top view of the oil-separating and sand-separating unit of the present invention.

[0023] Figure 4 yes Figure 3 The structural cross-section of the oil-separating and sand-separating unit along the AA direction.

[0024] Figure 5 yes Figure 3 The cross-sectional view of the oil-water separator and sand-separating unit along the BB direction.

[0025] Figure 6 This is a schematic diagram of the hydrolysis acidification unit of the present invention.

[0026] Figure 7 This is a schematic diagram of the contact oxidation unit of the present invention.

[0027] Figure 8 This is a schematic diagram of the secondary precipitation unit of the present invention.

[0028] Figure 9 This is a schematic diagram of the structure of the trickling filtration purification unit of the present invention.

[0029] Figure 10 This is a schematic diagram of the disinfection unit of the present invention.

[0030] Figure 11 This is a schematic flowchart of the multi-stage filter media resource utilization method for agricultural non-point source nutrient loss according to the present invention.

[0031] Among them, 1 is the oil-water separation and sedimentation unit, 101 is the first cylinder, 102 is the vertical partition plate, 101a is the sedimentation chamber, 101a1 is the first water inlet, 101a2 is the first sludge discharge port, 101b is the oil removal and carbon source replenishment chamber, 101b1 is the first water outlet, and 101b2 is the water collection box; 2 is the hydrolysis and acidification unit, 201 is the second cylinder, 201a is the second water inlet, 201b is the second water outlet, 202 is the orifice plate, and 203 is the composite packing; 3 is the contact oxidation unit, 301 is the first contact oxidation module, 301a is the third cylinder, 301a1 is the third water inlet, 301a2 is the third water outlet, 301b is the first fixed curtain-type biological rope packing, 301c is the first aeration pipe, and 302 is the second contact oxidation module. The oxidation module consists of: 302a (fourth cylinder), 302a1 (fourth inlet), 302a2 (fourth outlet), 302b (second fixed curtain-type biological rope packing), 302c (second aeration pipe), 4 (secondary sedimentation unit), 401 (fifth cylinder), 401a (fifth inlet), 401b (fifth outlet), 401c (second sludge discharge port), 5 (trickling filtration purification unit), 501 (sixth cylinder), 501a (sixth inlet), 501b (sixth outlet), 502 (water distributor), 6 (disinfection unit), 601 (tank), 601a (seventh inlet), 601b (seventh outlet), 602 (ultraviolet irradiation lamp), 7 (control unit), 8 (sludge return pump), 9 (air pump), a (sewage pipe), and b (sludge discharge pipe). Detailed Implementation

[0032] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0033] Reference Figure 1 and Figure 2This paper illustrates a specific embodiment of a multi-stage filter media resource recovery system for agricultural non-point source nutrient loss. The system generally includes, in sequence, an oil-water separation and sand settling unit 1, a hydrolysis and acidification unit 2, at least two contact oxidation units 3, a secondary sedimentation unit 4, a trickling filtration purification unit 5, and a disinfection unit 6, as well as a control unit 7 electrically connected to each treatment unit. The system adopts an integrated design and can be installed on a mobile carrier, a fixed integrated cabinet, or a modular assembly, compactly arranging the functional units to form a well-structured overall device. This not only reduces the footprint and facilitates transportation and installation but also better adapts to the needs of decentralized rural wastewater treatment. Through reasonable water flow connections between the units, continuous and efficient wastewater treatment is achieved, reducing overall construction costs.

[0034] In one embodiment, the units of this system can be arranged in a spatial layout with vertical layers and compact horizontal arrangement. For example, the oil-water separation and sand settling unit and the hydrolysis acidification unit can be arranged side by side, the contact oxidation unit and the secondary sedimentation unit can be connected one after the other, and the trickling filtration purification unit and the disinfection unit can be stacked one on top of the other. It can be directly placed on a simple concrete base or a mobile trailer without complex civil engineering. Addressing the dispersed nature of rural sewage collection, the system adopts a local treatment and reuse model, reducing leakage and energy consumption during sewage transportation. Furthermore, the number of devices can be flexibly increased or decreased according to the distribution of villages, forming a multi-point distributed treatment network. Compared to traditional centralized treatment facilities, this reduces pipeline construction costs and operation and maintenance difficulties.

[0035] Reference Figure 1-5 It shows a preferred embodiment of an oil-water separation and grit removal unit 1, which is used to remove suspended solids, grease and heavy metals from sewage and replenish carbon sources to sewage, laying the water quality foundation for subsequent biochemical treatment processes, and also providing the preconditions for sewage diversion and reuse.

[0036] The oil-water separator and grit removal unit 1 includes a first cylindrical body 101. A vertical partition plate 102, made of PPR, is located in the middle of the interior of the first cylindrical body 101, dividing the internal space into a grit removal chamber 101a on the left and an oil removal and carbon source replenishment chamber 101b on the right. A fiberglass support plate, in a grid pattern, is located at the bottom of the first cylindrical body 101, with a preferred distance of 400 mm between the fiberglass support plate and the bottom of the first cylindrical body 101. The vertical partition plate 102 extends downwards from the top of the first cylindrical body 101 for a certain length, with a height of 1000 mm. The preferred distance between its bottom and the fiberglass support plate is 100 mm. This gap allows the grit removal chamber 101a to connect with the lower part of the oil removal and carbon source replenishment chamber 101b, ensuring that wastewater, after grit removal treatment, can flow naturally to subsequent functional areas without additional power, simplifying the structure and reducing energy consumption.

