Rural sewage treatment device and treatment method

Abstract

The invention relates to the technical field of sewage treatment, and particularly discloses a rural sewage treatment device and a rural sewage treatment method.The rural sewage treatment device comprises a bottom anaerobic fermentation layer, a middle wetland layer and a top planting layer which are sequentially arranged in the sewage flowing direction, the bottom anaerobic fermentation layer is used for filtering suspended matters in the sewage by using a filler and decomposing organic matters in the sewage by using anaerobic flora; the middle wetland layer is used for removing nitrogen and phosphorus elements in the sewage by using plant root systems and filtering; the top planting layer is used for recycling the treated sewage and absorbing residual nutrients. The system has the characteristics of low operation and maintenance cost, modular structure, simple operation and the like, and has the potential of popularization and application in rural village and town areas.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and particularly relates to a rural sewage treatment device and a treatment method. Background Art

[0002] At present, the low density of village and town buildings and the random building layout of residents have led to extremely scattered rural sewage discharge and difficult centralized collection, and the process of rural sewage treatment is significantly lagging behind. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a rural sewage treatment device and a treatment method, which have the characteristics of low operation and maintenance costs, modular structure, simple operation, etc., and have the potential for popularization and application in rural and township areas.

[0004] The present invention is realized through the following technical solutions: A rural sewage treatment method includes the following steps:

[0005] S1. Drain the sewage to the bottom anaerobic fermentation layer. The bottom anaerobic fermentation layer includes a plurality of fermentation tanks connected in series in sequence and arranged in an array. Each fermentation tank is separated into a lower sewage fermentation area and an upper biogas collection area by a grid plate. A stirring component and fillers filled in a loose accumulation state are arranged inside the lower sewage fermentation area. By using the voids formed by the loose accumulation of the fillers, when the stirring component rotates, it can push the sewage and the fillers to flow synchronously, drive the sewage to fully contact with anaerobic bacteria, decompose the organic matter in the sewage by the anaerobic bacteria and generate biogas. At the same time, the sludge precipitates to the bottom of the lower sewage fermentation area until the set fermentation time.

[0006] S2. Pump the upper clear water to the middle wetland layer through the bottom water outlet pipe of the bottom anaerobic fermentation layer. During this process, the fillers in the bottom anaerobic fermentation layer are used to filter the suspended solids in the sewage at the same time. The pumped upper clear water is discharged to the middle wetland layer to filter the upper clear water, and emergent aquatic plants are used to absorb the nitrogen and phosphorus elements in the water until the set time. At this time, the upper clear water flows through the emergent aquatic plants in a snake shape, and the root secretion of the emergent aquatic plants promotes the formation of microbial films, and nitrification / denitrification reactions are carried out synchronously.

[0007] S3. Pump out the upper clear water treated by the treatment pool in the middle wetland layer, and use drip irrigation pipes to irrigate the salt-tolerant plants planted on the top planting layer. At the same time, use the water seepage pipe to recycle the excess water in the top planting layer to the treatment pool, and further degrade it through the matrix filtration and secondary metabolism of microorganisms and plant absorption in the middle wetland layer.

[0008] Preferably, the set fermentation time in step S1 is 6h - 8h, the set time in step S2 is 24h - 48h; the fillers are selected from volcanic rocks or polyethylene balls; the emergent aquatic plants are reeds or calamus.

[0009] For the large fluctuations in rural sewage COD (200 - 500 mg / L), a short - cycle fermentation + sequential control of series - connected tanks (the water level gauge automatically adjusts the water inlet sequence) is adopted, enhancing the anti - water - quality - shock ability. When the COD fluctuates by ±20%, the treatment efficiency is stable; the filler intercepts suspended solids, avoiding the blockage of the subsequent wetland layer and extending the service life of the device (the traditional process requires annual dredging due to blockage, while the dredging cycle of the present invention is extended to 3 - 5 years). The serpentine water flow path and the bottom - inlet design form a "bottom - in and top - out" plug - flow mode. The hydraulic retention time is extended from 12 - 18 h in the traditional process to 24 - 48 h, and the nitrogen and phosphorus removal rate is increased by 20 - 30%, meeting the national first - level B requirements; the plant roots secrete phenolic substances to promote the formation of microbial membranes, and the denitrification efficiency reaches 60% (about 40% in traditional constructed wetlands), reducing the aeration energy consumption by 30%. The drip irrigation + permeable pipe circulation system achieves a water reuse rate of 90%, saving 400 - 600 tons of water per year per module compared with the traditional direct - discharge process; the sludge is converted into organic fertilizer through aerobic fermentation (annual carbon reduction of 0.5 - 0.8 t / module), eliminating secondary pollution and reducing the disposal cost to 0.

