A rural sewage treatment system

Abstract

The present application relates to sewage treatment technical field, disclose a kind of rural sewage treatment system, including filter tank, biological filter, ecological filter, purification tank and disinfection tank, and filter tank is equipped with grating device;Biological filter is equipped with filler area and aeration pipe, and the sewage of treatment cavity is transported to biological filter by lifting pump;Ecological filter includes amphibious plant area, aquatic plant area and microalgae area, amphibious plant area includes first pool body and planted amphibious plant;Aquatic plant area includes second pool body and planted aquatic plant;Microalgae area includes third pool body and planted microalgae, and the upper portion of purification tank is equipped with water outlet, and multiple modified ceramsite columns are uniformly arranged in purification tank, and the inner pool wall in disinfection tank is equipped with multiple ultraviolet lamps.The present application is suitable for the change of water pollution load, improves sewage treatment stability, improves effluent quality, to reach reuse irrigation standard.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, in particular to a rural sewage treatment system. Background Art

[0002] With the continuous development of my country's modern economy and agricultural society, the living standards in rural areas are constantly improving. At the same time, the large-scale discharge of rural domestic sewage has gradually become a major problem threatening the safety of the rural ecological environment. Rural sewage is mainly a mixture of domestic sewage and processed sewage with agricultural products as raw materials. It basically does not contain heavy metals and toxic and harmful substances, contains a certain amount of nitrogen and phosphorus, and has good biodegradability.

[0003] The existing rural sewage treatment equipment has a relatively simple ecological treatment method for sewage, mainly relying on a single ecological wetland treatment. It has poor adaptability to changes in the influent pollution load and is prone to clogging, affecting the treatment stability. Moreover, the effluent after ecological wetland treatment flows directly into the water storage device without further treatment such as disinfection, making it difficult to meet high-standard reuse requirements. Summary of the Invention

[0004] The purpose of the present invention is to provide a rural sewage treatment system that has strong adaptability to changes in influent pollution load, improves sewage treatment stability, and enhances effluent water quality to meet reuse irrigation standards.

[0005] In order to achieve the above-mentioned purpose, the present invention provides a rural sewage treatment system, comprising a filter tank, a biological filter tank, an ecological filter tank, a purification tank and a disinfection tank connected in sequence, wherein a sewage inlet is provided above the filter tank, and a grid device is provided in the filter tank to separate the tank cavity into a sewage cavity and a treatment cavity; a filler area is provided in the biological filter tank, and an aeration pipe is provided below the filler area, and the sewage at the bottom of the treatment cavity is transported to the bottom of the aeration pipe by a lifting pump; the ecological filter tank comprises an amphibian plant area, an aquatic plant area and a microalgae area arranged in a step-like downward direction, the amphibian plant area comprises a first tank body and a first planting layer arranged above the first tank body, the first planting layer is planted with amphibians, the top surface of the first planting layer is slightly lower than the top surface of the first tank body, and the water outlet at the upper part of the biological filter tank is connected to the upper part of the first planting layer; the aquatic plant area comprises a second tank body and a first planting layer arranged above the first tank body, the first planting layer is planted with amphibians, the top surface of the first planting layer is slightly lower than the top surface of the first tank body, and the water outlet at the upper part of the biological filter tank is connected to the upper part of the first planting layer; the aquatic plant area comprises a second tank body and a A second planting layer is provided above the second tank body, wherein the second planting layer is planted with aquatic plants, the top surface of the second planting layer is lower than the top surface of the second tank body, the distance between the top surface of the first planting layer and the top surface of the first tank body is smaller than the distance between the top surface of the second planting layer and the top surface of the second tank body, and the water outlet at the lower part of the first tank body is connected to the upper part of the second planting layer; the microalgae area includes a third tank body, wherein microalgae are planted in the third tank body, the water outlet at the lower part of the second tank body is connected to the water inlet at the upper part of the third tank body, the water outlet at the lower part of the third tank body is connected to the water inlet at the bottom of the purification tank, a plurality of modified ceramsite columns are evenly arranged in the purification tank, the water outlet at the upper part of the purification tank is connected to the water inlet at the upper part of the disinfection tank, the inner tank wall in the disinfection tank is evenly provided with a plurality of vertically arranged ultraviolet lamps, and a water outlet is provided at the lower part of the disinfection tank.