[0037] The settling chamber 101a is filled with honeycomb inclined tube packing material made of polypropylene. Each packing tube has a regular hexagonal cross-section with an inscribed circle diameter of 50-80 mm, and they are arranged at a 60° angle to the horizontal, forming a parallel inclined plate structure to improve the settling efficiency of suspended solids. A clear water zone, preferably 200 mm high, is formed above the packing layer to prevent water flow disturbance from affecting the settling effect. A first inlet 101a1 is formed at the top of the settling chamber 101a. The distance between the first inlet 101a1 and the fiberglass support plate is preferably 980 mm. It is directly connected to the farmer's septic tank via a sewage lift pump to achieve directional sewage introduction. The lower part of the settling chamber 101a corresponds to the area below the fiberglass support plate. A first sludge discharge port 101a2 for discharging sludge is provided at the bottom of the first cylinder 101. The distance between the first sludge discharge port 101a2 and the bottom of the first cylinder 101 is preferably 190 mm. The first sludge discharge port 101a2 is connected to the external sludge return pump 8 through the sludge discharge pipe b. The sludge discharge pipe b is made of PVC material and is used to periodically discharge large particles of sludge and gravel that have settled to the bottom, to prevent sludge accumulation and blockage from affecting the operation of the unit, and at the same time to avoid hard impurities from impacting the subsequent biochemical unit.

[0038] The oil removal and carbon source replenishment chamber 101b is filled with adsorption packing and carbon source release packing. The adsorption packing is made of natural biomass such as pine bark, which is used to efficiently adsorb heavy metal ions in wastewater. The carbon source release packing is made of natural plant-based carbon source packing such as ordinary corn cobs, which releases carbon source through slow degradation, alleviating the problem of low carbon-to-nitrogen ratio commonly found in rural domestic wastewater and optimizing subsequent biochemical reaction conditions. In one embodiment, a maintenance port with a diameter of 500 mm is provided on the side wall of the grit chamber 101a. The maintenance port is sealed with a blind flange, and its installation position is 850 mm away from the bottom of the first cylinder 101.

[0039] The upper part of the oil removal and carbon source replenishment chamber 101b has a first outlet 101b1. The distance between the first outlet 101b1 and the fiberglass support plate is preferably 975 mm. It is equipped with a detachable water collection box 101b2 with a slag baffle to intercept floating oil and a small amount of residual suspended solids, further improving the quality of the effluent. The first outlet 101b1 is connected to the downstream hydrolysis acidification unit 2 and disinfection unit 6 through a PVC sewage pipe a. A PVC tee and a PVC ball valve are installed in the middle of the connecting pipe, and the pipe is connected to the disinfection unit 6 through the sewage pipe a, forming a diversion path for direct reuse of the pretreated raw water.

[0040] Domestic sewage is pumped from the first inlet 101a1 into the left-side grit chamber 101a via a sewage lift pump. Under the action of the honeycomb inclined tube packing, large particles settle rapidly by gravity. The sediment collects below the fiberglass support plate and is periodically discharged through the sludge discharge pipe b and the sludge return pump 8. After grit treatment, the sewage flows through the gap at the bottom of the vertical partition plate 102 into the right-side oil removal and carbon source replenishment chamber 101b. It then undergoes heavy metal adsorption by pine bark packing and carbon source replenishment by corn cob packing, while simultaneously achieving natural separation of floating oil. The final treated sewage can be distributed via two paths: if further treatment is required, it is discharged to the hydrolysis acidification unit 2 via the first outlet 101b1; if direct reuse is required, it is switched to the disinfection unit 6 via a three-way pipeline, where it is sterilized and its nutrients are retained for agricultural irrigation.

[0041] Reference Figure 1 and Figure 6 The illustration shows a preferred embodiment of the hydrolysis acidification unit 2, which is located downstream of the oil-water separation and grit removal unit 1. It is used to receive wastewater that has been pretreated by the oil-water separation and grit removal unit 1, convert large molecular organic matter in the wastewater into small molecular organic matter, and increase the ammonia nitrogen concentration. The subsequent deep treatment of the contact oxidation unit 3 optimizes the water quality conditions and enables the targeted agricultural reuse of high ammonia nitrogen water bodies, thereby enhancing the resource value of the system.

[0042] The hydrolysis acidification unit 2 includes a second cylindrical body 201, inside which a perforated plate 202 is installed, and a composite filler 203 is filled above the perforated plate 202. A grid-like fiberglass support plate is installed at the bottom of the second cylindrical body 201, with a preferred distance of 400 mm between the fiberglass support plate and the bottom of the second cylindrical body 201. The composite filler 203, which is spherical in shape, is filled above the fiberglass support plate; its core is made of modified polyurethane, and its outer shell is made of polypropylene.

[0043] The second inlet 201a is located at the upper part of the second cylinder 201, with a preferred distance of 975 mm between it and the fiberglass support plate. It is connected to the first outlet 101b1 of the oil-water separator and grit removal unit 1 via a PVC sewage pipe a, ensuring that the pretreated sewage can flow evenly from top to bottom into the packing layer for full contact and reaction with microorganisms. The second outlet 201b is located below the fiberglass support plate, with a preferred distance of 100 mm between it and the fiberglass support plate. One end of the PVC sewage pipe a connected to the second outlet 201b is connected to the downstream contact oxidation unit 3. A PVC tee and a PVC ball valve are installed in the middle of the pipe, and it is also connected to the disinfection unit 6 via the sewage pipe a, forming a path for direct reuse of high ammonia nitrogen water and realizing flexible switching of the treatment process.