[0010] A rural sewage treatment device adopting the aforementioned treatment method, comprising:

[0011] A bottom - layer anaerobic fermentation layer for filtering suspended solids in sewage using a filler and decomposing organic matter in sewage using anaerobic bacteria groups;

[0012] A middle - layer wetland layer arranged above and connected to the bottom - layer anaerobic fermentation layer for removing nitrogen and phosphorus elements in sewage using plant roots and filtering;

[0013] A top - layer planting layer arranged above and connected to the middle - layer wetland layer for reusing the treated sewage and absorbing residual nutrients.

[0014] Optionally, the bottom - layer anaerobic fermentation layer includes a plurality of fermentation tanks arranged in an array on a bottom fixing plate. The plurality of fermentation tanks are connected in series in sequence. Each fermentation tank is partitioned into a lower - layer sewage fermentation area and an upper - layer biogas collection area by a grid plate. A stirring component and a filler are arranged inside the lower - layer sewage fermentation area. The filler is volcanic rock or polyethylene balls with a particle size of 20 - 50 mm, and is filled in the lower - layer sewage fermentation area in a loose - packing state with a porosity of 40% - 50%; the stirring component is a frame - type stirring paddle or a spiral stirring rod; the blades / rods of the stirring component rotate in the gaps of the filler, and by using the gaps formed by the loose packing of the filler, when the stirring component rotates, it can push the sewage and the filler to flow synchronously; the upper - layer biogas collection area is communicated with a gas storage tank arranged in the farmer's kitchen through a collection pipe and an underground pipeline.

[0015] Further, the bottom end of the side of the lower - layer sewage fermentation area is communicated with one end of the sewage inlet pipe, the other end of the sewage inlet pipe is communicated with the household sewage drainage outlet of farmers through a water collecting pipe, and the top end of the side of the lower - layer sewage fermentation area extends to the top end of the middle - layer wetland layer through a bottom - layer water outlet pipe.

[0016] Further, a water level gauge is arranged at the top end of the lower - layer sewage fermentation area of each fermentation tank, which is used to automatically let the sewage enter the next tank after the previous tank is full, and the water is discharged in the order of water inlet.

[0017] Thus, in view of the problem of decentralized discharge of rural sewage, the present invention adopts a modular series design, with a short - cycle fermentation of 6 - 8 hours for a single tank, matching the fluctuation characteristics of sewage volume; the filler filters suspended solids (removal rate ≥ 60%), avoiding pipeline blockage, and the stirring component promotes the full contact between anaerobic bacteria and sewage, improving the decomposition efficiency of organic matter (COD removal rate ≥ 40%).

[0018] Optionally, the middle - layer wetland layer includes a middle - layer fixing plate erected above the bottom - layer fixing plate through a column, a treatment pool built on the top of the middle - layer fixing plate with anti - seepage membranes laid on the inner walls around the treatment pool, gravel matrix laid inside, the particle size of the gravel matrix is 10mm - 30mm, the thickness is 60cm - 80cm, and emergent plants are planted on the gravel matrix, and the emergent plants are reeds or calamus.

[0019] Thus, the middle - layer wetland layer set in the present invention has an anti - seepage membrane laid on the inner wall of the brick - built treatment pool, filled with 10 - 30mm gravel matrix (thickness 60 - 80cm), planted with reeds / calamus, with a serpentine water - passing channel inside, and the extension pipe enters water from below the matrix. The serpentine channel extends the water flow path by 1.5 - 2 times, making the sewage stay for 24 - 48 hours, promoting the formation of microbial film in combination with the root exudates of emergent plants, and synchronously completing nitrification / denitrification reactions, with nitrogen and phosphorus removal rates reaching 50 - 60% and 40 - 50% respectively; the gravel matrix further filters suspended solids (residual SS ≤ 20mg / L), solving the cost and pollution problems of traditional processes that rely on chemical agents for nitrogen and phosphorus removal.

[0020] Optionally, the top - layer planting layer includes a top - layer fixing plate erected on the bottom - layer fixing plate through a column and planting soil and ceramsite matrix laid in sequence on the top of the top - layer fixing plate, and salt - tolerant plants are planted on the planting soil; the top - layer planting layer is flush with the ground, and a through - slot communicating with the middle - layer wetland layer is opened in the center.

[0021] Further, a water seepage pipe is also laid between the planting soil and the top - layer fixing plate, the water seepage pipe leads to the treatment pool, the top end of the bottom - layer water outlet pipe extends into the interior of the treatment pool through the top of the side wall of the treatment pool, and one end of the bottom - layer water outlet pipe extending into the interior of the treatment pool is communicated with the top end of the extension pipe, the bottom end of the extension pipe is placed below the gravel matrix, and a water outlet is opened at the bottom end of the extension pipe.