[0006] As a preferred solution of the present invention, a recirculation zone, a sedimentation zone and a flow zone are provided in the biological filter tank. The filler zone and the recirculation zone are arranged side by side, and the recirculation zone is close to one side of the filter tank. The flow zone is located above the filler zone and the recirculation zone, and the sedimentation zone is located below the filler zone and the recirculation zone. A vertical partition is provided between the filler zone and the recirculation zone, and the partition extends downward to the top of the sedimentation zone. The recirculation zone is filled with slow-release carbon source biological filler.

[0007] As a preferred solution of the present invention, the filler area is filled with zeolite filler, the particle size of the zeolite filler is 10mm to 30mm, and the height of the filler area is 0.8m to 1.2m; the slow-release carbon source biological filler includes at least one of corn cobs, coconut shells and oyster shells, and the height of the recirculation zone is 0.5m to 0.7m.

[0008] As a preferred embodiment of the present invention, the amphibian is at least one of pennywort and iris, the aquatic plant is at least one of hornwort and canna, and the microalgae is Chlorella; the first planting layer and the second planting layer both include an upper first gravel layer and a lower second gravel layer, an air supply pipe is provided below the second planting layer, the particle size on the first gravel layer is 10 cm to 15 cm, and the particle size on the second gravel layer is 30 cm to 40 cm.

[0009] As a preferred solution of the present invention, a positioning baffle is horizontally provided in the middle of the filter tank, and the grille device is placed on the positioning baffle tilted from bottom to top toward the side away from the sewage inlet, the top of the grille device is connected to the top wall of the filter tank, and a water outlet is formed between the end of the positioning baffle and the side wall of the filter tank, and a water baffle horizontally staggered with the positioning baffle is provided in the filter tank, and the water baffle is located below the water outlet, and the area of ​​the water baffle is larger than the area of ​​the water outlet; a mechanical grille is provided on the upper side of the grille device, and a membrane grille is provided on the lower side of the grille device; a plurality of horizontally staggered baffles are provided in the disinfection tank from top to bottom.

[0010] As a preferred embodiment of the present invention, the method for preparing the modified ceramsite in the modified ceramsite column comprises the following steps:

[0011] Step 1: clean the ceramsite and put it into the oven for drying;

[0012] Step 2: adding the ceramsite treated in step 1 to the modified solution, and subjecting the ceramsite to ultrasonic treatment so that the ceramsite is in full contact with the modified solution, and then soaking the solution; wherein the modified solution is a mixed solution of FeCl3 and AlCl3, the concentration of the modified solution is 0.4mol / L to 0.8mol / L, and the modified solution is in a molar ratio of Fe 3+ :Al 3+ =(1~3):(1~2);

[0013] Step 3, draining the ceramsite treated in step 2 and drying it in an oven;

[0014] Step 4: calcining the ceramsite processed in step 3 at high temperature, and taking it out after cooling to obtain modified ceramsite.

[0015] As a preferred solution of the present invention, in step 1, the ceramsite is rinsed clean with deionized water and then dried in an oven at 110°C.

[0016] As a preferred solution of the present invention, in step 2, the ceramsite and the modified solution are treated by ultrasound for 30 minutes and then soaked for 24 hours; the concentration of the modified solution is 0.6 mol / L; the modified solution is prepared according to the molar ratio of Fe3+ :Al 3+ =1:2.

[0017] As a preferred solution of the present invention, in step 3, the drying temperature is 115°C.

[0018] As a preferred solution of the present invention, in step 4, the calcination temperature is 350° C. to 600° C., and the calcination time is 3 hours.