[0044] Wastewater pretreated by the oil-water separator and grit removal unit 1 is introduced into the second cylinder 201 through the second inlet 201a, and flows downward through the composite packing 203. The modified polyurethane material in the core of the composite packing 203 adsorbs a large number of hydrolytic acidifying microorganisms. These microorganisms decompose large organic molecules such as starch and protein in the wastewater into small organic acids through anaerobic metabolism, improving the biodegradability of the wastewater and laying the foundation for the organic matter degradation process in the subsequent contact oxidation unit 3. At the same time, ammonia nitrogen is released during the decomposition of nitrogen-containing organic matter by microorganisms, increasing the ammonia nitrogen concentration in the wastewater and forming a high-ammonia nitrogen water body suitable for the needs of specific crops. At this time, the pipeline ball valve can be adjusted by the control unit 7 according to the actual reuse needs. If further treatment is required, the wastewater is discharged to the contact oxidation unit 3 through the second outlet 201b. If targeted agricultural reuse is required, the three-way pipeline is switched to allow the wastewater to flow into the disinfection unit 6. After sterilization, it is used for irrigation of crops with high nitrogen requirements such as leafy vegetables, realizing the targeted reuse of high-ammonia nitrogen water bodies in farmland and improving resource utilization efficiency.

[0045] Reference Figure 1 and Figure 7 It shows a preferred embodiment of the contact oxidation unit, wherein at least two contact oxidation units 3 include two contact oxidation units 3 arranged in series, which are located downstream of the hydrolysis acidification unit 2 for receiving wastewater treated by the hydrolysis acidification unit 2, decomposing organic matter in the wastewater, oxidizing ammonia nitrogen to nitrate nitrogen, and converting organic phosphorus to inorganic phosphorus.

[0046] The contact oxidation unit 3 includes two first contact oxidation modules 301 and second contact oxidation modules 302 arranged in series, with the arrangement optimized according to the hydraulic residence time. The first contact oxidation module 301 is arranged to the right of the hydrolysis acidification unit 2, and the second contact oxidation module 302 is arranged behind the first contact oxidation module 301.

[0047] The first contact oxidation module 301 includes a third cylinder 301a. The lower part of the third cylinder 301a has a third inlet 301a1 for receiving wastewater from the hydrolysis acidification unit 2, and the upper part has a third outlet 301a2. The first contact oxidation module 301 is filled with a first fixed curtain-type biological rope packing material 301b, and a first aeration pipe 301c is disposed at its bottom. In this embodiment, the first fixed curtain-type biological rope packing material 301b filled inside the third cylinder 301a is made of polyethylene-polypropylene composite fiber, with a single fiber diameter of 0.1-0.3 mm and a spacing of 20-30 mm between adjacent curtains. A first aeration pipe 301c is installed below the packing material, extending from the top to the bottom of the third cylinder 301a. It is linked with the aeration blower and air pump 9 in the external electrical cabinet, and the aeration rate is maintained at 3-5 m³ / (m²・h) to ensure a stable dissolved oxygen concentration of 2-4 mg / L in the reaction zone within the module. A third inlet 301a1 is located at the bottom of the third cylinder 301a, preferably 300 mm away from the bottom. It is connected to the second outlet 201b of the hydrolysis acidification unit 2 via a PVC sewage pipe a, enabling low-level introduction and uniform water distribution of sewage. A third outlet 301a2 is located at the top of the third cylinder 301a, preferably 1370 mm away from the bottom, facilitating the overflow of sewage from top to bottom to the next module after sufficient reaction.

[0048] The second contact oxidation module 302 includes a fourth cylinder. A fourth inlet, connected to the third outlet 301a2, is formed in the middle of the fourth cylinder. A fourth outlet is formed at the top of the fourth cylinder. The second contact oxidation module 302 is filled with a second fixed curtain-type biological rope packing material 302b, and a second aeration pipe 302c is arranged at its bottom. In this embodiment, the interior of the fourth cylinder is filled with the second fixed curtain-type biological rope packing material 302b, whose material and specifications are the same as those of the first contact oxidation module 301. The second aeration pipe 302c arranged at the bottom of the fourth cylinder is also linked to the external aeration system to maintain the same aeration volume and dissolved oxygen concentration standards as the first module. The fourth inlet is located in the middle of the fourth cylinder, preferably 500 mm from the bottom of the fourth cylinder. It is connected to the third outlet 301a2 of the first contact oxidation module 301 through a pipeline, allowing wastewater to be introduced from the middle of the fourth cylinder, extending the contact time with the packing layer and enhancing the nitrogen and phosphorus conversion effect. The fourth outlet is located at the top of the fourth cylinder, and the distance between it and the bottom of the fourth cylinder is preferably 1365 mm. It is connected to the downstream secondary sedimentation unit 4 through PVC sewage pipe a, so that the sewage after two-stage oxidation conversion is introduced into the solid-liquid separation process.

[0049] Wastewater treated by the hydrolysis and acidification unit 2 enters the lower part of the first contact oxidation module 301 through the third inlet 301a1. Driven by the aeration system, it flows upward along the gaps in the bio-rope packing, forming a fully mixed gas-liquid-solid reaction environment. In the biofilm attached to the packing surface, heterotrophic microorganisms efficiently decompose organic matter such as COD and BOD in the wastewater through aerobic metabolism, achieving an organic matter removal rate of over 85%. Under suitable dissolved oxygen conditions, nitrifying bacteria in the inner layer of the biofilm gradually oxidize ammonia nitrogen in the wastewater to nitrite nitrogen, and finally convert it into nitrate nitrogen. At the same time, polyphosphate-accumulating bacteria simultaneously absorb and store inorganic phosphorus produced from the decomposition of organic phosphorus in the wastewater, realizing the directional conversion of nitrogen and phosphorus forms into nitrate nitrogen and inorganic phosphorus that are easily absorbed by crops.

[0050] After preliminary treatment by the first contact oxidation module 301, the wastewater overflows through the third outlet 301a2 to the fourth inlet of the second contact oxidation module 302. Entering from the middle of the fourth cylinder, it continues to flow upwards, completing deep oxidation treatment under the same operating conditions. This further improves the organic matter removal rate and nitrogen-phosphorus conversion efficiency, ensuring that the effluent quality meets the requirements for subsequent reuse. Finally, the wastewater, after two stages of series treatment, is discharged through the fourth outlet to the secondary sedimentation unit 4 for solid-liquid separation, laying the foundation for subsequent reuse or deep purification of high-nitrate nitrogen water. Furthermore, the number of contact oxidation units 3 can be configured as needed, such as three, four, six, etc.