[0022] As described above, the top planting layer provided by the present invention is composed of planting soil, ceramsite matrix and water infiltration pipes. Salt-tolerant plants (such as ice plants) are irrigated through drip irrigation pipes, and the sludge from the fermentation tank is discharged into the composting area through the sludge suction pipe. The drip irrigation + water infiltration pipe circulation system realizes the reuse of treated water (the reuse rate is 90%). The effluent COD ≤ 50mg / L meets the irrigation standard, avoiding water resource waste. The sludge is used as organic fertilizer after composting and maturation (the mortality rate of Ascaris eggs ≥ 95%), solving the secondary pollution problem of traditional sludge open stacking, and 1.2 - 1.5t / module of biological fertilizer is produced annually.

[0023] Preferably, the inside of the treatment pool is brick-built into a serpentine water passage for increasing the treatment time of sewage. The edge of the treatment pool is connected to the bottom end of the top fixing plate through a retaining net. At the same time, the bottom end of the middle fixing plate is connected to the bottom fixing plate through a retaining net. Between the top fixing plate, the middle fixing plate and the bottom fixing plate outside the retaining net, cobblestones and soil are filled in sequence from inside to outside.

[0024] As described above, cobblestones and soil are filled between the retaining net and the fixing plate of the present invention, a water suction pipe is equipped with a suction pump, and a sludge suction pipe is provided for the fermentation tank. The retaining net and the filler layer enhance the structural stability and anti-seepage performance. The automatic pumping and drainage system reduces the manual operation and maintenance intensity, and the operation and maintenance cost is reduced by 40% compared with the traditional process.

[0025] Further, the bottom end of the lower sewage fermentation area is communicated with one end of the sludge suction pipe, the other end of the sludge suction pipe is communicated with the composting area, and the composting area is arranged on the top fixing plate for reusing the extracted sludge as fertilizer.

[0026] Further, the top end of the treatment pool is communicated with the bottom end of the water suction pipe, the top end of the water suction pipe is communicated with the drip irrigation pipe buried in the planting soil, and a suction pump is arranged on the water suction pipe.

[0027] Compared with the prior art, the features and innovations of the present invention are as follows:

[0028] 1. Strong adaptability, flexible and decentralized layout can be achieved.

[0029] 2. High sewage treatment efficiency. After the sewage is treated by microorganisms, it is successively subjected to multi-stage treatment of the wetland layer and the planting layer.

[0030] 3. Low operation and maintenance cost, modular structure, simple operation and other features, having the potential for popularization and application in rural and township areas.

[0031] 4. Realize resource recycling. Among them, biogas can be used in rural kitchens, the effluent can be used for watering ground plants, and the sludge can be used as planting fertilizer.

[0032] 5. Integrating links such as comprehensive sewage treatment, agricultural planting, and energy recovery realizes a complete ecological cycle, which has certain symbolic significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The drawings described herein are used to provide a further understanding of the present application, and constitute a part of the present application. The schematic embodiments and descriptions thereof of the present application are used to explain the present application, and do not constitute an improper limitation to the present application. In the drawings:

[0034] Figure 1 is a schematic diagram of the overall structure of the present invention;

[0035] Figure 2 is a layout diagram of the serpentine water passing channel of the treatment tank of the present invention;

[0036] Figure 3 is a schematic diagram of the tank structure of the present invention.

[0037] Description of the reference numerals:

[0038] 1, bottom anaerobic fermentation layer; 11, bottom fixing plate; 12, sewage inlet pipe; 13, bottom outlet pipe; 14, fermentation tank; 15, collection pipe; 16, lower layer sewage fermentation area; 17, upper layer biogas collection area; 18, stirring assembly; 19, grid plate; 110, sewage extraction pipe;

[0039] 2, middle layer wetland layer; 21, treatment tank; 22, emergent plants; 23, water extraction pipe; 24, serpentine water passing channel;

[0040] 3, top layer planting layer; 31, top layer fixing plate; 32, salt-tolerant plants;

[0041] 4, through groove;

[0042] 5, column;

[0043] 6, retaining net. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] For the convenience of those of ordinary skill in the art to understand and implement the present invention, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0045] Embodiment 1

[0046] As Figures 1 - 3As shown in the figure, a rural sewage treatment device includes a bottom anaerobic fermentation layer 1, a middle wetland layer 2, and a top planting layer 3 arranged in sequence along the direction of sewage flow. Among them, the bottom anaerobic fermentation layer 1 is used to filter suspended solids in sewage by using fillers and decompose organic matter in sewage by using anaerobic bacteria groups; the middle wetland layer 2 is used to remove nitrogen and phosphorus elements in sewage by using plant roots and conduct filtration; the top planting layer 3 is used to reuse the treated sewage and absorb residual nutrients.