[0019] Compared with the prior art, the rural sewage treatment system according to the embodiment of the present invention has the following beneficial effects:

[0020] The present invention can intercept solid waste in sewage through the filter pool, effectively reduce the concentration of suspended pollutants, help protect the normal operation of subsequent treatment process equipment and reduce the treatment load; the sewage at the bottom of the filter pool is sent to the bottom of the filler area of ​​the biological filter pool by a lifting pump, and the sewage flows through the filler area from bottom to top. At the same time, the aeration pipe can provide oxygen for the aerobic biochemical reaction of microorganisms, realize denitrification and denitrification in the biological filter pool, and ensure the removal effect of organic pollutants and nitrogen and phosphorus in the sewage; the ecological filter pool adopts a multi-level ecosystem combination formed by amphibians, aquatic plants, and microalgae, and realizes denitrification and phosphorus removal of rural sewage through the biochemical degradation action of amphibians and aquatic plants and their root microorganisms. The microalgae can not only absorb nitrogen and phosphorus to purify sewage, but also absorb nutrients in sewage to achieve growth. It has strong adaptability to changes in influent pollution load, improves sewage treatment stability, and cooperates with the purification pool to enhance the phosphorus removal effect through the modified ceramsite column. Then, the ultraviolet lamp in the disinfection pool can effectively disinfect and sterilize, remove pathogenic microorganisms, and ensure the stability of the effluent water quality to meet the reuse irrigation standard. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments are briefly introduced below.

[0022] Figure 1 It is a structural schematic diagram of the rural sewage treatment system provided by the present invention;

[0023] In the figure, filter tank 1; sewage inlet 11; sewage chamber 12; treatment chamber 13; grille device 14; mechanical grille 141; membrane grille 142; lifting pump 15; positioning baffle 16; water retaining plate 17; biological filter tank 2; filling area 21; aeration pipe 22; upper water outlet 23 of the biological filter tank; return zone 24; sedimentation zone 25; flow zone 26; partition 27; ecological filter tank 3; amphibian plant area 31; first tank body 311; first planting layer 312; amphibian plant 313; lower outlet of the first tank body Water outlet 314; aquatic plant area 32; second tank body 321; second planting layer 322; aquatic plants 323; water outlet 324 at the lower part of the second tank body; microalgae area 33; third tank body 331; microalgae 332; water outlet 333 at the lower part of the third tank body; purification tank 4; water inlet 41 at the bottom of the purification tank; water outlet 42 at the upper part of the purification tank; modified ceramsite column 43; disinfection tank 5; ultraviolet lamp 51; baffle 52; water inlet 53 at the upper part of the disinfection tank; water outlet 54 is provided at the lower part of the disinfection tank. DETAILED DESCRIPTION

[0024] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0025] In the description of the present invention, it should be understood that the terms "up", "down", "left", "right", "front", "back", "top", "bottom", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0026] like Figure 1As shown, a rural sewage treatment system according to a preferred embodiment of the present invention comprises a filter tank 1, a biological filter tank 2, an ecological filter tank 3, a purification tank 4 and a disinfection tank 5 connected in sequence. A sewage inlet 11 is provided above the filter tank 1, and a grid device 14 is provided in the filter tank 1 to separate the tank cavity into a sewage cavity 12 and a treatment cavity 13; a filler area 21 is provided in the biological filter tank 2, and an aeration pipe 22 is provided below the filler area 21. The sewage at the bottom of the treatment cavity 13 is transported to the bottom of the aeration pipe 22 by a lifting pump 15; the ecological filter tank 3 includes an amphibian plant area 3 arranged in a step-like downward sequence. 1. Aquatic plant area and microalgae area 33. The amphibian plant area 31 includes a first tank body 311 and a first planting layer 312 arranged above the first tank body 311. The first planting layer 312 is planted with amphibians 313. The top surface of the first planting layer 312 is slightly lower than the top surface of the first tank body 311. The water outlet 23 at the upper part of the biological filter 2 is connected to the upper part of the first planting layer 312. The aquatic plant area includes a second tank body 321 and a second planting layer 322 arranged above the second tank body 321. The second planting layer 322 is planted with aquatic plants 323. The top surface of the second planting layer 322 is lower than the top surface of the second pool body 321, the distance between the top surface of the first planting layer 312 and the top surface of the first pool body 311 is smaller than the distance between the top surface of the second planting layer 322 and the top surface of the second pool body 321, the water outlet 314 at the bottom of the first pool body 311 is connected to the upper part of the second planting layer 322; the microalgae area 33 includes a third pool body 331, microalgae 332 is planted in the third pool body 331, the water outlet 324 at the bottom of the second pool body 321 is connected to the water inlet at the top of the third pool body 331, the The water outlet 333 at the bottom of the third pool body 331 is connected to the water inlet 41 at the bottom of the purification pool 4, and a plurality of modified expanded clay columns 43 are evenly arranged in the purification pool 4. The water outlet 42 at the top of the purification pool 4 is connected to the water inlet 53 at the top of the disinfection pool 5. The inner pool wall in the disinfection pool 5 is evenly provided with a plurality of vertically arranged ultraviolet lamps 51, and the lower part of the disinfection pool 5 is provided with a water outlet 54; preferably, a plurality of horizontally staggered baffles 52 are provided from top to bottom in the disinfection pool 5, which can slow down the water flow rate to prolong the residence time of the water body and prolong the irradiation and disinfection time of the water body by the ultraviolet lamp 51.