[0051] Reference Figure 1 and Figure 8 It shows a preferred embodiment of a secondary sedimentation unit 4, which is located downstream of the contact oxidation unit 3 and is used to receive wastewater treated by the contact oxidation unit 3. Solid-liquid separation is achieved through gravity sedimentation and inclined tube packing to remove suspended solids.

[0052] The secondary sedimentation unit 4 includes a fifth cylinder 401, which is arranged on the left side of the second contact oxidation module 302. The bottom of the fifth cylinder 401 is provided with a second sludge discharge port 401c, and the distance between the port and the bottom of the fifth cylinder 401 is preferably 190 mm. It is connected to the external sludge return pump 8 through the sludge discharge pipe b. The bottom of the fifth cylinder 401 is provided with a grid-like fiberglass support plate, and the distance between the fiberglass support plate and the bottom of the fifth cylinder 401 is preferably 400 mm.

[0053] The fifth cylinder 401 is filled with inclined tube packing material, specifically honeycomb inclined tube packing made of polypropylene. Each packing tube has a regular hexagonal cross-section with an inscribed circle diameter ranging from 50 to 80 mm, and they are uniformly arranged at a 60° angle to the horizontal, forming a parallel inclined plate structure. Simultaneously, the inclined tube packing layer occupies 60%-70% of the effective depth of the fifth cylinder 401, and a clear water zone with a preferred height of 200 mm is reserved above the packing layer.

[0054] The fifth inlet 401a is located at the top of the fifth cylinder 401, with a preferred distance of 1365 mm from the fiberglass support plate. It is connected to the fourth outlet of the second contact oxidation module 302 via PVC sewage pipe a, allowing the oxidized sewage to enter the cylinder from top to bottom and flow evenly through the inclined tube packing layer. The fifth outlet 401b is located in the middle of the fifth cylinder 401, with a preferred distance of 900 mm from the bottom of the fifth cylinder 401, corresponding to the lower part of the clear water zone. One end of the PVC sewage pipe a connected to the fifth outlet 401b is connected to the downstream trickling filter purification unit 5. A PVC tee and a PVC ball valve are installed in the middle of the pipe, and it is also connected to the disinfection unit 6 via sewage pipe a, forming a direct reuse path for high-nitrate nitrogen water and enabling flexible switching of the treatment process.

[0055] Wastewater treated by contact oxidation unit 3 is introduced into the top of the fifth cylinder 401 through the fifth inlet 401a, and flows evenly from top to bottom through the honeycomb inclined tube packing layer. Under gravity, suspended solids, detached biofilm, and other impurities in the water slide down the inner wall of the inclined tubes to the sludge collection area below the support plate, and gradually collect at the second sludge discharge port 401c. The sludge is then periodically discharged through the sludge discharge pipe b and the sludge return pump 8, ensuring the continuous and stable operation of the unit and recovering nutrients from the sludge. The clarified water rises through the packing layer to the upper clear water area, and is then discharged through the fifth outlet 401b in the middle, completing the solid-liquid separation process.

[0056] For further deep removal of nitrogen and phosphorus, the clean water is discharged to the trickling filter purification unit 5 through the pipeline. If targeted reuse is required, the three-way pipeline is switched to allow the clean water to flow into the disinfection unit 6. After sterilization, it is used for irrigation of fruit trees and other crops with high demand for nitrate nitrogen, meeting the differentiated needs of different crop growth stages for nitrogen forms and realizing the precise resource reuse of wastewater nutrients.

[0057] Reference Figure 1 and Figure 9 It shows a preferred embodiment of a trickling filtration purification unit 5, which is located downstream of the secondary sedimentation unit 4 and is used to receive wastewater separated by the secondary sedimentation unit 4, and to deeply remove nitrogen, phosphorus and residual pollutants from the wastewater.

[0058] The trickling filtration purification unit 5 includes a sixth cylinder 501, which is arranged on the left side of the secondary sedimentation unit 4. A grid-shaped fiberglass support plate is provided at the lower part of the sixth cylinder 501, and the distance between the fiberglass support plate and the bottom of the sixth cylinder 501 is preferably 400 mm.

[0059] The sixth cylinder 501 is filled with denitrification and dephosphorization packing arranged vertically. The upper denitrification packing is synthesized from industrial waste such as steel slag, iron slag, pumice, clay, and ferrous sulfate, with a particle size controlled at 50-100 mm and a thickness of 300 mm. The lower dephosphorization packing is synthesized from industrial waste such as fly ash, magnesium oxide, and calcium chloride, with a particle size of 30-80 mm and a thickness of 300 mm.

[0060] A water distributor 502 is installed at the top of the sixth cylinder 501, preferably a spray coil. A sixth inlet 501a is located at the top of the sixth cylinder 501, with a preferred distance of 960 mm between it and the fiberglass support plate. It is connected to the fifth outlet 401b of the secondary sedimentation unit 4 via a PVC sewage pipe a. After being introduced through the sixth inlet 501a, the sewage is evenly sprayed onto the surface of the top-layer denitrification packing by gravity flow from the water distributor 502, ensuring that the sewage permeates evenly through the two-stage packing layers from top to bottom, achieving sufficient contact and reaction with the packing. The sixth outlet 501b is located below the fiberglass support plate, with a preferred distance of 120 mm between it and the support plate, corresponding to the water collection space at the bottom of the sixth cylinder 501. It is connected to the disinfection unit 6 via sewage pipe a, allowing the deeply treated clean water to flow naturally into the disinfection unit 6.