[0047] Due to the characteristics of rural sewage being high in suspended solids, high in organic matter, and exceeding the standards of nitrogen and phosphorus, the present invention sets up a hierarchical treatment method of "pretreatment for turbidity reduction + biochemical nitrogen and phosphorus removal + advanced utilization": (1) Bottom anaerobic fermentation layer (front-end): Sewage first enters the bottom layer, where anaerobic bacteria groups are used to decompose macromolecular organic matter (such as cellulose in straw and feces), and at the same time, fillers (volcanic rock / polyethylene balls) intercept suspended solids. (2) Middle wetland layer (connecting the front and the back): After anaerobic fermentation, the suspended solids in the sewage have been significantly reduced (removal rate ≥ 60%). When it enters the middle layer, the roots of emergent plants (reed / calamus) and gravel matrix work together to remove nitrogen and phosphorus through adsorption and microbial metabolism. (3) Top planting layer (end utilization): After being treated by the middle layer, the sewage has reached a "low pollution" state (COD ≤ 80mg / L, nitrogen and phosphorus ≤ 15mg / L), and can be used to irrigate salt-tolerant plants. Placing it on the top layer can achieve irrigation by gravity flow (drip irrigation pipe + permeable water pipe circulation) without the need for additional power to lift; at the same time, the design of the top planting layer being flush with the ground can directly use natural rainfall to supplement water. The sequence of the bottom anaerobic fermentation layer 1, the middle wetland layer 2, and the top planting layer 3 arranged in sequence along the direction of sewage flow in the present invention cannot be reversed. If the sequence is reversed, high suspended solids directly entering the middle wetland will quickly block the plant roots and gravel matrix, resulting in the paralysis of the wetland system; moreover, the biogas generated by anaerobic fermentation needs to be collected upward, and the bottom layout is convenient for the biogas to naturally float to the collection area (above the grid board), avoiding the retention of biogas and affecting subsequent treatment. If the middle wetland layer is placed at the bottom, the high-concentration organic matter will inhibit the growth of wetland plants (anaerobic environment is likely to cause root rot), and the wetland layer requires an aerobic / anaerobic alternating environment to achieve nitrification-denitrification, and the bottom anaerobic environment cannot meet the requirements. If the top planting layer is placed at the bottom in reverse order, it will cause plant roots to rot due to waterlogging, and the ecological closed-loop of "treated water - planting - reflux" cannot be achieved.

[0048] As Figure 1As shown, the top planting layer 3 is flush with the ground. Salt-tolerant plants 32 are planted around the top planting layer 3. A through trough 4 is provided in the center, connecting to the middle wetland layer 2. Below the middle wetland layer 2 is the bottom anaerobic fermentation layer 1. The through trough 4 serves as a "connecting trough" between the middle wetland layer 2 and the top planting layer 3. It allows water purified by the middle wetland layer to flow naturally into the top planting layer, while allowing seepage water from the top planting layer to flow back, achieving: positive water supply: "quasi-clean water" (COD ≤ 80 mg / L, nitrogen and phosphorus ≤ 15 mg / L) treated in the middle wetland enters the top planting layer through the through trough 4 (pump pipe 23), providing irrigation water for the salt-tolerant plants 32. No additional powered water pipelines are required, and gravity flow is used to complete the connection from "wetland purified water to planting irrigation." Reverse reflux: The percolation water from the top planting layer (after being absorbed by plants and filtered by the matrix) can flow back to the middle wetland layer through the channel 4, forming a small cycle of "middle layer purification → top layer utilization → middle layer return", thereby improving the utilization rate of water resources. Compared with the design without circulation, the water reuse rate increases by 30%-40%.

[0049] like Figure 3 As shown, the bottom anaerobic fermentation layer 1 comprises multiple fermentation tanks 14 arranged in an array on a bottom fixed plate 11. The interior of each fermentation tank 14 is divided by a grid panel 19 into a lower sewage fermentation zone 16 and an upper biogas collection zone 17. The lower sewage fermentation zone 16 is equipped with a stirring assembly 18 and filler, which is made of volcanic rock or polyethylene balls. The bottom end of the lower sewage fermentation zone 16 is connected to one end of the sewage inlet pipe 12, the other end of which is connected to the farmer's household drain via a water collection pipe. The top end of the lower sewage fermentation zone 16 extends to the top of the middle wetland layer 2 via the bottom outlet pipe 13. The upper biogas collection zone 17 is connected to a gas storage tank located in the farmer's kitchen via a collection pipe 15 and an underground pipeline. A water level gauge is installed at the top of the lower sewage fermentation zone 16 of each fermentation tank 14. Once the previous tank is full, sewage automatically flows into the next tank, and water is discharged in the order of intake.