[0027] The present invention can intercept solid waste in sewage through the filter tank 1, effectively reduce the concentration of suspended pollutants (SS), help protect the normal operation of subsequent treatment process equipment and reduce the treatment load; the sewage at the bottom of the filter tank 1 is sent to the bottom of the filler area 21 of the biological filter tank 2 through the lifting pump 15, and the sewage flows from bottom to top through the filler area 21. At the same time, the aeration pipe 22 can provide oxygen for the aerobic biochemical reaction of microorganisms, realize denitrification and denitrification in the biological filter tank 2, and ensure the removal effect of organic pollutants and nitrogen and phosphorus in the sewage; the ecological filter tank 3 adopts amphibians 313, aquatic plants 323, and microalgae 33 The multi-level ecosystem formed by the amphibians 313 and aquatic plants 323, as well as their root microorganisms, removes nitrogen and phosphorus from rural sewage through biochemical degradation. Microalgae 332 not only absorbs nitrogen and phosphorus to purify sewage, but also absorbs nutrients from the sewage to grow. Furthermore, the microalgae 332 is highly adaptable to changes in influent pollution loads, improving sewage treatment stability. Furthermore, the modified ceramsite columns 43 in the purification tank 4 enhance phosphorus removal, while the ultraviolet lamps 51 in the disinfection tank 5 effectively disinfect and sterilize, removing pathogenic microorganisms and ensuring stable effluent quality that meets reuse irrigation standards. This integrated design adapts to the widespread dispersion of rural sewage treatment and allows for tailored application.

[0028] Exemplarily, the biological filter 2 is provided with a recirculation zone, a sedimentation zone 25 and a flow zone 26, the stuffing zone 21 and the recirculation zone are arranged side by side, and the recirculation zone is close to one side of the filter tank 1, the flow zone 26 is located above the stuffing zone 21 and the recirculation zone, the sedimentation zone 25 is located below the stuffing zone 21 and the recirculation zone, and a vertical partition 27 is provided between the stuffing zone 21 and the recirculation zone, and the partition 27 extends downward to the top of the sedimentation zone 25, so that the sedimentation zone 25 can effectively collect sediment, and the aeration pipe 22 is located below the stuffing zone 21, so as to avoid the sediment in the sedimentation zone 25 from turning over during the aeration process of the aeration pipe 22, and the lifting pump 15 transports the sewage at the bottom of the treatment chamber 13 Below the aeration pipe 22, the baffle 27 prevents the sewage from flowing directly into the recirculation zone. The recirculation zone is filled with slow-release carbon source biological fillers. In this way, the sewage sent from the bottom of the filter tank 1 to the biological filter 2 first flows from the bottom to the top through the filler zone 21. After the pollutants in the water are degraded by the microorganisms of the fillers in the filler zone 21, part of the sewage enters the recirculation zone from the flow zone 26 and then flows back to the filler zone 21. The other part of the sewage flows from the outlet of the upper part of the biological filter 2 in the flow zone 26 into the amphibian plant zone 31. In addition, the carbon source biological fillers release carbon sources in the recirculation zone, maintaining the stability of the carbon source concentration in the biological filter 2 and strengthening the denitrification and denitrification effect of the wastewater in this area, realizing the internal recirculation of sewage in the biological filter 2, controlling the influent pollution load, and ensuring the stability of the sewage treatment effect. It should be noted that the filler zone 21 and the recirculation zone are fixed to the biological filter 2 by a limit plate, and the horizontal axis of the filler zone 21 is at the same height as the horizontal axis of the recirculation zone.