[0061] The clarified wastewater, after solid-liquid separation in the secondary sedimentation unit 4, is introduced into the top of the sixth cylinder 501 through the sixth inlet 501a. It is then evenly dispersed onto the surface of the denitrification packing layer by the water distributor 502, and slowly seeps downwards under gravity, flowing sequentially through the denitrification and dephosphorization packing. When the wastewater comes into contact with the denitrification packing, the industrial waste-synthesized packing efficiently captures residual nitrogen in the water through physical adsorption and chemical complexation, achieving deep nitrogen removal. Subsequently, the wastewater permeates into the dephosphorization packing layer, where the packing converts phosphorus in the water into precipitates through chemical conversion reactions, which are then adsorbed and fixed. Simultaneously, the two-stage packing also assists in removing residual COD and other organic matter in the wastewater, further purifying the water quality. The purified water, after treatment by the two-stage packing, is finally discharged to the disinfection unit 6 through the sixth outlet 501b. After sterilization, it can be widely reused in agriculture or discharged ecologically.

[0062] Reference Figure 1 and Figure 10This document illustrates a preferred embodiment of a disinfection unit 6, used to kill harmful pathogens in wastewater and achieve resource recovery. The disinfection unit 6 includes a rectangular tank 601 with dimensions of 0.8 meters long, 0.6 meters wide, and 0.5 meters high, corresponding to an effective volume of 0.24 cubic meters. Combined with the system's 10-ton / day processing capacity, this allows the hydraulic retention time of wastewater within the tank to be stably maintained at 35 minutes. At least one ultraviolet lamp 602 is installed at the top of the tank 601 to irradiate the wastewater, killing bacteria, viruses, and other harmful microorganisms. The sidewall of the tank 601 forms a seventh inlet 601a and a seventh outlet 601b. The seventh inlet 601a is connected via corresponding pipes to an oil-water separation and grit removal unit 1, a hydrolysis and acidification unit 2, a secondary sedimentation unit 4, and a trickling filtration purification unit 5, respectively, and can receive wastewater treated through different pathways.

[0063] Wastewater from each pre-treatment unit is collected through corresponding pipelines to the seventh inlet 601a and introduced into the rectangular disinfection tank 601. The wastewater flows slowly within the tank 601 according to a preset hydraulic retention time. Simultaneously, the ultraviolet lamps 602 at the top of the tank 601 continuously operate, providing all-around ultraviolet disinfection of the wastewater, effectively killing harmful microorganisms and ensuring the safety and hygiene of the effluent. The disinfected water is then discharged through the seventh outlet 601b. Depending on the specific treatment route requirements, the disinfected water is directed to irrigation networks or ecological ditches, achieving flexible adaptation to different operating conditions.

[0064] Return to reference Figure 1The control unit 7 is electrically connected to the oil-water separation and grit removal unit 1, the hydrolysis and acidification unit 2, the contact oxidation unit 3, the secondary sedimentation unit 4, the trickling filtration purification unit 5, and the disinfection unit 6, respectively. In embodiments not shown, the hardware is a programmable logic controller (PLC), equipped with an operation panel, a signal acquisition module, a relay drive module, and a power supply module, integrated in an independent control box. The control unit 7 is electrically connected to the wastewater lift pump, sludge return pump 8, and the switching valves on wastewater pipe a and sludge discharge pipe b of the oil-water separation and grit removal unit 1, allowing for adjustment of the wastewater introduction rate, sludge discharge cycle, and the flow direction switching of pretreated wastewater. It is linked with the switching valves on the pipeline of the hydrolysis and acidification unit 2 to achieve path switching between high ammonia nitrogen water diversion and reuse and subsequent treatment. It is electrically connected to the aeration blower and air pump 9 of the contact oxidation unit 3, allowing for adjustment of the aeration volume to maintain the dissolved oxygen concentration in the reaction zone within a preset range, ensuring the effectiveness of organic matter degradation and nitrogen and phosphorus form conversion. It is connected to the switching valves on the pipeline of the secondary sedimentation unit 4 to regulate the sludge discharge cycle and the diversion of high nitrate nitrogen water. The trickling filtration purification unit 5 has no additional power actuators; it mainly ensures the stability of wastewater infiltration treatment indirectly through the switching valves on the linkage pipeline. It is electrically connected to the ultraviolet irradiation lamp 602 of the disinfection unit 6 and the switching valves on the pipeline to control the start and stop of the disinfection equipment and the switching of the reuse / discharge path of the disinfected water.

[0065] In addition, the control unit 7 is also equipped with sensing components, which may include dissolved oxygen sensor, ammonia nitrogen sensor, nitrate nitrogen sensor and flow sensor, to collect key water quality and operating parameters of each unit in real time and feed them back to the PLC module to realize automatic control.

[0066] In one embodiment, the oil-water separation and grit removal unit 1, the hydrolysis and acidification unit 2, the secondary sedimentation unit 4, and the trickling filtration purification unit 5 are all connected to the disinfection unit 6 through pipelines. The control unit 7 controls the valve group to open and close and switch paths, so that the sewage selectively flows through the oil-water separation and grit removal unit 1, the hydrolysis and acidification unit 2, the contact oxidation unit 3, the secondary sedimentation unit 4, and the trickling filtration purification unit 5 to form multiple treatment paths before entering the disinfection unit 6, ultimately adapting to different reuse needs in different scenarios. The main treatment paths include the following four.

[0067] Firstly, the raw water direct disinfection line: the effluent (raw water) from the septic tank of farmers is pre-treated by the oil and sand separator unit 1, which performs sand removal, oil removal, heavy metal adsorption and carbon source replenishment. Then, the pipeline valve group is switched by the control unit 7 and directly connected to the disinfection unit 6 to remove suspended impurities, toxic and harmful substances and harmful microorganisms from the sewage. It is suitable for scenarios where the water quality requirements are not high and water is urgently needed, such as field crop irrigation, forest irrigation and other areas with low water quality sensitivity. It can quickly provide water to crops and at the same time play a certain disinfection role, ensuring that the crop growth environment is relatively safe.