[0050] In the present invention, the filler in the lower sewage fermentation zone 16 is volcanic rock or polyethylene balls, with a particle size usually of 20 - 50 mm, and is filled in the lower sewage fermentation zone of the fermentation tank in a "loose accumulation" state; while the stirring assembly 18 is a "frame - type stirring paddle" or a "helical stirring rod", and its design features include: (1) Physical space compatibility: The blades / rods of the stirring assembly rotate in the gaps between the fillers, making use of the "voids in the loose accumulation" of the fillers (void ratio about 40% - 50%) to achieve "when stirring and rotating, promoting the synchronous flow of sewage and fillers". (2) Functional complementarity: The role of the filler is to "retain suspended solids + attach anaerobic flora", adsorb pollutants through the specific surface area and provide a microbial carrier; the role of the stirring assembly is to "enhance mass transfer" - making the sewage "forced convection" in the gaps between the fillers to avoid "sewage short - circuit", that is, part of the sewage directly flows out without contacting the fillers / flora, so that the efficiency of the anaerobic flora in decomposing organic matter is increased by 30% - 40%. The biogas collection area is connected to the household gas storage tank through underground pipelines to achieve energy recovery, and the gas production efficiency is 30 - 40 L / m³ of sewage.

[0051] As Figure 1 shown, the middle - layer wetland layer 2 includes a middle - layer fixing plate erected above the bottom fixing plate 11 through columns 5, and a treatment pool 21 built on the top of the middle - layer fixing plate with bricks. Anti - seepage membranes are laid on the inner walls around the treatment pool 21 to prevent sewage seepage. Gravel matrix is laid in the treatment pool 21, with a particle size of 10 mm - 30 mm and a thickness of 60 cm - 80 cm. Emergent plants 22 are planted on the gravel matrix, and the emergent plants 22 are reeds or calamus; the top end of the bottom outlet pipe 13 extends into the interior of the treatment pool 21 through the top end of the side wall of the treatment pool 21, and one end of the bottom outlet pipe 13 extending into the interior of the treatment pool 21 is communicated with the top end of an extension pipe. The bottom end of the extension pipe is placed below the gravel matrix, and a water outlet is opened at the bottom end of the extension pipe. With the above - mentioned structure, the sewage pumped out from the bottom - layer anaerobic fermentation layer 1 is successively introduced into the lower part of the gravel matrix through the bottom outlet pipe 13 and the extension pipe, and the gravel matrix is used to filter the sewage when the water level rises; the top end of the treatment pool 21 is communicated with the bottom end of a water extraction pipe 23, and a suction pump is arranged on the water extraction pipe 23.

[0052] As Figure 1 shown, the top - layer planting layer 3 includes a top - layer fixing plate 31 erected on the bottom fixing plate 11 through columns 5 and planting soil and ceramsite matrix laid successively on the top of the top - layer fixing plate 31. Salt - tolerant plants 32 are planted on the planting soil, and the salt - tolerant plants 32 are ice plants, etc.; the top end of the water extraction pipe 23 is communicated with a drip irrigation pipe buried in the planting soil; a water seepage pipe is also laid between the planting soil and the top - layer fixing plate 31, and the water seepage pipe leads to the treatment pool 21.

[0053] As Figure 2As shown in the figure, the inside of the treatment tank 21 is brick-built into a serpentine water passage 24 for increasing the treatment time of sewage. The edge of the treatment tank 21 is fixedly connected to the bottom end of the top fixing plate 31 through a retaining net 6. At the same time, the bottom end of the middle fixing plate is fixedly connected to the bottom fixing plate 11 through the retaining net 6. Between the top fixing plate 31, the middle fixing plate, and the bottom fixing plate 11 outside the retaining net 6, cobblestones and soil are filled in sequence from the inside out. The functions of the retaining net 6 set in the present invention include: (1) Structural strengthening (structural support + functional zoning): between the middle wetland layer 2, the top planting layer 3, and the bottom anaerobic fermentation layer 1, the "top fixing plate 31, the middle fixing plate, and the bottom fixing plate 11" are connected through the retaining net 6 to form a "three-dimensional framework support", avoiding the collapse of each layer due to the weight of the filler / substrate (especially the vertical load of the middle wetland gravel substrate and the top planting soil), and improving the overall structural stability of the device (the anti-settlement ability is increased by 40%-50%). (2) The functions of cobblestones + soil (anti-seepage + ecological buffer): Physically anti-seepage, large-sized cobblestones are filled inside to form a "coarse filtration layer" to block the sewage from seeping out; soil is filled outside, and the anti-seepage property of clay minerals is utilized (the soil permeability coefficient ≤ 10⁻ 7 cm / s) to construct a "secondary anti-seepage barrier" to ensure that the sewage does not leak and pollute the groundwater.