[0029] Exemplarily, the filler area 21 is filled with zeolite filler, the particle size of the zeolite filler is 10mm to 30mm, the height of the filler area 21 is 0.8m to 1.2m, and the zeolite filler has a porous structure, so that microorganisms can effectively attach and grow; the slow-release carbon source biological filler includes at least one of corn cobs, coconut shells and oyster shells, and the height of the recirculation zone is 0.5m to 0.7m, which can effectively maintain the carbon source concentration in the biological filter 2 and enhance the denitrification and denitrification effect of rural sewage.

[0030] Exemplarily, the amphibian 313 is at least one of pennywort and iris, the aquatic plant 323 is at least one of duckweed and canna, and the microalgae 332 is Chlorella; the first planting layer 312 and the second planting layer 322 both include a first gravel layer on the upper layer and a second gravel layer on the lower layer, and an air supply pipe 325 is provided below the second planting layer 322 to supply oxygen to the aquatic plants 323. The particle size on the first gravel layer is 10cm to 15cm, and the particle size on the second gravel layer is 30cm to 40cm; the growth of the amphibian 313 and the aquatic plants 323 and the absorption of nitrogen and phosphorus in sewage are improved, and the microalgae 332 uses Chlorella to effectively utilize nutrients in sewage to achieve rapid growth. The cultivated Chlorella can be further used as biomass energy, and its extract can be applied to multiple industrial fields, realizing resource application in the sewage treatment process.

[0031] Exemplarily, a positioning baffle 16 is horizontally provided in the middle of the filter tank 1, and the grille device is placed on the positioning baffle 16 from bottom to top toward the side away from the sewage inlet 11. The top of the grille device is connected to the top wall of the filter tank 1, and a water outlet is formed between the end of the positioning baffle 16 and the side wall of the filter tank 1. A water baffle 17 is provided in the filter tank 1, which is horizontally staggered with the positioning baffle 16. The water baffle 17 is located below the water outlet, and the area of ​​the water baffle 17 is larger than the area of ​​the water outlet. By setting the positioning baffle 16 and the water baffle 17, the impact force of sewage entering the bottom of the filter tank 1 can be slowed down, and will not affect the lifting pump 15 pumping sewage to the biological filter tank 2; the upper side of the grille device is provided with a mechanical grille 141, whose filtration accuracy is 20mm, which mainly intercepts large-volume garbage and large particle pollutants in the sewage; the lower side of the grille device is provided with a membrane grille 142, whose filtration accuracy is 0.75mm, which is used to automatically intercept and remove smaller particulate pollutants such as suspended matter and floating matter in the sewage, as well as smaller fiber materials and hair.

[0032] Exemplarily, the method for preparing the modified ceramsite in the modified ceramsite column 43 includes the following steps:

[0033] Step 1: clean the ceramsite and put it into the oven for drying;

[0034] Step 2: adding the ceramsite treated in step 1 to the modified solution, and subjecting the ceramsite to ultrasonic treatment so that the ceramsite is in full contact with the modified solution, and then soaking the solution; wherein the modified solution is a mixed solution of FeCl3 and AlCl3, the concentration of the modified solution is 0.4mol / L to 0.8mol / L, and the modified solution is in a molar ratio of Fe 3+ :Al 3+ =(1~3):(1~2);

[0035] Step 3, draining the ceramsite treated in step 2, placing it in a crucible and drying it in an oven;

[0036] Step 4: placing the ceramsite treated in step 3 into a muffle furnace for high-temperature roasting, and taking it out after cooling to obtain modified ceramsite.