[0068] Secondly, in the high ammonia nitrogen irrigation line, the effluent from the septic tank, after pretreatment by the oil-water separation and grit removal unit 1, is introduced into the hydrolysis and acidification unit 2 for biochemical transformation. Through the metabolic action of microorganisms attached to the composite packing material 203, the recalcitrant large-molecule organic matter in the wastewater is decomposed into easily biodegradable small-molecule organic acids, improving the biodegradability of the wastewater. Simultaneously, ammonia nitrogen from the nitrogen-containing organic matter is released, significantly increasing the ammonia nitrogen concentration in the effluent. The high ammonia nitrogen wastewater after hydrolysis and acidification is connected to the disinfection unit 6 via the switching valve group of the control unit 7. After sterilization, it is specifically used for irrigation of leafy vegetables, bok choy, and other crops with high ammonia nitrogen requirements. This provides sufficient nitrogen nutrition for crops, promotes crop growth, and enables the targeted reuse of high ammonia nitrogen water in farmland, improving resource utilization efficiency.

[0069] Thirdly, in the nitrate nitrogen irrigation line, septic tank effluent undergoes pretreatment via an oil-water separation and grit removal unit 1, followed by organic matter degradation and ammonia nitrogen release via a hydrolysis and acidification unit 2. It is then introduced into a two-stage, series-connected contact oxidation unit 3. Under the synergistic effect of an aerobic environment and bio-rope packing, heterotrophic microorganisms degrade the remaining organic matter, nitrifying bacteria oxidize ammonia nitrogen to nitrate nitrogen, and polyphosphate-accumulating bacteria simultaneously convert phosphorus into inorganic phosphorus. The wastewater then enters a secondary sedimentation unit 4, where solid-liquid separation is achieved through honeycomb inclined tube packing, removing detached biofilm and suspended solids while retaining high concentrations of nitrate nitrogen and inorganic phosphorus nutrients. Controlled by a control unit 7, high-nitrate nitrogen wastewater is directly connected to a disinfection unit 6 for further treatment and targeted reuse in orchards, fruit and vegetable plantations, and other similar settings. This meets the differentiated nitrogen requirements of crops at different growth stages, achieving precise resource-based wastewater reuse.

[0070] Fourthly, the deep purification line: after septic tank effluent undergoes oil-water separation, sand removal, hydrolysis acidification, contact oxidation, and secondary sedimentation, it is introduced into the trickling filter purification unit 5. The effluent permeates downwards through two stages of industrial waste-based synthetic packing material. The upper layer of nitrogen-removing packing removes residual nitrogen through physical adsorption and chemical complexation, while the lower layer of phosphorus-removing packing removes phosphorus through chemical conversion and precipitation. Simultaneously, it assists in removing residual COD and other pollutants, achieving deep wastewater purification. The treated wastewater, meeting standards, is then introduced into the disinfection unit 6. After sterilization, it can be used for rural landscaping, greenhouse vegetable irrigation, and livestock drinking water replenishment—scensus applications with stringent water quality requirements. This achieves deep wastewater purification and resource reuse, meeting the water needs of different rural scenarios and improving the efficiency of water resource recycling.

[0071] Reference Figure 11 This application also provides a method for utilizing the above-mentioned multi-stage filter media resource recovery system for agricultural non-point source nutrient loss, comprising the following steps: S1. Pretreatment and primary diversion: The effluent (raw water) from the farmer's septic tank is pumped into the oil-water separation and grit removal unit 1 via a sewage lift pump. In the grit removal chamber 101a, under the action of the honeycomb inclined tube packing, large suspended solids, silt, and gravel in the water are removed by gravity. Subsequently, the sewage flows through the gap at the bottom of the vertical partition plate 102 into the oil removal and carbon source replenishment chamber 101b. Natural biomass adsorption packing adsorbs heavy metals and traps floating oil, while plant-based carbon source packing slowly releases carbon sources to alleviate the problem of a low carbon-to-nitrogen ratio in the sewage, thus completing the pretreatment. The control unit 7 adjusts the pipeline valve group to achieve primary diversion based on the influent water quality and reuse requirements. If only basic treatment and emergency reuse are needed, the pretreated sewage is directly discharged into the disinfection unit 6. If further biochemical transformation and nutrient enrichment are required, it is discharged into the hydrolysis and acidification unit 2.

[0072] S2, biochemical conversion and secondary diversion: Wastewater pretreated by the oil-water separation and sedimentation unit 1 is introduced into the hydrolysis and acidification unit 2, and flows downward through the composite packing material 203. Relying on the anaerobic metabolism of microorganisms attached to the surface of the packing material, the recalcitrant large-molecule organic matter in the wastewater is converted into easily biodegradable small-molecule organic acids, improving the biodegradability of the wastewater. At the same time, nitrogen-containing organic matter is decomposed to release ammonia nitrogen, making the wastewater form a high-ammonia nitrogen water body. The control unit 7 performs secondary diversion regulation according to the crop nutrient requirements and water quality test data. If it is used for irrigation of leafy vegetables and other crops that require ammonia nitrogen, the high-ammonia nitrogen wastewater is directly discharged into the disinfection unit 6. If it is necessary to convert the nitrogen form to suit other crops, it is discharged into the contact oxidation unit 3.