[0054] As Figure 3 shown in the figure, the bottom end of the lower sewage fermentation area 16 is communicated with one end of the sludge suction pipe 110, and the other end of the sludge suction pipe 110 is communicated with the composting area. The composting area is fixed on the top fixing plate 31 and is used for reusing the extracted sludge as fertilizer.

[0055] In summary, the core differences between the treatment device of the present invention and the prior art are:

[0056] Innovation in the treatment process: Most of the prior art is single-stage treatment (such as single anaerobic or constructed wetland). The present invention adopts a three-stage series process of "anaerobic fermentation → wetland filtration → planting utilization", and the functions of each layer are coupled: the anaerobic layer decomposes organic matter and produces biogas, the wetland layer removes nitrogen and phosphorus, and the planting layer realizes the cycle of water and nutrients. The effluent quality reaches the first-class B standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants", which is 2 grades higher than the traditional single-stage process.

[0057] Advantages of modular design: Most of the existing devices are fixed tank bodies. The fermentation tanks of the present invention are connected in series in an array, which can be flexibly split and combined according to the distribution of farmers (each single module can treat 5-10 m³ / d). The installation period is shortened to 7 days (the traditional process takes 30 days), and the floor area is reduced by 30%, adapting to the scattered characteristics of rural homesteads.

[0058] Resource recycling integrity: The prior art lacks the utilization of energy and sludge resources. The present invention constructs a "sewage - energy - planting" closed loop by directly supplying biogas to the kitchen (saving 800 - 1000 yuan in gas fees annually), returning sludge compost to the field (reducing chemical fertilizer use by 20%), and irrigating with treated water (increasing plant yield by 15 - 20%), with the resource utilization rate increased by 50%.

[0059] Operation and maintenance cost control: The prior process requires regular operation by professional personnel (cost 0.8 - 1.2 yuan / m³). The present invention automatically controls the inflow and outflow of water through a water level gauge and periodically starts and stops the suction pump. It only needs to be inspected once a month, and the operation and maintenance cost is reduced to 0.3 - 0.5 yuan / m³, which is suitable for the current situation of weak operation and maintenance capabilities in rural areas.

[0060] Example 2

[0061] A rural sewage treatment method uses the treatment device described in Example 1. Specifically, during operation, it includes the following steps:

[0062] S1. Farmers discharge sewage through the household drainage outlet to the lower - layer sewage fermentation area 16 inside the fermentation tank 14 of the bottom - layer anaerobic fermentation layer 1. Under the action of the stirring component 18, the sewage is driven to fully contact with the anaerobic bacteria group. The anaerobic bacteria group decomposes the organic matter in the sewage and generates biogas. At the same time, the sludge precipitates to the bottom of the lower - layer sewage fermentation area 16 until the set fermentation time; among them, rural sewage itself contains a large number of anaerobic microorganisms (such as methanogens and hydrolytic acidifying bacteria in feces and straw). After the sewage enters the bottom - layer anaerobic fermentation layer 1, under the conditions of "anaerobic environment (DO ≤ 0.2mg / L)+packing carrier (volcanic rock / polyethylene ball)", the bacteria group naturally adheres and reproduces to form a stable anaerobic microbial community.

[0063] S2. The upper - layer clear water is pumped to the middle - layer wetland layer 2 through the bottom - layer water outlet pipe 13 of the bottom - layer anaerobic fermentation layer 1. During this process, the packing in the bottom - layer anaerobic fermentation layer 1 can be used to filter the suspended solids in the sewage at the same time. The packing is selected from porous materials such as volcanic rock or polyethylene ball, and the pore size is adapted to the size of the suspended solids. Thus, the surface pores can be used to intercept the suspended solids, and the extended pipe is used to discharge the pumped upper - layer clear water to the bottom of the gravel matrix of the middle - layer wetland layer 2. The upper - layer clear water is filtered by the gravel matrix, and the nitrogen and phosphorus elements in the water are absorbed by the emergent plants 22 until the set time; at this time, the upper - layer clear water flows in a snake - like manner through reeds or calamus, so as to promote the formation of microbial films by the plant root exudates and synchronously carry out nitrification / denitrification reactions.