[0037] The use of modified ceramsite has a good adsorption effect on phosphorus in sewage, reducing the phosphorus content in the treated effluent and improving the effluent water quality.

[0038] For example, in step 1, the ceramsite is repeatedly rinsed with deionized water, placed in a tray, and dried in an oven at 110°C.

[0039] For example, in step 2, the ceramsite and the modified solution are treated by ultrasound for 30 minutes and then soaked for 24 hours to allow the ceramsite to effectively adsorb the modified solution ions; the optimal concentration of the modified solution is 0.6 mol / L, and further increasing the ion concentration has little effect on the adsorption efficiency of phosphorus; the optimal molar ratio of the modified solution is Fe 3+ :Al 3+ =1:2, its phosphorus adsorption efficiency is the highest, Fe 3+ :Al 3+ =(1~3):1, the adsorption efficiency of phosphorus is lower than that of Fe 3+ :Al 3+ =1:2.

[0040] Exemplarily, in step 3, the drying temperature is 115°C.

[0041] Exemplarily, in step 4, the calcination temperature is 350°C to 600°C, and the calcination temperature is preferably 450°C. When the calcination temperature is 450°C, the phosphorus adsorption efficiency of the modified ceramsite is the highest, while when the calcination temperature is lower than or higher than 450°C, the adsorption efficiency of the modified ceramsite after sintering is reduced. This is because the temperature is too low, the sintering strength of the ceramsite is insufficient, the pore characteristics are not prominent, the surface crystals may be amorphous, and the adsorption sites are therefore reduced; and when the temperature is too high, the structural water and hydroxyl water are lost inside the ceramsite, and the crystal configuration is distorted, the internal space structure becomes irregular, and the surface adsorption sites are also reduced, thereby affecting the removal effect of organic matter. The calcination time can be 1h to 3h, and the calcination time is preferably 3h. The calcination time of 3h has the best adsorption effect on phosphorus, and further extension has basically no effect on improving the adsorption efficiency.

[0042] The test data of total phosphorus removal rate using different ceramsite columns and different modified solutions are shown in the following table:

[0043]

[0044]

[0045] It should be noted that, except for the ceramsite column type, Fe 3+ :Al 3+ Except for the above conditions of mixing ratio, total ion concentration and roasting time, other experimental conditions are the same.