[0073] S3. Nitrogen and phosphorus form conversion treatment: High ammonia nitrogen wastewater enters the two-stage series contact oxidation unit 3. Under the aerobic environment maintained by the aeration system, the wastewater flows along the gaps in the bio-rope packing material, making full contact with the biofilm on the packing surface. Heterotrophic microorganisms in the biofilm aerobically decompose the remaining organic matter, while nitrifying bacteria gradually oxidize ammonia nitrogen into nitrite nitrogen, and finally into nitrate nitrogen. At the same time, polyphosphate-accumulating bacteria absorb and store the inorganic phosphorus produced from the decomposition of organic phosphorus in the wastewater, realizing the directional conversion of nitrogen and phosphorus forms into nitrate nitrogen and inorganic phosphorus that are easily absorbed by crops, further purifying the water quality.

[0074] S4. Solid-liquid separation and three-stage diversion: Wastewater treated by contact oxidation unit 3 is introduced into secondary sedimentation unit 4, flowing downwards through the honeycomb inclined tube packing layer. Suspended solids, detached biofilm, and other impurities in the water slide down the inner wall of the inclined tubes under gravity to the bottom sludge collection area, and are periodically discharged through sludge discharge pipe b and sludge return pump 8, completing solid-liquid separation and obtaining clarified wastewater rich in nitrate nitrogen. Control unit 7 performs three-stage diversion based on the water quality requirements of the reuse scenario. If used for irrigation of fruit trees or other crops that require nitrate nitrogen, the high-nitrate nitrogen wastewater is directly discharged into disinfection unit 6; if a higher water quality standard is required, it is discharged into trickling filtration purification unit 5 for deep treatment.

[0075] S5. Deep purification treatment: Wastewater clarified by the secondary sedimentation unit 4 is introduced into the trickling filter purification unit 5, where it is evenly sprayed onto the surface of the upper denitrification packing by the water distributor 502. Under the action of gravity, it permeates and flows sequentially through the denitrification and dephosphorization packing. Through the physical adsorption, chemical complexation, and sedimentation of the industrial waste-synthesized packing, residual nitrogen, phosphorus, and residual COD and other pollutants in the water are deeply removed, further reducing the pollutant content of the wastewater and improving the effluent quality. The treated wastewater that meets the standards is then discharged into the disinfection unit 6.

[0076] S6. Disinfection and Targeted Reuse: Wastewater introduced into disinfection unit 6 via various pathways is allowed to settle in tank 601 for a preset hydraulic retention time. It is then disinfected by all-around irradiation from the top ultraviolet lamp 602, effectively killing bacteria, viruses, and other harmful microorganisms. After disinfection, the control unit 7 regulates the multi-pipeline diversion system, directing water to corresponding scenarios according to different reuse needs. Pre-treated direct-discharge water is directed to low-water-quality irrigation scenarios such as open fields and woodlands; high-ammonia-nitrogen water is directed to leafy vegetable irrigation scenarios; high-nitrate-nitrogen water is directed to orchards and fruit and vegetable plantations; and deeply purified water is directed to high-standard scenarios such as landscape water and precision vegetable irrigation, achieving precise reuse of wastewater resources.

[0077] The wastewater treated by this system achieves the following objectives: First, it reduces costs by using low-cost components, minimizing the use of power equipment, and optimizing treatment processes, thereby lowering construction and operation costs and making wastewater treatment facilities affordable for rural areas. Second, it enables resource recovery and reuse by converting nitrogen and phosphorus in wastewater into forms easily absorbed by crops through tiered treatment and targeted resource recovery, allowing for the targeted reuse of high-ammonia-nitrogen water bodies in farmland, improving resource utilization efficiency, and promoting the ecological cycle development of rural areas. Third, it enhances the adaptability of decentralized treatment by integrating systems, simplifying equipment structure, optimizing the layout of each unit and water flow connections, reducing reliance on professional operation and maintenance personnel, and enhancing the equipment's ability to cope with fluctuations in water quality and quantity in decentralized rural settings, ensuring stable and efficient operation.

[0078] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are included within the protection scope of the present invention. The embodiments described in this disclosure are intended as non-limiting examples, and other embodiments may take various and alternative forms. Furthermore, the drawings are not necessarily to scale and may present simplified expressions of various features of the present disclosure, including, for example, specific dimensions, orientations, positions, and shapes. Details associated with such features will be determined in part by the intended application and usage environment of the described embodiments.

[0079] The detailed description and accompanying drawings are supporting and descriptive of this teaching, but the scope of this teaching is defined only by the claims. While the best mode and some other embodiments for carrying out this teaching have been described in detail, various alternative designs and embodiments exist for practicing the teaching as defined in the appended claims. Furthermore, this disclosure expressly includes combinations and sub-combinations of the elements and features set forth above and below.

Claims

1. A multi-stage filter media resource recovery system for agricultural non-point source nutrient loss, characterized in that, include: The oil-water separator and grit removal unit is used to remove suspended solids, grease and heavy metals from wastewater and to replenish the wastewater with carbon sources. The hydrolysis acidification unit, located downstream of the oil-water separation and grit removal unit, is used to receive wastewater pretreated by the oil-water separation and grit removal unit, convert large molecular organic matter in the wastewater into small molecular organic matter, and increase the ammonia nitrogen concentration. At least two contact oxidation units are located downstream of the hydrolysis acidification unit to receive wastewater treated by the hydrolysis acidification unit, decompose organic matter in the wastewater, oxidize ammonia nitrogen to nitrate nitrogen, and convert organic phosphorus to inorganic phosphorus. The secondary sedimentation unit, located downstream of the contact oxidation unit, is used to receive the wastewater treated by the contact oxidation unit, thereby achieving solid-liquid separation and removing suspended solids. The trickling filtration purification unit, located downstream of the secondary sedimentation unit, is used to receive the wastewater separated by the secondary sedimentation unit and to deeply remove nitrogen, phosphorus and residual pollutants from the wastewater. The disinfection unit is used to kill harmful pathogens in wastewater and achieve resource recycling. The control unit is connected to the oil-water separation and sand settling unit, the hydrolysis and acidification unit, the contact oxidation unit, the secondary sedimentation unit, the trickling filtration and purification unit, and the disinfection unit, respectively. The oil-water separation and grit removal unit, the hydrolysis and acidification unit, the secondary sedimentation unit, and the trickling filtration purification unit are all connected to the disinfection unit through pipelines. Under the control of the control unit, the wastewater selectively flows through the oil-water separation and grit removal unit, the hydrolysis and acidification unit, the contact oxidation unit, the secondary sedimentation unit, and the trickling filtration purification unit to form multiple treatment paths before entering the disinfection unit.