[0064] S3. The upper layer of treated water from treatment tank 21 in the middle wetland layer 2 is pumped out using a pumping pipe 23. Drip irrigation pipes are used to irrigate salt-tolerant plants 32 planted in the top planting layer 3. Excess water is simultaneously recycled back to treatment tank 21 using a seepage pipe. Although the recycled water undergoes initial filtration through the top planting layer, it still contains residual nitrogen and phosphorus (5-10 mg / L) and dissolved organic matter (COD 30-50 mg / L). After returning to the middle wetland layer, it is further degraded through filtration through the gravel matrix, secondary metabolism by microorganisms, and absorption by plants.

[0065] Preferably, the set time in step S1 is 6-8 hours, and the set time in step S2 is 24-48 hours. Since rural sewage discharge is concentrated in the morning, midday, and evening (farmers cook and wash in the morning and evening), a 6-8 hour fermentation cycle can be used in conjunction with "diurnal batch processing" (e.g., drainage in the early morning → fermentation completes in the morning → discharge into the wetland layer), preventing prolonged sewage retention in the tank from deteriorating the anaerobic environment (e.g., pH drop and inhibition of methanogens). The middle wetland layer relies on the synergistic denitrification of nitrifying bacteria (aerobic) and denitrifying bacteria (anoxic), as well as plant root absorption and microbial phosphorus removal. Nitrifying bacteria convert ammonia nitrogen into nitrate nitrogen, requiring 12-24 hours to complete a metabolic cycle; denitrifying bacteria reduce nitrate nitrogen to nitrogen gas, requiring 12-24 hours to utilize organic matter as a carbon source. The efficiency of nitrogen and phosphorus absorption by plant roots increases with contact time, so a 24-48 hour retention time is used.

[0066] In summary, the innovative comparison between the treatment method of the present invention and the existing treatment method is as follows:

[0067] Time control strategy: The existing technology adopts a fixed fermentation cycle (12-24 hours). The present invention uses a short cycle of 6-8 hours + dynamic load adjustment of series tanks, which reduces energy consumption by 25% and improves processing efficiency by 30%.

[0068] Water flow path design: Existing processes mostly use linear water flow. The present invention uses a serpentine channel with water entering from the bottom of the extension pipe to increase the contact time between sewage and plant roots to ≥36h, and the pollutant removal rate is increased by 20-30%.

[0069] Ecological cycle logic: This invention constructs a three-way cycle of "sewage-biogas-sludge-planting", with the material utilization rate of the entire system reaching more than 95%, and the unit treatment cost is reduced to 0.5 yuan / m³, which is economically feasible.

[0070] It should be noted that the electronic components for realizing the above-mentioned timing, pumping and drainage, etc. are mature products on the market and can be purchased directly, so their circuit connection structure and principles will not be described in detail here.

[0071] The above embodiments are only used to illustrate the present invention rather than limit the technical solutions described in the present invention. Although this specification has described the present invention in detail with reference to the above respective embodiments, the present invention is not limited to the above specific implementation manners. Therefore, any modification or equivalent replacement made to the present invention; and all technical solutions and their improvements that do not depart from the spirit and scope of the invention are all covered within the scope of the claims of the present invention.

Claims

1. A rural sewage treatment method, characterized in that, It includes the following steps: S1. Drain the sewage to the bottom anaerobic fermentation layer. The bottom anaerobic fermentation layer includes multiple fermentation tanks arranged in series and in an array. Each fermentation tank is divided into a lower sewage fermentation area and an upper biogas collection area by a grid plate. A stirring component and fillers filled in a loose accumulation state are arranged inside the lower sewage fermentation area. By using the voids formed by the loose accumulation of the fillers, when the stirring component rotates, it can push the sewage and the fillers to flow synchronously, driving the sewage to fully contact with the anaerobic bacteria group. The anaerobic bacteria group decomposes the organic matter in the sewage and generates biogas until the set fermentation time; S2. Pump the upper clear water to the middle wetland layer through the bottom water outlet pipe of the bottom anaerobic fermentation layer. During this process, the fillers in the bottom anaerobic fermentation layer are used to filter the suspended solids in the sewage. The pumped upper clear water is discharged to the middle wetland layer for filtering, and emergent plants are used to absorb the nitrogen and phosphorus elements in the water until the set time; At this time, the upper clear water flows through the emergent plants in a snake shape, and the root exudates of the emergent plants are used to promote the formation of microbial membranes, and the nitrification / denitrification reaction is carried out synchronously; S3. Pump out the upper clear water treated by the treatment pool in the middle wetland layer, and use a drip irrigation pipe to irrigate the salt-tolerant plants planted on the top planting layer. At the same time, use a water infiltration pipe to recycle the excess water in the top planting layer back to the treatment pool.