[0046] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integral connection; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0047] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A rural sewage treatment system, characterized in that: It includes a filter tank, a biological filter tank, an ecological filter tank, a purification tank and a disinfection tank connected in sequence, a sewage inlet is provided above the filter tank, a grille device is provided in the filter tank to separate the tank cavity into a sewage cavity and a treatment cavity, a positioning baffle is horizontally provided in the middle of the filter tank, the grille device is tilted from bottom to top on the positioning baffle toward the side away from the sewage inlet, the top of the grille device is connected to the top wall of the filter tank, and a water outlet is formed between the end of the positioning baffle and the side wall of the filter tank, a water baffle is provided in the filter tank horizontally staggered with the positioning baffle, the water baffle is located below the water outlet, and the area of ​​the water baffle is larger than the area of ​​the water outlet; the grille device A mechanical grille is provided on the upper side of the device, and a membrane grille is provided on the lower side of the grille device; a plurality of baffles arranged horizontally and staggered are provided from top to bottom in the disinfection tank; a filler area is provided in the biological filter tank, and an aeration pipe is provided below the filler area. The sewage at the bottom of the treatment chamber is transported to the bottom of the aeration pipe by a lifting pump. A reflow area, a sedimentation area and a flow area are provided in the biological filter tank. The filler area and the reflow area are arranged side by side, and the reflow area is close to one side of the filter tank. The flow area is located above the filler area and the reflow area, and the sedimentation area is located below the filler area and the reflow area. A vertical partition is provided between the filler area and the reflow area, and the partition extends downward to set the The top of the sedimentation area, the recirculation area is filled with a slow-release carbon source biological filler; the ecological filter includes an amphibian plant area, an aquatic plant area and a microalgae area arranged in a step-like downward order, the amphibian plant area includes a first tank body and a first planting layer arranged above the first tank body, the first planting layer is planted with amphibians, the top surface of the first planting layer is slightly lower than the top surface of the first tank body, and the upper water outlet of the biological filter is connected to the upper part of the first planting layer; the aquatic plant area includes a second tank body and a second planting layer arranged above the second tank body, the second planting layer is planted with aquatic plants, the top surface of the second planting layer is lower than the top surface of the second tank body, and the top surface of the first planting layer is connected to the top of the first planting layer. The distance between the top surfaces of the first tank bodies is smaller than the distance between the top surface of the second planting layer and the top surface of the second tank body, and the water outlet at the bottom of the first tank body is connected to the upper part of the second planting layer; the microalgae area includes a third tank body, and microalgae are planted in the third tank body. The water outlet at the bottom of the second tank body is connected to the water inlet at the upper part of the third tank body, and the water outlet at the lower part of the third tank body is connected to the water inlet at the bottom of the purification tank. A plurality of modified ceramsite columns are evenly arranged in the purification tank, and the water outlet at the upper part of the purification tank is connected to the water inlet at the upper part of the disinfection tank. The inner pool wall in the disinfection tank is evenly provided with a plurality of vertically arranged ultraviolet lamps, and a water outlet is provided at the lower part of the disinfection tank.

2. The rural sewage treatment system according to claim 1, characterized in that: The filler area is filled with zeolite filler, the particle size of the zeolite filler is 10mm~30mm, and the height of the filler area is 0.8m~1.2m; the slow-release carbon source biological filler includes at least one of corn cobs, coconut shells and oyster shells, and the height of the recirculation zone is 0.5m~0.7m.

3. The rural sewage treatment system according to claim 1, characterized in that: The amphibian is at least one of pennywort and iris, the aquatic plant is at least one of hornwort and canna, and the microalgae is Chlorella; the first planting layer and the second planting layer both include a first gravel layer on the upper layer and a second gravel layer on the lower layer, an air supply pipe is provided below the second planting layer, the particle size of the first gravel layer is 10 cm to 15 cm, and the particle size of the second gravel layer is 30 cm to 40 cm.

4. The rural sewage treatment system according to claim 1, characterized in that: The preparation method of the modified ceramsite in the modified ceramsite column comprises the following steps: Step 1: clean the ceramsite and put it into the oven for drying; Step 2: Add the ceramsite treated in step 1 to the modified solution, and perform ultrasonic treatment to make the ceramsite fully contact with the modified solution, and then soak it; wherein the modified solution is a mixed solution of FeCl3 and AlCl3, the concentration of the modified solution is 0.4 mol / L~0.8 mol / L, and the modified solution is in a molar ratio of Fe 3+ :Al 3+ =(1~3):(1~2); Step 3, draining the ceramsite treated in step 2 and drying it in an oven; Step 4: calcining the ceramsite processed in step 3 at high temperature, and taking it out after cooling to obtain modified ceramsite.

5. The rural sewage treatment system according to claim 4, characterized in that: In the step 1, the ceramsite is rinsed clean with deionized water and then dried in an oven at 110°C.

6. The rural sewage treatment system according to claim 4, characterized in that: In the step 2, the ceramsite and the modified solution are treated by ultrasound for 30 minutes and then soaked for 24 hours; the concentration of the modified solution is 0.6 mol / L; the modified solution is prepared according to the molar ratio of Fe 3+ :Al 3+ =1:

2.

7. The rural sewage treatment system according to claim 4, characterized in that: In step 3, the drying temperature is 115°C.

8. The rural sewage treatment system according to claim 4, characterized in that: In step 4, the calcination temperature is 350° C. to 600° C., and the calcination time is 3 hours.

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