2. The system according to claim 1, characterized in that, The oil-water separator and sand-sinking unit includes a first cylinder, and a vertical partition plate is provided inside the first cylinder to divide the internal space of the first cylinder into a sand-sinking chamber and an oil removal and carbon source replenishment chamber. The vertical partition plate extends downward from the top of the first cylinder for a certain length, so that the lower parts of the sand-sinking chamber and the oil removal and carbon source replenishment chamber are connected. The settling chamber is filled with inclined tube packing material. A first water inlet is formed at the upper part of the settling chamber, and a first sludge discharge outlet is formed at the lower part. The first sludge discharge outlet is connected to a sludge return pump through a pipeline. The oil removal and carbon source replenishment chamber is filled with adsorption packing and carbon source release packing. A first water outlet is formed at the top of the oil removal and carbon source replenishment chamber. The first water outlet is used to discharge the treated wastewater to the hydrolysis acidification unit or the disinfection unit.

3. The system according to claim 2, characterized in that, The adsorption packing material is selected from natural biomass adsorption packing material, and the carbon source release packing material is selected from natural plant-based carbon source packing material.

4. The system according to claim 1, characterized in that, The hydrolysis acidification unit includes a second cylinder, inside which a perforated plate is provided, and above the perforated plate is a composite filler. The upper part of the second cylinder has a second water inlet, and the lower part has a second water outlet. The second water outlet is used to discharge the treated wastewater to the contact oxidation unit or the disinfection unit.

5. The system according to claim 1, characterized in that, The contact oxidation unit includes two first contact oxidation modules and a second contact oxidation module arranged in series. The first contact oxidation module includes a third cylinder, the lower part of which forms a third inlet for receiving wastewater from the hydrolysis acidification unit, and the upper part of which forms a third outlet. The first contact oxidation module is filled with a first fixed curtain-type biological rope packing material, and a first aeration pipe is configured at its bottom. The second contact oxidation module includes a fourth cylinder, a fourth inlet connected to the third outlet is formed in the middle of the fourth cylinder, a fourth outlet is formed at the top of the fourth cylinder, and the second contact oxidation module is filled with a second fixed curtain-type biological rope packing material, and a second aeration pipe is configured at the bottom of the second cylinder. The fourth outlet is used to discharge the treated wastewater to the secondary sedimentation unit.

6. The system according to claim 1, characterized in that, The secondary sedimentation unit includes a fifth cylinder, which is filled with inclined tube packing. The upper part of the cylinder has a fifth inlet for receiving wastewater from the contact oxidation unit, the middle part has a fifth outlet, and the lower part has a second sludge discharge outlet. The fifth outlet is used to discharge the treated wastewater to the trickling filter purification unit or the disinfection unit, and the second sludge discharge port is connected to the sludge return pump through a pipeline.

7. The system according to claim 1, characterized in that, The trickling filtration purification unit includes a sixth cylinder, which is filled with nitrogen removal packing and phosphorus removal packing arranged vertically, and a water distributor located above the nitrogen removal packing. The upper part of the sixth cylinder has a sixth inlet for receiving wastewater from the secondary sedimentation unit, and the lower part has a sixth outlet for discharging the treated wastewater to the disinfection unit.

8. The system according to claim 7, characterized in that, Both the nitrogen removal packing and the phosphorus removal packing are synthesized from industrial waste as raw materials. The particle size of the nitrogen removal packing is 50-100 mm, and the particle size of the phosphorus removal packing is 30-80 mm.

9. The system according to claim 1, characterized in that, The disinfection unit includes a tank body, the upper part of which is equipped with at least one ultraviolet irradiation lamp, and its side wall has a seventh water inlet and a seventh water outlet. The seventh water inlet is used to receive wastewater from the oil-water separation and sand settling unit, the hydrolysis acidification unit, the secondary sedimentation unit, or the trickling filtration purification unit.

10. A method for utilizing a multi-stage filter media resource recovery system for agricultural non-point source nutrient loss as described in any one of claims 1-9, characterized in that, Includes the following steps: Wastewater is treated by the oil-water separation and grit removal unit to remove suspended solids, grease and heavy metals, and a carbon source is added. The pretreated wastewater is then selectively discharged into the hydrolysis acidification unit or the disinfection unit. Wastewater pretreated by the oil-water separation and grit removal unit is discharged into the hydrolysis and acidification unit to convert macromolecular organic matter and increase ammonia nitrogen concentration. High ammonia nitrogen wastewater is selectively discharged into the contact oxidation unit or the disinfection unit. The wastewater treated by the hydrolysis acidification unit flows through the contact oxidation unit, where organic matter is decomposed and ammonia nitrogen is converted into nitrate nitrogen and organic phosphorus is converted into inorganic phosphorus. Then, solid-liquid separation is carried out in the secondary sedimentation unit, and high-nitrate nitrogen wastewater is selectively discharged into the trickling filtration purification unit or the disinfection unit. The wastewater treated by the secondary sedimentation unit is discharged into the trickling filtration purification unit, where nitrogen, phosphorus and residual pollutants are deeply removed before being discharged into the disinfection unit. After being disinfected, the wastewater discharged into the disinfection unit is directed to different agricultural irrigation scenarios according to the reuse needs.

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