2. The rural sewage treatment method according to claim 1, wherein The set fermentation time in step S1 is 6h - 8h, and the set time in step S2 is 24h - 48h; The fillers are selected from volcanic rock or polyethylene balls; The emergent plants are reeds or calamus.

3. A rural sewage treatment device adopted by the treatment method according to claim 1 or 2, characterized in that, It includes: The bottom anaerobic fermentation layer, which is used to filter the suspended solids in the sewage by using fillers and decompose the organic matter in the sewage by using anaerobic bacteria groups; The middle wetland layer, which is arranged above and connected to the bottom anaerobic fermentation layer, and is used to remove the nitrogen and phosphorus elements in the sewage by using plant roots and conduct filtration; The top planting layer, which is arranged above and connected to the middle wetland layer, and is used to reuse the treated sewage and absorb the residual nutrients.

4. The rural sewage treatment device according to claim 3, characterized in that, The bottom anaerobic fermentation layer includes multiple fermentation tanks arranged in an array on the bottom fixing plate. The multiple fermentation tanks are connected in series in sequence. Each fermentation tank is divided into a lower sewage fermentation area and an upper biogas collection area by a grid plate. A stirring component and fillers are arranged inside the lower sewage fermentation area. The fillers are volcanic rock or polyethylene balls with a particle size of 20 - 50mm, and are filled in the lower sewage fermentation area in a loose accumulation state with a porosity of 40% - 50%; The stirring component is a frame-type stirring paddle or a spiral stirring rod; The blades / rods of the stirring component rotate in the gaps of the fillers. By using the voids formed by the loose accumulation of the fillers, when the stirring component rotates, it can push the sewage and the fillers to flow synchronously; The upper biogas collection area is communicated with a gas storage tank arranged in the farmer's kitchen through a collection pipe and an underground pipeline.

5. The rural sewage treatment device according to claim 4, characterized in that The bottom end of the side of the lower sewage fermentation area is communicated with one end of the sewage inlet pipe, and the other end of the sewage inlet pipe is communicated with the household drainage outlet of the farmer through a water collection pipe. The top end of the side of the lower sewage fermentation area extends to the top end of the middle wetland layer through the bottom water outlet pipe.

6. The rural sewage treatment device according to claim 5, characterized in that A water level gauge is provided at the top of the lower sewage fermentation area of each fermentation tank, which is used to automatically allow sewage to enter the next tank after the previous tank is full, and the water is discharged in the order of water inlet.

7. The rural sewage treatment device according to claim 6, characterized in that, The middle wetland layer includes a middle fixing plate erected above the bottom fixing plate by columns, and a treatment pool built on the top of the middle fixing plate with bricks. Anti-seepage membranes are laid on the inner walls around the treatment pool, and gravel substrates are laid inside. The particle size of the gravel substrates is 10 mm - 30 mm, and the thickness is 60 cm - 80 cm. Emergent plants are planted on the gravel substrates, and the emergent plants are reeds or calamus.

8. The rural sewage treatment device according to claim 7, characterized in that, The top planting layer includes a top fixing plate erected on the bottom fixing plate by columns, and planting soil and ceramsite substrates laid in sequence on the top of the top fixing plate. Salt-tolerant plants are planted on the planting soil; the top planting layer is flush with the ground, and a through groove communicating with the middle wetland layer is opened in the center.

9. The rural sewage treatment device according to claim 8, characterized in that, A drain pipe is also laid between the planting soil and the top fixing plate, and the drain pipe leads to the treatment pool. The top end of the bottom drain pipe extends into the interior of the treatment pool through the top end of the side wall of the treatment pool, and the end of the bottom drain pipe extending into the interior of the treatment pool is communicated with the top end of an extension pipe. The bottom end of the extension pipe is placed below the gravel substrate, and a water outlet is opened at the bottom end of the extension pipe.

10. The rural sewage treatment device according to claim 9, characterized in that, The interior of the treatment pool is built into a serpentine water passage with bricks to increase the sewage treatment time; the edge of the treatment pool is connected to the bottom end of the top fixing plate by a retaining net. At the same time, the bottom end of the middle fixing plate is connected to the bottom fixing plate by a retaining net. Between the top fixing plate, the middle fixing plate and the bottom fixing plate outside the retaining net, cobblestones and soil are filled in sequence from the inside out; The bottom end of the lower sewage fermentation area is communicated with one end of a sludge suction pipe, and the other end of the sludge suction pipe is communicated with a composting area. The composting area is arranged on the top fixing plate and is used to reuse the extracted sludge as fertilizer; The top end of the treatment pool is communicated with the bottom end of a water suction pipe, the top end of the water suction pipe is communicated with a drip irrigation pipe buried in the planting soil, and a suction pump is arranged on the water suction pipe.

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